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Thermal-oxidative degradation and stabilization of polyformaldehyde
THERMAL-OXIDATIVE DEGRADATION AND STABILIZATION OF POLYFORMALDEHYDE * V. R. A L I S H O Y E V , M. B. N E I M A N , B. M. KOVARSKAYA and V. V. G U R Y A N O V A Scientific Research Institute for Plastics (Received 5 October 1961)
ONE of the most promising polymers at the present time is polyformaldehyde (PFA) which possesses high mechanical strength, high compression resistance, and good dielectric properties. However, PFA is extremely unstable and readily undergoes thermal and thermal-oxidative degradation [1,2]. Kern et al. [3] have shown that the thermal degradation of PFA begins at an appreciable rate at temperatures as low as 90 °. When the terminal hydroxyl groups are esterified, the initial limit of thermal degradation rises to 250 °. The thermal-oxidative degradation of the polymer begins above 160 °, free formaldehyde being liberated and the reaction accelerating. Kern points out the necessity for stabilizing PFA both by esterifying the terminal groups and by adding formaldehyde accepters and antioxidants. There is a considerable patent literature in which various additives are proposed for increasing the stability of PFA [4-9]. We have studied the kinetics of the oxidation of P F A with substituted terminal groups in the special vacuum apparatus described by Miller et al. [10]. It was found that large amounts of free formaldehyde were liberated which polymerized on the cold parts of the apparatus, and this explains the fall in pressure observed in the later stages of the process (Fig. 1). 4P, mm 160 123 80 40 I
0
I
40 80 Time,rain
I
120
FIG. 1. Change in pressure in the thermal oxidative degradation of polyformaldehyde. T = 170 °, P0= = 330 mm. * Vysokomol. soyed. 5: :No. 5, 644--648, 1963. 1340
Thermal-oxidative degradation and stabilization of polyform~ldehyd~
1341
In order to eliminate the polymerization of the formaldehyde, an apparatus was constructed (Fig. 2) in which all parts of the reaction vessel could be kept at the same temperature. As can be seen from Fig. 3, in the absence of oxygen at 145 ° the r~se in pressure due to the decomposition of the P F A takes place extremely slowly. However, in the presence of oxygen at the same temperature this process accelerates considerably (Fig. 3) and is characterized by the presence of an induction period which is considerably prolonged when oxidation inhibitors are added.
2
3 1
4G
20 2 -'-" 4----" --
_
_
_-
8O
120
1GO
T[me,min
FIG. 2
FIG. 3
FIG. 2. Plan of the apparatus: /--reaction vessel; 2--manometer; 3--cock; 4-- thermostat. FIG. 3. Increase in pressure in the thermal (1) and thermal-oxidative degradation (2) of polyformaldehyde at 145°.
In the oxidation products of P F A we found formaldehyde, oxides of carbon, hydrogen, and water. The results obtained in our study of the thermal-oxidative degradation of P F A have permitted the assumption t h a t this process takes place by a radical-chain mechanism but is not connected with degenerate branchings in hydroperoxides (as occurs in the oxidation of a number of other polymers), since the latter were not found. The problem of increasing the stability of PFA by the incorporation of effective additives consisting of formaldehyde acceptors and antioxidants is extremely complex. I t is known t h a t polyamide resins m a y be used as formaldehyde acceptors. In the present work, it was proposed to develop the method and give an evaluation of the efficiency of polyamide resins (as formaldehyde acceptors) and mixtures of them with various antioxidants as stabilizing additives for PFA.
