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1964 Volume 6 Issue 2
1964, 6(2): 87-94
Abstract:
In this work，the systems of cobalt compounds-aluminum alkyls were used in the polymerization of butadiene to study the catalytic acdvity and the microstructure of the polymers．The results showed： (1) The catalytic system of cobalt complex of the outer orbital type,such as CoX2Py，(RC00)2CoPy，cobalt acetylacetonate，etc．with (i-C4H9)2AlCl，(C2H5)2AlCl and (C2H5)2AlBr，is highly active for polymerizing butadiene；however，it can not form a stereospecific catalyst with(C2H5)2AlI．The content of cis-1，4-structure is higher then 92％． (2) The activity of the system of inner orbital type cobalt complex with (i-C4H9)2AlCl，(C2H5)2AlCl，and (C2H5)2AlBr is lower than the outer orbital type,but the catalyst has nO remarkable eftect oil the microstructure of poly-mers． (3) The order of the substituent halogen in R2AlX for increasing average mole-culer weight of the polymer products is Cl>Br>I． (4) At a definite mole ratio of H2O：(i-C4H9)3Al or C2H5AlCl2 it forms with CoCl2·4C5H5N a highly active stereo-specific catalyst for the polymerization of butadiene．The results were analysed and dis-cussed．
In this work，the systems of cobalt compounds-aluminum alkyls were used in the polymerization of butadiene to study the catalytic acdvity and the microstructure of the polymers．The results showed： (1) The catalytic system of cobalt complex of the outer orbital type,such as CoX2Py，(RC00)2CoPy，cobalt acetylacetonate，etc．with (i-C4H9)2AlCl，(C2H5)2AlCl and (C2H5)2AlBr，is highly active for polymerizing butadiene；however，it can not form a stereospecific catalyst with(C2H5)2AlI．The content of cis-1，4-structure is higher then 92％． (2) The activity of the system of inner orbital type cobalt complex with (i-C4H9)2AlCl，(C2H5)2AlCl，and (C2H5)2AlBr is lower than the outer orbital type,but the catalyst has nO remarkable eftect oil the microstructure of poly-mers． (3) The order of the substituent halogen in R2AlX for increasing average mole-culer weight of the polymer products is Cl>Br>I． (4) At a definite mole ratio of H2O：(i-C4H9)3Al or C2H5AlCl2 it forms with CoCl2·4C5H5N a highly active stereo-specific catalyst for the polymerization of butadiene．The results were analysed and dis-cussed．
1964, 6(2): 95-102
Abstract:
The curing process of epoxy resin with maleic anhydride has been examined with infrared spectroscopy，by following the functional group changes occuring in different curing stages at different temperatures． It has been found that the increase of mole-cular weight and the formation of cross—linkages in the epoxy resin are attained primarily via the esterification reaction，that is，the anhydride first reacts with the hydroxyl group in the resin to form a mono—ester and the newly formed carboxylic group reacts with an epoxy group to give a diester and a new hydroxyl group which can itself react with the anhydride． Under the influence of heat，the maleate structure formed in the esterifica-tion tends to isomerize into fumarate．This cis．trans isomerization reaction is tempera-turc-sensitive,but the extent of reaction is not appreciable below 60℃． At a curing temperature of 180℃ or higher。the carbon-carbon doubl~bonds in the maleate structures may undergo addition polymerization and thermal oxidation，resulting in the formation of new carbonyl and hydroxyl groups．
The curing process of epoxy resin with maleic anhydride has been examined with infrared spectroscopy，by following the functional group changes occuring in different curing stages at different temperatures． It has been found that the increase of mole-cular weight and the formation of cross—linkages in the epoxy resin are attained primarily via the esterification reaction，that is，the anhydride first reacts with the hydroxyl group in the resin to form a mono—ester and the newly formed carboxylic group reacts with an epoxy group to give a diester and a new hydroxyl group which can itself react with the anhydride． Under the influence of heat，the maleate structure formed in the esterifica-tion tends to isomerize into fumarate．This cis．trans isomerization reaction is tempera-turc-sensitive,but the extent of reaction is not appreciable below 60℃． At a curing temperature of 180℃ or higher。the carbon-carbon doubl~bonds in the maleate structures may undergo addition polymerization and thermal oxidation，resulting in the formation of new carbonyl and hydroxyl groups．
1964, 6(2): 103-107
Abstract:
