TREATMENT . CE WCCD
WITH UREA RESIN-FORMING SYSTEMS
Part 1 - Dimension .Stability
Nbvember 1946
.1.
4 .2
(No) IR1632
-3'
7.
'
UNITED STATES 11::TPARTMENT OF AGRICULTUR E
"--- LEORTST SERVIC E
ILLFORES'l-PRODUCTS LABORATOR Y
Madison, Wisconsi n
In Cooperation with the University of Wisconsi n
k
TREAThhNT OF WOOD WITH UREA RESIN-FORMING SYSTEM S
Part 1 --Dimensional Stability-
By MILL A. MILLETT, Chemis t
end ALFRED J . STAMM, Chemist
Forest Products Laborator-Y., . Forest Servic e
U . S . Department of Agriculture _
Summary
Thin cross sections of Sitka spruce, sugar maple, and white oak were impreg nated with urea-formaldehyde resin-forming systems, either in the form of commercial dimethylol-urea or as a mixture of urea and formalin. When properly
cured, antishrink efficiencies of 40 to 50 percent can be obtained with eithe r
of these resin mikes . This is about two-thirds of that obtainable with th e
water-soluble phenolic-treating-resins at the same resin content .
A2 to 1 ratio of formaldehyde to urea was shown to give the best results .
The urea-formalin mix was found to be somewhat superior to dimethylolurea i n
stabilizing the dimensions of wood .
Buffering the resin-forming system at a pH of 8 .0 not only gives higher anti shrink efficiencies but also prolongs resin life in the treating solution .
Cure conditions were found to be about the same as for the phenolic-treatin g
resins, namely, 310° to 320° F . for 20 minutes, or 220° F . for at least 4 8
hours . Lower temperatures than the latter required excessively long cur e
periods to give optimum antishrink efficiencies .
a
Urea-formalin mixes seem to have somewhat better stability than dimethylolure a
solutions when used under the same conditions .
Introduction
The treatment of wood with urea resin-forming systems has been highl y
publicized during the last few years (1, 2, 7) . Much of the early work o n
-Published in Modern Plastics, October 1946.
2
-Maintained at Madison 5, M ; ., in cooperation with the University o f
Wisconsin .
Report No . R1632
-1-
the subject was done at the Forest Products Laboratory
D . This wor k
showed that the formation of urea-formaldehyde resins in wood increased it s
hardness and water resistance . During the war, however, work on the treatment of wood with ure~Z resin-forming solutions was very limited because th e
early results were not so promising as those obtained with phenolic resin forming solutions (, 2, 10, 11, 12) . In the realization that peacetime
requirements may not be so exacting as those of wartime, the Forest Product s
Laboratory recently resumed research on this subject to obtain more extensive data on the properties of the treated products under various conditions .
The data presented in this article deal with the effects of variations i n
treatment on the dimensional stability of treated wood . Treatment variable s
considered were : formaldehyde-urea ratio, pHs resin content, and curing conditions . Small, thin cross sections of wood wore used as samples to obtai n
the ultimate results possible for completely treated wood, It must, o f
course, be realized that such results are not directly applicable to larger sized wood articles or lumber, Investigations on treatment of such large r
items are contemplated .
The effect; observed were evaluated by means of antishrink efficiency calculations . Antishrink efficiency is defined as the percentage reduction i n
cross-sectional shrinkage (tangential plus radial) between the water-soake d
and the oven dry condition which is caused by the treatment .
That Is,
Antishrink
efficiency
Shrinkage of
- Shrinkage o f
untreated sections
treated sections
100 -~
Shrinkage of untreated section s
At the completion of the tests on the . urea resin-forming systems ) matche d
sections were treated with a representative phenolic resin-forming system an d
tested to obtain directly comparable results .
Materials Use d
nee_
The measurements were made on thin oross sections of Sitka spruoe, white oak ,
and sugar maple prepared from air-dry stock . Specimens 3 by 3 inches in
cross section were cut from 6-foot long planks of each species . These wer e
jointed to make one face as nearly parallel to the annual rings as possible .