1342
V. R . ALTSHOYEV et al.
In order to solve this problem, the direct adsorption of formaldehyde b y polyamide resins was used. I t could be assumed that the most reactive polyamide resins with respect to formaldehyde would also prove the best accepters when added to the polymers. As the source of formaldehyde was used polyoxymethylene, the degradation of which under the conditions of the experiment was complete in the first three minutes. The experiments were carried out in the apparatus illustrated in Fig. 2. The materials investigated were alcoholic solutions of mixed polyamide resins of types 54; 548; and 548-27. Each of the resins tested gives a formaldehyde absorption curve characteristic for it under the same experimental conditions. In the initial period of the reaction, an increase in the pressure in the reaction vessel was observed which was mainly due to the liberation from the polyamide resins of low-molecular-weight products volatile at the temperature of the experiment. This was shown in analogous experiments with resins purified by precipitation from alcoholic solution, in which no rise in pressure was found. The formaldehyde absorption curves at 200 and 220 ° for various polyamide resins are given in Fig. 4. To evaluate the efficiency of the poly-
-'0--
FIG. 4. A b s o r p t i o n o f f o r m a l d e h y d e b y v a r i o u s p o l y a m i d e s . R e s i n 5 4 8 - - 2 0 0 ° (1) a n d 220 ° (2); r e s i n 5 4 - - 2 0 0 ° (3) a n d 220 ° (4); r e s i n 5 4 8 - 2 7 - - 2 0 0 ° (5) a n 4 220 ° (6).
amide resins with respect to formaldehyde quantitatively, it is possible to calculate the corresponding absorption velocities graphically, for example over the range from 40 to 80 min, when the liberation of gas has practically ceased and the rate of absorption is close to the initial rate. I f it is assumed that the corresponding sections of the curves are straight lines, then the following velocities are obtained: T e m p e r a t u r e , °C P o l y a m i d e resin: 54 548 548-27
200
220
0.16 0.23 0.23
0-30 0.30 0.46
Of the types of resin tested, the best must be considered resin 548-27, which has a comparatively high rate of absorption of formaldehyde and also a high tem-
Thermal-oxidative degradation and stabilization of polyformaldehyde
1343
perature coefficient of this rate. The latter factor must obviously ba taken into consideration, since as the temperature is increased (in processing or use) the amount of formaldehyde liberated rises.
The possibility of applying the results obtained with formaldehyde to P F A required confirmation. In fact, when P F A containing 1% of the appropriate polyamides was oxidized, similar results were obtained. In addition, turbine-blades of P F A containing 1, 2, and 5 % of resins 54, 548, and 548-27 were moulded in a laboratory moulding machine. Moulding was carried out at 220 and 240 ° with various times of holding the material in the cylinder of the moulding machine. The results obtained confirmed the results of the evaluation of the efficacy of the polyamides. In association with polyamide resin 548-27, we tested the action of various a n t i o x i d a n t s - derivatives of phenols, amines, naphthols, sulphur compounds, and esters: catechol phosphoric acid, 2 2 - 4 6 - 2,2'-methylene-bis-(4-methyl-6-tbutylphenol), 40-10 -- phenyleyclohexyl-p-phenylenediamine, ionol catechol phosphite, fl-naphthol, mercaptobenzimidazole, p-hydroxyneozone, and the like. The experiments were carried out at 200 ° and a pressure of oxygen of 200 mm. The interesting fact was found that the introduction into P F A of a polyamide alone or an antioxidant alone considerably diminished the formation of gas in the thermal-oxidative degradation of the polymer. (Fig. 5, curves 2 and 3). However, the simultaneous introduction into the polymer of a polyamide resin and an antioxidant was far more effective and led to a marked decrease in the formation of gas when P F A was oxidized (Fig. 5, curves 4, 5, 6, 7). We came to the same conclusion on the basis of our experiments on the processing of P F A in a laboratory moulding machine. It was found that the stability of the polymer depends essentially on the purity of the additives incorporated. Thus, the introduction of purified polyamide 548-27 and antioxidant 22-46 reduces the rate of thermal-oxidative degradation of the polymer by a factor of 2-3 in comparison with the effect of the same additives in the unpurified state. The investigations carried out showed that the most effective antioxidants, in admixture with polyamide resin 548-27, for P F A are the following: 22-46, p-hydroxyneozone, and Santovar " O " (2,5-di-t-butylhydroquinone). In evaluating the efficacy of the action of additives increasing the stability of PFA, it was of interest to establish the optimum ratios of polyamide and antioxidant. Various ratios of polyamide resin 548-27 and antioxidant 22-46 were taken at total concentrations of 2.5 and 1.5% with respect to the PFA. Measurements of the pressure in the system due to gas formation on the oxidation of P F A with time in the presence of the additives taken in various proportions are shown in Fig. 6. The optimum ratio of polyamide and antioxidant m a y be considered as 0.6:0.4. However, there is very little deviation from the optimum ratio over a wide range of ratios (40-80~/o of polyamide).
