Ind. Eng. Chem. Prod. Res. Dev. 1986, 25, 315-321
or phenol to form polymeric resins, pure HMF was reacted with urea or phenol in the presence of ammonium nitrate under conditions identical with those for polymerization with lactose as the reactant. Surprisingly, it was found that the reaction mixture (even after prolonged reaction times) did not yield any significant precipitate on addition of methanol. Also, the prominent peak at 196 nm that increased with reaction time in the lactose-containing reaction was absent in the pure-HMF-containing samples. Such observations indicate that polymers formed by the reaction of pure HMF and urea or phenol are different from the ones produced when the sugar is present. High molecular weight polymers, like the ones expected to form from lactose, would be insoluble in methanol in addition to having a high wavelength of maximum absorption in both the visible and near-UV regions. These results suggest that HMF formation alone is not a governing factor in polymer formation and that there are other pathways available for the polymerization reactions. It is therefore logical to assume that reaction of HMF with urea or phenol produces short chain polymers that are soluble in methanol, but when lactose is present these polymers may react with other monomers such as furfural, other related furans, and monosaccharides such as glucose or galactose and their isomerization products. Thus the polymer formed will be a complex array of different molecules in which HMF is present only as a small fraction of the whole polymer chain. A qualitative test to determine if free sugars are being incorporated into the polymers obtained showed the presence of a mixture of carbohydrates including glucose, galactose, and mannose in the resinous polymers (Viswanathan, 1985). The results are in agreement with the constituents of colorants in cane sugar refineries’ final molasses as per Tsuchida and Komoto (1970). Such products are thought to have resulted from advanced Maillard and caramelization reaction of sugars, among others. Since the final product contains intact sugar molecules, it implies that hydroxyl groups are available that could be
315
cross-linked and yield a higher molecular weight. The reaction between phthalic anhydride and secondary hydroxyls in a carbohydrate is known to result in a threedimensional network of macromolecules accompanied by release of energy (Brasseur and Champetier, 1946, 1947). This reaction is probably taking place in the particle boards, and in addition the copper ions should be catalyzing the glyptal formation. On the basis of these facts, the improved performance of the whey permeate-based resin in the presence of phthalic anhydride is understandable.
Acknowledgment This research was supported by the Cheese Research Institute and the University-Industry Research Program of the Graduate School and the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI 53706. Although the research described in this paper has been funded in part by the US. Environmental Protection Agency through Contract No. 68-02-4043 to Chemical Process Corp., Greenfield, WI, it has not been subject to the Agency’s peer and administrative review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. Thanks are also due to Dr. Tom Richardson for helpful comments. We acknowledge the help of the Office of Research in Science and Technology, University of Arkansas, Little Rock, AR, for the typing of this manuscript. Registry No. NH4NOB,6484-52-2;H2NCONH,,57-13-6; C6H40H, 108-95-2; Cu2+,15158-11-9; phthalic anhydride, 85-44-9.
Literature Cited Brasseur, P.; Champetier, G. Bull. SOC. Chim. F r . 1947, 117-122. Brasseur, P.; Champetier, G. Bull. SOC.Chim. F r . 1948, 265-271. Tsuchida, H.; Komoto, M. Roc. Res. SOC.Jpn. SugarRefin. Technol. 1970, 22, 66-76. Viswanathan, T.; Richardson, T. Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 644-647. Viswanathan, T. Ind. Eng. Chem. Prod. Res. Dev. 1985, 2 4 , 176-177.
Received for review July 17,1985 Accepted November 18,1985
Properties of Styrene-Maleic Anhydride Copolymers Eugene R. Moore MichiQan Applled Science and Technology Laboratories, Dow Chemical Company, Mldand, Michigan 48640
A series of carefully prepared copolymers with several maleic anhydride levels, each at three molecular weights, has been prepared and characterized. This paper will briefly discuss the preparation of these polymers and then will present data on molecular weight, T,, heat distortion temperatures, thermal stability, and melt viscosity.
Introduction In order to better understand the relationship among maleic anhydride (MA) content, molecular weight, and physical properties, a series of 16 copolymerswith styrene were prepared. Three levels of solution viscosity were prepared at 0%, 5%, 18%, 25%, and 33% maleic anhydride and one at 48%. These copolymers were produced in quantities of 800-1000 lb by using continuous polymerization and devolatilization equipment. Sample collection was not 0196-432116611225-0315$01.50/0
started until the composition and solution viscosity were within target range and the unit was operating at steady state. To assure uniformity, each copolymer sample was thoroughly mixed in a large tumble blender before characterization was started.
