AN ABSTRACT OF THE THESIS OF
Michael Milota
in
Forest Products
Title:
Master of Science
for the degree of
presented on
August 7, 1980
THE EFFECTS OF DIISOCYANATE-POLYOL RESINS ON THE PROPERTIES
OF PARTICLEBOARD
Redacted for privacy
Abstract approved:
James B. Wilson
The ability of the resin to deform plastically can be an
important factor when considering the mechanical properties of particleboard.
Between resin droplets there exists an unbonded region
that forms the surface for a crack.
When particleboard is deformed
stress concentrations develop at the crack tips in the voids.
A
resin that deforms plastically may help to redistribute the stress.
Through this process energy would be absorbed and a stronger board
realized.
Urea- and phenol-formaldehyde resins currently used in the
particleboard industry are believed to be brittle and unable to
perform in this manner.
In addition, urea-bonded particleboard
releases formaldehyde, which has been increasingly under attack as a
health hazard, whereas, isocyanate bonded boards have no record of
toxic emissions.
This research is designed to utilize agents for
crosslinking and plasticizing to develop diisocyanate-polyol resins of
varying mechanical properties, make boards with these resins and
establish relationships between the resin and board properties.
The resin components used in this study include a polymeric
diisocyanate (PMDI), a triol (Triol), ethylene glycol (Eg), and three
polyethylene glycols with molecular weights of 1000, 1450 and 3200
(Peg 1000, Peg 1450 and Peg 3200).
The PMDI was mixed in varying
proportions with one or more of the polyols to make a resin to produce particleboard.
The internal bond, modulus of rupture (dry and
boiled), modulus of elasticity, work to maximum load, linear expansion, fracture toughness and thickness swell of the particleboard
were tested.
The board properties resulting from the various resins
were compared to one another and to the resin fracture energy.
Improvements of up to 26 percent for internal bond and nine percent for modulus of rupture were obtained when Peg 1000 was added to
unmodified PMDI.
The greatest increase in properties occurred when
the PMDI/Peg 1000 equivalent ratio was 6/1 or 12/1.
Increasing the
polyol molecular weight, while maintaining a constant PMDI/polyol
equivalent ratio of 12/1, increased the board properties.
When the
polyol was changed from Eg to Peg 1000, internal bond increased 30
percent and modulus of rupture increased 29 percent.
Using Peg 1450
to further increase the polyol molecular weight caused a slight decrease in most properties in comparison to Peg 1000, however, they
were superior to those obtained when Eg was used as the polyol component.
The resin fracture energy increased with increasing polyol
molecular weight.
Combinations of three polyols, Eg, Peg 1000 and
Triol, at a constant PMDI/polyol equivalent ratio of 12/1 were examined and in some cases more than one polyol as the polyol component
yielded better board properties than a single polyol.
Crosslinking
with Triol and plasticizing with Peg 1000 generally improved the
strength characteristics of the board.
THE EFFECTS OF DIISOCYANATE-POLYOL
RESINS ON THE PROPERTIES OF PARTICLEBOARD
by
Michael Milota
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
Completed August 7, 1980
Commencement June 1981
APPROVED:
Redacted for privacy
Associate Professor of Forest Products
in charge of major
Redacted for privacy
Head of Department of Forest Products
Redacted for privacy
Dean of Graduate Scho
A
Date thesis is presented
Typed by Linda S. Crooks for
August 7, 1980
Michael Milota
COMMITTEE MEMBERS
Redacted for privacy
James B. Wilson (Major Professor)
Redacted for privacy
Donald R. Langmo
(Graduat
Representative)
Redacted for privacy
Murray Laver r
Redacted for privacy
Timotfiy C. Kennedy
ACKNOWLEDGEMENTS
Appreciation is due my major professor, Dr. James B. Wilson,
for being an unfailing source of encouragement and constructive advice.
Without Jim this project would have never been completed.
A thank you is also extended to Dr. Murray Laver for his
significant contribution to the success of this research.
I would like to express appreciation to the other members of my
committee, Dr. Timothy C. Kennedy and Dr. Donald R. Langmo, and to
my department head, Dr. Helmuth Resch for doing so well their parts
in helping me complete the graduate program.
Lastly I find it hard to express my gratefulness to my mother
Anne Milota (1927-1980) and to my father C. A. Milota who have
unselfishly given SO much to me.
TABLE OF CONTENTS
INTRODUCTION
TV.
OBJECTIVE
3
LITERATURE REVIEW
Isocyanates
Historically
Preparation
Reaction
Use of Isocyanates with Wood
Adhesive Mechanical Properties
Testing Adhesive Properties
4
4
4
5
6
6
9
11
PROCEDURE
Obtaining Materials
Resin Formulation
Making the Particleboard
Cutting Diagram
Static Bending
Boiled NOR Test
Fracture Toughness
Internal Bond
Linear Expansion and Thickness Swell
Resin Properties
Statistical Treatment
15
15
15
RESULTS
29
DISCUSSION
37
CONCLUSIONS
56
BIBLIOGRAPHY
57
APPENDIX A
61
APPENDIX B
62
19
20
22
22
23
23
25
25
27
LIST OF FIGURES
Page
Figure
1
Tapered double cantilever beam specimen
14
2
Board cutting diagram
21
3
Fracture toughness specimen attached to metal
blocks
24
4
5
6
7
8
9
10
11
12
13
14
15
NOR,
ratio
a,
MOE and WMI versus
PMDI/Polyol equivalent
38
Fracture toughness, boiled NOR, linear expansion
and thickness swell versus PMDI/Peg 1000 equivalent
ratio
39
Hypothetical adhesion and cohesion versus PMDI/
Polyol equivalent ratio
41
NOR, MOE, IB and WML versus polyol component of
varying molecular weight
42
Fracture toughness, boiled NOR, linear expansion
and thickness swell versus polyol components of
varying molecular weight
44
Resin fracture energy versus resins with polyol
components of varying molecular weights
45
NOR, IB, MOE and WML versus equivalent percents
of polyol components
47
Fracture toughness, boiled NOR, linear expansion
and thickness swell versus equivalent percents
of polyol components
48
Resin fracture energy versus the equivalent percents of the resin polyol components
49
Resin fracture energy versus the equivalent percents of the resin polyol components
51
NOR, IB, MOE and WML versus equivalent percents
of polyol components
53
Fracture toughness, boiled NOR, linear expansion
and thickness swell versus equivalent percents
of polyol components
54
16
Resin fracture energy versus the equivalent percents of the resin components
55
LIST OF TABLES
Page
Table
1
Proportions of resin components
17
2
Boardmaking data; resin viscosity and temperature
and board density at 72°F and 65 percent relative
humidity
18
Board properties obtained by changing the polyol
component from Peg 1000 to Triol
30
Board properties obtained by changing the polyol
component from Eg to Triol
31
Board properties obtained by changing the polyol
component from Eg to Peg 1000
32
Board properties obtained by changing the isocyanate
to polyol ratio
33
Board properties obtained by varying the polyol
molecular weight
35
Resin fracture energies obtained from tapered
double cantilever beam test
36
3
4
5
6
7
8
THE EFFECTS OF DIISOCYANATE-POLYOL
RESINS ON THE PROPERTIES OF PARTICLEBOARD
I.
INTRODUCTION
Often, by choice, two or more dissimilar materials are used in a
composite to achieve a superior property that cannot be attained from
the materials individually.
Examples of this concept include concrete,
reinforced plastics and dispersion hardened metals.
In the Forest
Products industry, particleboard is one such composite material.
The
advantages of a composite like particleboard are that the strength
reducing growth characteristics inherent in wood are evenly dispersed
throughout the product, that any size or shape raw material can be
produced, and that the raw material used is compatible with the increasing practice of small-log, short-rotation forestry.
Particleboard, however, does not exhibit strength properties as
high as solid wood.
to two sources.
The weakness of particleboard may be attributed
First, when two dissimilar materials are joined
together, shear stresses develop at the interface when deformation
occurs due to loading, drying, or temperature changes.
If the shear
stress exceeds the strength of either of the materials, failure occurs.
Second, between resin droplets at the particle interfaces there exist
unbonded regions which form cracks or flaws.
The inherent flaws in
particleboard are larger than those found in clear-solid wood
(Ilcewicz 1980).
If the flaw size is larger, the stress concentra-
tion is greater, and failure occurs at a lower load level.
If a resin could be formulated to increase its ability to deform,
the resin-wood boundary conditions would be modified and the interface stresses reduced.
This same deformable resin would necessarily
be located at the tips of the inherent cracks.
At the crack tip, the
resin by deforming plastically could relieve the stress concentration,
thus arresting crack propagation.
This paper studies the properties of particleboard as a function
of the mechanical properties of the adhesive.
To produce resins with
varying mechanical properties a polymeric diisocyanate will be used
in combination with various polyols.
Isocyanate resin was selected
because its high reactivity with hydroxyl groups makes it easy to
formulate resins, and because of the recent interest shown by the
particleboard industry in isocyanates.
The proportion of isocyanate to polyol in the resin mixture will
be varied to determine if an optimum proportion of resin components
exists.
While holding a constant proportion of isocyanate to polyol
based on functionality, the polyol molecular weight will be varied
and combinations of various dials and triols will be used as the
polyol component.
The resins will be tested using a crack extension
test to obtain the resin fracture energy.
This resin property will
in turn be compared to the board properties.
The board properties
examined include modulus of rupture (dry and boiled), internal bond,
modulus of elasticity, work to maximum load, fracture toughness,
linear expansion and thickness swell.
3
II.
OBJECTIVE
To develop a series of diisocyanate-polyol resins which,
when cured, will have a wide range of mechanical properties.
To produce particleboard from this series of resins and establish relationships between the mechanical properties of the resin
and the mechanical properties of the board.
4
III.
LITERATURE REVIEW
Isocyanates
The product of isocyanate-polyol reactions, polyurethanes, are
They are,
one of the latest polymers to gain commercial importance.
however, somewhat misnamed as they can neither be derived from or
broken down to the monomer urethane (ethyl carbamate).