Full-length specimens 2 by 2 inches in cross section were then cut with th e
faces parallel and at right angles to the jointed face, These were out into
thin arose sectiona3/32 inch &n the fiber direction, All edges were lightl y
sanded to remove any loose fibers, thus facilitating measuring and weighing .
Such cross sections have been found most suitable for all antishrink
efficiency measurements (2., 11) as they are much better matched than when ou t
in any other way . They furnish both radial and tangential dimensions large
enough for precise measurement, and they are very easily treated due to the
fact that every fiber is cut across at least once, Variations due to non:
uniformity of treatment are thus eliminated . Hence, the data represent Report No, R1632
-2
the optimum antishriia.k efficiency .ob
'able with uniform distribution o f
the treating agent - throughout" the • structure .
Fresh commercial dimethylolurea was- obtained from the E . I. du Pont 'do
Nentnir s 83 `Compahr under the - trade ham
' e of "Arboneeld ." Crystal'iurea and
formalin solution were also obtained from the s lams source .
The water-soluble pheno±ic-treating rosin used for c mparativo tests was• ' ob.
tabled from Interlake Chemical Corporation, formerly the Central Px~odes s
Company, and designated as No . 1652 . It is representative of the various
water-soluble rosins used for making impreg and"Comprog . ( 3) ;
A series, of borax, borib acid, 'sodium carbonate buffers was prepared •s.s
directed by Clark (4+) with pH values 7 .0, 8 .0, 8 .6, 9 .2, 10 .0, containing
about 1 percent of buffer solids .
Resin-forming Variable s
Formalderde to Urea Ratio
In order to-• study`'the effect ' of varying the formaldehyde to urea 'ratio on
the antishrink efficiency, throe series of solutions were prepared in whic h
the ratio varied from 0 .67 to 1 to 6 to 1, all solutions being held to a 2 0
percent rosin-forming solids content by weight . The first series containe d
unbuffered dimethylolur.ea, . the sec6nd dimethylolurea buffered. at a, pH of g ,
and the third consisted of urea-formalin mixes also buffered at a pH of 8 .
In the last two series 50 cubic centimeters of buffer solution was substituted for the same amount of
ter . The treating was conducted as follows :
iLv
1hree•cross sections of oven-dry spruce ; numbered consecutively,-were placed '
in a- cyrstallizingdish to which had been added 100 grams of the resin solo*
tion . After ooveri.ng .with a watch glass, the dishes were placed in a vacuu m
desiccator and evacuated for 15 minutes with a water aspirator pump to re move entrapped air . Folloiring this the sections were allowed to stand in -the
treating solution overnight to allow for thorough diffusion into the cell wall structure . The, treated sections were placed on paper tovrelling fo r
about .10 minutes to remov©. surplus They were then -weighed and the
radial and tangential dimensions measured' with' a dial gage . Three adjacent,
control sections were treated in . thesame runner, using 100 grams of distil;led wator Sow .tho sections i a-tching those treated . With the unbuffere d
rosin _sys 'teis and. 1Qb grams of solution made up of 50 grams of distille d
water and „
grams" of, buffer solution for those matching the sections treated
with the buffered resin `systems . This same treating procedure was followed '
throughout the entire study .
A pr_e1iminary- group of test specimens was cured by air drying for 24- hours ,
followed : by 2l1- fours,at 220° . F . '. '.welling tests on those specimens showe d
very low antishriiik efficiencies and indicated that a large proportion o f
the ` resin-forming solids wire leached out during the soaking period . Consequently, a new series eras prepared and curing accomplished by air dryin g
Report No . R16
„3„
for 24. hours, press curing for 20 minutes_at 3'10° F ., and oven drying fo r
24 hours at 220? F .
This procedure, -which is the same as that usuall y
used for antishrink efficiency tests on phenolic resins, gave, as will b o
shown later, practically complete cure of the resin .
The cured sections, after weighing and measuring, were placed in a vacuum desiccator partly filled with water . A vacuum was pulled for 1 hour with a '•
water . aspirator pump .