Experimental Section Polymer Synthesis. A recirculated coil reactor similar to that defined by Zimmerman and O’Connor (1967) was used for polymerization. Tube bundles were used to 0 1986 American Chemical Society
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Table I. Synthesis Conditions for Styrene-Maleic Anhydride Copolymers 4 cP8 8 CP 12 CP 0% MA 129 114 polymzn temp, "C 153 8.5% MEK 4.5% MEK 5.0% MEK feed compnn 13.5 7.2 polymzn rate, %/h 26.9 236 249 211 exit temp,b " C
MA In Polvmer IWt. 56)
".
5 % MA 126 0.11%' 10.2% MEK 4.9% MEK 2.2% MA 1.9% MA 14.6 polymzn rate, % / h 27.1 210 234 exit temp,b " C
86 0.025%d 5.5% MEK 2.0% MA 7.1' 246
18% MA 129 89 0.015%d 0.012%' 3.6% MEK 1.5% MEK 9.3% MA 10.3% MA 10.9' polymzn rate, % / h 27.5 240 244 exit temp,b "C
77 0.02270~ 6.0% MEK 8.5% MA 11.1' 253
25% MA 80 117 0.0077%' 0.008770~ 13.2% MEK 4.9% MEK 14.6% MA 11.2% MA 11.g polymzn rate, % / h 25.0 249 exit temp,b " C
77 0.0020%d 17.5% MEK 11.5% MA 9.d 257e
33% MA 93 104 0.00096%d 0.025%' 3.5% MEK 23.0% MEK 17.0% MA 19.0% MA 5.2g polymzn rate, % / h 14.5 268 256' exit temp,b "C
76 0.0097%d 24.0% MEK 15.5% MA 9.6 256e
polymzn temp, "C feed compn"
154
polymzn temp, "C feed compnn
polymzn temp, "C feed compna
polymzn temp, "C feed compne
48% MA polymzn temp, " C feed compn"
172
39.5% MEK 28.5% MA polymzn rate, % / h 5.31 239' exit temp,b " C OInitiator, MEK, MA, balance styrene. bFrom the stripper. Benzoyl peroxide. dAzobis(isobutyronitrile). e Mechanical stripper used. 'Single-pass mode (no recycle stream). 810 wt % in MEK.
provide extra heat-transfer surface. The total reactor capacity was 112 lb of styrene (at room temperature). In order to produce homogeneous copolymers good agitation was needed. This was provided with a positive displacement gear pump (see Figure 2) capable of recirculating the coil volume once every 60 s in addition to a two-impeller, in-line mixer. Conversion to polymer was such that the solids level was between 40% and 60% for all of the copolymers produced (solids were constant for each copolymer). The unreacted monomer and solvent were removed continuously in a vacuum stripper. For most of the copolymers the polymerizer output was forced (positive displacement feed pumps with a pressure controller on the output) through a heat exchanger into a vacuum chamber. This allowed the volatile monomer and solvent to be heated and vaporized within seconds. The melted polymer was pumped from the vacuum chamber as thin strands which were cooled and chopped continuously. The volatile components were condensed in a refrigerated exchanger. For most of the copolymers the condensate was returned to the polymerizer as it was condensed in the manner described by Hanson and Zimmerman (1957). In these runs, styrene and molten maleic anhydride were added as
0
1.0
2.0 3.0 4.0 5.0 MA Level In Monomer (Wt. %I
6.0
7.0
Figure 1 Monomer-polymer composition relationship for styrenelmaleic anhydride copolymers changes with temperature (Moore, 1975).