V. R. ALISEOYEVet al.
1344
I n parallel with the m e t h o d described for the s t u d y of t h e r m a l - o x i d a t i v e degrad a t i o n of P F A a n d the action of additives on it, we used the t h e r m o g r a v i m e t r i o m e t h o d for the same purpose. This m e t h o d has been described in a n u m b e r of papers, p a r t i c u l a r l y for investigating the d e g r a d a t i o n o f epoxide resins [11].
4Rmm ~0
/ 240
IGO
80
80
1S0 240 Tame,rain
320
FIG. 5. Increase in pressure in the thermal-oxidative degradation of polyformaldehyde with added resin 548-27 and antioxidants. /--Polymer without additives; 2-- polymer + 2 % of resin; 3-- polymer + 2 ~/o of antioxidant 22-46; 4--polymer+l.2°/o of resin+0.8°/o of antioxidant 22-46; 5--Delrin; 6-polymer+l.2~o of resin +0"8~o of hydroxyneozone; 7--polymer-F1.2°/o of resin+ 0"8~o of the antioxidant Santovar "O".
4P,mrn 24O
180
°I ;
I
AntioxidQr# ~2 22-46
I
04
I
O~B
I
~8
Resin 548-27
Fro. 6. Degradation of polyfomaldehyde as a function of the composition of the mixture. T = 200 °, P0s= 200 ram. With the addition of 2"5~o of stabilizing mixture--resin 548-27 and. antioxidant 22-46. On the ordinate axis-increase in pressure in the reaction vessel after 80 rain (1) and after 100 rain(2).
Thermal-oxidative degradation and stabilization of polyformaldehyde
1345
We carried out a study of thermal oxidation from the change in weight of PFA under conditions of linear increase in temperature in air on a "Derivatograf" apparatus. Curves of the rate of loss in weight, the temperature, and differential thermal analysis were recorded simultaneously (Fig. 7). Comparison of the curves 300
~200 too L
I
J
~ 4 0 _
2O
3-~
I
L
60
80
Time,rain
Uot 0 02 Ant~oxidant 22-46
I00 Fro. 7.
04
i~6
G8
1 Resin 548 -27
FIG. 8.
FIG. 7. Curves of the investigation of polyformaldehyde in the "Derivatograf": / - - r i s e in temperature; 2--differential thermal analysis curve; 3-loss in weight; 4 - - r a t e of change of weight. FIG. 8. Loss in weight of the sample as a function of the content ofpolyamide resin 548-27 and antioxidant 22-46 in the mixture. Total c o n c e n t r a t i o n - 2.5%. Curves 1 and 2--loss in weight of the sample at 240 and 230 °, respectively.
of loss in weight with the curves of the rise in pressure when PFA is oxidized shows their complete agreement. An analogous picture is found on comparing results relating to the optimum ratios of polyamide and antioxidants by the two methods: measurement of the pressure and of the loss in weight. The results given in Fig. 6 (from pressure measurements) coincide complety with those of change in weight (Fig. 8). CONCLUSIONS
(1) The absorption of formaldehyde by various polyamide resins has been studied and the most effective formaldehyde acceptor has been found. (2) It has been shown that mixtures of polyamide resin and antioxidant of a definite composition are good po!yformaldehyde stabilizers.