The dynamic mechanical properties of epoxy resins cured with maleic anhydride have been studied over the 25—250℃ temperature region using a vibrating reed method．The temperature dependence of Young’S modulus and the internal fric-tion for the cured epoxy resin is typical for a slightly crosslinked polymer． A pronounced dispersion rigion is noted near 150℃ (which varies with the degree of cure)，and is accompained by a prominent drop in Young’S modulus in this region．The loss peak is due to the glass transition in the epoxy resin network since above this temperature the specimens exhibit a rubberlike behaviour． Results presented here agree well with those of other investigators．However．the glass transition temperature deter-mined bv internal friction peak is much higher than that determined from the thermo-mechanical curves by Kargin et al.，this difference suggests that the external force applied during a thermo-mechanical curve determination may produce certain mechano-chemical effects in the epoxy resin network．Experimental data obtained on the relation between the degree of crosslinking and the glass transition temperature are given and discussed．
The dynamic mechanical properties of epoxy resins cured with maleic anhydride have been studied over the 25—250℃ temperature region using a vibrating reed method．The temperature dependence of Young’S modulus and the internal fric-tion for the cured epoxy resin is typical for a slightly crosslinked polymer． A pronounced dispersion rigion is noted near 150℃ (which varies with the degree of cure)，and is accompained by a prominent drop in Young’S modulus in this region．The loss peak is due to the glass transition in the epoxy resin network since above this temperature the specimens exhibit a rubberlike behaviour． Results presented here agree well with those of other investigators．However．the glass transition temperature deter-mined bv internal friction peak is much higher than that determined from the thermo-mechanical curves by Kargin et al.，this difference suggests that the external force applied during a thermo-mechanical curve determination may produce certain mechano-chemical effects in the epoxy resin network．Experimental data obtained on the relation between the degree of crosslinking and the glass transition temperature are given and discussed．
1964, 6(2): 108-116
Abstract:
Effects of peregal O，sodium oleyl sulphate，sulphated castor oil，sodium methylene dinaphthyl sulphonate and casein on the structure and mechanical properties of natural rubber latex film have been studied．Experimental results show that the addition of stabilizer between 0.25—1.00 phr．at room temperature decreased the swelling in water。the amount of water extracts and the dielectric loss tangent to attain a minimum，but at the same time improved the mechanical properties and the shrinkage of the film to attain a maximum．By further increasing the film—forming temperature，the thermal movement as well as the increased solubility of stabilizer in the rubber caused the tight linking of the latex’globules which decreased the swelling as well as improved the mechanical properties．On further vulcanizing the film it caused a little decrease in the swelling due to rapid crosslinking of the rubber molecules． It is suggested that the appearance of maximum or minimum on the property—stabilizer content curves is connected wich the stability of the latex and the solubility of the stabilizer in the rubber．
Effects of peregal O，sodium oleyl sulphate，sulphated castor oil，sodium methylene dinaphthyl sulphonate and casein on the structure and mechanical properties of natural rubber latex film have been studied．Experimental results show that the addition of stabilizer between 0.25—1.00 phr．at room temperature decreased the swelling in water。the amount of water extracts and the dielectric loss tangent to attain a minimum，but at the same time improved the mechanical properties and the shrinkage of the film to attain a maximum．By further increasing the film—forming temperature，the thermal movement as well as the increased solubility of stabilizer in the rubber caused the tight linking of the latex’globules which decreased the swelling as well as improved the mechanical properties．On further vulcanizing the film it caused a little decrease in the swelling due to rapid crosslinking of the rubber molecules． It is suggested that the appearance of maximum or minimum on the property—stabilizer content curves is connected wich the stability of the latex and the solubility of the stabilizer in the rubber．
1964, 6(2): 117-123
Abstract:
The sound velocity in a fibre shows a pronounced anisotropy，that is，the sound velo-city along the axis of an oriented fibre is much greater than that perpendicular to it，and therefore it may be used as a measure of the molecular orientation a in the fibre， α=1-C2u-C2 where C and Cu are velocities of sound along an oriented fibre and a completely un-oriented fibre respectively．The apparatus used consisted of a pulse generator which sends a pulse of 70~tsec duration with a repetition frequency of 100 times per second to the moving coil of a loud speaker．The fibre was coupled to the vibrating membrane through a spring clamp．When exited by the pulse，the system underwent damped oscillation with a natural frequency of about 4000 Hz．At the other end of the fibre，about 200 cm from the clamp，a crystal pick-up was located，the output of which was sent to an oscilloscope with the sweep circuit triggered by the pulse voltage．The time of propagation of the longitudinal vibration along the fibre from the clamp to the pick-up was observed from the oscilloscope record，and the sound velocity in．