FLAME-RESISTANT CH LORINE-CONTAINING POLYESTER RESINS H .
C .
VOGT,
PAULS
D A V I S ,
E .
J.
F U J I W A R A , A N D
K .
C .
FRISCH'
Wyandotte Chemicals Corp., Wyandotte, Mich. 48192 N e w types of unsaturated, flame-resistant polyester resins containing the trichloromethyl group have been developed by reaction of 1 , l , l -trichloropropylene oxide with maleic anhydride and other dibasic anhydrides. Reinforced plastics have been prepared from these resins by crosslinking with vinyl monomers and employing glass fibers and other materials as reinforcing agents. This initial studly deals specifically with evaluation studies carried out with a system consisting of CI trichloromethyl-containing polyester and styrene in a 1 to 1 weight ratio. Curing characteristics of this resin system a t room temperature, as well as elevated temperatures, are described. This cross-linked system possesses, in addition to excellent flame resistance and weatherability, high heat distortion values, good dimensional stability, low water adsorption, and excellent chemical resistance. N o evidence of air inhibition is observed during curing, as is frequently encountered with some commercial resins. This system qualifies under MIL-R-7575-B, Grade A, Class 3,
THEincreasing trend1 toward flame-retardant plastics in recent years has placed major emphasis on the development of new and eficient flame-retardant components in resins and resin c'omposites. An imposing number of literature and patent references reveal the growing interest in imparting flame resistance to unsaturated polyesters, particularly for use in reinforced plastics. Among the methods employed to reduce the rate of combustion in unsaturated polyesteir compositions are the addition of nonreactive inorganic and/or organic flame-retardant additives, reactive flame-retardant components in either the acid (or anhydride) or diol moiety of the molecule, and flame-retardant vinyl monomer or crosslinking agents. These methods have been reviewed recently by Nametz (1967), Boenig (1964), and others. Among the elements employed in the preparation of reactive flame-retardant components, phosphorus and halogens have been most widely used, either singly or in combinations with other elements, such as antimony. A great number of halogen-containing, reactive diols, polyols, anhydrides, and other functional group-containing intermediates have been prepared. Among these are tetrachloro- and tetrabromophthalic anhydrides (Chae et al., 1967; Michigan Chemical Corp., 1965; Nordlander and Cass, 1947; Pape et al., 1968; Spatz and Koral, 1966), and especially chlorendic acid and anhydride. The use of the latter in self-extinguishing polyester resin systems has been described by numerous investigators (Robitschek, 1954; Robitschek anld Bean, 1957). Very recently, Palm et al. (1967) and Ohse and Cherdron 'i966) described flame-resistant polyesters based on i?-trichloromethy!-8lactones. Polymers containing the CCij group are most effective in imparting flame-retardant characteristic properties to polymeric systems. A new family of unsaturated polyesters containing the trichloromethyl group has been prepared using 3,3,3' Present address, Polymer Institute, University of l)etroit, ' Detroit, Mich.
trichloropropylene oxide (TCPO) (Davis, 1966). T.his highly chlorinated (65.9% C1) epoxide is a colorless liquid with physical properties as shown in Table I. Polyester Preparation and Description
Dibasic acid anhydrides, such as maleic and phthalic anhydrides, can be made to react readily with TCPO to yield the corresponding polyesters. Of special interest are the polyesters prepared by the reaction of TCPO and maleic anhydride (PCE resins) :
3,3,3-Tric h 10100 propyleneoxide M a l e i c (TCPO) anhydride
Polychloroester ( P C E )
P C E resins can be prepared with or without solvent, utilizing Lewis acid ype catalysts such as BF3, AlC13, and SnCL (Davis, 1966). These resins are nontacky, glassy solids a t room temperature possessing the properties given in Table 11. Characteristics of Uncured PCE-Styrene Mixtures
As suggested by its structure, the PCE resin reacts readily with vinyl monomers in the presence of catalyst t o yield plastics with a high degree of fire resistance. F tyrene, methyl methacrylate, diallyl phthalate, and triallyl cyanurate, among others, react with the P C E resin. P C E resin and styrene are completely miscible; typical physical properties of these solutions are described in Table 111. The effect of temperature on the viscosity of P C E resinstyrene mixtures is graphically shown in Figure 1. The stem follows normal temperature-viscosity behavior, ~ - 5 %
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1, March 1970
105
1°1OOOE
Table 1. Physical Properties of 3,3,3-Trichloropropylene Oxide (TCPO) Molecular weight Boiling point, 745 mm., C. Boiling point, 100 mm., C. Boiling point, 20 mm., C. Vapor pressure, mm. a t 25"C. Specific gravity a t 25" C. Refractive index a t 25"C. Freezing point, C. Flash point, F. Fire point, O F." Latent heat of vaporization, kcal./mole Heat of combustion, kcal./mole Specific heat, cal,/gram/" C., 25" C. Viscosity a t 25"C., cs. Solubility in water, gram/lOO grams a t 25" C. Solubility of water in, gram/lOO grams a t 25°C. Solubility in organic solvents a t 25"C. Ethanol 1-Butanol Acetone Benzene Heptane Mineral oil
2,000 5'000;
161.5 151 89 52.5 3.5 1.4880 1.4745 -38 166 245 10.1 396 0.286 1.605 0.47 0.15 Miscible Miscible Miscible Miscible Miscible Miscible
1,000
\
\
500
4
.z
loo=
7
50:
.8
20 IO :
5-
r ix,
0
-20 -40
-60 -80 -100
Temp, *C
Figure 1 . Variation of viscosity with temperature of PCEstyrene solutions
Cleueland open cup.