1346
B. M. KOVARSKAYAet al.
(3) I t has been shown t h a t the curves of pressure increase a n d curves o f loss in weight equally well describe the kinetics o f the t h e r m a l - o x i d a t i v e d e g r a d a t i o n of p o l y f o r m a l d e h y d e . Translated by B. J. HAZZARI) REFERENCES
1. N. S. YENIKOLOPYAN and N. S. VARDANYAN, ZhVKhO ira. Mendeleyeva, 7: 194, 1962 2. L. S. DUDINA and N. S. YENIKOLOPYAN, Vysokomol. soyed. 4 : 869, 1962 3. W. KERN and H. CHERDRON, Makromolek. Chem. 40 : 101, 1960 4. Brit. Pat. 748846, 1956; J. Appl. Polymer Sei. 1 : 185, 1959 5. Israeli Pat. 10397, 1948; Chem. Abstr. 52 : 15127, 1958 6. U.S. Pat. 2920059, 1960; Chem. Ahstr. 54 : 12656, 1960 7. U.S. Pat. 2934518, 1960; Ref. zh. khim. 4P209, 1962 8. U.S. Pat. 2810708, 1957; Chem. Abstr. 52 : 798, 1958 9. German Fed. Rep. Pat. 1076363, 1960; Chem. Abstr. 54 : 13527, 1960 10. V. B. MILLER, M. B. NAIMAN and Yu. A. SHLYAPNIKOV, Vysokomol. soyed. 1: 1703, 1959 11. N. S. ANDERSON, Polymer, 2: 451, 1961
THERMAL-0XIDATIVE DEGRADATION OF A POLYCARBONATE* B. M. KOVARSKAYA, M. S. AKUTIN, A. I. SIDNEV, M. P. YAZVIKOVA a n d M. B. NEIMAN Scientific Research Institute for Plastics (Received 6 October 1961)
T H E change in the properties of p o l y c a r b o n a t e s a t high t e m p e r a t u r e s a n d in t h e presence of o x y g e n has h a r d l y been studied. Nevertheless, this question is o f u n d o u b t e d t h e o r e t i c a l i n t e r e s t a n d also of great practical i m p o r t a n c e , since polycarbonates undergo d e g r a d a t i o n in the processing a n d use articles m a d e from them. T h e r e is some i n f o r m a t i o n in the literature on the n a t u r e of the ageing o f polycarbonate. Thus, Christopher [1] gives the change in the m e c h a n i c a l properties of p o l y c a r b o n a t e films on the prolonged action of high t e m p e r a t u r e s (140-160°). A proposed mechanism of the ageing o f p o l y c a r b o n a t e s u n d e r the action o f irradiation has also been considered [2, 3].
* Vysokomol. soyed. 5: No. 5, 649-654, 1963.
ONE of the most promising polymers at the present time is polyformaldehyde (PFA) which possesses high mechanical strength, high compression resistance, and good dielectric properties. However, PFA is extremely unstable and readily undergoes thermal and thermal-oxidative degradation [1,2]. Kern et al. [3] have shown that the thermal degradation of PFA begins at an appreciable rate at temperatures as low as 90 °. When the terminal hydroxyl groups are esterified, the initial limit of thermal degradation rises to 250 °. The thermal-oxidative degradation of the polymer begins above 160 °, free formaldehyde being liberated and the reaction accelerating. Kern points out the necessity for stabilizing PFA both by esterifying the terminal groups and by adding formaldehyde accepters and antioxidants. There is a considerable patent literature in which various additives are proposed for increasing the stability of PFA [4-9]. We have studied the kinetics of the oxidation of P F A with substituted terminal groups in the special vacuum apparatus described by Miller et al. [10]. It was found that large amounts of free formaldehyde were liberated which polymerized on the cold parts of the apparatus, and this explains the fall in pressure observed in the later stages of the process (Fig. 1). 4P, mm 160 123 80 40 I
0
I
40 80 Time,rain
I
120
FIG. 1. Change in pressure in the thermal oxidative degradation of polyformaldehyde. T = 170 °, P0= = 330 mm. * Vysokomol. soyed. 5: :No. 5, 644--648, 1963. 1340
Thermal-oxidative degradation and stabilization of polyform~ldehyd~
1341
In order to eliminate the polymerization of the formaldehyde, an apparatus was constructed (Fig. 2) in which all parts of the reaction vessel could be kept at the same temperature. As can be seen from Fig. 3, in the absence of oxygen at 145 ° the r~se in pressure due to the decomposition of the P F A takes place extremely slowly. However, in the presence of oxygen at the same temperature this process accelerates considerably (Fig. 3) and is characterized by the presence of an induction period which is considerably prolonged when oxidation inhibitors are added.
