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Structure formation in polyamide copolymers
Structure formation in polyamide copolymers
465
product formed by interaction of a powdered, ozonized vulcauiT.ate and polyester resin is a single entity with its own individual properties. It is evident that in the polymerization of the polyester resin initiated by the peroxide groups of ozonized vulcanizates the molecules of the latter combine chemically with the polyester-acrylate molecules to form a unified, three-dimensional polymeric structure. The combination of properties of the two cross]inl~ed polymers determines the properties of the modified polymeric products obtained by interaction of these two polymers. CONCLUSIONS
(1) When a polyester-acrylate is heated in the presence of previously ozonized, powdered vulcanizates hardening occurs, with formation of modified products possessing a combination of the properties of the two polymers. (2) The nature of the structure of these products is suggested. Translated by E. O. PHILLIPS REFERENCES 1. B. A. DOGADKIN, I. A. TUTORSKII~ I. I. TUGOV, V. S. AL'TZITSER, L. S. KROKHINA and V. A. SHERSHNEV, Vysokomol. soyed. 3: 729, 1961 2. A. A. BERLIN, Khim. prgm. 2: 102, 1960 3. V. Ye. GUL' et al., Rus. Pat. No. 138034; Byull. izobr. No. 16, 1962
STRUCTURE FORMATION IN POLYAMIDE COPOLYMERS* M. B. KONSTANTINOPOL'SKAYA, Z. YA. BERESTNEVA a n d V. A. K A R G I N L. Ya. Karpov Physicochemical Institute
(Received 6 M a y 1964)
ACCORDING to contemporary ideas the process of crystallization of polymers is a multi-stage process, the first stage of which is the formation of bundles of crystallized chain molecules. On the basis of existing experimental data it may be considered that the course of the structure formation process will depend mainly on the structure of these bundles, which in turn is dependent on both the structure of the polymer chains and on the nature of the intermolecular interaction. * Vysokomol. soyed. 7: No. 3, 420-422, 1965.
466
M. B. KONSTANTINOPOL'SKAYAe~ ~d.
Thus in polyethylene plate*like monocrystals with the folded conformation of the bundles grow easily. I n polystyrene, where there is greater intermolecnlar interaction, the crystallization process is considerably, retarded but the structure-formation process ends in formation of plate-like crystals similar to those of polyethylene. It was therefore of interest to examine in detail the crystallization process in polyamides, where the intermolecular interaction forces are due to hydrogen bonds. It is well known that in Nylon 6 plate-like crystals form readily [1]. The formation of spherulite structures is characteristic of Nylons 6,6 and 6,10 [2, 3]. In a polyamide copolymer (Nylons 6; 6,6 and 6,10) a wide diversity of structures would be expected. From a solution of a copolymer in ethylene glycol we have previously obtained fibrillar crystals [4]. I n the present work a more detailed study was made of the process of structure formation in a polyamide copolymer (Nylons 6; 6,6 and 6,10) in relation to various factors, i.e. molecular weight, nature of the solvent and temperature. The specimens, prepared by depositing a hot solution of the copolymer on a carbon support at various temperatures were studied in a JE!~I-SJ electron microscope. Firstly a study was made of the effect of molecular weight on the crystallization process. For this purpose the copolymer was fractionated by fractional precipitation. The molecular weights were calculated by means of the formula [5], [7]=0.29 × 10-eM 1,3. I t was found that the molecular weight of the copolymcr has no significant effect on the process of structure formation. Fractions of different molecular weight give similar electron micrographs. I n contrast to polyolefins structure formation in the copolymer is controlled not only by the temperature of preparation of the specimens but also by the nature of the solvent. Thus from solution in cresol at temperatures from 30 to 180 ° only spherulites of fibrillar structure form (Fig. 1). From solution in formic acid (90 ~ ) again only spherulitic structures are obtained (Fig. 2). The most interesting structures were obtained from solutions of the copolymer in ethylene glycol. Crystals of fibrillar structure (Figs. 3 and 4) are formed when the specimens are prepared at 90 °. Individual fibrils lying parallel to one another and forming the planes a n d boundaries of the crystals are clearly seen in the photographs. Occasionally larger fibrils are formed at this temperature and because of their lower mobility these cannot aggregate into crystals but lie at random on ~he support (Fig. 5). A small increase in temperature of the support ( ~ 100°), leading to more rapid evaporation of the solvent and enabling the process of structure formation to be interrupted at one of its stages, produces such poorly packed planar formations that it is easy to see the component fibrils (Fig. 6). It is noteworthy that in contrast to polyolefins, platelets of very small dimensions can be seen in the photomicrographs of the copolymcr. Under the given conditions structures
Structure formation in polyamide copolymers
FIGS. 1-6. Polyamido oopolymers: 1--prepared from solution in cresol; g--from solution in formic acid; 3-5--from solution in ethylene glycol at 90°; 6--from the same solution at 100%