Table II. Properties of Solid PCE Resins 70 chlorine 46 Molecular weight, Mn" Color 5% hydroxyl Acid number Density Softening Doint (Durrans) 7c unsaturation (calcd.) I
a
_
2300 Amber 1 4.6 1.5 ca. 70"C. (158"F.) ca. 8
Gelled I after 16hs
/ I
40:rs
64hrs
I
64hrs
Ebullioscopic method.
with lower temperature-viscosity coefficients evident with the higher concentrations of styrene. The influence of silica filler a t varying concentrations on the viscosity ot P C E resin-styrene formulations is shown in Figure 2. The graph shows normal behavior and relationships. Curing of PCE Resin-Styrene Systems
Several peroxide-type catalysts were evaluated for the curing of the PCE-styrene system (Figure 3). Benzoyl and acetyl peroxides were very effective. Crosslinking was eventually obtained with all catalyzed systems. Exploratory pot life (storage stability) studies were conducted, using Gardner tubes to determine viscosity changes, which are indicative of rates of gelation, with various catalyst systems. Results of this study (Figure 4) indicate that there is no significant viscosity change at room temperature with any of the catalyst systems
Table 111. Properties of PCE Resin-Styrene Solutions Styrene monomer concentration, wt. % Viscosity, 25" C. (77" F.), C.P.S. Specific gravity, 25"C. (77" F.), g./cm.* Refractive index, n: Flash point (Cleveland open cup) C. F.
106
70 5.5 1.04 1.5450
38 100
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
60 10 1.09 1.5447 40 104
50 23 1.16 1.5445 40 104
40 91 1.23 1.5441 43 109
30 154 1.31 1.5437 43 109
175
lir
185 0:
PA
6
9
I 235
I
3
I
I
1
1 1
1
5
0
io
I I
1 IDI-t-BdTIL
1
PERhXIDE
I
I
250
I 1
I
I
~
I
15
1
I
20
25
CURING T I M E
I
1
30
35
i
40
I
C
79
79 i 7 4 45
MINUTES
Figure 3. Influence of various peroxides on PCE resin cures
40% Siyrene c
2
3
4
5
6
%Silica Thixotropic Agent (CAB-0-SIL)
Figure 4. Pot life chairacteristics of PCE-styrene solution using various catalysts Catalyst ecluivalent to 19'0 benzoyl peroxide No stabilizer used
Table IV. Gel Times of PCE-Styrene Accelerated with Dimethylaniline
Benzoyl Peroxide,
Dimethylaniline,
92
Gel Time," Min.
Peak Exotherm, F.
Time to Peak, Min.
r /O
2.0 1.5 1.25 1.0 0.75 0.5 1.o 1.o 1.0 1.o 1.o
0.6 0.6 0.6 0.6 0.6 0.6 0.4 0.6 0.8 1.o 1.2
5 9 11 11 13 14 34 27 21 22 20
227 197 184 156 153 102 140 142 138 134 122
13.0 18.2 17.2 23.3 23.0 35.0 56.5 40.6 34.8 20.8 22.1
"Time from addition of catalyst to point Lchere resin has gelled sufficiently to support 3.6-gram weight. Table V. Gel Times of PCE Resin Accelerated with Dimethyl-p-toluidine
for approximately 5 hours, and only nominal viscosity changes occur in 16 to 21 hours with catalysts normally used for higher-temperature curing systems. The PCE resin system contained 40% styrene and was not inhibited. Room Temperature Curing Formulations for PCE Resins
The PCE polychloroester sirups can be cured at room temperature with formulations composed of a catalyst and an accelerator. Several of these catalyst systems are described. T o achieve maximum physical properties, a thermal postcure is suggested. Dimethylaniline-Benzoyl Peroxide. The effects of dimethylaniline on the room-temperature curing behavior of the PCE solution are shown in Table IV. Initially, a 1.0% benzoyl peroxide concentration was used with varying amounts of dimethylaniline. I n these tests, the exotherm peaked at 0.6% amine. This concentration was selected for use in a study of the effects of varying benzoyl peroxide concentrations. Table I V indicates that a catalyst concentration of 1.25% benzoyl peroxide with 0.6% dimethylaniline prodluces a room-temperature gelation. Dimethyl-p-toluidinie-Benzoyl Peroxide. Similar techniques employed with the dimethylaniline formulation were used in studiles with dimethyl-p-toluidine as an accelerator (Table V). I n this system, 0.4% dimethyl-
%
Gel Time," Min.