2
3 1
4G
20 2 -'-" 4----" --
_
_
_-
8O
120
1GO
T[me,min
FIG. 2
FIG. 3
FIG. 2. Plan of the apparatus: /--reaction vessel; 2--manometer; 3--cock; 4-- thermostat. FIG. 3. Increase in pressure in the thermal (1) and thermal-oxidative degradation (2) of polyformaldehyde at 145°.
In the oxidation products of P F A we found formaldehyde, oxides of carbon, hydrogen, and water. The results obtained in our study of the thermal-oxidative degradation of P F A have permitted the assumption t h a t this process takes place by a radical-chain mechanism but is not connected with degenerate branchings in hydroperoxides (as occurs in the oxidation of a number of other polymers), since the latter were not found. The problem of increasing the stability of PFA by the incorporation of effective additives consisting of formaldehyde acceptors and antioxidants is extremely complex. I t is known t h a t polyamide resins m a y be used as formaldehyde acceptors. In the present work, it was proposed to develop the method and give an evaluation of the efficiency of polyamide resins (as formaldehyde acceptors) and mixtures of them with various antioxidants as stabilizing additives for PFA.
1342
V. R . ALTSHOYEV et al.
In order to solve this problem, the direct adsorption of formaldehyde b y polyamide resins was used. I t could be assumed that the most reactive polyamide resins with respect to formaldehyde would also prove the best accepters when added to the polymers. As the source of formaldehyde was used polyoxymethylene, the degradation of which under the conditions of the experiment was complete in the first three minutes. The experiments were carried out in the apparatus illustrated in Fig. 2. The materials investigated were alcoholic solutions of mixed polyamide resins of types 54; 548; and 548-27. Each of the resins tested gives a formaldehyde absorption curve characteristic for it under the same experimental conditions. In the initial period of the reaction, an increase in the pressure in the reaction vessel was observed which was mainly due to the liberation from the polyamide resins of low-molecular-weight products volatile at the temperature of the experiment. This was shown in analogous experiments with resins purified by precipitation from alcoholic solution, in which no rise in pressure was found. The formaldehyde absorption curves at 200 and 220 ° for various polyamide resins are given in Fig. 4. To evaluate the efficiency of the poly-
-'0--
FIG. 4. A b s o r p t i o n o f f o r m a l d e h y d e b y v a r i o u s p o l y a m i d e s . R e s i n 5 4 8 - - 2 0 0 ° (1) a n d 220 ° (2); r e s i n 5 4 - - 2 0 0 ° (3) a n d 220 ° (4); r e s i n 5 4 8 - 2 7 - - 2 0 0 ° (5) a n 4 220 ° (6).
amide resins with respect to formaldehyde quantitatively, it is possible to calculate the corresponding absorption velocities graphically, for example over the range from 40 to 80 min, when the liberation of gas has practically ceased and the rate of absorption is close to the initial rate. I f it is assumed that the corresponding sections of the curves are straight lines, then the following velocities are obtained: T e m p e r a t u r e , °C P o l y a m i d e resin: 54 548 548-27
200
220
0.16 0.23 0.23
0-30 0.30 0.46
Of the types of resin tested, the best must be considered resin 548-27, which has a comparatively high rate of absorption of formaldehyde and also a high tem-
Thermal-oxidative degradation and stabilization of polyformaldehyde
1343
perature coefficient of this rate. The latter factor must obviously ba taken into consideration, since as the temperature is increased (in processing or use) the amount of formaldehyde liberated rises.