separate streams in exactly the same ratio that they were desired in the product. The correct polymer composition could then be quickly attained, since multiple adjustments were not needed. Only adjustment in temperature (or initiator content) was needed to correct molecular weight. Initiator and "makeup" methyl ethyl ketone (MEK), to compensate for condenser losses, were added as a third stream. In seven of the runs (with slower polymerization rates) condensate was not reused. These have been designated in Table I as "single pass" runs. In these runs, many more adjustments were needed since both the solution viscosity and the MA content would change with each adjustment. Temperature (and occasionallyinitiator concentration) was adjusted to get the correct solution viscosity, and then alternatingly the MA feed rate was adjusted to obtain the correct composition in the copolymer. Since temperature influenced polymerization rate, a change in temperature resulted in a change in solids level, which in turn changed the MA level. The adjustment of MA was simplified by assuming that all MA in the feed ended in the copolymer. This can be stated as MAF = MAcS (1) where MAF is the percentage of MA monomer in the feed, S is the fraction of polymer solids measured in the reactor, and, MAc is the percentage of MA desired in the product copolymer. This assumption is accurate a t low levels of MA but becomes less accurate at higher levels, as shown by the monomer-polymer composition diagram of Figure 1. The data of Figure 1 were obtained during the synthesis of these copolymers from analysis of the monomer stripped from the polymer (recycle stream) and analysis of the polymer. The reactivity ratios are then rl = 0 (since MA cannot homopolymerize) 13,
r2 = (n - l ) / x
\YJ
where n = mol of styrene in polymer/mol of MA in polymer and x = mol of styrene in monomer/mol of MA in monomer. These data have been reported earlier (Moore, 1975). It was also found that the monomer-polymer composition relationship is a function of temperature. This adds somewhat to the difficulty of maintaining the correct MA content while the temperature is adjusted to correct the solution viscosity when in the "single pass" mode. The synthesis assembly is shown schematically in Figure 2. The use of a few percent MEK solvent was found by Zimmerman and O'Connor (1967) to prevent the accu-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 2, 1986 PIC
Table 11. Measured Maleic Anhydride Content and 10 wt % MEK Solution Viscosity (25 "C) of Styrene Copolymers target target solution viscosity MA level, 70 4 CP 8 CP 12 CP 0% MA 0% MA 0% MA 12.51 cP 0 4.06 CP 7.98 CP 5.0% MA 5.1% MA 5 4.9% MA 12.10 CP 3.92 CP 8.17 CP 17.7% 18.1% MA 18 18.0% MA 4.07 CP 7.98 CP 12.32 CP 25 25.4% MA 24.6% MA 24.9% MA 8.11 CP 12.04 cP 3.96 CP 32.7% MA 33 32.9% MA 32.9% MA 7.94 CP 12.41 CP 4.19 cP 48 48.0% MA 4.03 CP
0-7
-
c
I
317
Polymer Product
n U Initiator Soln.
Figure 2. Schematic of the synthesis procedure used to produce styrene/maleic anhydride copolymers.
mulation of a "gel like" heat transfer inhibiting material on reactor walls. MEK was used in all of these polymerizations for that purpose. Molecular weight (MW) was determined in tetrahydrofuran (THF) by using gel permeation chromatography for weight and number average. A separate determination of number-average MW was carried out by using high-speed solution osmometry (HSO), also in THF. Solution viscosities were measured at 25 "C with 10 wt % solids in methyl ethyl ketone (MEK) and are reported in units of centipoise. High-shear melt viscosity was measured on a capillary rheometer, which has been described elsewhere (Karam et al., 1955). The shear stress of lo7dyn/cm2 was selected because it was believed to approximate the shear in modern, high-speed injection molding equipment. Measurements were taken at three temperatures where possible. Thermogravimetric analysis was carried out in air at a heating rate of 10 "C min. The weight of a 15-17-mg powdered sample was continuously recorded. Heat distortion measurements were carried out by using standard ASTM techniques (ASTM D1525-65T at 264 psi for Vicat and ASTM D 648 at 264 psi for deflection temperature under load or DTUL). Samples for DTUL were annealed for 2 h at a temperature 25 "C below the Vicat softening point. Glass-transition temperature was determined by using differential thermal analysis (DTA) with powdered samples heated, in air, at 25 "C/min. The linear coefficient of thermal expansion was determined by using ASTM D 696. Maleic anhydride measurements were carried out by titrating a 5-g sample in pyridine solution with 0.1 N alcoholic KOH and using thymol blue indicator. Average polymerization rate was determined by measuring the total polymer produced for an extended period of time. Since the reactor capacity was known to be 112 lb, the rate of polymerization was calculated as R = 100 P/112
(3)
where P is the average weight (pounds) of product produced in 1 h and R is the polymerization rate as percentage of reactor capacity per hour. Volatile level of the products was determined by heating a small quantity of resin granules in a vacuum oven. One to two grams in an aluminum dish were placed in a 213 "C oven for 30 min while under a high vacuum (2-5-mmHg
0
8
9
8
Q 8 8
Weight Av Molecular Weight
Figure 3. High-shear melt viscosity vs. molecular weight for styrene/maleic anhydride copolymers.
absolute pressure). Weight loss during this period was converted to percent volatile.