Peak Exothenn, Min.
Time to Peak, Min.
0.1 0.2 0.4 0.6 0.8 0.4 0.4 0.4 0.4 0.4 0.4
21.5 9.5 6.0 4.5 3.5 3.0 4.0 4.0 6.0 6.0 10.0
86 113 162 151 125 185 173 176 163 142 112
35.0 18.8 15.2 64.0 10.3 13.8 15.3 10.3 15.2 18.6 17.8
Benzoyl Peroxide,
Dimethyl-ptoluidine,
7; 1.o 1.o 1.o 1.0 1.0 2.0 1.5 1.25 1.0 0.75 0.5
"Time from addition of catalyst to point where resin has gelled sufficiently to support 3.6-gram lead weight.
toluidine developed optimum temperature when 1.O% benzoyl peroxide was used. Cobalt Naphthenate-Methyl Ethyl Ketone Peroxide. The effects of methyl ethyl ketone peroxide catalyst and 6% solution of cobalt naphthenate concentrations are reported in Table V I . For many applications, a room-temperature cure will produce good over-all physical properties which Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1, March 1970
107
Table VI. Gel Times of PCE Resin (50%) Using Methyl Ethyl Ketone Peroxide and Cobalt Naphthenate
MEK Peroxide, r /C
1.o 1.5 2.0 1.o 1.o 1.o 1.0
Cobalt Naphthenute, 0/c
Gel Time," Min.
SPI Gel Time,b Min.
1.o 1.o 1.o 0.5 1.0 1.5 2.0
61 31 24 88 61 44 40
2 1.5 1.25 1.50 2 3 12
Table VII. Effect of Styrene Concentration on SPI Cure Characteristics
Time to Peak Peak Exotherm, Exotherm, Min. F. 27 21 9 10 27 31 37
203 229 334 340 200 203 210
"Time from addition of catalyst to point where resin has gelled sufficiently to s u p p o ~ 3.6-gram weight. 'Standard 1800F. SPI exotherm curve test procedure.
can be improved somewhat by postcuring a t 100"to 150" F. for 15 minutes to 1 hour. Elevated-Temperature Curing Formulations for PCE Resins
% Styrene
SPI Gel Time," Min.
SPI cure Time," Min.
Peak Exotherm, F
9 11 15
17 19 23 16 18
410 44 1 457 475 483
30 40 50 60 70
8 9
"Standard 180" F. SPI exotherm c u m test procedure.
possible to add laminate layers or coatings onto the cured PCE surface and achieve an excellent bond. Confirmation of these results is shown graphically in Figure 6. SPI gel characteristics are reported for samples as prepared, degassed before curing to remove any entrapped air, and air being bubbled through the system. The data appear to establish the absence of air inhibition with the PCE resin. Shrinkage and Fillers
I n most cases an oven-cure or elevated-temperature cure system is desirable because of shorter cure time, greater mold turnover, and more reproducible performance of fabricated components compared to the performance of room-temperature cured products. At 0.5 to 2% benzoyl peroxide, excellent cures of the PCE-styrene systems are obtained. As would be expected, the SPI exotherms decrease as the concentration of peroxide decreases (Figure 5). An increase in styrene concentration is accompanied by a slight increase in SPI gel time and cure time, the peak exotherm being influenced to a slight degree (Table VII).
I n general, polyester resin specific gravities vary between 1.15 and 1.40 in the uncured state and approach 1.25 in the cured unreinforced state. This difference between the uncured and cured specific gravities makes possible a per cent shrinkage calculation.