The most
common way to prepare a polyurethane is through the polyaddition
reaction of a di- or polyfunctional hydroxyl compound with a diisocyanate.
This basic reaction can be represented symbolically as
0
It
HO-R-OH + OCN-R'-NCO + OCN-R'-NH-C-O-R-O-C-NH-R'-NCO
A linear repeating structure, however would not probably occur due to
branching on the active hydrogen of the urethane group.
Isocyanates
are used to produce the urethanes that comprise many everyday items
such as the foams and plastics used in the furniture and automobile
industries.
In this study isocyanates will be used as a particle-
board resin, binding wood particles into a urethane matrix.
Historically
In 1937 research into the use of isocyanates was begun by
Professor Otto Bayer and the German I. G. Farbenindustrie.
German
industries during World War II pioneered the use of urethanes as
elastomers, foams, coatings and adhesives.
After the war, several
U.S.A. companies (Dupont, Monsanto, Goodyear and Lockheed) became
interested in these products and developed a similar industry.
In
5
1954 the three major suppliers of isocyanates were Mobay, a company
formed by Bayer of Germany and Monsanto, National Aniline and Dupont
(Saunders et al. 1962).
Today, Mobay, Arco, Rubicon, BASF and Upjohn
supply most of the isocyanates for the urethane industry.
Preparation
To date the only commercially important method of preparing isocyanates is by the phosgenation of primary amines (Remirez 1979).
R-NH2 + COC12
RNCO + 2HC1
The phosgenation approach is expensive due to a high energy requirement, and has the additional disadvantage that it produces hydrochloric
acid as a byproduct.
For these reasons it is desirable to find an
alternate method of producing isocyanates without phosgene.
Arco,
in 1977, announced just such a process and expects to be using it
commercially by mid-1981 (Remirez 1979).
This process, if perfected,
could conceivably lead to a substantial reduction in the cost of
producing isocyanates.
To form a polymeric urethane the isocyanate component must be
more than monofunctional.
In most cases difunctional isocyanates
(diisocyanates) are used.
Two common isocyanates used in the urethane
industry are 2,4-toluene diisocyanate (TDI) and 4,4'-diphenylmethane
diisocyanate (MDI).
handling.
TDI is very volatile and requires special
MDI, although toxic, has a low vapor pressure and with
proper ventilation can be used for particleboard.
At the present time
MDI shows the most promise of any isocyanate for use as a particleboard
adhesive (Deppe 1977).
Pure MDI is a solid at room temperature but
polymeric methylene diphenyl diisocyanate (PMDI) is a liquid and will
be used in this study.
higher polymers of MDI.
PMDI is mostly MDI plus some isomers and
The price of PMDI is less than that of MDI.
A list of all abbreviations used in the text can be found in Appendix
A.
Reaction
Isocyanate groups react with any active hydrogen, although
The
hydrogen transfer is not essential for the isocyanate to react.
reaction of an isocyanate with an alcohol (including water) is
typical of an isocyanate-active hydrogen reaction.
The active
hydrogen attaches itself to the nitrogen of the isocyanate and the
hydrogen active compound attaches to the carbon of the isocyanate.
The reaction is usually exothermic, resulting in a stable product.
In the case of an alcohol reacting with an isocyanate the stable
product is called a urethane.
This is the reaction that will occur
as the resins cure in this study.
In the case of water, an unstable
product results (a carbamic acid) and it decomposes to an amine.
Use of Isocyanates with Wood
Various German and French patents issued in the 1950's and 1960's
describe the use of isocyanate resins for the bonding of wood.
By
1972, Bayer AG of Leverkusin and Deutsche Novopan Gmb H of Gottingen
had developed economical methods for the commercial production of
isocyanate-bonded particleboard.
After that, in Europe, the use of
7
isocyanate resins for particleboard increased from 35 tons in 1972 to
1500 tons in 1973 (Loew et al. 1974).
Isocyanate particleboard resins
recently became commercial in the United States with the opening of
a particleboard plant by Ellingson Timber Company at Baker, OR.
The mechanical and weathering properties of isocyanate bonded
particleboard are generally as good or better than boards made in a
similar manner with comparable amounts of urea or phenolic resin
(Deppe 1971).
Internal bond (IB) strengths for 35 lb/ft3 boards
range from 60 psi for boards made with one percent resin to 160 psi
for boards made with eight percent resin (Loew et al. 1974).
Modulus of rupture (MOR) values range from 1800 to 3000 psi for
boards with resin contents of one to eight percent by weight.
Decay
and fire retardants can be added to isocyanate bonded particleboard
during manufacture with results that are comparable to phenolic
boards treated in the same manner.
Urethane groups are believed to be formed between isocyanate
groups of the resin and hydroxyl groups of the fibrous cell wall of
wood.
2ickerman (1975) reported calorimetric evidence for the forma-
tion of primary bonds between an isocyanate and wood, as opposed to
electrostatic or secondary forces.
Rowell (1975) cites work in which
wood was treated with various isocyanates to improve its dimensional
stability.
The antishrink efficiency of the treatments was attributed
to the isocyanate attaching to the hydroxyl groups of the cell wall.
The level of toxicity of isocyanate bonded particleboard is of
concern to anyone who produces or uses it.
The main resin component,
MDI, is toxic if the vapor concentration exceeds the threshold limit
8
value (TLV) of 0.02 parts per million (Upjohn Chemical Company 1975).
The vapor pressure in a production area can be kept well below the
TLV with proper ventilation.
A protective vapor mask and gloves
should be worn while handling the material.
Particleboard bonded with
MDI, on the other hand, has no record of releasing harmful vapors
during service.
This is a favorable property when compared to urea-
formaldehyde particleboard from which formaldehyde is released
The combustion gases
throughout the life of the board (Johns 1979).
released from burning isocyanate particleboard do not differ in
toxicity from the combustion gases associated with phenolformaldehyde bonded particleboard (Deppe 1977).
Some production problems are encountered when using isocyanate
resins.
Isocyanates stick tenaciously to almost anything, including
metal caul plates, no completely effective release agent has been
developed.
U.S. Patent 3,870,665 (Diehr et al. 1975) covers several
release agent formulations which catalyze the formation of isocyanurates from isocyanates to prevent sticking.
Teflon caul plates and
phenolic resin in the outer board layers have been tried with only
limited success (Deppe 1977).
Ellingson Timber Company uses veneer
on the outer surfaces of the board to prevent sticking in their
product, Elcoboard.
by isocyanate resins.
that uses cauls.
Another problem is the lack of tack displayed
This limits their use to a production line
Clean-up is a much more difficult task when using
isocyanate resins since they react with water to form hard, crystalline amines.
For this reason, acetone must be used to clean equipment
during a mill shut-down.
Some work has been done to make isocyanate
9
resins water emulsifiable (Johnson et al. 1976).
These resins,
however, tend to have a reduced potlife.
Adhesive Mechanical Properties
The molecular structure of an adhesive is ultimately going to
determine its mechanical properties.
Some molecular characteristics
which affect mechanical properties are molecular weight, degree of
crosslinking, stiffness of unit chains, intermolecular forces,
crystallization and ease of chain segment rotation.
Molecular weight, or degree of polymerization, plays an important
role in determining the bending, impact, and tensile strengths and
abrasion and tear resistance of polymers.
Up to the critical degree
of polymerization no significant strength exists.
The critical degree
of polymerization is 50 to 100 for most polymers.
After the critical
degree of polymerization is exceeded the strength properties increase
sharply at first and then become constant as the degree of polymerization reaches 300 to 400 (Mark 1979).
The molecular organization of a polymer will have a large affect
on its properties.
Secondary molecular forces include hydrogen
bonding, dispersion (London) forces and the interaction of permanent
dipoles.
These are weaker than primary bonds and are more readily
affected by temperature and stress.
The intermolecular attractive-
ness of secondary bonds is reduced by steric hindrance, like charges,
or anything that tends to increase intermolecular distances.
Dispersion forces act between all molecules due to a resonance between
virtual dipoles.
Virtual dipoles arise because of the randomness of
10
They account for 75 to 100
electron location in the orbitals.
percent of the total molar cohesion, the force that holds molecules
together.
The presence of a permanent dipole determines whether a
molecule is polar.
Alignment of regular repeating structures leads
to crystallinity of the polymer and increased secondary forces.
If
secondary forces are too great the polymer lacks flexibility, and if
there are not enough interacting groups, the material will be weak.
If primary bonding sites are available between molecular units,
crosslinking will result.
This can cause a crystalline material to
become more elastic, and a soft material to become more brittle
(e.g. the vulcanization of rubber).
Molecular organization pertains
to orientation, crystallinity and crosslinking (Mark 1979).
Varying the amount of rigid versus flexible parts of a molecule
will affect the mechanical properties of the polymer comprised of the
molecule.
The urethane polymers used in this study contain ether
groups which are flexible, and aromatic groups which are rigid.
Strong intermolecular forces are present with urethane groups while
only moderate intermolecular forces are present with aromatic groups
(Saunders 1962).
Seefried et al.
(1975) used polycaprolactone diols
of varying molecular weights in combination with MDI to produce a
series of urethane elastomers.
Polycaprolactone diol, the soft or
plasticizing segment, was used to impart elastomeric character to the
polymer.
Soft segment crystallization occurred when the molecular
weight of the diol was greater than 3000.
As the molecular weight
of the polycaprolactone decreased, ultimate elongation decreased and
hardness increased.
Other properties showed no constant trend.
When
a hard segment, 1,4-butane diol, was varied these trends reversed and,
11
in addition, tensile strength decreased as the amount of hard segment
increased.
When TDI was used instead of MDI the polymers exhibited
lower strength properties.
Testing Adhesive Properties
The engineering of adhesive properties became increasingly important when adhesives capable of bonding metals were developed for
the production of lightweight aircraft parts.
In tests done on ten
adhesives by Kuenzi et al. (1963), aluminum tubing was glued end-toend and tested in torsion to determine the shear modulus, modulus of
elasticity, Poisson's ratio, shear and tensile stress strain curves
and shear and tensile strengths.