The possibility of applying the results obtained with formaldehyde to P F A required confirmation. In fact, when P F A containing 1% of the appropriate polyamides was oxidized, similar results were obtained. In addition, turbine-blades of P F A containing 1, 2, and 5 % of resins 54, 548, and 548-27 were moulded in a laboratory moulding machine. Moulding was carried out at 220 and 240 ° with various times of holding the material in the cylinder of the moulding machine. The results obtained confirmed the results of the evaluation of the efficacy of the polyamides. In association with polyamide resin 548-27, we tested the action of various a n t i o x i d a n t s - derivatives of phenols, amines, naphthols, sulphur compounds, and esters: catechol phosphoric acid, 2 2 - 4 6 - 2,2'-methylene-bis-(4-methyl-6-tbutylphenol), 40-10 -- phenyleyclohexyl-p-phenylenediamine, ionol catechol phosphite, fl-naphthol, mercaptobenzimidazole, p-hydroxyneozone, and the like. The experiments were carried out at 200 ° and a pressure of oxygen of 200 mm. The interesting fact was found that the introduction into P F A of a polyamide alone or an antioxidant alone considerably diminished the formation of gas in the thermal-oxidative degradation of the polymer. (Fig. 5, curves 2 and 3). However, the simultaneous introduction into the polymer of a polyamide resin and an antioxidant was far more effective and led to a marked decrease in the formation of gas when P F A was oxidized (Fig. 5, curves 4, 5, 6, 7). We came to the same conclusion on the basis of our experiments on the processing of P F A in a laboratory moulding machine. It was found that the stability of the polymer depends essentially on the purity of the additives incorporated. Thus, the introduction of purified polyamide 548-27 and antioxidant 22-46 reduces the rate of thermal-oxidative degradation of the polymer by a factor of 2-3 in comparison with the effect of the same additives in the unpurified state. The investigations carried out showed that the most effective antioxidants, in admixture with polyamide resin 548-27, for P F A are the following: 22-46, p-hydroxyneozone, and Santovar " O " (2,5-di-t-butylhydroquinone). In evaluating the efficacy of the action of additives increasing the stability of PFA, it was of interest to establish the optimum ratios of polyamide and antioxidant. Various ratios of polyamide resin 548-27 and antioxidant 22-46 were taken at total concentrations of 2.5 and 1.5% with respect to the PFA. Measurements of the pressure in the system due to gas formation on the oxidation of P F A with time in the presence of the additives taken in various proportions are shown in Fig. 6. The optimum ratio of polyamide and antioxidant m a y be considered as 0.6:0.4. However, there is very little deviation from the optimum ratio over a wide range of ratios (40-80~/o of polyamide).
V. R. ALISEOYEVet al.
1344
I n parallel with the m e t h o d described for the s t u d y of t h e r m a l - o x i d a t i v e degrad a t i o n of P F A a n d the action of additives on it, we used the t h e r m o g r a v i m e t r i o m e t h o d for the same purpose. This m e t h o d has been described in a n u m b e r of papers, p a r t i c u l a r l y for investigating the d e g r a d a t i o n o f epoxide resins [11].
4Rmm ~0
/ 240
IGO
80
80
1S0 240 Tame,rain
320
FIG. 5. Increase in pressure in the thermal-oxidative degradation of polyformaldehyde with added resin 548-27 and antioxidants. /--Polymer without additives; 2-- polymer + 2 % of resin; 3-- polymer + 2 ~/o of antioxidant 22-46; 4--polymer+l.2°/o of resin+0.8°/o of antioxidant 22-46; 5--Delrin; 6-polymer+l.2~o of resin +0"8~o of hydroxyneozone; 7--polymer-F1.2°/o of resin+ 0"8~o of the antioxidant Santovar "O".
4P,mrn 24O
180
°I ;
I
AntioxidQr# ~2 22-46
I
04
I
O~B
I
~8
Resin 548-27
Fro. 6. Degradation of polyfomaldehyde as a function of the composition of the mixture. T = 200 °, P0s= 200 ram. With the addition of 2"5~o of stabilizing mixture--resin 548-27 and. antioxidant 22-46. On the ordinate axis-increase in pressure in the reaction vessel after 80 rain (1) and after 100 rain(2).
Thermal-oxidative degradation and stabilization of polyformaldehyde
1345
We carried out a study of thermal oxidation from the change in weight of PFA under conditions of linear increase in temperature in air on a "Derivatograf" apparatus. Curves of the rate of loss in weight, the temperature, and differential thermal analysis were recorded simultaneously (Fig. 7). Comparison of the curves 300
~200 too L
I
J
~ 4 0 _
2O
3-~
I
L
60
80
Time,rain
Uot 0 02 Ant~oxidant 22-46
I00 Fro. 7.