70 volume change = 100 x specific gravity (cured-uncured) specific gravity cured The volume change, as would be expected, is dependent upon the styrene concentration (pure styrene has a volume shrinkage of approximately 14%), as shown in Figures
Air Inhibition
The PCE-styrene formulations, when used in thin laminates or coatings, are generally not subject to air inhibition on the air-exposed surface. When a typical cobalt naphthenate-methyl ethyl ketone peroxide cure is employed with PCE-styrene resins, no wax is required to prevent air inhibition. It is therefore LEGEND R E S I N SYSTEM TREATMENT P R I O R TO CURE
---
RESIN. 60/40 PCE/STIRME CATALYST. BENZOYL PEROXIDE BATH TFXPERATURE 180'F
450-
I1
425 -
iiw CLXVE
CATALYST.
5
........
WXWM EXOTHERM.
NORMAL . .. DEGASSED BEFORE CURE A I R BWBBLED INTO SYSTEM ~
O F
315 I1 Ill IV V VI
350 "
2
325-
g
303-
6-
ajo-
275
1.0 0.75 0.50
0.40 0.25
1170 448
4 18 366 258 201
V
225
VI
203 -
!75 2
6
4 TIME
TIME
YIR
Figure 5. SPI exotherm curves for uninhibited PCE resin
108
8
MINUTES
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
Figure 6. SPI gel characterization Catalyst 1 % benzoyl peroxide
10
7 and 8. Fibrous or granular fillers reduce shrinkage, in proportion to the volume of filler present. The literature reports that the linear shrinkage is also affected by the curing conditions and the postcure used. Qualitative data indicate that the common types of fillers, such as calcium carbonate, clays, antimony oxides, and asbestos fibers, do not adversely influence the structural properties of the resin. Physical Properties of Cured PCE-Styrene Systems
To prepare the unfilled castings, the P C E resin styrene monomer was catalyzed using 0.5 weight % benzoyl peroxide. Overnight cure a t 60" to 70" C. gave a Barcol hardness of 28. Complete cure with a Barcol hardness of 38 to 40 was achieved by postcuring a t 100OC. for 6 hours. The physical properties of this resin are described in Table VIII.
,
s o / r o l +
,
a
,
1
,
, 7 9 10 11 VOLLIIETRIJ CLRE ShRINKPGE I
12
Figure 7. Effect of PCE-styrene concentration on per cent volumetric cure shrinkage
Fire-Retardant Properties. The fire-retardant properties of the P C E formulation (PCE-styrene, 50/50) were determined using the following test methods. Burning Rate, Inch Min. Glass laminate
Casting
0.05 0.05
0.18 0.18
0.00
0.00
ASTM D 757-49 (Globar) Initial After 48-hr. water boil ASTM D 635-63
As determined by the ASTM D 635-63 test procedure, all samples are nonburning. After 30 days a t 300"F., the clear, unfilled castings still exhibited the same nonburning characteristics as the original panels. The fire retardance is, as would be anticipated, affected by the type of reinforcement and the amount and type of filler used in fabrication. Addition of fillers, such as antimony trioxide, improves the fire retardance of the P C E resin system without appreciably affecting the physical properties of the plastic or the cure characteristics. The influence of antimony oxide does not become apparent if the castings are evaluated according to the ASTM D 757-49 (Globar) method, but become apparent if tested according to the ASTM D 635-63 test method. Since all P C E resin samples tested were nonburning by the ASTM D 757-49 method, the snuff-out time was determined-time required for the flame to extinguish itself after the burner flame has been removed. These results, for varying concentrations of styrene and antimony trioxide, are shown in Table IX. All samples are nonburning by ASTM D 635-63. Electrical Properties
Polyester resins, in general, are considered to have good over-all electrical properties, particularly with respect to loss factor, arc resistance, and dielectric strength a t high frequencies. The literature reports that the power factor normally increases with increasing temperature, while the use of glass reinforcement tends to lower these characteristics. Low water absorption properties generally are indicative of good electrical properties. The P C E resin with glass fiber laminates, prepared in accordance with MIL-R-7575, has excellent characteristics (Table X). The effect of styrene concentration on the electrical properties of unfilled PCE resins is shown in Table X I . Chemical and Solvent Resistance ,O/?O
40/60
50/50
DO/LO
?0/30
PCE R E S I N / S T f R E N E RATIO
Figure 8. Relation between PCE-styrene concentration a n d density of cured and uncured systems
The chemical resistance of a completely cured polyester resin is a function of its chemical composition, molecular weight of the polyester backbone, degree of crosslinking, type of monomer, and other factors. Industrial environ-
Table VIII. Physical Properties of Unfilled Casting
Styrene
Tensile Strength, P.S.I
Flexural Strength, P.S.I.
