Rudolph D. Deanin
THERMOSET RESINS RESEARCH AT UMASS LOWELL
Professor
Plastics Engineering Department
University of Massachusetts Lowell
Lowell, Massachusetts 01854
(978)-934-3426
October 4-5, 2004
This paper is presented by invitation of TRFA. It is publicly
distributed upon request by the TRFA to assist in the communication of
information and viewpoints relevant to the thermoset industry. The
paper and its contents have not been reviewed or evaluated by the
TRFA and should not be construed as having been adopted or
endorsed by the TRFA.
THERMOSET RESINS RESEARCH AT UMASS LOWELL
Rudolph D. Deanin
Plastics Engineering Department
University of Massachusetts Lowell
Lowell, Massachusetts 01854
This is a review of typical exploratory research projects on
thermoset plastics at UMass Lowell, particularly those on epoxy resins
and polyurethanes.
Epoxy/Urethane Copolymers. Epoxy resins generally give
rigid products of high modulus, strength, heat deflection temperature,
electrical and chemical resistance. Polyurethanes are designed mainly
to give rubbery products of high elongation, rebound, impact strength,
abrasion resistance, dielectric constant and dissipation factor. These
two polymer families share many mutual and/or complementary
functional groups, curing agents, and cross-linking reactions. Thus it
should be possible to copolymerize them with each other to produce a
wide range of combination of properties for different practical
applications. Homogeneous copolymerization should give properties
linearly proportional to composition; whereas, if one polymer crosslinked faster than the other, phase separation might give S-shaped or
even U-shaped curves for properties vs. epoxy/urethane ratio.
A standard DGEBA epoxy and an isocyanate prepolymer were
mixed in ratios from 100/0 to 0/100 and cured with Moca as mutual
cross-linking agent. The polyurethane cured in 1 hour, whereas the
epoxy took 7 hours, so there was probably phase separation in the
finished product.
Epoxy/Urethane Ratio
100/0 90/10 80/20 70/30 60/40 50/50 40/60 30/70 20/80 10/90 0/100
Shore D Hardness
Tensile Modulus, KPSI
Tensile Strength, KPSI
Ultimate Elongation, %
90
187
13
8
88
158
11
8
87
138
11
8
87
126
9
12
84
103
6
21
81
69
5
43
Flexural Modulus, KPSI
Flexural Strength, KPSI
Rebound, %
Izod Notched Impact, FPI
380
361 338 326 238
165
16
14
13
13
10
6
15
14
9
12
14
17
0.8
0.8
1.0
1.3
1.7
2.6
72
23
4
150
64
6
2
167
51
2
18
5.4
Abrasion Loss, g/5000c
0.32 0.24 0.50 0.79 0.93 0.87 0.55
Heat Deflection Temp.oC
102
94
88
65
55
51
Volume Resistivity, 1012oc 2210
629 368
186
87
57
6.6
Dielectric Constant
4.6
4.5
4.4
4.2
3.9
4.1 4.4
Dissipation Factor
0.015
Water Absorption, 1 Day, % 0.05
MEK Absorption, 1 Day, %
0.1
50
3
1
200
41
2
1
277
39
3
2
379
16
3
2
0.5
0.3 0.2
20
22
23
7.4
9.9 NB
4
0.4
31
NB
0.25
0.04
0.02
0.01
1.3
4.7
0.7
5.7
0.4
6.6
0.4
7.2
0.015 0.013 0.011 0.012 0.014 0.019 0.024 0.036 0.047 0.048
0.06 0.08 0.08 0.09 0.14 0.26 0.30 0.51 0.68 0.91
0.2
1.0
9.5 13.5 15.7 30.7 36.9 38.5 47.8 50.1
Increasing epoxy produced increasing hardness, modulus, strength,
heat deflection temperature, volume resistivity, water and solvent
resistance. Increasing urethane produced increasing elongation,
rebound, impact strength, abrasion resistance, dielectric constant,
dissipation factor, water and solvent absorption. Linear or log plots
gave S-shaped curves for most properties, indicating 2-phase systems.
U-shaped curves for rebound, dielectric constant and loss indicated
chances for synergistic improvement; while those for modulus,
strength, and especially abrasion indicated problems of incompatibility.
A follow-up study on thermoplastic blends of phenoxy resin with
thermoplastic polyurethane gave surprisingly similar results,
suggesting that copolymerization was a minor factor in properties.
Polyurethane Flame Retardance was produced by
substituting monobrominated toluene diisocyanate for normal toluene
diisocyanate in TDI/sorbitol rigid 2-pcf foam.
BrTDI/n-TDI
0/100
0/100
Sb2O3
Rating – ASTM D1692 – Burning Rate
2.6
B
B
4.2
3.9
17/83
17/83
2.5
4.8
SE
SE
2.6
1.3
34/66
34/66
1.3
2.6
SE
SE
2.7
1.9
68/32
100/0
5.5
-
NB
SE
0.0
2.4
One-sixth substitution of BrTDI decreased burning rate and was selfextinguishing. One-third substitution decreased burning rate further.
Two-thirds substitution produced non-burning foam. And 100%
substitution was self-extinguishing even without antimony oxide
synergist. As compared with conventional flame-retardant polyols,
bromine on the benzene ring would be much more stable.