the fibre calculated． Since the mechanical properties of fibre depend considerably on the moisture regain and tension，the effect of relative humidity and tension in the fibre on the sound velocity were studied．The best choice of the experimental conditions for the determination of molecular orientation by the sound velocity method appears to be the following：room tempera-ture，28—30℃；relative humidity，60％；and under a tension somewhat below the cri-tical Young’s modulus of the fibre．The sound velocities in the fibres of different draw ratios (r) were determined and extrapolated to r=1 to give the value for Gu Experimental results indicate that the degree of molecular orientation of monofils of Nylon 6 increases to approximately 80％ after drawing and after-treatment．The degree of orientation for several products of Nylon 6 fibre such as yarns，mono-fils，and cords was determined．Fibres that possess greater breaking length show higher degree of orientation．
The sound velocity in a fibre shows a pronounced anisotropy，that is，the sound velo-city along the axis of an oriented fibre is much greater than that perpendicular to it，and therefore it may be used as a measure of the molecular orientation a in the fibre， α=1-C2u-C2 where C and Cu are velocities of sound along an oriented fibre and a completely un-oriented fibre respectively．The apparatus used consisted of a pulse generator which sends a pulse of 70~tsec duration with a repetition frequency of 100 times per second to the moving coil of a loud speaker．The fibre was coupled to the vibrating membrane through a spring clamp．When exited by the pulse，the system underwent damped oscillation with a natural frequency of about 4000 Hz．At the other end of the fibre，about 200 cm from the clamp，a crystal pick-up was located，the output of which was sent to an oscilloscope with the sweep circuit triggered by the pulse voltage．The time of propagation of the longitudinal vibration along the fibre from the clamp to the pick-up was observed from the oscilloscope record，and the sound velocity in．the fibre calculated． Since the mechanical properties of fibre depend considerably on the moisture regain and tension，the effect of relative humidity and tension in the fibre on the sound velocity were studied．The best choice of the experimental conditions for the determination of molecular orientation by the sound velocity method appears to be the following：room tempera-ture，28—30℃；relative humidity，60％；and under a tension somewhat below the cri-tical Young’s modulus of the fibre．The sound velocities in the fibres of different draw ratios (r) were determined and extrapolated to r=1 to give the value for Gu Experimental results indicate that the degree of molecular orientation of monofils of Nylon 6 increases to approximately 80％ after drawing and after-treatment．The degree of orientation for several products of Nylon 6 fibre such as yarns，mono-fils，and cords was determined．Fibres that possess greater breaking length show higher degree of orientation．
1964, 6(2): 124-129
Abstract:
A simple and general method for evaluating the condition of gelation for three dimensional polycondensation and copolycondensation reactions is presented. By reasonable development of Flory's method, the author suggested a new concept for the critical condition of gelation, namely, that the probability for a central branch point to be connected to themselves attains unity. According to this concept without referring to the molecular size distribution function, equations for the gel point for various generalized reaction types were obtained,which include almost all types of reactions encountered in practce. The results previously obtained by other authors appear as special cases of this paper.
A simple and general method for evaluating the condition of gelation for three dimensional polycondensation and copolycondensation reactions is presented. By reasonable development of Flory's method, the author suggested a new concept for the critical condition of gelation, namely, that the probability for a central branch point to be connected to themselves attains unity. According to this concept without referring to the molecular size distribution function, equations for the gel point for various generalized reaction types were obtained,which include almost all types of reactions encountered in practce. The results previously obtained by other authors appear as special cases of this paper.
1964, 6(2): 138-141
Abstract:
Based on Charlesby's definition of the sol quantity, the parameters for the internal structure of the cross-linking polymer were calculated for the cases of the initial molecular weight distribution of Flory and of Schulz type. The sol portion should give no contributions to the swelling and the equilibrium elastic modulus of the cross-linked sample, and the free chain ends of the gel molecules should be taken into consideration. Revised formulae for the swelling and the elastic properties of cross-linked polymers are presented.
