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1965 Volume 7 Issue 3
1965, 7(3): 149-159
Abstract:
1．The effect of some transition metal salts upon the rate of oxygen—absorption by cis．polybutadiene has been studied；the salts used were acetylacetonates of Co++，Cu++，Fe+++．Mn++ and Ni++．The results show that the relative catalytic activities of these compounds depend on their cationic redox potential in the order： Co++>Mn++>Fe+++>Cu++ and Ni++．It was also found that as the concentration of the salts is in-creased．the initial rate of oxygen-absorption is also increased，while the maximum rate is only accelerated by Co++．but inhibited by Cu++ and nearly unaffected by Fe+++ and Ni++．2．Comparison has been made between the effects of bivalent cobalt salts：cobalt halides，stearate，and acetylacetonate，upon the oxygen—absorption rate． It was shown that the relative catalytic activities of different halides are similar to each other．but are slightly less active than the tWO organic salts．The effect of cobalt acetylacetonate on the maximum rate is slightly greater than that of cobalt stearate． Furthermore．it was also found that the maximum rate of oxygen-absorption is proportional to the square root of the concentration of these cobalt salts within the temperature range from 60°to 80℃． The apparent activation energy of the initial stage was found to be decreased by cobalt salts from 20 kcal／mole for the raw polymer to 16 kcal／mole：but that of the maximum rate was not affected，the value of which was 14 kcal／mole．3．The effects of four binary mixtures，acetylacetonates of Co++——Fe+++，Co++一Cu++，Co++——Ni++。and Fe+++—Cu++，on the rate of oxygen．absorption have also been inves．tigated．It was found that with the exception of the Co++—Ni++ system．all the rest showed that the more active component was inhibited by the less active one．Meanwhile，the inhibition effect depended markedly upon the molar ratio of the two components in two different ways，one with an optimum value and the other with a limiting value．Moreover，as the molar ratio was increased to 1：1 0，the effect of the Co++—Fe+++ sys—tem was synergistic，i．e．the value being greater than additive．
1．The effect of some transition metal salts upon the rate of oxygen—absorption by cis．polybutadiene has been studied；the salts used were acetylacetonates of Co++，Cu++，Fe+++．Mn++ and Ni++．The results show that the relative catalytic activities of these compounds depend on their cationic redox potential in the order： Co++>Mn++>Fe+++>Cu++ and Ni++．It was also found that as the concentration of the salts is in-creased．the initial rate of oxygen-absorption is also increased，while the maximum rate is only accelerated by Co++．but inhibited by Cu++ and nearly unaffected by Fe+++ and Ni++．2．Comparison has been made between the effects of bivalent cobalt salts：cobalt halides，stearate，and acetylacetonate，upon the oxygen—absorption rate． It was shown that the relative catalytic activities of different halides are similar to each other．but are slightly less active than the tWO organic salts．The effect of cobalt acetylacetonate on the maximum rate is slightly greater than that of cobalt stearate． Furthermore．it was also found that the maximum rate of oxygen-absorption is proportional to the square root of the concentration of these cobalt salts within the temperature range from 60°to 80℃． The apparent activation energy of the initial stage was found to be decreased by cobalt salts from 20 kcal／mole for the raw polymer to 16 kcal／mole：but that of the maximum rate was not affected，the value of which was 14 kcal／mole．3．The effects of four binary mixtures，acetylacetonates of Co++——Fe+++，Co++一Cu++，Co++——Ni++。and Fe+++—Cu++，on the rate of oxygen．absorption have also been inves．tigated．It was found that with the exception of the Co++—Ni++ system．all the rest showed that the more active component was inhibited by the less active one．Meanwhile，the inhibition effect depended markedly upon the molar ratio of the two components in two different ways，one with an optimum value and the other with a limiting value．Moreover，as the molar ratio was increased to 1：1 0，the effect of the Co++—Fe+++ sys—tem was synergistic，i．e．the value being greater than additive．
1965, 7(3): 160-170
Abstract:
A study has been made of the influences of some factors (types and concentration of coagulants，etc) upon the ionic deposition of natural rubber latex with coagulants．It was found that the rate of deposition varied with the types of coagulants，in the order of calcium chloride>calcium nitrate>calcium acetate>barium chloride>barium acetate．The mechanical properties of wet-·gel and dry-film with barium acetate were quite good．The ageing characteristics of dry—film deposited with calcium salts were poorer than that with barium salts．especially for the chlorides．The amount of ionic deposition，the initial concentration of wet—gel，and the mechani-cal properties of wet-gel increased with the concentration of coagulant． But when cal-cium chloride was used，the mechanical properties of wet-gel attained a maximum at a concentration of 15％．During the ionic deposition，the concentration of wet-gel was found to decrease at first and then a slight increase after the minimum value was reached．The properties of wet-gel underwent similar changes．Both the deposition method and the carrier of coagulant had pronounced effects upon ionic deposition．According to the above results．the ionic deposition of natural rubber latex can be considered to be proceeding in three stages：(a)coagulation；(b)the transition stage；(C)gelation．From the experimental data，we are able to prove that the Sandomirskii’s kinetic equation of ionic deposition is a reasonable one；but it is probably better to express the whole course of ionic deposition by an empirical equation of the type.