Discussion of Results Table I1 contains the measured levels of MA and of solution viscosity of the copolymers. The measured level of MA deviated by no more than 0.4% and solution viscosity by no more than 0.4 CP from the target values. Molecular weight decreased as MA content increased at a constant solution viscosity. Table 111shows, for example, that a 33% MA increase causes a small M , drop at 4 cP and a progressively larger one at 8 and 12 cP. This viscosity behavior indicates a tendency for the higher MA molecules to be more extended in the MEK solvent. The agreement between M , measured by HSO and GPC supports the accuracy of the GPC calibration. One additional data point has been included at 33% MA and 2.5 cP. Erratic results were obtained on the 48% MA sample, apparently due to limited T H F solubility. High-shear (10' dyn/cm2) melt viscosity is shown in Table IV at several temperatures. As expected, the viscosity increases both as solution viscosity increases and as MA content increases. For example, going from 4 to 12 cP increases the melt viscosity about the same as adding 20% MA and remaining at 4 cP. The relationship between viscosity, molecular weight, and MA content is more clearly seen in Figure 3 where log
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 2, 1986 500000,
.-----
/
/
1000 500 0
5
1
30
10 15 20 25 % Maleic Anhydride
500
35
Figure 4. High-shear melt viscosity vs. percent maleic anhydride for styrene copolymers.
-
I
E . R. Moore
9/12/84
480°F
440°F l/Temp. ( O R 1
400°F
Figure 7. High-shear melt viscosity vs. temperature for high solution viscosity styrene/maleic anhydride copolymers. 380 I
9/12/84
dynes/cm sq (Poise)
lomok
4 Centipoise Solution Visc
Temp. For 5% Wt. Loss, "C
I-
340
a *
a
320 10"C/Min. In Air
300
2nd Degree Fit
280 0
500
I
I
480°F
I
I
440°F 11Temp ( K )
I
400'F
Figure 5. High-shear melt viscosity vs. temperature for low solution viscosity styrene/maleic anhydride copolymers.
1
0
2
0 3 0 SIMA Wt., %
4
0
5
0
Figure 8. Thermal stability of styrene/maleic anhydride copolymers, as indicated by the temperature ("C) required for a 5% weight loss while heating at a rate of 10 "C/min. 400 I Temp. For 10% Wt. Loss, "C
t360t
380
Melt Viscosity At l o 7 dvnes/cm sa (Poise)
a
a
8
100000 - 043
Heating Rate
t
320 3001 0
10"CIMin. In Air 2nd Degree F i t
I
10
I
I
20 30 SIMA Wt.. %
40
I
50
Figure 9. Thermal stability of styrene/maleic anhydride copolymers, as indicated by the temperature ("C) required for a 10% weight loss while heating at a rate of 10 "C/min. lOOOk 5oQ 480°F
440'F l/Temp. ( K )
4OO0F
Figure 6. High-shear melt viscosity vs. temperature for medium solution viscosity styrene/maleic anhydride copolymers. q, at 440 OF is plotted against log MW and in Figure 4 where log q7 is plotted against percentage of MA. Figures