They found that the less rigid ad-
hesive had greater resilience in elastic behavior than the more rigid
adhesives, but the work to failure showed no trend.
Adhesive joints in wood can be weakened or destroyed by the
shrinking and swelling of the adherend, especially at large grain
angles.
There are two ways to combat this, use an adhesive that is
very rigid and restricts the swelling or use a flexible adhesive
that can deform with the wood.
With the former, the stress concen-
tration at the wood-resin interface may exceed the strength of the
adherend causing it to fail.
Simpson et al. (1968, 1970) tested cast
films produced from epoxy resins containing varying amounts of flexibilizer.
Flexibilizer is a seldom used term in the plastics industry
for an additive which makes a resin or elastomer more flexible
(Whittington 1968).
With an increase in the proportion of polysulfide
flexibilizer, the maximum stress and modulus of elasticity decreased
12
in a linear manner.
The strain at failure and work to failure both
increased with flexibilizer content.
This study demonstrated that
the properties of adhesives can be manipulated for a required mechanical performance.
Krueger et al. (1964, 1965) reported three techniques for
determining the mechanical properties of an adhesive; stress relaxation at a constant strain, shear modulus at a given strain rate, and
creep at a constant stress.
All three techniques used a small segment
of adhesive film in a joint and recorded the deformation photographically.
In other work, Krueger (1966) studied the effects of glueline
thickness, wood density and adhesive flexibility on the strength of
an epoxy-polysulfide adhesive subjected to moisture changes.
The
density of the lumber appeared to contribute the most to the strength
loss.
A flexible, strain-absorbing adhesive had beneficial effects,
especially where the grain of the adherends were at large angles.
Mijovic et al. (1979a, 1979b) used a tapered double cantilever
beam specimen (TDCB) for testing the fracture energy of adhesives
as related to the resin postcure time and wood grain angle.
Problems
associated with testing adhesives in tension or shear exist because
the adhesive is strongest in these properties and wood failure occurs.
The most stringent condition occurs when the adhesive bond is loaded
in cleavage, the condition used in the fracture mechanics approach.
For the TDCB test the critical strain energy (GIc) is derived as a
function of the load necessary for crack extension (P), the crack
length (a), the width of the beam (b), and the specimen compliance
(C) according to the following formula:
13
G
=
X
P2
2b 3a
A diagram of the specimen can be found in Figure 1.
By tapering the
homogeneous, isotropic specimen and using strength of materials
formulae, the compliance can be made to vary linearly with "a" so that
aC/a is a constant.
Thus the formula for G
4P
It then becomes necessary to only measure P.
c
becomes:
2
GIc =
Eb2
where in is a constant dependent on specimen geometry.
10
Isocyanate glneline
Resorcinol
gluelines
5.8
2.2
6.6
Figure 1.
Tapered double cantilever bean specimen.
All dimensions are in inches.
15
IV.
PROCEDURE
Obtaining Materials
Approximately 750 pounds of dried Douglas-fir [Pseudotsuga
menziesii (Mirb.) Franco] particles were donated for this study by the
Duraf lake Division of Willamette Industries at Millersburg, Oregon.
The PMDI resin component, Isonate 143L, and a triol, Isonol 93, were
donated by the Upjohn Company of La Porte, Texas.
Other chemicals,
such as the polyethylene glycols, were obtained from chemical supply
dealers.
Resin Formulation
To produce the various boards needed for this study it was
necessary to formulate 18 different resins.
In preliminary work,
prepolymers were prepared in a standard resin kettle equipped with a
heating mantel, nitrogen purge, and mechanical stirrer.
From the
prepolymers prepared in the kettle, resins were formulated with only
limited success.
In some cases a high viscosity prevented the resins
from being sprayed on to the particles and in other cases the
prepolymer was unstable and its viscosity increased with time, making
it impossible to make and use the same resin twice in exactly the
same way.
During this preliminary work it was noted that at
temperatures well below those encountered during hot pressing, the
resin components reacted very rapidly.
With this in mind, the resin
components were mixed together and sprayed on the particles, assuming
that they would react during the press cycle to cure the board and
16
form a polymer.
No difference in properties was found between boards
made with a cooked resin and boards made with the uncooked resin
components, therefore cooking was eliminated as a step in resin
formulation.
Due to a short pot life the 18 resins used in this study were
mixed immediately prior to furnish blending.
The ratios of the resin
Some resins are deleted from the
components can be found in Table 1.
table since they were unusable or unsatisfactory as particleboard
resins.
In the table, the first number is the equivalent proportion
of a resin component.
The number in parenthesis is the weight fraction
based on a total resin weight of 1000 units.
An equivalent proportion
is based on the functionality of the components.
For example, a
12/1 equivalent ratio would mean that there are 12 NCO groups for
each hydroxyl group in the resin.
The PMDI component, 1431, was added
to a Waring blender and to that the polyol component(s) was added.
The mixture, which was only slightly miscible, was mechanically
agitated for 15 seconds with the blender on high speed.
vided for intimate mixing of the resin components.
This pro-
The viscosity
and recorded temperature of each resin are given in Table 2.
Viscosities were measured using a Brookfield spindle-type viscometer.
In general, the resins containing greater amounts of high molecular
weight polyols had higher temperatures and viscosities.
In some
cases the mixture would change from a translucent yellow to an
opaque white indicating that a reaction was taking place.
This was
generally observed with the polyethylene glycols as they were heated
to the liquid state prior to mixing.
When a polyethylene glycol with
a molecular weight of 3200 (Peg 3200) was mixed with PMDI a rapid
17
Table 1.
Proportions of resin components. The first value is the
equivalent proportion, the second is the weight proportion
based on a total weight of 1000 units.
Resin
Isocyanate
Number'
1
12 (982)
Ethylene
glycol
1 (18)
12 (775)
Polyethylene
glycol
1000
-
(-)
Triol
-
Polyethylene
glycol
1450
(-)
-
(-)
-
(-)
(-)
1 (225)
- (-)
3
12 (951)
-
(-)
- (-)
1
(49)
-
(-)
4
24 (866)
1
(8)
1 (126)
-
(-)
-
(-)
5
24 (854)
- (-)
1
(124)
1
(22)
-
(-)
6
24 (966)
1 (8)
- (-)
1
(26)
-
(-)
(-)
- (-)
- (-)
- (-)
(-)
- (-)
1 (296)
(87)
1
(15)
- (-)
10
1 (1000)
11
12 (704)
- (-)
12
36 (893)
1
(5)
1
13
3
(463)
- (-)
1 (537)
-
(-)
-
(-)
16
6 (633)
- (-)
1 (367)
-
(-)
-
(-)
18
24 (873)
- (-)
1 (127)
19
48 (932)
-
(-)
1 (68)
20
96 (965)
-
(-)
1
(135)
(-)
(-)
-
(-)
-
(-)
-
(-)
-
(-)
1Resins 7, 8, 9 and 14 are not included since they did not produce
satisfactory particleboard.
18
Table 2.
Board
Numberl
Boardmaking data;
resin viscosity and temperature and
board density at 72 F and 65 percent relative humidity.
Viscosity,
Centipoise
Temperature,
F
Board
Density,
1bs/ft3
1
60
72
40.3
2
78
80
40.3
3
69
72
39.6
4
62
69
40.5
5
75
86
40.0
6
68
72
39.8
10
61
68
40.7
12
57
82
40.2
13
130
130
37.7
16
70
115
38,3
18
75
95
37.8
19
69
90
38.0
20
65
92
37.5
'Resins 7, 8, 9 and 14 are not included since they did not produce
satisfactory particleboard.
19
reaction occurred, causing the resin to foam over the side of the
beaker and rapidly increase in viscosity.
Making the Particleboard
The moisture content of wood furnish can be adjusted during
blending by adding water to the resin.
When using nonemulsifiable
isocyanate resins it is necessary to keep the resin and the application equipment dry.
For this reason the moisture content of the
furnish was adjusted prior to blending.
An air spray gun and a drum
blender were used to add water to the furnish to obtain a nine percent
moisture content (oven dry basis).
The wood furnish was then stored
in plastic bags until needed.
Blending the wood particles and the resin was accomplished using
a four foot diameter drum-type blender.
An air spray gun was mounted
horizontally in the center of the drum which rotated in a vertical
plane at 35 rpm.
With 4.1 pounds of furnish, 0.21 pounds of resin
were added to the blender.
This provided a sufficient amount of wood
and resin for two boards plus 15 percent to make up for blender loss.
The time to spray on the resin was recorded and the furnish was
allowed to tumble for an additional two minutes to possibly improve
the resin distribution.
To form the mat, the furnish was sprinkled by hand onto a caul
plate surrounded by a deckle box.
This allowed the particles to lie
in a horizontal plane with a random orientation.
By forming the
material into a mat of uniform thickness, a board of uniform density
was produced.
The target density was 40 lbs/ft3 with a board thickness
20
of 1/2 inch.
The actual board densities, based on the volume and
weight at 72°F and 65 percent relative humidity, are given in Table 2.
A sheet of aluminum foil was included between caul plate and the mat.
This was done to prevent the caul plates and the board from sticking
together since isocyanate resins stick tenaciously to metal platens
(Mobay Chemical Company 1978).
After pressing, the aluminum foil
was peeled (not easily) from the board.
A press temperature of 350°F was used to cure the resin.
The
press closing time, the time from the beginning of mat compression
until the press meets the stops, was 30 seconds.
The pressure was
maintained (after press closing) at 720 psi for 30 seconds, after
which the pressure was reduced, over a period of 30 seconds to 250
psi.
This pressure was held for four minutes and then released,
again over a period of 30 seconds.
After pressing the boards were
marked and placed in a conditioning room at 72°F and 65 percent
relative humidity for three weeks.
Under these conditions the boards
reached an equilibrium moisture content of about seven percent.
Cutting Diagram
After conditioning, the boards were cut into test specimens
according to Figure 2.
From each board were cut two 3-by-14-inch
static bending specimens, one 3-by-14-inch boiled MOR specimen, one
3-by-15-inch linear expansion/thickness swell specimen and two
7/8-by-14-inch creep specimens.