A study has been made of the influences of some factors (types and concentration of coagulants，etc) upon the ionic deposition of natural rubber latex with coagulants．It was found that the rate of deposition varied with the types of coagulants，in the order of calcium chloride>calcium nitrate>calcium acetate>barium chloride>barium acetate．The mechanical properties of wet-·gel and dry-film with barium acetate were quite good．The ageing characteristics of dry—film deposited with calcium salts were poorer than that with barium salts．especially for the chlorides．The amount of ionic deposition，the initial concentration of wet—gel，and the mechani-cal properties of wet-gel increased with the concentration of coagulant． But when cal-cium chloride was used，the mechanical properties of wet-gel attained a maximum at a concentration of 15％．During the ionic deposition，the concentration of wet-gel was found to decrease at first and then a slight increase after the minimum value was reached．The properties of wet-gel underwent similar changes．Both the deposition method and the carrier of coagulant had pronounced effects upon ionic deposition．According to the above results．the ionic deposition of natural rubber latex can be considered to be proceeding in three stages：(a)coagulation；(b)the transition stage；(C)gelation．From the experimental data，we are able to prove that the Sandomirskii’s kinetic equation of ionic deposition is a reasonable one；but it is probably better to express the whole course of ionic deposition by an empirical equation of the type.
1965, 7(3): 171-177
Abstract:
The effects of the degree of vulcanization on the ionic deposition rate and the physico-mechanical properties of wet-gel and dry-film from vulcanized natural rubber 1atex were studied．Experimental results indicate that different degrees of vulcanization gave no signifi-cant changes in the ionic deposition rate．This is due to the fact that the ionic deposi-tion rate depends upon the colloidal properties only and is not affected by the intra-globule structure．The kinetics of ionic deposition from vulcanized natural rubber latex is similar to that from the unvulcanized latex．It can be expressed by the following equation： q一0.01070t1-3 where q is the amount of deposit，t is the deposition time．The physico-mechanical properties of wet-gel improved at first，and declined again with further vulcanization．This phenomenon is explained by the diffusion of the chain segments and the redistribution of cross-links of the cross-linked molecules between rubber particles．The properties of dry-film are similar to those of wet-gel．
The effects of the degree of vulcanization on the ionic deposition rate and the physico-mechanical properties of wet-gel and dry-film from vulcanized natural rubber 1atex were studied．Experimental results indicate that different degrees of vulcanization gave no signifi-cant changes in the ionic deposition rate．This is due to the fact that the ionic deposi-tion rate depends upon the colloidal properties only and is not affected by the intra-globule structure．The kinetics of ionic deposition from vulcanized natural rubber latex is similar to that from the unvulcanized latex．It can be expressed by the following equation： q一0.01070t1-3 where q is the amount of deposit，t is the deposition time．The physico-mechanical properties of wet-gel improved at first，and declined again with further vulcanization．This phenomenon is explained by the diffusion of the chain segments and the redistribution of cross-links of the cross-linked molecules between rubber particles．The properties of dry-film are similar to those of wet-gel．
1965, 7(3): 178-184
Abstract:
The effect of some factors on the graft copolymerization of styrene tO polyvinyl alcohol induced by γ-irradiation has been studied，and a preliminary estimation was made on the properties of the graft products．The grafting occured very readily if a proper amount of water was added to the system． It was shown that the rate of grafting in-creased sharply with the increase of water content in the polymer film and then levelled off．while the rate of homopolymerization increased more slowJY and levelled off rapidly at a lower water content．The effect of dose rate on the grafting process at room tem-perature was studied，and it was found that the grafting was entirely diffusion—controlled with the dose rate larger than 100 r／min．at which the dose rate exponent of the relation V=KP approached zero．The plot of the amount of grafting with temperature in the range of 10—80℃ passed through a maximum at 60℃ and then fell off，while the homo-polymerization increased steadily all over the temperature range and showed an auto-acceleration at temperatures above 60℃ presumably owing tO the gel effect．The presence of oxygen has an inhibiting effect on the grafting．It was found that the homopolymeriza-tion could be remarkably inhibited，with only slight reduction in the grafting，by the pre-sence of a proper amount of oxygen or air．The graft product is soluble in dimethylformamide at 150℃．The swelling ratio of the product in boiling water or in boiling benzene was found to change linearly with the grafting．It was also found that the resistance of the film to acid or alkali was signifi．candy improved by the grafting．
The effect of some factors on the graft copolymerization of styrene tO polyvinyl alcohol induced by γ-irradiation has been studied，and a preliminary estimation was made on the properties of the graft products．The grafting occured very readily if a proper amount of water was added to the system． It was shown that the rate of grafting in-creased sharply with the increase of water content in the polymer film and then levelled off．while the rate of homopolymerization increased more slowJY and levelled off rapidly at a lower water content．The effect of dose rate on the grafting process at room tem-perature was studied，and it was found that the grafting was entirely diffusion—controlled with the dose rate larger than 100 r／min．at which the dose rate exponent of the relation V=KP approached zero．The plot of the amount of grafting with temperature in the range of 10—80℃ passed through a maximum at 60℃ and then fell off，while the homo-polymerization increased steadily all over the temperature range and showed an auto-acceleration at temperatures above 60℃ presumably owing tO the gel effect．The presence of oxygen has an inhibiting effect on the grafting．It was found that the homopolymeriza-tion could be remarkably inhibited，with only slight reduction in the grafting，by the pre-sence of a proper amount of oxygen or air．The graft product is soluble in dimethylformamide at 150℃．The swelling ratio of the product in boiling water or in boiling benzene was found to change linearly with the grafting．It was also found that the resistance of the film to acid or alkali was signifi．candy improved by the grafting．
1965, 7(3): 185-192
Abstract:
Beads were first prepared by the suspension copolymerization of styrene and divinyl-benzene in the presence of polystyrene．The swelling coefficient in toluene，apparent density，and percentage of porosity of the copolymer were then determined．The beads were later transformed into weakly basic anion exchange resins by the following methods：(1)The copolymer was chloromethylated and then reacted with tetraethylene-penta-amine．(2)The copolymer was nitrated and then reduced either by stannous chloride or by sodium polysulfide．From the experimental results，it was shown that the products obtained above possess higher exchange capacity，better mechanical property，and higher reaction rates for the in-troduction of ion exchange groups into the backbone structure than that obtained by the conventional method.
Beads were first prepared by the suspension copolymerization of styrene and divinyl-benzene in the presence of polystyrene．The swelling coefficient in toluene，apparent density，and percentage of porosity of the copolymer were then determined．The beads were later transformed into weakly basic anion exchange resins by the following methods：(1)The copolymer was chloromethylated and then reacted with tetraethylene-penta-amine．(2)The copolymer was nitrated and then reduced either by stannous chloride or by sodium polysulfide．From the experimental results，it was shown that the products obtained above possess higher exchange capacity，better mechanical property，and higher reaction rates for the in-troduction of ion exchange groups into the backbone structure than that obtained by the conventional method.