The sections were then allowed to soak for a- period
of I . week in running water to remove any unpolymerized resin-forming chemicals . The sections were agairr .weighed and measured, then air dried for 2 4
hours and oven dried'for .24 hours at 220° F . -All-the-antishrink effi. ciency values were calculated on the basis of the dimension changes .betwee n
the 1-eached s
condition and the final. oven-chry 'condition . The variation of antishrink efficiency with formaldehyde to urea ratio is shown
table 1 .
Ilen
Although . in 'practice wood is rarely subjected to such severe leaching' as was
used in these tests, the high degree .-of-leaching. makes' it possible' to differ-"
entiate between cured and uncured resin and, gives..the_-antishrink efficienc y
under the most severe exposure conditions . Experience has shown that . the
antishrink efficiency obtained with soluble chemicals in, successive 30 t o
90 percent relative humidity cycles-decreases with the number of cycles .
Antishrink efficiencies' determined by the method given here have not shown- a decrease with age of the specimen oe number of cycles . • .
A resin rriix having a ratio of 2 moles of formaldehyde to .1 • mole of ure a
gave . the hi,ghost ' ant_ ;shrink efficienoy .- At this ratio there is , no appreciable difference in the three resin systems tested . Buffering, however ,
greatly increases the -working life of the treating `system and prevents '
deposition of ineffective resin within the wood . Unbuffered dimethylolure a
gives_ a considerable amount of sediment during the treating period, and th e
amount increases daily without further use of the treating solution .- The
presence of this nonafitishrink effective precipitate is indicatedin column .
2 of the-table where high apparent resin contents were obtained-withou t
corresponding high and antishrink - efficiency values . The rawer resin:-content values for' the buffered-systems with ratios.: or formaldehyde to urea both less than 2 to I and more than-2U 1 sugges q that;
below this ratio free urea is leached out'and above this' ratio free formaldehyde is leached out of the sections during the soaking period . In the unbuffered :system it appears that, resin is formed throughout •the r r- do - range Of
.
1tolto.2to1 .
After treatment of the wood ; the pH-of the unbuffered treating system s
ranged from 5 .5 for the 0 .67 to i - formaldehyde 'to urea ratio to 4 .0 for th e
6 to 1 ratio, as a'result of extraction of acid from the wood . Under thes e
acidic conditions the resin tends to precipitate very rapidly . Although
the precipitation is not' sufficiently rapid to reduce the =antishrrink efficiency on the first treatment of such small sections', reuse of the solution '
after -precipitation has occurred will give considerably redubed antishrink
efficiency values . Buffered dimethylolurea at a 2 to 1 ratio showed only a
Report No . R1632
-tE
slight precipitate ate, week after troa mng, w,liriie'tthe corresponding fluff red''
urea-formalin treating -solution- was still'' perfectly : clear three weeks `after
treatment .
4
pH of Sys-tom
In' studying' the influence . of pH; on" the antishrink effectiveness of the ureaformaldehyde-resin system, two series'-of solutions were prepared, both having, a-2 to 1- form aldehyde to-Urea ratio and a resin-forming -solids conten t
of 20 peroent .... The . first series was prepared . from eommercia:l dimethylolure a
buffered at pH valueslof 7 .0, r6, 9 .2, 10 .0,;- the = .Second from a urea-formalin
mix buffered at the same pH : values . -The treating, curing, and tasting 'pro- '
cedu bs were the same as used in . thepreceding study . Figures'•1 and 2 show'
the results obtained with Sitka spruce . The pH values plotted are those in '
equilibrium with the treated wood . In all eases there is a= slight drop i n
pH due to the acidity of the wood . Stronger-buffers could have maintained a
constant `pH ; fey are, howeiel-'='unnecessary to accomplish--the degree of
stabilization -f the solution needed-in treatting Sitka spruce . Moro acidi c
woods, however,
.yyr: quire-the use . of=arc . buffer .