After testing, each static bending
specimen was reduced to two 2-by-l-inch fracture toughness specimens
and two 2-by-2-inch internal bond specimens.
21
14
FT
IB
SE3
IB
LE/TS
3
IB FT
2
9K-1-0
iSB
T
2
16
FT
Creep
3
FT
IB
../..01%
egeMillOrAeftelep
Boiled MOR
14
16
Figure 2.
Board cutting diagram. IB = internal bond, FT =
fracture toughness, SB = static bending, LE/TS =
linear expansion/thickness swell and MOR = moduAll dimensions are in inches.
lus of rupture.
22
Static Bending
The static bending specimens were tested on an Instron testing
machine with a loading head rate of 0.20 inches per minute and a chart
speed of 7.87 inches per minute.
The loading was center point with a
12 inch span according to ASTM D-1037 (1977).
From the load-
deflection curve, values of modulus of elasticity (MOE), modulus of
rupture (MOR) and work to maximum load (WML) were determined according
to the following formulae:
MOE =
(3)
P1L3/(4bd3y1)
MOR = 3PL/(2bd2 )
(4)
WML = A/(bdL)
(5)
where P is the maximum load, L is the span, b is the specimen width,
d is the specimen thickness, P1 is the load at the proportional
limit, yl is the deflection at the proportional limit and A is the
area under the load-deflection curve.
Boiled MOR Test
In accordance with Canadian Standards Association standard
CAN3-0188.0-M78 (1978) the specimens were placed in boiling water for
two hours followed by a one hour cold soak.
excessive swelling or warp were noted.
Boards exhibiting
The static bending test was
done on the boiled specimens while they were still wet and their
modulus of ruptures were determined using the formula for static
bending.
Calculations were based on the dry specimen dimensions.
23
Fracture Toughness
In order to test the fracture toughness of the particleboard a
flaw had to be introduced in the specimen.
This was done by making
The
a 0.68 inch cut parallel to the surface with a bandsaw blade.
cut was then extended to 0.75 inches using a bandsaw blade filed in
a manner so that the cut ended at a sharp point (Lei 1978).
specimen, attached to metal blocks, is shown in Figure 3.
The
The
specimen was loaded in tension on a Tineous Olsen testing machine
using a loading head rate of 0.39 inches per minute.
The equation
used to calculate the fracture toughness (KIc) in this study is the
same as used for flakeboard (Lei at al. 1980).
K1c = ac (a)1/2. Y(a/W)
(6)
(for a/W < 0.6)
where
Y(a/W) = 1.99-0.41(a/W)+18.7(a/W)2-38.48(a/W)3+53.85(a/W)4
(5c = maximum force/N-0
W
= specimen width (two inches)
t
= specimen thickness (one inch)
= crack length (0.75 inches)
Internal Bond
The internal bond (IB) or tensile strength perpendicular to the
surface specimens were weighed to check density, attached to metal
blocks using a hot-melt adhesive and pulled in tension.
head rate of 0.16 inches per minute was used.
A loading
The internal bond
24
E---0.75
1.0
Metal Block
0.5
Particleboard
Metal Block
1.0
2.0
Figure 3.
H----1.0
Fracture toughness specimen attached to metal
blocks.
All dimensions are in inches.
25
1
strength was calculated by dividing the maximum load by the specimen
cross-sectional area.
Linear Expansion and Thickness Swell
For linear expansion (LE) measurements, the specimens were
allowed to condition at 72°F and 65 percent relative humidity for
three weeks.
After reaching practical equilibrium, their length,
thickness, and weight were measured.
The specimens were then allowed
to condition at 90°F and 90 percent relative humidity for three weeks
after which their length, thickness, and weight were remeasured.
Linear expansion was reported as the change in length per original
length per change in moisture content.
Thickness swell was reported
as the change in thickness per original thickness per change in
moisture content.
Resin Properties
In an effort to test the resin mechanical properties a composite
was made by mixing 40 weight percent resin with dry wood flour and
pressing at 350°F for 20 minutes.
Stops were used so that the final
thickness of the resulting resin plate was 0.125 inches.
The resin
plates were made at two different densities, 50 lbs/ft3 and 75 lbs/ft3.
Dog-bone specimens were cut from the plates using a 20,000 rpm router.
These were tested in tension and the modulus of elasticity and the
stress at failure computed.
The fracture energy of the resin was determined using tapered
double cantilever beam specimens.
Straight grain, flat sawn,
26
1/2-by-3-inch Douglas-fir lumber was obtained from a local lumber
yard.
Each piece was jointed on the 1/2 inch face, then cut to
ten-inch lengths in a manner that reduced wood growth irregularities.
Each specimen was numbered and a 1/8 inch strip was cut off the
jointed edge.
This strip was marked so that it could be reattached
with the same orientation to the 3-by-10-inch piece, replacing the
saw kerf with a resorcinol glueline.
An isocyanate resin was
applied, using an air spray brush and a spread of five pounds per
1000 square feet, on the jointed face of each of two strips and a
piece of teflon tape, 1-3/4 inches long, was placed at one end of
the glueline.
This tape prevented bonding in that region, thereby
making an initial crack.
The two 1/8 inch strips were then assembled
so that the slope of grain (if any) tended to make the crack, started
by the teflon, propagate through the isocyanate adhesive and not
into the wood.
for two minutes.
The strips were then placed in a hot press at 350°F
The 3-by-10 inch strips were glued back onto the
laminated wood strips so that the orientation of the piece relative
to the strip was the same as before the strip was cut.
that the MOE of the beam was as uniform as possible.
This insured
The specimen
was then cut and drilled as shown in Figure 1.
The load was applied on pins placed through the holes near the
front of the specimen and the crack opening was measured by attaching
a clip strain gauge to the front of the specimen.
A loading head rate
of 0.04 inches per minute was used and approximately five to ten
readings of the load at crack extension were obtained from each
specimen.
After crack extension (evidenced by a drop in the load)
the loading head was reversed until the load dropped below 11 pounds.
This
The head was thenmoved until the next crack extension occurred.
was repeated for the length of the specimen.
It was observed during
testing that the crack tip was in the tapered part of the specimen
while the first several readings were taken.
For this reason, only
the first two readings from each specimen will be used to ensure that
they come from the tapered region.
Statistical Treatment
To test the statistical significance of the data a Statistical
Package for the Social Sciences (SPSS) was employed.
A one-way
analysis of covariance was performed on the internal bond values and
This technique adjusted for
the densities associated with them.
density differences between the specimens and yielded a mean internal
bond strength for each board based on the overall average density
(39.2 lbs/ft3).
A Tukey multiple comparison confidence interval
(Neter et al. 1974) was used to test for differences between the mean
internal bond strengths of particleboard made with different resins.
To do this a confidence interval was set up as follows:
D - T s(D) < pl - p2 < D + T
(D)
where
D =
2
-
s(D) = s 2
2,_ ,
(T1)+s ky2)
MSE
MSE
n1
n2
2MSE
T = 0.71 q(1-0(; r; n -r)
n = number of specimens per board (seven)
(7)
28
nt = total number of specimens (112)
r
= number of boards (14)
q
= percentile of the studentized range distribution
MSE = mean sum of squares residual
If the confidence interval included zero, then there was no statistical difference between the two means.
A one-way analysis of variance was done on all other board and
resin properties.
The SPSS program arranged the boards into over-
lapping, statistically similar groups.
As an example of this
consider three sets of data, A, B and C, where statistically A is the
same as B, and B is the same as C, but A and C are different.
would be divided into two groups, A-B and B-C.
produced the basic statistics for each data set.
These
The SPSS program also
The pertinent
computer printout material can be found in Appendix B.
29
V.
RESULTS
A total of 36 boards were made using 18 different resins to show
the effect on board properties of polyol component mix, polyol
molecular weight and isocyanate to polyol equivalent ratio.
Not all
18 resin types were used successfully due to viscosity problems caused
by the rapid reaction of the resin components.
The first group of particleboard was made by maintaining a
constant isocyanate to polyol equivalent ratio.
The polyol component
consisted of two different di- or trifunctional alcohols in varying
proportions based on equivalents.
For example, if the two alcohols
were ethylene glycol (Eg) and Isonol 93 (Triol), then three combinations of these two would be used.
The three polyol combinations would
be 100 percent Eg, 50 equivalent percent Eg and 50 equivalent percent
Triol, or 100 percent Triol.
The 50-50 equivalent percent mixture of
Eg and Triol would be the same as a 24-76 weight percent mixture.
This was done for Peg 1000 and Eg, Peg 1000 and Triol and, as in the
example, Eg and Triol.
The results from these comparisons are
presented in Tables 3, 4 and 5.
In the second group of particleboard the isocyanate to polyol
ratio was varied to find an optimum polyol level.
This was only done
with Peg 1000 as the polyol component.
Isocyanate to polyethylene
glycol ratios ranged from three to 96.
To have an isocyanate to
polyol ratio less than three would be difficult as the pot life would
be very short and to have it above 96 would seem trivial because pure
MDI would be approached.
This data is presented in Table 6.
Table 3.
Board Properties obtained by changing the polyol component from Peg 1000 to Triol. A constant
isocyanate to polyol ratio of 12/1 was maintained.
Equivalent Ratio
PMDI/Eg/Peg
1000/Triol
Internal
Bond Adjusted for
Density}
psi
Modulus
of
Rupture,
psi
Modulus
Work to
of
Maximum
Elasticity,
Load,
psi
in-lbs
Fracture
Toughness,
psi
Linear
Expansion,
1
----x104
,8%mc
Thickness
Swell,
1
Boiled
MOB,
psi
&6mcx103
.3
in
12/0/1/0
150.0
1,664
321,783
1.77
113.7
4.56
8.83
568
12/0/0.5/0.5
158.0
1,640
401,113
1.32
114.5
3.89
7.14
529
12/0/01
153.9
1,570
357,459
1.36
104.2
4.15
7.22
678
1
Internal bond values are adjusted to a density of 39,2
lbs/ft3
Board properties obtained by changing the polyol component from Eg to Triol.
isocyanate to polyol ratio of 12/1 was maintained.