1965, 7(3): 193-200
Abstract:
The stereospecific polymerization of butadiene catalysed by homogeneous systems formed by combination of trialkyl aluminium with β-diketone chelates of rare earth ele-ments has been studied．It has been shown that combinations of the following rare earth chelates with triethyl aluminium could induce cis-1，4 stereospecific polymerization of butadiene： NdB3(B=benzoylacetonate)，NdB，NdBTA(BTA=benzoyltrifluoroacetonate)，NdTTA(TTA=thenoyltrifIuoroacetonate)，PrB3，PrB，PrBTA，PrTTA，YB3，YBTA，and LaBTA．These homogeneous systems appear to possess much higher catalytic activity than those of the heterogeneous systems formed by combination of triethyl aluminium with halides of lanthanons studied earlier．Up to a certain extent of catalyst concentration，the catalytic activities of these systems increase with increasing ratio of Al/chelate or chelate/butadiene (molar ratio)．The polymerization has an induction period and it is found that the rate of polymerization is of first order with respect to the monomer concentration and approximately of first order to the chelate concentration．With the NdB3-Al(C2H5)3 system．the activation energy of polymerization has been determined tO be 13.0±0.5 kcal/mole．Both polymerization rate and microstructure of polybutadiene depend upon the nature of the rare earth metal in the chelates rather than that of the ligands in various chelates，and the praseodymium and neodymium chelate systems gave higher catalytic activity．It is interesting tO note that polybutadienes obtained with these homo-geneous systems always have a 1，2-structure content less than 1％，with 1ittle or even no geI formation．The intrinsic viscosities of the polymers obtained varying from 4一5 to 1，depend on the Al/chelate and chelate/butadiene ratios．Variation in alkyl groups on the aluminium component results in a marked difference in catalytic activity．The Al(i-C4H9)3 system exhibits low activity and Al(C2H5)2Cl system is inactive．
The stereospecific polymerization of butadiene catalysed by homogeneous systems formed by combination of trialkyl aluminium with β-diketone chelates of rare earth ele-ments has been studied．It has been shown that combinations of the following rare earth chelates with triethyl aluminium could induce cis-1，4 stereospecific polymerization of butadiene： NdB3(B=benzoylacetonate)，NdB，NdBTA(BTA=benzoyltrifluoroacetonate)，NdTTA(TTA=thenoyltrifIuoroacetonate)，PrB3，PrB，PrBTA，PrTTA，YB3，YBTA，and LaBTA．These homogeneous systems appear to possess much higher catalytic activity than those of the heterogeneous systems formed by combination of triethyl aluminium with halides of lanthanons studied earlier．Up to a certain extent of catalyst concentration，the catalytic activities of these systems increase with increasing ratio of Al/chelate or chelate/butadiene (molar ratio)．The polymerization has an induction period and it is found that the rate of polymerization is of first order with respect to the monomer concentration and approximately of first order to the chelate concentration．With the NdB3-Al(C2H5)3 system．the activation energy of polymerization has been determined tO be 13.0±0.5 kcal/mole．Both polymerization rate and microstructure of polybutadiene depend upon the nature of the rare earth metal in the chelates rather than that of the ligands in various chelates，and the praseodymium and neodymium chelate systems gave higher catalytic activity．It is interesting tO note that polybutadienes obtained with these homo-geneous systems always have a 1，2-structure content less than 1％，with 1ittle or even no geI formation．The intrinsic viscosities of the polymers obtained varying from 4一5 to 1，depend on the Al/chelate and chelate/butadiene ratios．Variation in alkyl groups on the aluminium component results in a marked difference in catalytic activity．The Al(i-C4H9)3 system exhibits low activity and Al(C2H5)2Cl system is inactive．
1965, 7(3): 201-206
Abstract:
The influences of the initial monomer concentration，catalyst concentration and polymerization temperature on the molecular weight of polybutadiene have been studied．It was found that the reciprocal of degree of polymerization(DP)gave linear relation-ships with [monomer]-1，[CoCl2·C5H5N4]1-2 and [Et2AlCl]1-2． From the temperature de-pendence of DP an activation energy for the chain termination of ca．14 kcal／mole was obtained．From the studies of the effect of adding some electron—donor compounds and heptane during polymerization on the molecular weight of polymer，linear relations be-tween DP-1 and [electron-donor] or [heptane] were obtained．If the slope of these straight lines could be regarded as chain transfer coefficient,then the values obtained are 1．87，0.36，0.19，0.14 and 0.0012 for triethylamine，tetrahydrofuran，pyridine，ethylthio-ether and heptane respectively．