•
Figure 1 indicates that =buffering at- a pH of 800 gave . the .bast antishrink
efficiency values,'-tho reason being that too alkaline asolution in the rang e
tested retards- polymerization and -gives- 'a higher rosin loss on leaching as ., is
indicated in figure '2 . On the. other hand ? if the solution becomes too acidic ,
polymerizatton occurs• too rapidly, causing an ineffective precipitate withi n
the cell cavities s'aand also in the solution which practically nullifies its
reuse value,
~
'
Resin Gontent '
Variations of the antishrink 'efficiency with resin content w6re studied . by ,
treating Sitka -spruce-•cross sections with . solutions having resin-formin g
solids concentrations of 5, 10, 15, 25, and 30 percent ; all solutions being
buffered at pH of 8 and having a 2 to , : formaldehyde to urea ratio . Treating slid cuir iaxig conditions ' 'were. the same as previously described . The previous data for 20 percent resin -concentrationwere also included in th e
comparisons :
- Figure 3 shows that the antishrink efficiency .is almost identical fo r
dimethylolurea and ►area-formalin systems and increases rapidly with in creasing resin content up to about 25 percent . Figure 3 also indicates tha t
at the higher resin Contents the urea-formalin mixes are more completel y
fixed in the wood structure than the dimethylolurea .
Cure Conditions
For studying the effect of curing conditions, such as temperature, time, an d
relative humidity, on the antishrink efficiency, dimethylolurea and ureaformalin systems were prepared having a resin-forming . solids content of 25
percent
81632:
Report No .
and a formaldehyde to urea ratio,of 2 to 1 . Bot h. solutions were buffered a t
a pH of g . Sitka spruce cross sections were treated-in the usual way, ai r
dried for 24 hours, and then cured under conditions of increasing severity ,
as indicated in table 2 . Cured resin-content values before leaching were
between 30 and 35-percent for all the specimens . Table 2indicates that there is very little resin polymerization at room
temperature .. Even after a month most of the resi n .forming .solids are leached _
from .the wood . There is a marked difference i n. apparent resin content and
antisbrink efficiency .betvjeen the specimens -_cure d ; at 160° F . in a . dry
atmosphere and those cured at 75 percent re,.ati :ve,humidity in a desiccato r
over saturated sodium chloride . The presence of excess moisture seems t o
prevent the rapid drying to a moisture content below which diffusion ca n
take place . Then drying is so retarded, outward diffusion of resin-formin g
chemicals from the cell walls to the cell cavitiesoocurs, followed b y
curing of the resin in this structure wher e , it is i,ne'fective in dimensional
control . Even in a dry atmosphere antishrink efficiency values_ approachin g
those for oven cure were obtained only after at least 10 days' curing .
Oven curing at 220° F . gave fairly good antishrink efficiency values in 4 8
hours, although better results were obtained with a somewhat longer period .
Press curing at . 320° F ..,gave :the best..antishrink „efficiency values ; a heating
period of 10 minutes being most practical . From these results it is apparent
that urea-formaldehyde resins require about the same curing ' conditions as ar e
used for•=the water-soluble phenolic-treating resins ( 'Q, 2, 11) . .
The use of a heat activated, potentially acidic catalyst to insure polymeriza tion has been proposed (2) . These catalysts are neutral in reaction at. .normal
room temperature, becoming acidic at higher temperatures . No information o n
this modification was obtained in the present investigation, but it is evident
that almost complete polymerization occurs without the presence of smell a
catalyst, even for Sitka spruce, a wood-which is not highly acidic, whe n
the pH of the treating solution stays above 7 .5 after treatment . It i s
doubtful that any greater antishrink efficiency could be .obbta .ned by the us e
of a potentially acidic catalyst although the rate of cure might be aoceler ¢
ated . There . are a number of disadvantages to the use o ',su .ch 'a catalyst .
Some heating is required to dissolve dimethylolurea• and:-the catalyst thu s
might be activated ; .cau-singprecipitation of resin before treatment could b e
started . Furthermore :some slightly alkaline buffo r,, .eompatible with the
catalyst and not interfering with its-. , action, would have to be included to
allow reuse of the solution and prevent precipitation of .rosin befor e - it_ _
enters the cell-wall structure of the wood . There also . is, the danger,ttiiat
use of too much catalyst-would result in gradual weakening of the product
through acidic hydrolysis of the cellulose . Acid-catalyzed urea and phenoli c
glues have lost favor as. .a .result of the hydrolytic degradation action on th e
wood .