Table 4.
Equivalent Ratio
PMDI/Eg/Peg
1000/Triol
Internal
Bond Adjusted for
Modulus
Density];
psi
of
Rupture,
Modulus
Work to
Maximum
of
Load,
Elasticity,
in-lbs
psi
Fracture
Toughness,
psi\ri7-1
Linear
Expansion,
1
Q%mc
x10
4
A constant
Thickness
Swell,
1
L%mcx
103
Boiled
MOR,
psi
.3
psi
in
12/1/0/0
114.9
1,284
377,047
0.95
89.8
4.77
8.27
422
12/0.5/0/0.5
160.1
1,722
357,863
1.65
107.0
4.01
6.51
534
12/0/0/1
153.9
1,578
357,457
1.36
104.2
4.15
7.22
678
1
Internal bond values are adjusted to a density of 39.2 lbs/ft3
Table 5.
Board properties obtained by changing the polyol component from Eg to Peg 1000.
isocyanate to polyol ratio of 12/1 was maintained.
Equivalent Ratio
PMDI/Eg/Peg
1000/Triol
Internal
Bond Adjusted for
Densitlq-
Modulus
of
Rupture,
psi
Modulus
of
Elasticity,
psi
Work to
Maximum
Load,
in-lbs
Fracture
Toughness,
psi IT
Linear
Expansion,
1
mcx10
4
A constant
Thickness
Boiled
Swell,
MOR,
1
psi
^X 10
3
6,%mc
.3
psi
in
12/0/1/0
150.0
1,664
321,783
1.77
113.7
4.56
8.83
568
12/0.5/0.5/0
142.6
1,675
364,203
1.58
102.3
4.12
8.29
529
12/1/0/0
114.9
1,284
377,047
0.95
89.9
4.77
8.27
422
1
Internal bond values are adjusted to a density of 39.2 lbs/ft3
Table 6.
Board properties obtained by changing the isocyanate to polyol ratio.
Peg 1000, was used in each case.
Equivalent Ratio
PMDI/Peg 1000
Modulus
of
Rupture,
psi
Modulus
of
Elasticity,
psi
Work to
Maximum
Load,
in-lbs
Fracture
Toughness,
psi 57
Linear
Expansion,
1
%mcx10
4
Thickness
Swell,
Q%mcx10
1
3
Boiled
MOR,
psi
in3
108.6
858
167,787
1.24
58.6
4.56
13.91
130
147.9
1,537
250,441
2.15
119.4
3.78
10.17
302
12
150.3
1,664
321,783
1.77
113.7
4.56
8.83
568
24
90.5
1,242
281,858
1.10
44.9
3.40
6.76
352
48
82.8
1,247
277,726
1.09
50.7
3.34
6.45
433
96
75.7
1,107
267,551
0.89
34.3
3.29
7.16
393
3
1
Internal
Bond Adjusted fof
Density,
psi
The same polyol,
Internal bond values are adjusted to a density of 39,2 lbs/ft3
34
The last group of particleboard compares polyol size to particleboard properties.
The polyols used include three difunctional
alcohols; Peg 1450, Peg 1000 and Eg.
A fourth polyol, Peg 3200, could
not be mixed into a stable resin because a high temperature was
necessary to keep it in a liquid state and the pot-life was very
short.
The board properties, as a function of the size of the polyol
component, are given in Table 7.
When the resin plates were tested, extreme variability was encountered between the samples and it was decided that the test would
not yield any useful information about the resin properties.
The
double tapered cantilever beam test was used as a measure of the resin
properties.
The results of this test are presented in Table 8.
Table 7.
Polyol
Component
Board properties obtained by varying the polyol molecular weight.
to polyol ratio of 12/1 was maintained.
Internal
Bond Adjusted for
Density ,1
Modulus
of
Rupture,
psi
Modulus
of
Elasticity,
psi
psi
Work to
Maximum
Load,
in-lbs
in
Fracture
Toughness,
psi
A constant isocyanate
Linear
Expansion,
1
6,%mc
x104
Thickness
Boiled
3
MOR,
psi
1
xlO
3
114.9
1,284
377,047
0.95
89.1
4.77
8.27
422
Peg 1000
150.3
1,664
321,783
1.77
113.7
4.56
8.83
568
Peg 1450
149.8
1,509
362,797
2.04
88.4
3.35
9.20
388
Eg
1
Internal bond values are adjusted to a density of 39.2 lbs/ft3
36
Table 8.
Resin fracture energies obtained from tapered double cantilever
beam test. A constant isocyanate to polyol ratio of 12/1 was
maintained.
Equivalent Ratio
Fracture Energy (Gic)
PMAI/Eg/Peg
1000/Triol/
Peg 1450
lb/in
12/1/0/0/0
0.163
12/0/1/0/0
0.194
12/0/0/1/0
0.193
12/0.5/0.5/0/0
0.196
12/0/0.5/0.5/0
0.239
12/0.5/0/0.5/0
0.130
12/0/0/0/1
0.214
37
VI.
DISCUSSION
The role that the polyol level plays in determining the resin
and board properties is demonstrated using PMDI and Peg 1000.
Statis-
tically significant differences in board mechanical properties were
obtained for each property between at least two of the PMDI/Peg 1000
equivalent ratios.
Different mechanical properties were usually
noted between boards made with either a 6/1 or 12/1 equivalent ratio
of PMDI/Peg 1000 and the other boards.
4 and 5.
This is evidenced in Figures
Each value is plotted with its respective standard error.
The standard error is the standard deviation divided by the square
root of the sample size.
Values for the standard errors can be
found in Appendix B.
The board made with the resins containing a 6/1 equivalent ratio
of PMDI/Peg 1000 contains about 0.128 pounds of the isocyanate component, whereas, a board with a 96/1 equivalent ratio contains 0.196
pounds of the isocyanate component.
The latter contains 53 percent
more isocyanate component by weight but consistently exhibits lower
mechanical properties.
This, in itself, shows that the polyol
component of the resin must interact with the isocyanate, greatly
affecting the quality of the resin.
Hypothesizing about what happened to the resin can possibly
explain these differences in properties.
At very low isocyanate to
polyol ratios the resin probably has a reduced opportunity to react
with the wood because the isocyanate is surrounded by so much
polyol.
The high concentration of hydroxyl groups due to the polyol
in the resin may cause much of the isocyanate to react with the
1800
200
ai 1500
1150
1200
0
0
-0
0
50
900
600
3
6
48
24
12
Isocyanate/Polyol Ratio
35
96
3
6
48
24
12
Isocyana1a/Polyol Ralio
96
3
6
48
24
12
Isocyanale/Polyo1 Ratio
96
2.5
1
.)4
2.0
a 30
3
1.5
25
2
3
15
1
3
6
12
24
48
96
0.5
IsocyanaIe/Polyol Ratio
Figure 4.
MOR, IB, MOE and WMI, versus PMDI/Polyol equivalent ratio,
160
800
120
a 600
ui
180
0
2 400
2
140
200
0
3
a
12
24
48
96
0
3
Isocyanale/PoIvol Ratio
6
24
48
12
IsocyanaIe/Polyoi Ratio
96
16
5.2
4.6
3.4
2.8
3
6
12
24
48
Isocyanato/Polyol Ballo
Figure 5.
96
4
3
12
24
48
Isocyanale/PoIyol Ratio
Fracture toughness, boiled MOR, linear expansion and thickness swell
versus PMDI/Peg 1000 equivalent ratio.
96
40
polyol before it gets a chance to react with the wood.
This reaction
might happen during the mat forming process or, more than likely,
when the mat is in the press.
After the press closes and the
temperature of the resin becomes sufficient to cause a reaction, the
isocyanate finds a hydroxyl group in the polyol component of the
resin before it finds a hydroxyl group in the wood.
The isocyanate
reacts with the hydroxyl in the resin and the adhesion between the
resin and the wood is less than if the isocyanate had reacted with a
hydroxyl in the cell wall.
On the other hand, when the isocyanate to
polyol ratio is too high, the isocyanate reacts with the wood but
the internal structural integrity of the resin is low because of the
lack of urethane bonding resulting in a poor cohesive strength.
The
proposed relationship, depicted graphically in Figure 6, dictates that
both adhesion and cohesion are necessary for a good bond and that
if one is weaker than the other, that mechanism controls the failure.
The board physical properties, linear expansion and thickness
swell shown in Figure 7, do not exhibit the characteristic hump at an
equivalent ratio of 6/1 or 12/1 as noted with the mechanical properties.
No explanation is given as to why linear expansion and
thickness swell are greatest at the lower isocyanate to polyol
equivalent ratios except that the resins containing higher proportions
of the polyol component might be more hygroscopic.
Also, since
greater proportions of polyol leave less isocyanate to react with
the wood, more hydroxyl groups might be available in the cell wall
to help swell the wood.
optimum
ratio
Increasing lsocyanate/ Polyol Ratio --->
Figure 6.
Hypothetical adhesion and cohesion versus PMDI/Polyol equivalent ratio.
42
1750
16C)
a 1500
140
co.
cc
3 120
21250
1000
100
Peg 1000
Peg 1000
Peg 1450
Peg 1450
Potyol Component
PoIyoi Component
2.5
5
12.0
3
1.0
2
0.5
Peg 1000
Peg 1450
Poiyol Component
Figure 7.
Eg
Peg1000
Peg 1450
Poiyoi Component
MOR, IB, MOE and WML versus polyol component of varying
molecular weight. The PMDI/Polyol ratio was 12/1 for
all cases.
43
When the isocyanate to polyol equivalent ratio is held constant,
but the molecular weight of the polyol varied, differences appeared in
the board properties.
These are shown in Figures 7 and 8.
Statisti-
cally significant differences occurred for NOR, IB, WML and linear
expansion when the polyol molecular weight was changed.
The fracture
energy of the resin increased with increasing molecular weight as
shown in Figure 9, although the increase was not enough to be
statistically significant.