The influences of the initial monomer concentration，catalyst concentration and polymerization temperature on the molecular weight of polybutadiene have been studied．It was found that the reciprocal of degree of polymerization(DP)gave linear relation-ships with [monomer]-1，[CoCl2·C5H5N4]1-2 and [Et2AlCl]1-2． From the temperature de-pendence of DP an activation energy for the chain termination of ca．14 kcal／mole was obtained．From the studies of the effect of adding some electron—donor compounds and heptane during polymerization on the molecular weight of polymer，linear relations be-tween DP-1 and [electron-donor] or [heptane] were obtained．If the slope of these straight lines could be regarded as chain transfer coefficient,then the values obtained are 1．87，0.36，0.19，0.14 and 0.0012 for triethylamine，tetrahydrofuran，pyridine，ethylthio-ether and heptane respectively．
1965, 7(3): 207-210
Abstract:
A polyethylene crystal whisker has been obtained from dilute polyethylene solution in trichloroethylene. Its basic structural units are hexagonal laminar crystals. On the basis of analysis of its electron microphotograph, a structural model of this crystal whisker has been suggested. The basic structural units of this crystal whisker may be plaited and bent. It means that they are not perfect crystal lamellae.
A polyethylene crystal whisker has been obtained from dilute polyethylene solution in trichloroethylene. Its basic structural units are hexagonal laminar crystals. On the basis of analysis of its electron microphotograph, a structural model of this crystal whisker has been suggested. The basic structural units of this crystal whisker may be plaited and bent. It means that they are not perfect crystal lamellae.
1965, 7(3): 211-215
Abstract:
A micro．method for the molecular weight determination of polyamides by the end-group titration has been studied． A sample of 10—20 mg was dissolved in 4 ml of neu-tral benzyl alcohol at 120—170°and then titrated under bubbling of nitrogen with 0.02 N methanol-water solution of potassium hydroxide and hydrochloric acid．by using the syringe-micrometer type ultramicro burettes which read to 3.10-4 ml．The indicators used were phenophthaleinthymol blue (6：1) for carboxyl-group and bromophenol blue for amino-group．The anhydrous neutral benzyl alcohol may be prepared by the adsorption chromatographic method with Al2O3-CaO-NaHCO3 as adsorbents．The oxidation of benzyl alcohol to acids may be avoided in the absence of oxygen and light．
A micro．method for the molecular weight determination of polyamides by the end-group titration has been studied． A sample of 10—20 mg was dissolved in 4 ml of neu-tral benzyl alcohol at 120—170°and then titrated under bubbling of nitrogen with 0.02 N methanol-water solution of potassium hydroxide and hydrochloric acid．by using the syringe-micrometer type ultramicro burettes which read to 3.10-4 ml．The indicators used were phenophthaleinthymol blue (6：1) for carboxyl-group and bromophenol blue for amino-group．The anhydrous neutral benzyl alcohol may be prepared by the adsorption chromatographic method with Al2O3-CaO-NaHCO3 as adsorbents．The oxidation of benzyl alcohol to acids may be avoided in the absence of oxygen and light．
1965, 7(3): 216-220
Abstract:
The three theoretical molecular weight distribution functions——the Flory．Poisson and Korshak distributions------are analysed and compared on the basis of the dependence of the width index xw/xn on the extent of reaction p．The logical error associated with the Korshak distribution is readily shown． After removal of monomer and oligomers from a polycondensation system，which obey the Flory distribution，the width of the mole-cular weight distribution of the resulting polymer is much lower than the theoretical width of the Flory distribution．and is close to that of the Poisson distribution．
The three theoretical molecular weight distribution functions——the Flory．Poisson and Korshak distributions------are analysed and compared on the basis of the dependence of the width index xw/xn on the extent of reaction p．The logical error associated with the Korshak distribution is readily shown． After removal of monomer and oligomers from a polycondensation system，which obey the Flory distribution，the width of the mole-cular weight distribution of the resulting polymer is much lower than the theoretical width of the Flory distribution．and is close to that of the Poisson distribution．