.4
Report NO . R1632
.
6-
Urea-formalin Treatment of Oak
r
-
- -
..
.,
..
,
Because of the possibility that a more acidic wood' might promote-resin curin g
under milder conditions than thos e' found for .Sitka spruce ;'- 'it was decided' to
try the treatment on white oak, using urea dissolved in formalin in which th e
resin-forming solids content was 25 percent, and the formaldehyde to ure a
ratio was 2 to 1 under three different
conditions : (a) unbuffered ; (b )
buffered, as in the spruce series at a pH of 8 ; (c) buffered with a sodium - '
hydroxide-borax system to a . pH of about 9 .5 (2) . The treating conditions
were the same as those tsdd for spruce . Table 3 shows the results obtaine d
under' various .cur& conditions .
The-general conclusions reached from a study or table 3 and from obs'ervation's
during treatment ' are,similar to those found for the spruce serie s ';- :namelyp
unbuffered urea-rosin systems €u•e • not . stable in acidic . solutions (pH of i '
after -treatment of oe.kj"and `m .ch of the= resin polymerization ,occurs befor e
the wood is thoroughly' im0egnatSd .-resulting in high apparent resin bbntent l
without correspondingly high antishrink efficiency . Buffering at a pH o f
9 .5 retards polymerization .
In the case of the borax-boric ao .d-sodium-oarbonate buffered systbiii ; the
antihrink efficiency values were not so high as those obtained on Sitk a
spruce ' for the ' raeon that -the buffering capacity, was not high enough t o
take care of the acidity of white oak (pH bf5'.5 ' after treatment) . Thu's'
there was some tendency for resin polymerization before thor-cugh treatmen t
had taken place : 'Cure conditions,-however, seemed to be about the same as
thoserequired for the Sitka spruce . -
'
r
Comparison of'Urea-formaldehyde and Phenol-formaldehyde Resin s
A comparative study of-the urea-resin and-the phenolic-reslinebysteiiis wa s
mad e- on two species of wood, one a hardwood (sugar maple) and the oth r a
softwood (Sitka ' spruce ) under ` identical conditions . fiatched cros's •` sections
were prepared from each species and treated-with pheholic and urea resins at
concentrations of 0, 5, 10, 15, 20, and 30 percent resin-forming solids .
Interlake phenolic treating resin No . 1652 and a urea-formalin mix with a" 2
to 1 formaldehyde to urea ratio, buffered at a pH of 8, were the resins used .
Treatment was the same as described before'hnd all samples were cured in a
hot press for 20 minutes at 315° to 320° P .; followed by 24 hours at 220° F .
in the oven . Swelling measurements were made in the usual way .
Figure ? shows the r'es n• Content }- Atishr'ink efficiency curves obtained on th e
two resin systems . At 30 percent resin-content the urea rein gives an anti shrink efficiency of about 44 percent, while the phenolic resin gives a n
antishrink efficiency of about 67 percent . In other words, urea resins ar e
about two-thirds as effective as phenolic resins in reducing swelling an d
shrinking in wood . A phenolic-resin content of only 13 percent gives th e
same antishrink efficiency as a urea-resin content of 30 percent . The pric e
advantage of urea resin forming systems over the phenolic-resin-formin g
Report No . R163?
-7 -
systems is thus. nullified by the fact that considerably less phenolic resi n
is required to give the same degree of dimensional stabilization . The
lower rosin contents of the sugar maple compared to the Sitka spruce are du e
to the fact that the void volume per unit weight of wood is much less for the
denser maple and hence the solution take-up is loss .
It should be remembered that these results were obtained under laborator y
controlled conditions and on thin cross sections where uniform impregnatio n
was assured . Treatment of larger wood specimens introduces treating, dis tribution, and curing difficulties that will reduce the antishrink efficiencies obtainable with both urea and phenolic resins . Consideration
should also be given to the relative durability or aging qualities of the
two resins under conditions of high humidity, since the relatively goo d
initial antishrink effectiveness of the urea resins may drop off rapidl y
with exposure to a warm humid atmosphere, which might be predicted fro m
the instability of urea-resin glues under these conditions .