Heat Distortion, c. F . ) (0
Hardness, Barcol
Impact Test, Unnotched
40 50 60 70 80 90 95
7800 8505 8700 9048 8982 9346 7962
14,890 13,978 14,260 14,231 12,694 12,007 10,704
118 (230) 112 (234) 112 (234) 105 (222) 105 (222) 99 (210) 56 (133)
41 40 39 39 39 32 30
... ...
C.
5.1 4.9 4.3 4.1 3.75
Water Absorption, R 24 hr./RT
4 hr./10O0 C.
0.40 0.41 0.39 0.44 0.43 0.43 0.54
0.10 0.12 0.15 0.10 0.09 0.06 0.04
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1, March 1970
109
Table IX. Snuff-Out Time" for PCE-Styrene Castings with Varying Concentrations of Antimony Oxide 0
%
% Sbz03 2
1
3
4
Snuff-Out Time, See.
Styrene 40 50 60
15 63 180
6 12 65
1 1 34
1 1
22
0 1 16
"Seconds required for flame to extinguish itself after burner flame has been remoued.
Table X. Electrical Characteristics of PCE Resin-Glass Fiber laminate
Dielectric constant 1 Kc 100 Kc Dissipation factor 1 Kc
4.13 4.09 0.0059 0.0036
100 Kc
Laminate construction 12 plies 181-A172 Fiberglas cloth Resin 60/40 PCE-styrene 1.0% benzoyl peroxide Cure. 120 minutes at 180°F. under 30-p.s.i. pressure Nominal thickness, % inch
Factors Affecting Properties of Cured Reinforced PCE Resins
Table XI. Effect of Styrene Concentration on Electrical Properties of Unfilled PCE Resins
Resin styrem
Dielectric Constant
Dissipation Factor
Ratio
100
lo3
lo6
100
io3
lo6
50150
3.77 3.84
3.77 3.82
3.72 3.79
0.0041 0.0050
0.0031 0.0037
0.0061 0.0048
40160
ments involving chemical exposure have many variables with respect to temperature, concentration of combinations of chemicals in liquid and vapor phase abrasion, etc. Therefore, it is difficult to predict, on the basis of laboratory data alone, how any polyester construction will stand up on exposure to a particular industrial environment. T o gain a prefatory insight into the behavior of the PCE composition in various chemical media, roomtemperature immersion tests were run on 60/40 P C E resinstyrene plastic. In selecting the test liquids, only materials reported in the literature as highly destructive toward the commercially used polyester composition were employed. These chemicals may be divided into three groups: I.
Alkaline Compounds A. 26% to 2870 aqueous ammonia B. 50% sodium hydroxide C. 5% barium hydroxide D. Clorox 5% NaOCl (alkaline action together with oxidative influence) 11. Acidic Compounds A. 50% nitric B. 100% glacial acetic acid (acidic nature together strong organic solvent effect) 111. Solvents A. Ethylene dichloride (usually causes strong corrosion by surface creasing and embrittlement) B. Distilled water 1 10
I n general, most polyester resins are not recommended for use with liquid oxidizing agents (nitric, chromic, or concentrated sulfuric acids), nor should they be exposed to solutions whose pH is greater than 10 (sodium or ammonium hydroxide). Reinforced polyesters, on the other hand, are usually satisfactory for continuous exposure to water, salts, and nonoxidizing acids up to temperatures of 100"F., with possible extension in some cases to 140" F. I n this preliminary evaluation, an unfilled 40% styrene content resin was used. This styrene concentration was employed to evaluate the chemical resistance of the PCE polymer, rather than that of the styrene matrix. The cured, unfilled castings reported in Table XI1 were only slightly affected by inorganic acids and bases such as 50% "03 and 50% NaOH for a total of 270 days. However, 28% ammonium hydroxide had a pronounced effect on the physical properties, as did glacial acetic acid and ethylene dichloride. Distilled water, 5% sodium hypochlorite, and 5% barium hydroxide had no or only slight influence on the physical properties.