5-7 show the effect of temperature on 7., These plots of log q7 against 1/T in each viscosity range show that viscosity at higher MA levels drops more rapidly as temperature is increased. This results in lower processing temperatures than would be projected from polystyrene data. The thermal stability of these copolymers, as determined by TGA, is shown in Table V and Figures 8 and 9. The
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 2, 1986 319 Table 111. Molecular Weight of S-MA Copolymers' by High-Speed Osmometry (HSO) and Gel Permeation Chromatography (GPC) 10% MEK viscosity % MA 4 CP 8 CP 12 CP 0 M,,(HSO) 87500 M,,(HSO) 148000 M, (HSO) 164000 M, (GPC) 195 100 M, (GPC) 366900 M, (GPC) 491 500 M, (GPC) 90400 M,,(GPC) 160700 M,,(GPC) 211 100 M,/M, (GPC) 2.16 M,/M, (GPC) 2.28 M,/M, (GPC) 2.33 5 M,,(HSO) 82 000 M,,(HSO) 158000 M, (HSO) 174000 M, (GPC) 175200 M, (GPC) 345300 M, (GPC) 456 700 M,,(GPC) 82000 M,,(GPC) 146600 M,,(GPC) 187600 M,/M, (GPC) 2.14 M,/M,, (GPC) 2.36 M,/M,, (GPC) 2.43 18 M,,(HSO) 75400 M, (HSO)117 168 M, (GPC) 184300 M, (GPC) 288300 M, (GPC) 431 300 M, (GPC) 84000 M,,(GPC) 120700 M,,(GPC) 177300 M,/M, (GPC) 2.20 M,/M, (GPC) 2.39 M,fM,, (GPC) 2.43 25 M, (HSO) 79600 M,,(HSO) 108000 M,,(HSO) 145000 M, (GPC) 177800 M, (GPC) 287800 M, (GPC) 350600 M, (GPC) 79600 M,,(GPC) 112000 M,,(GPC) 136200 M,/M, (GPC) 2.26 M,fM, (GPC) 2.57 M,fM, (GPC) 2.57 33 M,,(HSO) 75 174 M, (HSO) 94582 M,,(HSO) 125600 M, (GPC) 146400 M, (GPC) 226700 M, (GPC) 281400 M,,(GPC) 65 150 M,,(GPC) 93 500 M,/M,, (GPC) 2.25 M,/M,, (GPC) 2.43 'At 2.5 CPand 33% MA:
M,,(HSO) = 36000; M, (GPC) = 84200; M, (GPC) = 40000.
Table IV. Melt Viscosity (P) of Styrene-Maleic Anhydride Copolymers at a Shear Stress of 10' dyn/cm2 10% MEK viscosity 4CP 8 CP 12 CP % temp, 17, temp, 17, temp, 17, MA O F P "F P O F P 0 400 3634 420 11486 420 19175 420 1413 440 5947 440 11731 440 981 460 3437 460 7477 5 400 3601 420 18994 440 18156 420 1875 440 9232 460 10293 440 1030 460 5853 480 6 410 18 420 23834 460 32100 440 149458 440 9344 480 11000 460 46744 460 4132 500 5 221 25 440 29002 440 112900 440 262788 460 11224 460 47683 480 4742 Table V. Thermal Stability of Styrene-Maleic Anhydride Copolymer as Indicated by Thermal Gravimetric Analysis 10% MEK viscosity 4 CP 8 CP 12 CP % % wt temp, % wt temp, % wt temp, MA loss OC loss OC loss OC 1 0 295 1 285 1 285 2 2 2 308 300 297 330 5 317 315 5 5 345 10 10 334 332 10 275 5 1 1 1 297 280 2 289 2 2 312 298 312 5 5 5 333 320 328 10 10 10 354 340 1 1 1 302 305 297 18 312 320 2 2 2 313 333 340 332 5 5 5 347 355 347 10 10 10 1 301 317 275 25 1 1 310 329 2 2 2 318 327 345 342 5 5 5 342 357 355 10 10 10 294 1 1 1 290 275 33 308 308 2 2 2 308 325 328 330 5 5 5 341 10 10 338 343 10 155 48 1 217 2 5 310 10 332
I
Vicat Distortion
340
-
4 CPS (2.9S°F/%MA: Least Squares Lines
200 0
10
20
30
40
50
MA Wt., %
Figure 10. Vicat softening point (ASTM D1525-65T at 264 psi) of styrenelmaleic anhydride copolymers is influenced by solution viscosity.