This increase was expected since the
greater molecular weight of the polyol should lend flexibility and
energy absorbing capacity to the resin.
Because the type of resin
was the only variable in this part of the experiment, it should be
responsible for any variation in the board properties.
One would
expect that as the polyol molecular weight increased, the modulus of
elasticity would decrease.
Indeed this does occur, probably because
the longer chain polyol lends more flexibility to the resin,
decreasing the modulus of elasticity.
In addition, other strength
properties should increase with increasing polyol molecular weight
because the longer chain polyol is more able to deform, reducing
stress concentrations.
This occurred for all mechanical properties
between the boards made with the isocyanate-ethylene glycol resin and
the boards made with the isocyanate-polyethylene glycol 1000 resin as
expected.
However, all the mechanical properties, with one exception,
work to maximum load, decreased when the resin was changed from the
1000 molecular weight to the 1450 molecular weight polyethylene
glycol.
This decrease is either the result of an inherently low
strength polymer or something in the experiment caused the lower
44
750
Peg 1000 Peg1450
Poiyoi Component
Peg 1000 Peg 1450
Polypi Component
55
MIW
25
Figure 8
Eg
Peg 1000 Peg 1450
Poiyol Component
Peg 1000 Peg 1450
Poiyol Component
Fracture toughness, boiled MOR, linear expansion and
thickness swell versus polyol component Of varying
molecular weight. The PMDI/Polyol ratio was 12/1 for
all cases.
45
Peg 1000
Peg1450
Polyol Component
Figure 9.
Resin fracture energy versus resins with polyol
The
components of varying molecular weights.
PMDI/Polyol ratio was 12/1 for all cases.
46
properties.
Peg 1000 and Peg 1450 are solids at room temperature and
must be heated before the resins can be mixed.
Peg 1450 must be
heated to a higher temperature than Peg 1000 and possibly this higher
temperature caused the isocyanate to react prematurely, weakening the
wood-resin bond.
This phenomena was noted when Peg 3200 was used.
The resin was mixed and a very rapid reaction occurred causing the
resin to foam out of the beaker.
If a problem in resin formulation
did not exist with the PMDI-Peg 1450 resin then this may indicate
that, as with the resin isocyanate to polyol ratio, there is some
optimum molecular weight which yields the best resin performance.
Holding a constant isocyanate to polyol equivalent ratio and
varying the type of polyol from 100 percent Eg to 100 percent Peg
1000 increases the board properties as evidenced in Figures 10 and
11.
Statistically, only the increase in internal bond and work to
maximum load are significant.
This increase was expected because,
as the resin was changed, the resin fracture energy (Figure 12)
increased.
The increase was due to the Peg 1000 imparting an energy
absorbing capacity to the resin.
A 50 percent Eg-50 percent Peg 1000
mixture of the polyol components in the resin increased the board
properties almost as much as if all of the polyol component had been
Peg 1000.
This might be attributed to the fact that on a weight
basis the Peg 1000 makes up a large proportion of the polyol component.
If a board made with the 50-50 Eg-Peg 1000 mixture at a 12/1
equivalent ratio is compared to a board made with a resin that has
a 24/1 equivalent ratio of PMDI/Polyol (Table 6), the former board
shows superior strength properties.
This seems to indicate that the
47
150
2000
o.140
SOO
C
Si 120
1000
100
0
100
50
SO
100 Eg
0 Peg
0
100
50
50
100Eg
0 Peg
Poiyot Components, %
Polyol Components.%
2.0
4.0
re)
1TJ
3.5
3.0
0
100
50
SO
100 E.g
0 Pig
Poiyol Component. °is
Figure 10.
0.5
0
100
SO
SO
100 Eg
0 Peg
Poiyol Components, %
MOR, IB, MOE and WML versus equivalent percents of
polyol components. The PMDI/Polyol ratio was 12/1
for all cases.
48
160
1'100
40
0
100
0
100
SO
SO
100 Eg
0 Peg
PoiyoI Components.%
50
50
100 Eg
0 Peg
Polyol Components,%
9.5
5
CID
to 8.5
7.5
3
0
100
SO
SO
100E9
OP%
Polyol Compomm%
Figure 11.
0
100
50
SO
100Eg
0 Peg
Pot yot Components,%
Fracture toughness, boiled MOR, linear expansion and
thickness swell verses equivalent percents of polyol
compopents. The 1:)MDI /Polyol ratio was 12/1 for all
cases.
49
300
100
0
100
Figure 12.
100 Eg
50
0 Peg
50
Polyol Components, %
Resin fracture energy versus the equivalent percents
of the resin polyol components. The PMDI/Polyol ratio
was 12/1 for all cases.
50
equivalent ratio of the components is still important, that is, a
12/1 equivalent ratio is more favorable than a 24/1 equivalent
ratio and that the proportions on a weight basis are of lesser
importance.
Except for the ethylene glycol, the two boards are identical,
yet their properties differ, demonstrating that the ethylene glycol
plays a roll in strengthening the adhesive.
This also says that a
lot of the plasticizing component may not be necessary and that
something cheaper could replace part of it while retaining a favorable
isocyanate to polyol equivalent ratio, thereby possibly reducing the
resin cost.
There were no statistical differences in the board properties
between the boards made with Peg 1000 and Triol as the polyol component.
Also, no statistical difference was present between the
fracture energies of the resins made with either Triol or Peg 1000 as
the polyol component (Figure 13).
Though statistical differences
did not appear between the boards made with Peg 1000 and Triol, as
a group they had noticeably better strength properties than any other
board in the study.
very rigid.
One way to make an adhesive strong is to make it
Another way is to make it plastic so that it can move
with the adherend, thus reducing the stress concentrations (Simpson
et al. 1970).
The triol probably tends to make a strong bond via the
first method, by crosslinking and producing a rigid adhesive.
The
polyethylene glycol will follow the later method, making a flexible
resin that reduces stress concentrations.
Thus, both polyols tend
to enhance the resins properties, however, they accomplish this task
51
100
0
100
Figure 13.
100 Peg
50
0 Triol
50
Polyol Components, %
Resin fracture energy versus the equivalent percents
of the resin polyol components. The PMDI/Polyol
ratio was 12/1 for all cases.
52
by different means.
This interpretation may be illustrated by
examining the data for work to maximum load and fracture toughness.
The work to maximum load was greatest for the board with Peg 1000 as
the polyol component and fracture toughness was least for the board
containing no Peg 1000.
This indicates that the boards containing
Peg 1000 may be more energy absorbing than the boards with a greater
amount of Triol.
When the isocyanate to polyol equivalent ratio was held constant
and the polyol changed from Eg to Triol, the IB, NOR, WML and fracture
toughness were at a maximum when a 50-50 equivalent percent mixture
of Eg and Triol was used as the polyol components (Figures 14 and 15).
The resin fracture energy, Figure 16, however, did just the opposite
and had its lowest value when the 50-50 mixture was used as the polyol
component.
No explanation is given for this.
Thickness swell and
linear expansion are less when Triol is present in the polyol
component which may be due to crosslinking in the resin causing a
reduction in the swelling.
53
2000
1000
0
100
50
50
0
100
lOOEq
0 Tnoi
Polyol Components, %
50
2.0
4.5
3.0
100 Eg
0 Tnol
Polyol Components. %
SO
0
100
SO
SO
1005;
0 Trio
Polyo/ Components.%
Figure 14.
as
o
UX,
so
1004
OThoi
PolyolComponents.%
SO
MOR, IS, MOB and WML versus equivalent percents of polyol
The PMDI/Polyol ratio was 12/1 for all cases.
components.
54
125
SOO
2 500
2
co
75
0
100
50
100 Eg
so
0 Tnol
Poiyol Components. %
400
0
100
100 Eg
0 Triol
Poiyol Components.%
so
50
9
Sc
744
I
4.0
3.5
0
100
Figure 15.
100 Eg
0 Triol
Poiyol Components. %
50
SO
0
100
50
50
100 Eg
0 Trial
Poiyol Components.%
Fracture toughness, boiled MOR, linear expansion and
thickness swell versus equivalent percents of,polyol
components. The PMDI/Polyol ratio was 12/1 for all
cases.
55
300
100
0
100
Figure 16.
50
100 Eg
0 Triol
50
Polyol Components, To
Resin fracture energy versus the equivalent percents
The PMDI/Polyol ratio was
of the resin components.
12/1 for all cases.
56
VII.
CONCLUSIONS
The experimental findings presented in this paper lead to the
following conclusions regarding the polyol components in isocyanate
bonded particleboard.
There exists an optimum polyol level in an isocyanate-polyol
particleboard resin.
In the case of Isonate 143L and polyethylene
glycol 1000, the optimum equivalent ratio is about 6/1 or 12/1.
At
this polyol level all board mechanical properties are at a maximum.
Within the limits of the experiment, increasing the weight of
the polyol component of the resin had favorable effects on the board
mechanical properties.
However, with some properties there appears
to be an optimum molecular weight, above which the board properties
begin to decrease.
In most cases modulus of rupture and modulus of elasticity were
inversely related, that is, an increase in modulus of rupture is
accompanied by a decrease in modulus of elasticity for the resins
tested.
Polyethylene glycol 1000 and Isonol 93 are superior to ethylene
glycol when used as the polyol component in combination with Isonate
143L.
In some cases a mixture of two or more polyols is superior to
only one polyol for use as the polyol component in an isocyanate
particleboard resin.
57
BIBLIOGRAPHY
Agranoff, J. Editor. 1979.
New York.
Hill.
Modern Plastics Encyclopedia. McGraw
Standard methods
1977.
American Society for Testing and Materials.
of evaluating, the properties of wood-based fiber and particle
panel materials.
ASTM Desig. D1037-72.
Standard test methods for
Canadian Standards Association.
1978.
mat-formed wood particleboards and waferboard. CAN3-0188.0-M78.
Canadian Standards Association.
Cross, T.A.
1979.
Engineering.
1978.
Waferboard.
CAN3-0188.2-M78.
How to evaluate urethane coatings.
12(10):
Chemical
153.