Conclusions
The data indicate that optimum dimensional stabilization of wood wit h
urea resin-forming systems is obtained with a treating mix having a rati o
of formaldehyde to urea of 2 to I . The treating solution should preferabl y
be buffered at a pH of about 8 to avoid premature precipitation of resin forming solids from the solution . Urea-formalin mixes are preferable t o
dimethylolurea, both from the standpoints of dimensional stability of th e
wood and rouse of the treating .solution .
The curing temperatures necessary to obtain reasonably good dimensiona l
stability of wood treated with urea resin-forming systems are considerabl y
higher than those previously recommended . The use of lower temperatures i s
one reason why many who have tried the treatment were unable to get dimonsional stabilization approaching the optimum values given in this report .
The only known advantages of treating wood with urea resin-forming system s
in preference to phenolic resin-forming systems are lighter color and a
lesser tendency to impart odor,or taste to materials in contact with the wood .
The publicized price advantage of the urea resin-forming systems is nullifie d
by the fact that considerably loss phenolic resin is needed to give the at e
s
antishrink efficiency . This, ooupled with the fact that urea resin-forming e
have to be carefully buffered, indicates that they are less desirable treat ing agents for wood when dimensional stabilization is the prime objective .
Further data are needed to find out if any other properties are improve d
more by urea resins than they are improved with phenolic resins, Scant y
data obtained up to the present time inuioate that such improvements are no t
probable .
Report No . R163_2
-8-
Literature
Cite d
1 . Berliner, J . F . .T . Southern Lumberman, Dec . 15, 1943, pp . 140=141 .
2.
-
Chem . Ind . 54(5) :60-682 (1944) .
Burr, H . K ., and Stainm, A. J . Comparison of commercial water-solubl e
phenol-formaldehyde resinoids for wood impregnation .
Forest Products Laboratory Ropt . No . 1354, 20 pp . (1943 ,
revised 1945) .
4 . Clrark, W . M . The -determination. of hydrogen ions . . 3rd ed ., Williams
& Wdltins Co ., Baltimore (1925), 717 pp .
5.
Forest Products-Laboratory urea-plasticized woo d . (uralloy), Forest
Products Laboratory Rcpt . No . R1277, 6 pp ., revised 1943 .
6.
Loughborough, W . K . Process for resinifying lignocellulosi c
.materials . U. S . Patent 2 ,3 1 3,953, 1943 .
Manchester, H . American Forest 6 0(7)4334-335, 365, July 1 914 ;
Re'ader's Digest 45(265) :43-44, August 1944 0
5 . Smidth, L .' Process for treating fibrous materials and products s o
1, produced . U.S . Patont ,2,37(,200 .
9.
Stamm, A. J ., and Seborg,•-R . M . Ind . Eng . Chem . 31 :597-902 (1939) . -
10 .
Trans . Amer . Inst . Chem . Eng .
37 :M5-398 -( 19L[1-)
' 11 .
12 .
'
Forest Products Laboratory . resinwood (improg) . Forest Products Laboratory Rcpt . No .
1350, 9 pp ., revised 1943 .
Forest Products .Laboratory resin treated laminated compressed wood '(compreg) . tFores t
Pro-ducts .Laboratory Rept . No . 1351, 13 pp ., .revise d
.
194 . .
ik :
Report No . R1632
-9-
Table 1 .--Effect of•formaldehyde to urearatioupon the antishrink
efficiency of Sitka spruc e
Formaldehyde :
Unbuffered
Buffered
Buffere d
:
dimethylolurea
dimethylolurea
urea-formali
n
to
(pH
8
.0)
:
.0
)
urea
(pH 8
------------------- ------------------- --------------- ----• ratio
Anti- : Resin :
Anti: Resin .
Anti- : Resin :
:
:
content
:
shrink
:
content
:
shrin k
: content
shrink
after :efficiency : after :efficiency : after :efficiency
' :leaching :
:leaching :
:leaching :
..-i, :
:
.
:
.