467
468
M. B. KONSTANTINOPOL'SKAYA~ ~ .
FIGS. 7-10. Polyamide copolymers: 7--from the same solvent a t 100~; 8 - - f r o m the same solvent a t 120°; 9, 1 0 - - f r o m the same solvent at 150 °. FIG. 11. Crystals of eopolymer etched with formic acid. FIG. 12. a - - S p h e r u l i t e of polyamide eopolymer; b - - t h e same spherulite etched with formic acid.
Structure formation in polyamide eopolymers
469
reminiscent of spherulites are formed in addition to plates made up of fibrils. I n Fig. 7 it is clearly seen that the spherulite consists of very thin, curled platelets, each of which is in turn made up of fibrils. However, a further increase in temperature (120 °) promotes the formation of spherulites of a rather different type (Fig. 8). These spherulites grow by direct outgrowth of fibrils, and evidently the finer component fibrils are arranged at right angles to the direction of growth of a large fibril. At still higher temperatures (150 °) it is possible to observe the initial stages of formation of the spherulites shown in Fig. 8. In Fig. 9 it can be seen that the spherulite grows by the growth of individual fibrils on to a nucleus. It should be added that often at the ends of the fibrils an alternating strip structure can also be seen (Fig. 10). I n order to study the nature of the structural elements of all the crystalline formations described above they were etched with formic §cid. For preparation of specimens of the required structure the specimens were prepared on platinum grids at the appropriate temperatures and examined in the electron microscope. Subsequently droplets of formic acid (10~o) were deposited on the grids and after 3 minutes the acid was removed with filter paper. Figure 11 shows a photomicrograph of fibrillar crystals after etching with formic acid. The very thin fibrils, of thickness ~ 100 A, forming the crystals are clearly seen. Etching of the fibrillar spherulitic structures leads to a rather different result. Figure 12a shows a photomicrograph of an untreated spherulite and Fig. 12b shows the same spherulite after etching. I t can be seen that the main fibrils forming the spherulite are as it were broken down to their component short fibrils. A similar picture is obtained after thermal degradation by boiling a solution of the copolymer. Thus the fibrils composing the spherulites in the copolymer consist of small structural elements disposed along the direction of growth of the fibril, and they have an alternating strip structure (Fig. 10). Consequently in the polyamide copolymer (l~ylons 6; 6,6 and 6,10), in contrast to regular polyamides, at all temperatures of preparation it is possible to produce specimens containing only fibrillar formations including fibrillar crystals. It should be noted that in this copolymer the planes and boundaries of the crystals are formed by direct aggregation of fibrils in a parallel arrangement. It is evident that the irregularity and alternation of regularly composed blocks in the polymer chains affects the structure of the primary structural elements, i.e. the bundles, that determines the nature of their mutual packing. It is the more loosely packed bundles that aggregate into fibrils as a result of the large forces ofintermolecular interaction. Subsequent structure formation occurs by building up of fibrils, up to the formation of fibrillar crystals. From the above results it may be concluded that the plate-like crystals with the folded conformation of the molecular bundles, that have been observed and well studied in polymers, are not the only type. Fibrillar crystals can be formed by direct aggregation of the bundles.
470
YE. •. ZVYAGINTSEVAand A. I. SHATENSHTEIN CONCLUSIONS
(1) A study has been made of structure formation in a polyamide copolymer (l~ylons 6; 6,6 and 6,10) from various solvents. (2) At all temperatures of preparation of the specimens only fibrillar formations arise and the crystals also have a fibrillar structure. (3) By etching of specimens with formic acid it was possible to distinguish elementary components of the fibrillar formations, of width ~ 100 A. Tran,slate,d by E. O. PHILLIPS REFERENCES 1. 2. 3. 4.