04
i~6
G8
1 Resin 548 -27
FIG. 8.
FIG. 7. Curves of the investigation of polyformaldehyde in the "Derivatograf": / - - r i s e in temperature; 2--differential thermal analysis curve; 3-loss in weight; 4 - - r a t e of change of weight. FIG. 8. Loss in weight of the sample as a function of the content ofpolyamide resin 548-27 and antioxidant 22-46 in the mixture. Total c o n c e n t r a t i o n - 2.5%. Curves 1 and 2--loss in weight of the sample at 240 and 230 °, respectively.
of loss in weight with the curves of the rise in pressure when PFA is oxidized shows their complete agreement. An analogous picture is found on comparing results relating to the optimum ratios of polyamide and antioxidants by the two methods: measurement of the pressure and of the loss in weight. The results given in Fig. 6 (from pressure measurements) coincide complety with those of change in weight (Fig. 8). CONCLUSIONS
(1) The absorption of formaldehyde by various polyamide resins has been studied and the most effective formaldehyde acceptor has been found. (2) It has been shown that mixtures of polyamide resin and antioxidant of a definite composition are good po!yformaldehyde stabilizers.
1346
B. M. KOVARSKAYAet al.
(3) I t has been shown t h a t the curves of pressure increase a n d curves o f loss in weight equally well describe the kinetics o f the t h e r m a l - o x i d a t i v e d e g r a d a t i o n of p o l y f o r m a l d e h y d e . Translated by B. J. HAZZARI) REFERENCES
1. N. S. YENIKOLOPYAN and N. S. VARDANYAN, ZhVKhO ira. Mendeleyeva, 7: 194, 1962 2. L. S. DUDINA and N. S. YENIKOLOPYAN, Vysokomol. soyed. 4 : 869, 1962 3. W. KERN and H. CHERDRON, Makromolek. Chem. 40 : 101, 1960 4. Brit. Pat. 748846, 1956; J. Appl. Polymer Sei. 1 : 185, 1959 5. Israeli Pat. 10397, 1948; Chem. Abstr. 52 : 15127, 1958 6. U.S. Pat. 2920059, 1960; Chem. Ahstr. 54 : 12656, 1960 7. U.S. Pat. 2934518, 1960; Ref. zh. khim. 4P209, 1962 8. U.S. Pat. 2810708, 1957; Chem. Abstr. 52 : 798, 1958 9. German Fed. Rep. Pat. 1076363, 1960; Chem. Abstr. 54 : 13527, 1960 10. V. B. MILLER, M. B. NAIMAN and Yu. A. SHLYAPNIKOV, Vysokomol. soyed. 1: 1703, 1959 11. N. S. ANDERSON, Polymer, 2: 451, 1961
THERMAL-0XIDATIVE DEGRADATION OF A POLYCARBONATE* B. M. KOVARSKAYA, M. S. AKUTIN, A. I. SIDNEV, M. P. YAZVIKOVA a n d M. B. NEIMAN Scientific Research Institute for Plastics (Received 6 October 1961)
T H E change in the properties of p o l y c a r b o n a t e s a t high t e m p e r a t u r e s a n d in t h e presence of o x y g e n has h a r d l y been studied. Nevertheless, this question is o f u n d o u b t e d t h e o r e t i c a l i n t e r e s t a n d also of great practical i m p o r t a n c e , since polycarbonates undergo d e g r a d a t i o n in the processing a n d use articles m a d e from them. T h e r e is some i n f o r m a t i o n in the literature on the n a t u r e of the ageing o f polycarbonate. Thus, Christopher [1] gives the change in the m e c h a n i c a l properties of p o l y c a r b o n a t e films on the prolonged action of high t e m p e r a t u r e s (140-160°). A proposed mechanism of the ageing o f p o l y c a r b o n a t e s u n d e r the action o f irradiation has also been considered [2, 3].
* Vysokomol. soyed. 5: No. 5, 649-654, 1963.