Based on Charlesby's definition of the sol quantity, the parameters for the internal structure of the cross-linking polymer were calculated for the cases of the initial molecular weight distribution of Flory and of Schulz type. The sol portion should give no contributions to the swelling and the equilibrium elastic modulus of the cross-linked sample, and the free chain ends of the gel molecules should be taken into consideration. Revised formulae for the swelling and the elastic properties of cross-linked polymers are presented.
1964, 6(2): 142-144
Abstract:
Dimethyldichlorosilane (55.14-55.31% Cl) was hydrolysed continuously with 8% aqueous hydrochloric acid and the hydrolysate product (a mixture of siloxanes) was cracked continuously with a preformed solution of potassium silanolate under reduced pressure (10-20mm Hg). By this means the fraction of octamethylcyclotetrasiloxane was obtained in 92-96% yield (based on dimethyldichlorosilane). The cracking conditions were discussed.
Dimethyldichlorosilane (55.14-55.31% Cl) was hydrolysed continuously with 8% aqueous hydrochloric acid and the hydrolysate product (a mixture of siloxanes) was cracked continuously with a preformed solution of potassium silanolate under reduced pressure (10-20mm Hg). By this means the fraction of octamethylcyclotetrasiloxane was obtained in 92-96% yield (based on dimethyldichlorosilane). The cracking conditions were discussed.
1964, 6(2): 145-147
Abstract:
A method of preparation of 2-furoic acid 2-furylcarbinol cation exchange resin in bead form is described.The strength, exchange properties, and decolori2ing abilities of the resin were studied.
A method of preparation of 2-furoic acid 2-furylcarbinol cation exchange resin in bead form is described.The strength, exchange properties, and decolori2ing abilities of the resin were studied.
1964, 6(2): 148-152
Abstract:
Vinyl ferrocene (Ⅰ), acryloyl ferrocene (ferrocenyJ vinyl ketone) (Ⅱ), trans-cinnamyl ferrocene (Ⅲ), and furylacryloyl ferrocene (Ⅳ) were synthesized, among which (Ⅳ) was unknown in literature, (Ⅰ) and (Ⅱ) could be homopolymerized and copolymerized with styrene and methyl methacrylate using ABN as initiator, (Ⅲ) and (Ⅳ) could not be homopolymerized, but could be copolymerized with styrene or methyl methacrylate.
Vinyl ferrocene (Ⅰ), acryloyl ferrocene (ferrocenyJ vinyl ketone) (Ⅱ), trans-cinnamyl ferrocene (Ⅲ), and furylacryloyl ferrocene (Ⅳ) were synthesized, among which (Ⅳ) was unknown in literature, (Ⅰ) and (Ⅱ) could be homopolymerized and copolymerized with styrene and methyl methacrylate using ABN as initiator, (Ⅲ) and (Ⅳ) could not be homopolymerized, but could be copolymerized with styrene or methyl methacrylate.
1964, 6(2): 153-158
Abstract:
The kinetics of pyrolysis of two epoxide resins，hardened by maleic anhydride and by triethylenetetraamine，were studied by thermo—gravimetry．A comparison of various methods isothermal and non-isothermal thermo-gravime-try shows that the non-isothermal method gave sufficiently accurate kinetic data，as the isothermal method．The non-isothermal method is less time consuming and probably gives more representative values for the whole heating range．Kinetic data of isomerization of epoxy-groups have been obtained by differential thermal analysis．Useful informations about the chemical changes thking place in the heating process of epoxide resins can be obtained by ioint use of non-isothermal thermo-gravimetry，dif-ferential thermal analysis and thermo—mechanical methods．
The kinetics of pyrolysis of two epoxide resins，hardened by maleic anhydride and by triethylenetetraamine，were studied by thermo—gravimetry．A comparison of various methods isothermal and non-isothermal thermo-gravime-try shows that the non-isothermal method gave sufficiently accurate kinetic data，as the isothermal method．The non-isothermal method is less time consuming and probably gives more representative values for the whole heating range．Kinetic data of isomerization of epoxy-groups have been obtained by differential thermal analysis．Useful informations about the chemical changes thking place in the heating process of epoxide resins can be obtained by ioint use of non-isothermal thermo-gravimetry，dif-ferential thermal analysis and thermo—mechanical methods．