temperature for 5% and 10% weight loss were plotted since they seemed less influenced by minor volatile variations. A statistical curve fitting program was used to get the best second-degree fit. The curve increase indicates that the copolymer reached maximum stability at about 20% MA. This stability increase helps maintain the copolymer intact at the higher processing temperatures required for higher MA. The Vicat softening temperatures are shown in Figure 10. The higher molecular weight (8 and 12 cP) samples were somewhat higher and had a steeper slope. The Vicat is seen to increase linearly with maleic level. The 4-cP samples increase at a rate of 2.98 O F / % MA, while the 8and 12-cP samples increase at 3.36 O F / % MA. Very similar results are seen in Figure 11 for the annealed heat deflection temperatures (DTUL).In this case both the high- and low-viscosity copolymers increased at the same rate of 2.96 OF/% MA. Glass-transition temperatures do not appear to be dependent on viscosity, as was heat distortion. This would be expected, since both of the heat distortion temperatures are rate dependent but Tgis not. Since there was no
320
Ind. Eng. Chem. Prod. Res. Dev., Val. 25, No. 2, 1986 360
r
1
Deflection Temp., 'F
1
%
Volatile
340
3.0
2.0
280 1.0
260
220E 24ot
// 10
20 30 MA, %
J
Granules 25% Voiatiteon ' : 1 SMA
.*..''
8.0 CPS
1
0
160
0 4 CPS (2,96"F/%MA) 8 & l,Z CF'S(,Z96°.';"""~~ -Least Squares Line
700 -_0
c1
150
140 130 120 Heat Distortion, "C
110
100
Figure 14. Vicat softening point of styrene/25% maleic anhydride copolymers as a function of volatile content. 50
40
Figure 11. Annealed deflection temperature under load (ASTM D648 at 264 psi) of styrene/maleic anhydride copolymers is influenced by solution viscosity. 360
r----
1
Glass Transition
Temp., "F 320
1
/*I
280 260 240
2.8
2.67"Fl%MA
- Least Squares
1
2.6 0
10
0
20 30 MA%
40
50
Figure 12. Glass-transition temperatures of styrene/maleic anhydride copolymers, as determined by differential thermal analysis (25 C / min).
3601 340'
300 280 320
20
30
40
50
MA %
Figure 15. Effect of maleic anhydride content on the linear coefficient of expansion of styrene copolymers. Table VI. Volatile Content (wt %)a of S-MA Copolymers 10% MEK viscosity % MA 4 CP 8 CP 12 CP 0 5 0.45 0.46 0.80 18 0.10 0.36 0.68 25 0.65 0.40 0.50 33 0.65 0.49 45 0.82 213 "C for 30 min at 2-5 mmHg.
260 240
Vi~el.3.08~F/%MA
OEF. TEM.-2.8B0FI%MA
220
TgZ.67°F/%MA
2000
10
10
20 30 MA %
40
50
Figure 13. Average relationship between Vicat softening point, deflection temperature, and glass-transition temperature of styrene/maleic anhydride copolymers.
distinction between viscosities, the best fit to the combined data was made and is shown in Figure 12. The Tgappears to also be linear with MA and increases at 2.67 OF/added % MA. To allow comparison of these three measures of heat resistance, all the data for each technique were av-
eraged together (4, 8, and 1 2 cP). The result is shown in Figure 13. Vicat values are seen to be highest, with DTUL being next and very close to the Tgvalues, which were the lowest. It was known that volatile content influenced heat distortion values. To quantify this relationship, about 40 different sets of stripping conditions were used during the preparation of the 25% MA 8 CPcopolymer. This resulted in copolymer with volatile contents ranging from about 0.4% to 4.5%. These results are shown in Figure 14. The first percent volatile makes the greatest difference; above this the effect is linear, with about a 12 "C drop per each added percent volatile. Measured volatile contents of the copolymers is shown in Table VI. They were below 0.5 except for three values of 0.68-0.82. There were no trends with increasing MA content or molecular weight. It seems likely that variations in volatile content account for the scatter in the heat re-
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Ind. Eng. Chem. Prod. Res. Dev. 1988, 25, 321-328
sistance data of Figures 10-13. While a trend is not apparent from the data in Table VI, the scatter in Figure 14 indicates a random deviation of perhaps 0.3% volatile. The linear coefficient of expansion as a function of maleic anhydride content is shown in Figure 15. These values did not appear dependent on molecular weight. It is interesting to note that the coefficient of expansion decreases about 20% while going from 0% to 33% MA. This could be of importance in applications where plastics and metals or glass are used for separate parts in an assembly and thermal cycling is involved. Some advantages in fiberglass modified composites would also be anticipated. Since the fibers and polymer are heated during processing, the subsequent cooling and shrinking of the composite creates undesirable “prestressing” of the interface. Reducing the relative shrinkage should produce a stronger composite structure.