Rigid Solid Polyurethane Plastics were produced by reacting
toluene diisocyanate with a high-functionality polyol, a hexol of MW
675. Cast sheets were baked to cure.
Shore D Hardness
Barcol Hardness
Tensile Modulus, PSI
Tensile Strength, PSI
Ultimate Elongation, %
Flexural Strength, PSI
Notched Izod Impact Strength, FPI
Abrasion Loss, mg/100 cycles
Heat Deflection Temperature, oC
Swelling in Acetone, %
90-92
82-84
600,000
13,250
1.5
18,000
0.5
25
87
0.3
Thus choice of polyol functionality can produce a broad range of
polyurethane properties from elastomers to rigid plastics.
Reinforced Polyurethane Rigid Foam was produced by
adding 0-50% of ¼-inch glass fibers to a standard rigid foam
formulation based on methyl glucoside and polymethylene polyphenyl
isocyanate.
Glass Fiber Added, %
0
10
20
30
40
50
Overall Density
2.33 2.78 3.27 3.59 5.18 6.33
Polyurethane Density
2.33 2.49 2.67 2.79 3.64 4.38
Flexural Modulus, PSI
1327 2376 2947 3296 3837 6136
Flexural Strength, PSI
55
76
90
94 111 148
Compr. Mod. Parallel, PSI
537 713 761 856 1349 1697
Perpendicular 229 341 401 503 546 571
Compr. Str. Parallel, PSI
31
33
35
39
54
72
Perpendicular
17
19
20
23
32
40
Glass fibers restricted foam expansion somewhat, but increase in
properties was greater than increase in density, offering an overall
improvement in balance of properties.
Thermoset Recycling would offer distinct benefits in economics
and environmental protection. Some thermosets contain labile bonds
which offer such possibilities. Vulcanized rubber is recycled
commercially by using mechanical shear, heat, and chemical energy to
break weak bonds. Polysulfide rubber contains S-S bonds which are
weak enough to open under mechanical or chemical stress. Polyester
and polyamide bonds are hydrolyzable. Polyurethane bonds are
hydrolysable and somewhat reopenable by heat; some rubber molders
report that they can chop up scrap and remold it. Urea-formaldehyde
is too hydrolyzable for its own good.
More difficult are thermosets with no labile bonds. Here perhaps
the best that can be done is to grind the thermoset polymer to a fine
particle size and use it as a filler. Ground vulcanized rubber is a useful
filler in thermoplastic vulcanizates. Ground reinforced polyester is
recommended as a filler in virgin reinforced polyester.
In one studystandard DGEBA epoxy resin was cured with
triethylene tetramine, a polyamide, or dodecenyl succinic anhydride,
by casting and oven curing. Cured resins were ground to pass a 500micron screen. Then 20% of such recycle was used in the next batch
of the same virgin formulation.
Curing Agent
Recycle
Polyamine
0
20
Polyamide
0
20
Rockwell L Hardness 120
129
Flexural Modulus,KPSI 475
336
Flexural Strength,KPSI 16
6
HDT, oC
103
90
Vol. Res., 1015 oc
1.7
1.3
118
121
383
364
12
12
60
54
0.7
2.3
Anhydride
0
20
121
122
358
368
12
7
70
71
12.1
7.2
Most properties held up well. There were some gains and some losses.
When the ground recycle was pre-soaked in virgin resin before cure,
there were some indications that properties could be improved by
activating the recycle in this way.
In another study, a phenolic molding powder was molded and
cured, then ground, ball-milled, and screened into fractions 10-20
mesh, 60-120 mesh, and -200 mesh. These were blended back into
virgin molding powder, molded again, and tested.
Virgin/Recycle
100/0
90/10
80/20
70/30
Rossi-Peakes Flow
Spiral Flow
Flexural Modulus, KPSI
Flexural Strength, KPSI
HDT, oC
0.64
5.5
1320
9.5
161
0.54
4.5
1070
8.1
164
0.51
4.1
1110
7.9
163
0.34
0.3
1150
7.8
163
Moldability was good up to 20% recycle, but difficult at 30%. Properties
were still good at 30%. Particle size 10-120 mesh worked well, but
-200 mesh gave lower properties. Soaking the regrind in acetone,
alkali, phenol, and phenoxy solution did not provide useful activation.
For long-range research, incorporation of labile bonds into
thermoset resins in general should offer increased possibilities for
recycle in the future.
Biography
Rudolph D. Deanin received an A.B. in Chemistry from Cornell
University in 1941, and M.S. and Ph.D. in Organic Chemistry from the
University of Illinois in 1942 and 1944. He directed polymer and
plastics research and development for the Government Synthetic
Rubber Program, Allied Chemical Corporation, and DeBell & Richardson
Inc. Since 1967 he has been Professor of Plastics Engineering at the
University of Massachusetts Lowell, where he founded and directs the
plastics graduate programs. He is the author of 12 books, 325
chapters and research papers, and 36 patents. He received the 1985
SPE award for outstanding achievements in education, the 1989 PIA
award for research on polymer blends and plastics recycling, and the
1989 ALCA memorial lectureship for his work on polymer structureproperty relationships, was elected a Fellow of the SPE in 1994, and
was elected to the Plastics Academy Hall of Fame in 2000.