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
A critical review of the over-all curing problem indicated that five variables need to be characterized for optimum properties-styrene and catalyst concentrations, cure time, temperature, and pressure. Previous work has shown that both cure time and temperature are critical factors in preparing glass fiber-reinforced laminates, but pressure is not. A statistical study using a Graeco-Latin square technique indicated that optimum physical properties of a glass fiber liminate are obtained under the following conditions. Catalyst concentration (benzoyl peroxide) of 1.5%;. P C E resin-styrene monomer 50150 weight ratio. Press temperature 220" F. (105" C.) . Press time 30 to 120 minutes, 60 minutes being most desirable. 30-psi. pressure. These conditions, when applied to a 12-ply 181-A172 Fiberglas cloth, gave a laminate with physical properties as described in Table X I I I . The effects of styrene content, catalyst concentration, press temperature, and press time, and the properties of P C E laminates are described in Table XIV. From these results, it becomes evident that the flexural strength is proportional to the resin-styrene ratio (Figure 9); as the styrene content was increased, the flexural strength increased. A similar pattern seems to be evident for the influence of the catalyst; an increase in benzoyl peroxide concentration is accompanied by an increase in flexural strength (Figure 10). Press temperature, as well as press time, under the conditions studied, had only a very slight influence on flexural strength (Figures 11 and 12). Preparation of glass fiber hand layups indicated no significant differences in the operability of the resin with glass of various finishes. The vinyl silane finish A-172 glass provided good wettability. I t was concluded that the compatibility with Fiberglas cloth finishes was comparable to that of commercial resins of the same class, while the properties of the Fiberglas laminates were comparable to laminates made with commercial systems. The physical properties of a 12-ply 181-A172 Fiberglas cloth laminate with 50150 PCE resin-styrene ratio, cured under the conditions described above, have been tabulated
Table XII. Resistance of PCE Resin to Chemical Attack
Reagent
Initial Hardness
Days 31
2
10
33 33 33 33 33 33 33 33 Orig. Thick ness, Inch
25 25 33 33 0" 32 33 33
15 0 32 33
10
31
0.025 0.023 0.024 0.019 0.020 0.024 0.020 0.022 Initial Weight,
0.0 +0.004 0.0 +0.001
+o .oo1
G.
10
31
7.320 7.270 7.400 7.160 7.480 7.430 7.430 7.360
+0.190 +0.230 -0.010 -0.010
+0.305 +0.550 0.0 0.0
0.0 -0.030 +0.010
+0.020 -0.010 +0.020
52
,
94
150
2 70
Change in Barcol Hardness Time Glacial acetic acid 28% ammonium hydroxide 5% barium hydroxide 5% sodium hypochlorite Ethylene dichloride 50% nitric acid 50% sodium hydroxide Distilled water
Glacial acetic acid 28% ammonium hydroxide 570 barium hydroxide 5% sodium hypochlorite Ethylene dichloride 50% nitric acid 50% sodium hydroxide Distilled water
Glacial acetic acid 28% ammonium hydroxide 5% barium hydroxide 5% sodium hypochlorite Ethylene dichloride 50% nitric acid 50% sodium hydroxide Distilled water a
0
...
...
...
...
...
32 33
28 33
32 32
33 33
33 33
...
...
...
...
...
...
...
...
...
33 33 33
33 33 33
33 33 33
32 33 33
29 33 33
29 33 33
Days
...
+0.005 0.0 -0.001
+0.020 +0.002 +0.002
52 94 Change in Thickness with Time +0.003 +0.005 +0.020 +0.015 +0.002 +0.004 +0.001 +0.001
...
...
...
0.0 0.0 0.0
+0.001 +0.001 0.0
-0.001 0.0 0.0
150
2 70
+0.006 +0.007 +0.002 +0.001
+0.006 +0.007 +0.001 0.0
+0.001 0.0 0.0
0.0 0.0 0.0
150
210
+1.100
+0.980
+0.060 +0.030
+0.100 +0.030
+0.130 +0.010 +0.070
+0.150 +0.070 +0.070
...
...
Days
...
...
52 94 Change in Weight with Time +0.610 +0.610 +0.470 -0.010 0.0 -0.010 0.0 ... .., +0.020 +0.080 0.0 -0.050 +0.020 +0.030
...
...
Sample disintegrated
Table XIII. Typical Physical Properties of PCE-Styrene, 5 0 / 5 0 , laminate
PCEStyrene 50/50
MIL-R7575-B Requirements
Tested under Standard Conditions Flexural strength, flatwise, Ultimate strength, p s i . Initial modulus of elasticity Ultimate tensile strength, p.s.i. Ultimate compressive strength, flatwise, p s i . Flammability, inches per minute Water absorption, 24 hours' immersion, 7c change in weight Barcol Hardness Specific gravity Resin content, %
MIL-R7575-B Requirements
-0.013 None 54,700
0.1 (max.) 0.1 (rnax.)
Fluid, anti-icing (isopropyl alcohol) 53,700 2.92 x lo6 40,300
50,000 2.5 x lo6 40,000
43,600 N.B.
35,000 1.0 (rnax.)
0.03 64-67 1.86 36.7
0.5 (max.) 55
7% change in weight 5% change in thickness Ultimate flexural strength, p s i .