Summary A series of copolymers with six levels of maleic anhydride were prepared (each at three characteristic solution viscosity levels) continuously in well-stirred reactors. These polymers provide a “grid” which allowed both the effect of molecular weight and MA content on physical properties to be determined. This paper reports molecular weight data, high-shear melt viscosity, thermal stability, heat distortion temper-
atures (Vicat and DTUL, Tg)and linear coefficient of expansion on these polymers.
Acknowledgment
I extend my thanks to L. C. Chamberland and A. W. Hanson for their generous support and encouragement; to W. E. O’Connor, H. Mashue, R. Carlson, L. Ciezeck, R. Owens, R. Salisbury, M. Fryer, V. Cook, and C. Pawloski for synthesis assistance; to L. E. Smith I11 and T. R. Wayt for characterization; to W. Charlesworth for melt viscosity and physical properties; to E. T. Wagoner for thermal gravimetric analysis, differential thermal analysis, glasstransition temperature, and gel permeation chromatography; to C. Boyd for high-speed osmometry measurement of M,; and to K. Dennis and W. Alexander for solution viscosity MA determination and other helpful assistance. Registry No. (styrene) (maleic anhydride) (copolymer), 9011-13-6; polystyrene, 9003-53-6. Literature Cited Hanson. A. W.; Zimmerman, R. L. Ind. Eng. Chem. 1057,49,1803-1806. Karam, H. J.; Cleereman, K. J.; Williams, J. L. Mod. Plast. 1055,32(7),129. Moore, E. R. “Reactivity Ratios from Pilot Plant Data”; part of a symposium of polymerization methods and kinetics presented at the National AIChE meeting, Boston, Sept 1975. Zimmerman, R. L.; O’Connor, W. E. US. Patent 3336267,Aug 15, 1967.
Received for review May 24, 1985 Accepted December 9, 1985
Water Immersion of Polysulfide Sealants. 1. Effect of Temperature on Swell and Adhesion Peter J. Hanhela, Robert H. E. Huang, and D. Brenton Paul* Department of Defence, Defence Science and Technology Organlsation, Materiels Research Laboratorles, Ascot Vale, Victoria 3032, Australia
The suitability of polysulfide sealants for appllcations involving contact with hot water has been assessed through
changes in swell, permeability, peel strength, and lap shear strength that result from immersion at 25-90 O C . Peel and lap shear strengths decline with prolonged contact times, but this is ascribed to swelling rather than thermal effects. A dichromate-cured sealant (PR-1422) gave a standard saturation time-swell curve, whereas with manganese dioxide cured materials (PR-1750, Pro-Seal 899) a linear relationship existed over wide time (>100 days) and swell (160%) ranges. The generality of this behavior was established by examination of laboratory sealants prepared from various combinations of curing agents and polysulfide prepolymers. Permeability studies confirmed that continual swelling of manganese dioxide cured sealants leads to a volume swell level, between 80 and 120%, where water transmission occurs freely and sealing fails. Dichromate-cured materials were consequently more effective sealants in hot water than those cured with manganese dioxide.
Introduction In applications involving water contact, such as the sealing of joints in reservoirs, polysulfide sealants are required to maintain a sealing function for many years. Studies of the effect of long-term water immersion on properties of polysulfide sealants have, however, been virtually restricted to evaluation of adhesive performance at ambient temperature (Karpati, 1980; Lee, 1982). Situations in which sealants are required to function in hot water are not common, but one example concerns the operation of the environmental control system in some
combat aircraft. This involves the use of a water-filled integral fuselage tank to cool the heat exchange unit, and during flight the water can attain temperatures approaching 100 OC. Although sealing of such tanks has been attempted using polysulfides approved for fuel tank use, leakage has occurred more frequently than from the fuel cells. Polysulfide sealanta that are available for sealing aircraft fuel tanks generally meet the requirements of either MIL-S-83430 (high-temperature resistant sealants) or MIL-S-8802,for which the thermal resistance criteria are
Ol96-432l/86/l225-0321$QI.5O/Q 0 1986 American Chemical Society