:
: Percent : Percent : Percent : Percent
: Percent; : Percent
'
2 .0
6 .9
.
1 .6
:
15.2
:
10 . 3
22 .6
.
18 .9
:
22 .8
:
41 .1
.
24.3
:
44.8
:
25.3
.
15.4
:
31 . 7
28 .2
:
11 .2
:
28 . 8
16 .9
:
7 .1
:
26.7
0 .67
.
20 .4
.
3 .5
.
7 .3
:
1 .0
:
31 .9
:
19.8
:
13 .0
:
4.1
1 .2
:
37 .3
:
31 .9
:
17 .9
;
2 .0
:
30 .8
.
41 .1
.
20,3
3 .0
:
24.2
.
30.7
:
11 .6
4.0
:
17 .4
:
27 .1
.
9 .1
:
11 .7
:
20 .7
5.8
:
-
1
Report No . R1632
Table 2 .-=Effect ofvryfa
durinSconditions upon the' antishr_ink efficienc y
of Sitka spruc e
Cure condition
Temperature :Relative :
:humidity
: Dimethylolurea series : Urea-formalin serie s
Time
:
:
Resin
: Antishrink , : Resin
;.Antishrink
content ; efficiency : content :efficiency
afte r
,after
.leaching :
leaching
° F.
Approx .
70
; Percent
:
:
Approx . :
30 :
.
10
20
30
: Percent
:
Percent
:
:
:
10 . 0
8.1
Percent
. Percent
75
5
10
30
1 .9
4,0
4 .4
.,
. 23 .1
22,0
22 .3
Approx . :
-2
10
20
30
14 .0
16 .0
15 :2
26 .8
31 . 5
30. 2
18 .9
21 .7
21 .1
Approx . :
0
2
10
20
22 .7
25 .2
26 .9
38 . 2
43 . 0
47 . 6
27 .5
29 .$
30 .9
a
40 .3
43 . 6
43,0
44 . 3
114 .3
31 .6
31 .1
31 .8
32 .8
33 .3
t
. ::
16o
220
Days
:
:
:
:
7 .4
8 .7
16.1
18 . 8
5 .7
7 .5
8 .1
:
27,4
26 .9
26,0
4
z
10 .7
17 .3
13 .3
T
4 -
'10 . 0
20 . 0
20 . 6
* 35 . 3
38 . 0
37 . 4
3
40 . 6
48 . o
. 48 . 6
:Minutes
320
:
Approx . ;
0 :
5
10
20
40 .
6o
:
26.5
28 .0
27,3
27 .8
27 .4
5
Report No . R1632
:
50 . 6
51 .3
52 .0
52 . 6
52 . 0
Table
-Effect of varying the . pFi and curing conditions upon_the antishrink efficiency of white oak
Cure conditions :
Tempera- : - Tine
ture :
° F.
: -
:• Rein :Antishrinki Rcsin :Antishrink : Resin .
: content efficiency : content :eff iciency : content
: after
. after :
: -after :
:leaching
:leaching :
:leaching :
:Percent : Percent
Approx . : I day
70
:10 days :
220
3 hours :
:20 hours :
:10 days :
Report No . R163 2
: Buffered (pH 8 .0) : Buffered (pH
Unbuffered
214 .3
:
21 .4
:
24 .1
25 .4
:
:
24 .9
:
•
:Percent : Percent
0
0
.
.
15 .3
15 .4
10 .4
:
21 .6
15 .3
" 26.4
: -22 .9
: 22 .1
. '
.
5 .2
.
'19 .3
:
35,6
:
:Antishrink
:eff iciency
.
:
:Percent
.
5.2
"3 .8
3,7
6.2
-27 .5
:
944
12 .0
9 .5)
Percent
:
:
3.6
6. 8
:
9 .9
:
19 .8
28 0 6
:
V
.1
I.
h
O
h
(GOOM JO 1H9/34f J O
S/SV9 NO 1 N30b/3d)
9N/HO 1137 NO /WS-7Y JO SSO7
.
-•
O
O
O
N
(1N30Y3d) AON3/7/333 NN/YHS-/1NV