Synthesis and characterDearlove, T.J.,
and G.A. Campbell.
1977.
ization of isocyanate-terminated polyurethane prepolymers.
1499-1509.
Journal of Applied Polymer Science. 21:
Delmonte, J.
1975.
High-performance urethane adhesives.
29-31.
Age 18(12):
Adhesives
Deppe, H.J.
1977.
Technical progress in using isooyanate as a
binder in particleboard manufacture. Presented at the 11th
Particleboard Symposium, Pullman, Washington.
Diehr, H.J., K.J. Kraft, H.I. Sachs.
U.S. Patent 3,870,665.
11, 1975. Assigned to Bayer AG, Germany.
March
Plastics engineering handbook of the
1976.
Frados, J. Editor.
Society of the Plastics Industry. Van Nostrand Reinhold Company, New York.
Gemeinhardt, P.G., W.C. Darr, and J.H. Saunders. 1962. Rigid urethane
foams derived from crude tall oil. I and EC Product Research and
Development.
1(2):
92-96.
Hartman S.
1969.
Modified wood with aqueous polyurethane systems.
For. Prod. J .
39-42.
19(5):
Presented
1979.
Interactions of wood and formaldehyde.
Johns, B.
at the 13th Particleboard Symposium, Pullman, Washington.
Johnson F., A. Metcalfe, 0. Erngtson, and P. Mayrdofer. U.S. Patent
3,996,154. December 7, 1976. Assigned to Imperial Chemical
Industries.
Krueger, G.P.
1966.
Behavior of an epoxy-polysulfide adhesive in
wood joints exposed to moisture content changes. USDA For. Ser.
Res. Paper FPL 24.
58
Krueger, G.P., and R.F. Blomquist. 1964. Performance of a rigid and
a flexible adhesive film in lumber joints subjected to moisture
content changes.
USDA For. Ser. Res. Paper FPL 076.
Krueger, G.P., and R.F. Blomquist. 1965. Experimental techniques for
determining the mechanical behavior of flexible structural adhesives in timber joints. USDA For. Ser. Res. Paper FPL 21.
Determination of mechanical
Kuenzi, E.W., and G.H. Stevens.
1963.
properties of adhesives for use in the design of bonded joints.
USDA For. Ser. Res. Note FPL 011.
Lei, Y.K.
1978.
PHD thesis.
Corvallis.
On the fracture mechanics of oriented flakeboard.
Dept. of Forest Products, Oregon State U.,
Fracture toughness of oriented
Lei, Y.K., and J.B. Wilson.
1980.
154-161.
flekeboard. Wood Science and Tech.
12(3):
Isocyanate as a binder for particleLoew, G., and H.I. Sachs.
1974.
board. Presented at the 8th Particleboard Symposium, Pullman,
Washington.
Maloney, T.M. 1977.
manufacturing.
Modern particleboard and dry-process fiberboard
Miller Freeman Publications, San Francisco.
Marceau, J.A., Y. Noji, and J.C. Mcmillian. 1977. A wedge test for
evaluating adhesive-bonded surface durability. Adhesives Age
20(10):
28-34.
Mark, H.F., 1979a. Cohesive and adhesive strength of polymers - Part
Adhesives Age 22(7):
35-40.
Mark, H.F., 1979b. Cohesive and adhesive strength of polymers - Part
Adhesives Age 22(8): 45-50.
Southern hardwoods
1976.
Marra, A.A., R.F. Day, and W.A. Housknecht.
12-19
in wood foam composites. For. Prod. J. 26(2):
Mijovic, J.S., J.A. Koutsky.
1979a. Effect of wood grain angle on the
fracture properties and fracture morphology of wood-epoxy joints.
Wood Science and Tech. 11(3): 164-168.
Mijovic, J.S., J.A. Koutsky. 1979b. The effect of postcure time on
the fracture properties and nodular morphology of an epoxy resin.
Journal of Applied Polymer Science. 23(4): 1037-1042.
Mobay Chemical Corporation and the Canadian Eastern Forest Products
Evaluation of Mondur E-441 and Mondur MR polyLabratory.
1978.
meric isocyanates as binders for Aspen Waferboard.
59
Applied linear statistical models.
Neter, J., W. Wasserman. 1974.
Richard D. Irwin, Inc. Homewood, IL.
Engineering properties of adhesives.
1973.
Reinhart, T.J.
Age 16(7): 35-41.
Remirez, R.
12(4):
1979.
Isocyanates on the move.
80-83.
Adhesives
Chemical Engineering
McGraw-Hill, Inc.
Rodriguez, F. 1970.
New York.
Principles of polymer systems.
Rowell, R.M., 1975.
disadvantages.
Chemical modification of wood: advantages and
USDA For. Serv. FPL. Approved Technical Article.
Saunders, J.H. and K.C. Frisch. 1962. Polyurethanes: chemistry and
technology. John Wiley and Sons, Inc., New York.
Mechanical behavior of
1978.
Schjelderup, H.C. and W.B. Jones, Jr.
Adhesives Age 21(2): 35-38.
cast adhesive films.
,
Seefried, C.G., J.V. Koleske, and F.E. Critchfield. 1975a. ThermoEffects of soft-segment
I.
plastic urethane elastomers.
19:
2493-2502.
variations. Journal of Applied Polymer Science.
Seefried, C.G., J.H. Koleske, and F.E. Critchfield. 1975b. Thermoplastic urethane elastomer.
II. Effects of variations in hardsegment concentration. Journal of Applied Polymer Science.
19:
2503-2513.
Seefried, C.G., J.V. Koleske, and F.E. Critchfield. 1975c. 'ThermoEffects of variations in
III.
plastic urethane elastomers.
Journal
of
Applied
Polymer Science. 19:
isocyanate structure.
3185-3191.
Shoemaker. P.D., H.O. McQueary. U.S. Patent 3,919,017.
11, 1975. Assigned to Ellingson Timber Company.
November
Simpson, W.T., and V.R. Soper. 1968. Stress-strain behavior of films
of four adhesives used with wood. USDA For. Ser. Res. Note FPL
0918.
Tensile stress-strain behavior
1970.
Simpson, W.T., and V.R. Soper.
of flexiblized epoxy adhesive films. USDA For. Ser. Res. Paper
FPL 126.
1975.
Upjohn Chemical Company.
isocyanate components.
Safety information: isocyanate and
Whittington, L.R. 1968. Whittingtons Dictionary of Plastics, Technomic Publishing Company., Inc. Stamford, Conn.
60
Wood Handbook.
1974.
USDA For. Ser. FPL.
Zicherman, J.B , 1975. Urethanes and composite wood products.
25(6):
Prod. J.
21-25.
For.
APPENDICES
61
APPENDIX A
List of Abbreviations
Eg
Ethylene glycol
FT
Fracture toughness
IB
Internal bond
LE
Linear expansion
MDI
Methylene diphenyl diisocyanate
MOE
Modulus of elasticity
MOR
Modulus of rupture
MW
Molecular weight
NCO
Isocyanate group
Peg 1000
Polyethylene glycol (MW = 1000)
Peg 1450
Polyethylene glycol (MW = 1450)
Peg 3200
Polyethylene glycol (MW = 3200)
PMDI
Polymeric methylene diphenyl diisocyanate
TDCB
Tapered double cantilever beam
TDI
Toluene diisocyanate
TLV
Threshold limit value
TS
Thickness swell
Work to maximum load
62
APPENDIX B
Basic Statistics for Board and Resin Properties
The basic statistics for each board and resin property are presented as given in the SPSS program computer printout.
refers to the type of resin used in the board.
portions are given by number in Table 1.
The group number
The resin component pro-
Following the basic statistics
for each property are the results of the Student-Newman-Keuls procedure.
This procedure separates the resins into statistically similar subsets.
Internal bond adjusted for density
Bl.
G-F4'41.41/
EAi
LE
TA
..AG)USIE
126.'3.5
GLAIE
1
2
3
7
,
4
7
,
10
7
12
13
16
7
1e
17
11
19
CUv;P.IA%-.S
*
- --iNEi
,E-GOR r -
-g
INEPEHZENTS
UNA C.ASTED
-7
-7.21
-,..
26.5,2
2-:-.4-v
23.o2
3c
3.6 .,;..6za _ _
13. 31
21.40
25.01.
13.7c
29 .19
!I . 21-
- 10 .05
20.95
21.12
2 t .25
1.64
1,..' 9
27.06
-30.1.i
--
19,05
..3t .35
11..* 3
50 .14
....6.36
7 ..5.3,.....,...2_,
-54.99
.7
. 9,
MULTIP4-E m SQUARED
8
.4,49
a
74:
63
32.
Modulus of rupture
GRP
Gr. F
GPP
GRP
GP
3.75D3
-7
3
1
157i. 0030
1639.7500
1722.7500
1517.7R GO1509.5500
1_675,
10
GRF 11
1:2c.3206
v5.027
112.3434
or .6 'il.i3
Z..,--- .
35.3693
1 70 77'36
4
56
1437.5036
GRP 20
*.1U3
226.6 368
3966
1
1 C1.2coe
22o .5 5'- 0
GP 19
5.1
110.0550
1537.7500
1241.7500
1247.2500
1107.0000
GFP 16
GPP 18
TOTA.L.
121 .94.
14-2.7591.
10,3.356
GRPr-13
ERPOR
243.6912
15-6.2500
GPF 12
STANCAr3
STiNOARD
-.1JE
--1-111511TS
2:35..."1o2
f4
4
5
6
GrP
GRP
AN-
COUNT
GPOUP-
64.4294
1
:::0.6333
113294
-.04313
91.1363
3 0.8 '6 36
132.2 727
Subset 1
Group
Mean
13
20
859
1107
20
1107
18
19
1242
1247
Subset 2
Group
Mean
1
1284
Subset 3
Group
18
19
Mean
1242
1247
Group
Mean
12
1546
3
1
1284
11
10
16
1509
1518
1538
5
1578
1638
10
1518
Subset 4
Group
Mean
1284
11
1509
Group
5
1640
1664
1675
10
16
Mean
1
2
16
12
1538
1546
12
1546
1578
3
1578
4
Subset 5
Group
Mean
Group
Mean
11
1509
2
1664
1518
4
1675
1538
6
1723
3
5
1640
64
B3.