...
Standard test fluids, hydrocarbon and isooctane
... ...
Tested at 160" F. after ECxposure to 160" F. for % Hour Flexural strength, flatwise Ultimate strength P.S.I. Initial modulus of elassticity
PCEStyrene 50/50
% change in weight 90change in thickness Ultimate flexural stiength, p.s.i.
-0.004 None 52,900
0.1 (rnax.) 0.1 (max.)
Dielectric constant As determined at 10,000 megacycles 4.23 After 24 hours' immersion No change
No change
...
Loss tangent 50,500 2.66 x lo6
40,000 2.3 x lo6
Tested after Immersion in Chemical Fluids for 24 Hours Hydraulic fluid, petroleum base, aircraft and ordnance % change in weight +0.009 0.2 (rnax.) % change in thickness None 0.2 (rnax.) Ultimate flexural strength, p.s.i. 53,000 ...
As determined After 24 hours' immersion
0.0064 0.0079
0.020 (max.) 0.020 (max.)
Laminate Construction 12 plies 181-A172 Fiberglas cloth Resin, 50/50 resin-styrene 1.5% benzoyl peroxide Cure 1 hour a t 220" F; 30-p.s.i. pressure Nominal thickness, ?4 inch
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1, March 1970
111
Table XIV. Properties of PCE laminates Used in Statistical Study
%
Press Time, Min.
Press Temp., F
Flexural Strength, P.S.I.
Flexural Modulus, l o 6 P.S.I.
Spec ifk Gravity
Resin Content, %
70130 60 140 50150 40160
0.5 0.75 1.5 1.o
30 90 60 120
200 200 200 200
45,800 51,800 61,500 54,500
2.23 2.49 3.05 3.01
1.87 1.84 1.82 1.83
45.7 43.6 36.6 37.3
51-5 51-6 51-7 51-8
70130 60140 50150 40160
0.75 0.5 1.0 1.5
60 120 30 90
220 220 220 220
55,300 50,600 53,200 62,100
2.59 2.72 2.82 2.94
1.92 1.88 1.85 1.85
41.1 40.1 34.1 35.9
51-9 51-10 51-11 51-12
70130 60140 50150 40160
1.0 1.5 0.75 0.5
90 30 120 60
240 240 240 240
53,800 57,400 58,700 59,600
2.95 2.66 2.95 3.02
1.94 1.86 1.84 1.84
39.4 41.3 34.6 36.3
51-13 51-14 51-15 51-16
70130 60140 50150 40160
1.5 1.o 0.5 0.75
120 60 90 30
260 260 260 260
54,600 50,800 49,000 58,200
2.73 2.60 2.60 2.86
1.89 1.89 1.84 1.84
42.7 39.5 39.6 36.1
Sample No.
a
ResinStyrene Ratio
Catalyst,"
51-1 51-2 51-3 51-4
Luperco ATC (50% benzoyl peroxide in tricresyl phosphate)
;5or
2
70/30
1
I
60/40
50/50
40/60
-1 Y
RESIN/STYRENE RATIO
Figure
Figure 11. Effect of press time on flexural strength
9. Effect of PCE-styrene ratio on flexural strength
z
200
1
220
PRESS TEMPERATURE
240
2 0
'F
Figure 12. Effect of press temperature on flexural strength BENZOYL PEROXIDE CATALYST, PERCENT
Figure 10. Effect of benzoyl peroxide concentration on flexural strength
in Table XIV. These results meet the qualification requirements of government specification, MIL-R-7575-B, Grade A, Class B, resin polyester, low-pressure laminating. Conclusions
New types of unsaturated, flame-resistant polyester resins containing the trichloromethyl group were developed by reaction of l,l,l-trichloropropyleneoxide with maleic anhydride and other dibasic acid anhydrides. Reinforced plastics were prepared from these resins by crosslinking with vinyl monomers and employing glass fibers and other materials as reinforcing agents. 1 12
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1 , March 1970
Evaluation of the PCE resin-styrene system in 1 to 1weight ratio shows that the cured plastic possesses properties equal or superior to those obtained from current commercial flame-resistant, unsaturated polyesters. I n addition to excellent flame resistance and weatherability, these plastics exhibit high heat distortion, good dimensional stability, low water adsorption, and excellent chemical resistance. No evidence of air inhibition is observed during the curing of this highly styrenated system, as is encountered frequently with some commercial resins. This system qualifies under government specification, MIL-R-7575-B, Grade A, Class 3. Handling characteristics and behavior are equivalent to those of conventional commercial resins in such applications as premix molding and hand layup operations.