D. V. BADJLNH and P. H. HARRIS, J. Polymer Sei. 41: 540, 1959 F. gHOUl{Y, J. Polymer Sci. 26: 375, 1957 A. KELLER, J. Polymer Sci. 17: 392, 1955 M. B. KONSTANTINOPOL'SKAYA, Z. Y&. BERESTNEVA and V. A. KARGIN, Dokl. Akad. Nauk SSSR 151: 1108, 1963 5. V. V. KORSHAK and S. A. PAVLOVA, Izv. Akad. Nauk, Otd. khim. nauk, 1107, 1955
POLYMERIZATION OF METHYL ACRYLATE, METHACRYLONITRILE AND ACRYLONITRILE, INITIATED BY KNH2 IN SOLUTION, SUSPENSIONS OF LiNH2 AND Ba (NH~)2 IN LIQUID NHs, AND BY SOLID KNH~* Y E . N. ZVYAGINTSEVA a n d A. I . SHATENSHTEII~ L. Ya. Karpov Physicochemical Institute
(Received 7 May 1964)
IN A PREVIOUS communication [1] we showed that the molecular weight (MW) of polymethylmethacrylate (PMMA) obtained by polymerization initiated by amides of alkali and alkaline-earth metals is dependent on the phase state of the amide (solution or suspension in liquid NHs, or solid amide without solvent). The presence of a solid phase (even in the presence of a large quantity of liquid l~rHs) caused a considerable increase in the MW of the polymer. The question arises whether this is true for monomers other thall MMA. We have carried out experiments on the polymerization of methyl acrylate (MA), methacrylonitrile (1VIAl) and acrylonitrile (AN) in a solution of KNH~, in suspensions of Li_N~2 and Ba(NH2) ~ in liquid NH s and on solid KNH~. Control experiments were carried out on MMA, confirming the previous results. * Vysokomol. soyed. 7: :No. 3, 423-426, 1965.
465
product formed by interaction of a powdered, ozonized vulcauiT.ate and polyester resin is a single entity with its own individual properties. It is evident that in the polymerization of the polyester resin initiated by the peroxide groups of ozonized vulcanizates the molecules of the latter combine chemically with the polyester-acrylate molecules to form a unified, three-dimensional polymeric structure. The combination of properties of the two cross]inl~ed polymers determines the properties of the modified polymeric products obtained by interaction of these two polymers. CONCLUSIONS
(1) When a polyester-acrylate is heated in the presence of previously ozonized, powdered vulcanizates hardening occurs, with formation of modified products possessing a combination of the properties of the two polymers. (2) The nature of the structure of these products is suggested. Translated by E. O. PHILLIPS REFERENCES 1. B. A. DOGADKIN, I. A. TUTORSKII~ I. I. TUGOV, V. S. AL'TZITSER, L. S. KROKHINA and V. A. SHERSHNEV, Vysokomol. soyed. 3: 729, 1961 2. A. A. BERLIN, Khim. prgm. 2: 102, 1960 3. V. Ye. GUL' et al., Rus. Pat. No. 138034; Byull. izobr. No. 16, 1962
STRUCTURE FORMATION IN POLYAMIDE COPOLYMERS* M. B. KONSTANTINOPOL'SKAYA, Z. YA. BERESTNEVA a n d V. A. K A R G I N L. Ya. Karpov Physicochemical Institute
(Received 6 M a y 1964)
ACCORDING to contemporary ideas the process of crystallization of polymers is a multi-stage process, the first stage of which is the formation of bundles of crystallized chain molecules. On the basis of existing experimental data it may be considered that the course of the structure formation process will depend mainly on the structure of these bundles, which in turn is dependent on both the structure of the polymer chains and on the nature of the intermolecular interaction. * Vysokomol. soyed. 7: No. 3, 420-422, 1965.