Modulus of elasticity
ST4N:)6ii.0
SI,:iNJ4F3
COUNT
-GROUP-GRP
-7163.2703-
1116.6619
1677c7.700
23033.323:
3o179.6132
13552.0503
201050.2-'00.
2-.7202.-203
126,31.7102
34'1765i.,
4-401.310,
22230.12
3
3i7,47-i.5001
36..203.5003
6
357663.203
GP 11
36,013.2130U
246700.13000
GP 16
GP 19
GP 20
431113.0000
26502.100
362797. 700
-
TOTAL
130/.0407
2504-1.0000
G-FP 10
33343.9393
1,311.5=40
70,30.7176
20051.3200322.004-:
30326.2E01
4
GFP 12
GRP 13
00637.67:.6
3770,7.0000
321763.5000
i
-GFP-'2
GFP
GRP
GFP
GFP
GPP
.LEIATION
tif..Att
277726.0000
267550.7500
25219.3567
13025.-64.42
31E26.402,
1,3163.1250
12771.2500
130
65,6.5233
17353.629/
31167.29
56
Subset 1
Group
Mean
13
167,787
Subset 2
Group
Mean
16
20
-11
246,700
250,441
267,551
2
3
6
19
277,726
18
281,858
2
321,784
Subset 3
Group
Mean
321,784
Group
Mean
377,047
1
357,460
'
5
401,113
357,863
12
362,798
10
364,019
4
364,203
65
B4.
Work to maximum load
STNOARO
GROUP
GPP
1
GrP
3
GitP
4
5
GPP
6
GRP
4
4
i.3e0o
1.5c75
1.3225
i.6450
1.2100-
4
4
4
4
4
4
GRP 10
GRP 11
GP F 12
GP 16
4
S
GP 20
TOTA4
.1122
.1536
.164t
.0772
.1$191
. 9
.1275-
a-41Z
.1027
.1152
.1-35
2023
.2304
0970
.1.163
.2357
.ci25
4
1657
.1164
.1372
.3292
155i
.3702
2.0475
1.-47F
I .i:. g7
2.1525
1.1225
1.9900
4
GFP li
GRP 19
.0736
.06eZ
.1472
9511
r:rrirtr- -----;r6-43.3314
4
GRP- -2--
5TAN.04R3
JE4iATiati
COUNT
1.4227
- zo
Subset 1
Group
Mean
20
0.8925
1
0.9500
19
1.0900
18
10
13
1.1025
1.2100
1.2400
,
Group
Mean
5
3
1.3225
1.3600
19
18
Subset 2
Group
Mean
1.0900
Group
Mean
1.5475
1.5875
10
13
12
Subset 3
Group
Mean
1.2100
Group
Mean
1.6450
Subset 4
Group
Mean
1.5475
6
12
1.1025
4
1.2400
10
13
1.2100
1.2400
6
5
1.3225
3
1.3600
12
1.5475
2
1.7700
4
1.5875
3
1.3600
1.6450
6
1.6540
Subset 5
Group
Mean
5
1.3225
2
11
16
1.7700
2.0475
2.1525
2
1.7700
11
2.0475
4
1.5875
66
B5.
Fracture toughness
STANOARO
COUNT
1
GRP
-GRP- 2
GP 3
GP 5
GKP
6
-GRP 10 -
GP 11
GP 12
GRiTr-1-3'
GRP 1.6.
ts
104.1E25
11.4.5250
107.037-7
1.12A2.5.1_
c
8
-,'-'
c
vtt.. ."
_GRP la
GPP 19
..
A
z
,..
GP 20
TCTAL.
1..1.7-25-Cr
23-
..
112
-
7.2E44
-.-62.-44---
23.54.67
12.3-'3712o.... 131
51.4.9.30
29.6999
2d.61,32
69.8000
,....,
ST:04C)AR,0
E
.Cft:
UE4iAT-ZO4
44E4i4-
9.373Z
.1.9.0UO_
13.5005
13.7243
--.5.- 151-0.4273
1E.4473
22.3373
3o.4522
92.13-c-2,
o,1.40.00
;Ja...,Apo
-51:.5%710
1131.3C25
1.2..to7*
10.i.,:35
.5.5755
2.3737
6.3S.64
3-.522T-----29.6.201
16,0529
c.7/40
17.9504
-4,E,aao
50.7000
34.312E
27.0t6E
Subset 1
Group
Mean
20
18
19
34.3
44.9
50.7
13
11
88.4
89.8
13
58.6
Subset 2
Group
Mean
58.6
1
10
92.9
Subset 3
Group
Mean
Group
Mean
11
88.4
6
107.0
1
89.8
2
113.7
10
12
92.9
98.6
5
114.5
16
119.4
4
102.3
3
104.2
67
Linear expansion
36.
GiP
GFP
GFP
GRP
1
2
2
3
2
2
2
2
2
2
,
GPP
GFP
Vf..Uri
:.;TAtir.2ARO
.5735
r----z=---
.41078
.0055
..
.0-'60
.11776
.0269
.097 ..4.
.027
CtitINT
GFt...JUP
6
GRP 10
GPP 11
GRP 1.2
' G7F 13
GRP 16
2
2
-
'
2
2
P
GPP 19
T07AL
0-683.0193
-
....-
95,
-1 i t
4735
.5175 - --
- - ---
2
2
GP 20
Ei-RGR
.4029
.:F.--2-9:0---...25
. "-..h713
,....0 00
.3943
.0323
...I) 1v.3
.0053
16,
. 01.7*
.
.3130
.0125
.3297
.099!
... or70 130 i
.312436'21
.0340
.00aa
.01.13
.
25,
Subset 1
Group
Mean
Group
Mean
20
0.3940
5
0.4680
19
0.4000
11
18
16
12
0.4020
0.4070
0.4525
0.4525
4
6
0.4975
0.4735
3
0.4995
10
0.5125
Subset 2
Group
Mean
Group.
Mean
16
12
0.4525
0.4645
10
13
0.5125
0.5490
5
0.4680
.
2
0.5495
6
0.4735
1
0.5735
4
0.4947
3
0.4995
68
B7.
Thickness swell
-GROUP--
COUhT
GRP
1
GFP
GRP
3
2
(.
2
GP
GP
2
5
E
Gi-P- id
2
2
2
G.7P
2
11
GP 12
-GF7 IT
GT:I:*
16
STANDARD
.7590
..111,41
.-033
.0630'
.T_Ilir
.al5n
.1174
.Z5C6
.0297
.1132
.c940
.6339
.01.'1
.02..0
...:1140
.0113
.39
-r-0
-nil. 3 u-
2
2'
c
.9750
.5E10
.F190
.660
2i
.7955
2
GRP 15
GP 19
G=P 20
TCTAL.
STANDARD,
1.-1EV.ATION
=--A ii-
2
2
..ERi":4.1
.024.0
.0210
.0730
.0103
.0173
.00a0
.0170
.00'19
.1730
.0230
.0370
.0o.0
.IsTa _
.0057
are4
.2--,7
.0325
.0400
.0671i.
Subset 1
Group
Mean
Group
Mean
Group
Mean
19
0.6190
12
0.7560
16
0.9750
Subset 2
Group
Mean
13
1.3430
6
0.6330
1
0.7590
18
20
0.6510
0.6880
4
0.8050
2
0.8140
5
0.6940
3
0.7030
10
11
0.8140
0.8830
69
B8.
Boiled MOR
S7A!'.1;)
T. ,r4;7341Q..:
C OUKT
GF-OtiP
GFP
GFP
GRP
GFP
GPP
1
e
3
2
2-2
2
GFP
GPP 10
2
2
2
GF P
2
GP
5
1.2
2
SR-P
z
G P 16
2
GP_P
2
GP
GP
1.14.
19.
20
TOTAL
2
2
2e
422.0000
-5-6-5. .
ERROR
it.f. 'LOS -
St:-: AO-
0
. train
r TTI.-311T7-
71113-0-
5d.6 e.199
b77.5001
a-zs_...aa Oil
000
:5, 300
.e2,22.:/4
-o+.0000
1:.3 .f..1
11...3 curl
F:.15-gr3
1.3.0003
114.4)4+2
10.F.:000
3.0000
5 '3.,.5.o00
13c.,..71::
13.0000
39.0000
95.5003
302.3000
a
b ,17
t3.4.3003
3S+-3. 0000
rsz ITTIT13-
4,33.0000
4.544
-0
a
13.0000
0
6.0003
3
11.3137
S 357
Subset 3.
Group
Mean
13
130.
Subset 2
Group
Mean
16
302
Group
Mean
433
1
18
352
11
388
10
393
20
393
11
388
10
393
20
393
1
19
422
433
4
422
19
433
2
3
5
678
688
422
19
Subset 3
Group
Mean
18
352
Group
Mean
4
6
529
534
Group
Mean
11
388
10
393
20
393
Group
Mean
6
534
12
555
568
4
6
12
Subset 4
3.
529
2
Subset 5
Group
Mean
529
534
555
568
70
B9.
Resin fracture energy
_GROUP_
GRP.
1
GRP
GRP
3
4
8
SRP--2
8
6
6
GRP 5
8-
6
7
GRP
GRP
TOTAL
STANDARD
ERROR
STANDARD
OMNI
1.!BAN_
_
.1627
_DEVIATION
.0556
---------.4-9.44---------10-4.508
.0E36
.1933
.1958
.2..3.90.___
.1303
.2141_
-
6
8
.0595
.0300
----
----.0-8L5
_
.1196
.0260
.0243
--is-4P-
".--0-2192 --
:Nil
.044
1920
50
Subset 1
Group
Mean
6
0.1303
1
0.1627
3
0.1933
2
0.1942
4
0.1958
7
0.2141
Subset 2
Group
Mean
1
0.1627
3
0.1933
2
0.1942
4
0.1958
7
0.2141
5
0.2390