The P C E resins differ from the majority of the standard polyester resins because they contain structurally stable chlorine, leading to a high degree of flame resistance and improved environmental stability. Acknowledgment
Special appreciation is expressed to the Battelle Memorial Institute, Columbus, Ohio, for developing some of the data reported. literature Cited
Boenig, H . V., “Unsaturated Polyesters. Structure and Properties,” pp. 173-83, Elsevier, Amsterdam, New York, 1964. Chae, Y. C., Rinehart, W. M., Shull, C. S., Cass, R . A., Rohrbacker, R . J., 22nd Annual Technical Conference, S P I Reinforced Plastics Division, Washington, D . C., 1967. Davis, P. (to Wyandotte Chemicals Corp.), U. S. Patents 3,251,903 (May 17, 1966), 3,254,057 (May 31, 1966). Michigan Chemical Corp., Brit. Patent 988,304 (April 7, 1965); C A 62, 1646Bh (1965).
Nametz, R. C., Id.Eng. Chem. 59, No. 5, 99 (1967). Nordlander, B., Cass, W. J., J . A m . Chem. Soc. 69, 2679 (1947). Ohse, H., Cherdron, H., Makromol. Chem. 95, 283 (1966). Palm, R.,Ohse, H., Cherdron, H., Angew. Makromol.. Chem. 1, 1 (1967). Pape, P. G., Nulph, R. J., Nametz, R. C., 23rd Annual Technical Conference, S P I Reinforced Plastics/ Composites Division, Washington, D. C., 1968. Robitschek, P., Bean, C. T., Ind. Eng. Chem. 46, 1628 (1954). Robitschek, P., Bean, C. T. (to Hooker Electrochemical Co.), U. S. Patents 2,779,700, 2,779,701 (Jan. 29, 1957). Spatz, S. M., Koral, M. (to Allied Chemical Corp.), Can. Patent 741,390 (Aug. 23, 1966).
RECEIVED for review September 22, 1969 ACCEPTED December 19, 1969 Washington SPI Meeting on Reinforced Plastics, 1969.
ESTERS OF ISOMALIC ACID AS PRIMARY PLASTICIZERS IN POLY(VINYL CHLORIDE) NONTOXIC FORMULATIONS F A U S T O B A R G E L L I N I ’
A N D
LUIGI B E N E D E T T I ’
Research Centers, Montecatini Edison S.p . A., Port0 Marghera, Venice, and Bollate, Milano, Italy
Esters of higher aliphatic alcohols with isomalic acid and their acyl derivatives weire prepared, and some were evaluated in PVC-based formulations. Because of their low toxicity, these esters are expected to find application in nontoxic forrnulations. The best results were obtained with di( 2-ethylhexyl) 0-acetyl isomallate and di( 2-ethylhexyl) 0-propionyl isomalate, the properties of which are comparable to those of tributyl 0-acetyl citrate, but the acyl isomalate esters show better low temperature flexibility.
COMPOUNDED PVC flexible films may be competitive with films such as cellophane and polyethylene as foodpackaging material, because of the present availability of particular low toxcity plasticizers. This paper describes the preparation of sorne esters of isomalic acid and gives a technological evaluation of them in suitable PVC compounds. Isomalic acid [methylhydroxymalonic acid, CHsC(OH)(COOH),] has long been known; in 1876 Schmoger prepared it from methylbromomalonic acid and silver oxide. Only recently could i t be obtained industrially, starting with acetone (via 2-cyano-2-hydroxypropionamide) (Marangoni and Nenz, 1962, 1965; Nenz et al., 1963, 1964, 1965, 1966) or with ketene or acetic anhydride (via 1,ldicyanoethyl acetate) (Brunner, 1892; Marangoni et al., 1967). Present address, Divisione Petrolchimica e Resine (DIPR), Montecatini Edison S.p.A., Brindisi, Italy Present address, Direzione Centrale delle RiCerche (DIRI), Montecatini Edison S.p.A., Largo Donegani 1, Milano, Italy
Because the acid has low toxicity (Cima, 1966), comparable to that of the organic acids normally used in the foodstuff industry, its esters might find acceptance for end uses involving contact with food (Benedetti and Marangoni, 1965). However, very little is known about isomalate and acyl isomalate and their toxicity. Only the ethyl (Eskola and Moutinen, 1947) and n-butyl (Colonge et al., 1947) esters were reported before 1965. Type and Properties of Products Studied
This paper describes results obtained with the acyl derivatives of higher alcohol esters (Bargellini et al., 1966, 1968) having the following chemical structure:
R-COO
\
I
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9,No. 1, Morch 1970
1 13