466
M. B. KONSTANTINOPOL'SKAYAe~ ~d.
Thus in polyethylene plate*like monocrystals with the folded conformation of the bundles grow easily. I n polystyrene, where there is greater intermolecnlar interaction, the crystallization process is considerably, retarded but the structure-formation process ends in formation of plate-like crystals similar to those of polyethylene. It was therefore of interest to examine in detail the crystallization process in polyamides, where the intermolecular interaction forces are due to hydrogen bonds. It is well known that in Nylon 6 plate-like crystals form readily [1]. The formation of spherulite structures is characteristic of Nylons 6,6 and 6,10 [2, 3]. In a polyamide copolymer (Nylons 6; 6,6 and 6,10) a wide diversity of structures would be expected. From a solution of a copolymer in ethylene glycol we have previously obtained fibrillar crystals [4]. I n the present work a more detailed study was made of the process of structure formation in a polyamide copolymer (Nylons 6; 6,6 and 6,10) in relation to various factors, i.e. molecular weight, nature of the solvent and temperature. The specimens, prepared by depositing a hot solution of the copolymer on a carbon support at various temperatures were studied in a JE!~I-SJ electron microscope. Firstly a study was made of the effect of molecular weight on the crystallization process. For this purpose the copolymer was fractionated by fractional precipitation. The molecular weights were calculated by means of the formula [5], [7]=0.29 × 10-eM 1,3. I t was found that the molecular weight of the copolymcr has no significant effect on the process of structure formation. Fractions of different molecular weight give similar electron micrographs. I n contrast to polyolefins structure formation in the copolymer is controlled not only by the temperature of preparation of the specimens but also by the nature of the solvent. Thus from solution in cresol at temperatures from 30 to 180 ° only spherulites of fibrillar structure form (Fig. 1). From solution in formic acid (90 ~ ) again only spherulitic structures are obtained (Fig. 2). The most interesting structures were obtained from solutions of the copolymer in ethylene glycol. Crystals of fibrillar structure (Figs. 3 and 4) are formed when the specimens are prepared at 90 °. Individual fibrils lying parallel to one another and forming the planes a n d boundaries of the crystals are clearly seen in the photographs. Occasionally larger fibrils are formed at this temperature and because of their lower mobility these cannot aggregate into crystals but lie at random on ~he support (Fig. 5). A small increase in temperature of the support ( ~ 100°), leading to more rapid evaporation of the solvent and enabling the process of structure formation to be interrupted at one of its stages, produces such poorly packed planar formations that it is easy to see the component fibrils (Fig. 6). It is noteworthy that in contrast to polyolefins, platelets of very small dimensions can be seen in the photomicrographs of the copolymcr. Under the given conditions structures
Structure formation in polyamide copolymers
FIGS. 1-6. Polyamido oopolymers: 1--prepared from solution in cresol; g--from solution in formic acid; 3-5--from solution in ethylene glycol at 90°; 6--from the same solution at 100%
467
468
M. B. KONSTANTINOPOL'SKAYA~ ~ .
FIGS. 7-10. Polyamide copolymers: 7--from the same solvent a t 100~; 8 - - f r o m the same solvent a t 120°; 9, 1 0 - - f r o m the same solvent at 150 °. FIG. 11. Crystals of eopolymer etched with formic acid. FIG. 12. a - - S p h e r u l i t e of polyamide eopolymer; b - - t h e same spherulite etched with formic acid.
Structure formation in polyamide eopolymers
469
reminiscent of spherulites are formed in addition to plates made up of fibrils. I n Fig. 7 it is clearly seen that the spherulite consists of very thin, curled platelets, each of which is in turn made up of fibrils. However, a further increase in temperature (120 °) promotes the formation of spherulites of a rather different type (Fig. 8). These spherulites grow by direct outgrowth of fibrils, and evidently the finer component fibrils are arranged at right angles to the direction of growth of a large fibril. At still higher temperatures (150 °) it is possible to observe the initial stages of formation of the spherulites shown in Fig. 8. In Fig. 9 it can be seen that the spherulite grows by the growth of individual fibrils on to a nucleus. It should be added that often at the ends of the fibrils an alternating strip structure can also be seen (Fig. 10). I n order to study the nature of the structural elements of all the crystalline formations described above they were etched with formic §cid. For preparation of specimens of the required structure the specimens were prepared on platinum grids at the appropriate temperatures and examined in the electron microscope. Subsequently droplets of formic acid (10~o) were deposited on the grids and after 3 minutes the acid was removed with filter paper. Figure 11 shows a photomicrograph of fibrillar crystals after etching with formic acid. The very thin fibrils, of thickness ~ 100 A, forming the crystals are clearly seen. Etching of the fibrillar spherulitic structures leads to a rather different result. Figure 12a shows a photomicrograph of an untreated spherulite and Fig. 12b shows the same spherulite after etching. I t can be seen that the main fibrils forming the spherulite are as it were broken down to their component short fibrils. A similar picture is obtained after thermal degradation by boiling a solution of the copolymer. Thus the fibrils composing the spherulites in the copolymer consist of small structural elements disposed along the direction of growth of the fibril, and they have an alternating strip structure (Fig. 10). Consequently in the polyamide copolymer (l~ylons 6; 6,6 and 6,10), in contrast to regular polyamides, at all temperatures of preparation it is possible to produce specimens containing only fibrillar formations including fibrillar crystals. It should be noted that in this copolymer the planes and boundaries of the crystals are formed by direct aggregation of fibrils in a parallel arrangement. It is evident that the irregularity and alternation of regularly composed blocks in the polymer chains affects the structure of the primary structural elements, i.e. the bundles, that determines the nature of their mutual packing. It is the more loosely packed bundles that aggregate into fibrils as a result of the large forces ofintermolecular interaction. Subsequent structure formation occurs by building up of fibrils, up to the formation of fibrillar crystals. From the above results it may be concluded that the plate-like crystals with the folded conformation of the molecular bundles, that have been observed and well studied in polymers, are not the only type. Fibrillar crystals can be formed by direct aggregation of the bundles.
470
YE. •. ZVYAGINTSEVAand A. I. SHATENSHTEIN CONCLUSIONS
(1) A study has been made of structure formation in a polyamide copolymer (l~ylons 6; 6,6 and 6,10) from various solvents. (2) At all temperatures of preparation of the specimens only fibrillar formations arise and the crystals also have a fibrillar structure. (3) By etching of specimens with formic acid it was possible to distinguish elementary components of the fibrillar formations, of width ~ 100 A. Tran,slate,d by E. O. PHILLIPS REFERENCES 1. 2. 3. 4.
D. V. BADJLNH and P. H. HARRIS, J. Polymer Sei. 41: 540, 1959 F. gHOUl{Y, J. Polymer Sci. 26: 375, 1957 A. KELLER, J. Polymer Sci. 17: 392, 1955 M. B. KONSTANTINOPOL'SKAYA, Z. Y&. BERESTNEVA and V. A. KARGIN, Dokl. Akad. Nauk SSSR 151: 1108, 1963 5. V. V. KORSHAK and S. A. PAVLOVA, Izv. Akad. Nauk, Otd. khim. nauk, 1107, 1955
POLYMERIZATION OF METHYL ACRYLATE, METHACRYLONITRILE AND ACRYLONITRILE, INITIATED BY KNH2 IN SOLUTION, SUSPENSIONS OF LiNH2 AND Ba (NH~)2 IN LIQUID NHs, AND BY SOLID KNH~* Y E . N. ZVYAGINTSEVA a n d A. I . SHATENSHTEII~ L. Ya. Karpov Physicochemical Institute
(Received 7 May 1964)
IN A PREVIOUS communication [1] we showed that the molecular weight (MW) of polymethylmethacrylate (PMMA) obtained by polymerization initiated by amides of alkali and alkaline-earth metals is dependent on the phase state of the amide (solution or suspension in liquid NHs, or solid amide without solvent). The presence of a solid phase (even in the presence of a large quantity of liquid l~rHs) caused a considerable increase in the MW of the polymer. The question arises whether this is true for monomers other thall MMA. We have carried out experiments on the polymerization of methyl acrylate (MA), methacrylonitrile (1VIAl) and acrylonitrile (AN) in a solution of KNH~, in suspensions of Li_N~2 and Ba(NH2) ~ in liquid NH s and on solid KNH~. Control experiments were carried out on MMA, confirming the previous results. * Vysokomol. soyed. 7: :No. 3, 423-426, 1965.