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1965 Volume 7 Issue 4
1965, 7(4): 221-228
Abstract:
The kinetics of the polycondensation between diphenyl-dichlorosilane and bisphenol-A in equal mole ratio has been studied．As the velocity of the polvcondensation in the molten state is unstable，the kinetic order can not be evaluated．However，after dilution with solvents such as naphthalene，diphenyl ether，acetophenone，etc．to certain degree，the kinetics of the polycondensation in the initial stage followed a second order reaction． Fur- thermore，at the same temperature，the stronger is the polarity of the solvent，the greater is the reaction rate．By plotting the logarithm of rate constants in certain range of tempera-tures against the reciprocal of the absolute temperature．a linear relationship is obtained．The activation energy of the polycondensation in naphthalene，diphenyl ether， and aceto-phenone was found to be 17.1．24.8 and 10.3 kcal/mole respectively．The reaction may be catalysed bv the Lewis bases and their salts．It is assumed that the complexity of the polycondensation kinetics in the molten state is a manifestation of the changing reaction rate due to the changing polarity of the polycondensation system． An SN2 mechanism for the reaction has been suggested．
The kinetics of the polycondensation between diphenyl-dichlorosilane and bisphenol-A in equal mole ratio has been studied．As the velocity of the polvcondensation in the molten state is unstable，the kinetic order can not be evaluated．However，after dilution with solvents such as naphthalene，diphenyl ether，acetophenone，etc．to certain degree，the kinetics of the polycondensation in the initial stage followed a second order reaction． Fur- thermore，at the same temperature，the stronger is the polarity of the solvent，the greater is the reaction rate．By plotting the logarithm of rate constants in certain range of tempera-tures against the reciprocal of the absolute temperature．a linear relationship is obtained．The activation energy of the polycondensation in naphthalene，diphenyl ether， and aceto-phenone was found to be 17.1．24.8 and 10.3 kcal/mole respectively．The reaction may be catalysed bv the Lewis bases and their salts．It is assumed that the complexity of the polycondensation kinetics in the molten state is a manifestation of the changing reaction rate due to the changing polarity of the polycondensation system． An SN2 mechanism for the reaction has been suggested．
1965, 7(4): 229-234
Abstract:
The phosphonitrilochloride trimer (PNCl2)3 was synthesized．Condensation resins and molded asbestos plastics have been prepared from (PNCl2)3 and dihydric henols or (PNCl2)3 and the mixture of phenol and dihydric phenols．The oxidation decomposi-tion temperature of condensation resins was determined tO be 275—280℃．The water absorption of the molded plastics was found to be 0.37—1.0％ by weight，the flexuraI strength，482—772 kg／cm2 but impact strength only 3.00—5.25 kg-cm／cm2．The molded plastics have specific resistance to flame，and the water resistance was certainly improved，as compared to the phosphonitrilochloride polymers．
The phosphonitrilochloride trimer (PNCl2)3 was synthesized．Condensation resins and molded asbestos plastics have been prepared from (PNCl2)3 and dihydric henols or (PNCl2)3 and the mixture of phenol and dihydric phenols．The oxidation decomposi-tion temperature of condensation resins was determined tO be 275—280℃．The water absorption of the molded plastics was found to be 0.37—1.0％ by weight，the flexuraI strength，482—772 kg／cm2 but impact strength only 3.00—5.25 kg-cm／cm2．The molded plastics have specific resistance to flame，and the water resistance was certainly improved，as compared to the phosphonitrilochloride polymers．
1965, 7(4): 235-244
Abstract:
Using the fundamental equations of solar radiation received by a horizontal plane and an isolated inclined plane，we have discussed the characteristics of solar radiation incident upon the polymer specimen mounted on the exposure rack．If solar radiation is the main factor influencing the weathering of polymers，we suggest that the exposure rack should be set according to the following angles facing south in different seasons：where aM1.2，αM3.4 and αMg are the optlmum exposure angles to give the maximum rate of outdoor weathering in different seasons，and φ is the geographical latitude of the location．
Using the fundamental equations of solar radiation received by a horizontal plane and an isolated inclined plane，we have discussed the characteristics of solar radiation incident upon the polymer specimen mounted on the exposure rack．If solar radiation is the main factor influencing the weathering of polymers，we suggest that the exposure rack should be set according to the following angles facing south in different seasons：where aM1.2，αM3.4 and αMg are the optlmum exposure angles to give the maximum rate of outdoor weathering in different seasons，and φ is the geographical latitude of the location．
1965, 7(4): 245-251
Abstract:
1965, 7(4): 252-256
Abstract:
1965, 7(4): 257-259
Abstract:
The influence of pH on the copolymerization of acrylonitrile with acrylamide (85: 15) in 52% NaSCN solution at 60±0.1℃, initiated by azobisisobutylnitrile has been studied. It was found that the polymerization rate decreases both at low and high pH values of the copolymerization system. The intrinsic viscosity of copolymer increased with increasing pH of the polymerization medium.
The influence of pH on the copolymerization of acrylonitrile with acrylamide (85: 15) in 52% NaSCN solution at 60±0.1℃, initiated by azobisisobutylnitrile has been studied. It was found that the polymerization rate decreases both at low and high pH values of the copolymerization system. The intrinsic viscosity of copolymer increased with increasing pH of the polymerization medium.
1965, 7(4): 260-263
Abstract:
A suitable procedure for the determination of molecular weight distribution of vinyl chloride-acrylonitrile copolymer by the gradient elution method has been worked out. Good results were obtained under the following conditions: solvent-precipitant system: ac-etone-methanol; temperature gradient: 2-40℃; flow rate: 20 ml/hr; charge of polymer: 0.6 g/25 g glass beads.
A suitable procedure for the determination of molecular weight distribution of vinyl chloride-acrylonitrile copolymer by the gradient elution method has been worked out. Good results were obtained under the following conditions: solvent-precipitant system: ac-etone-methanol; temperature gradient: 2-40℃; flow rate: 20 ml/hr; charge of polymer: 0.6 g/25 g glass beads.
1965, 7(4): 264-267
Abstract:
The kinetics of crystallization of undrawn and drawn (300%) polyethylene tereph-thalate fibres has been studied dilatometrically. The experimental curves conform to Avrami's equation, with n equal to 2.8 and 1.2 for the undrawn and drawn fibres respectively. The crystallization rate is significantly decreased by stretching and the rate is slower, the greater is the molecular chain orientation in the fibre.
The kinetics of crystallization of undrawn and drawn (300%) polyethylene tereph-thalate fibres has been studied dilatometrically. The experimental curves conform to Avrami's equation, with n equal to 2.8 and 1.2 for the undrawn and drawn fibres respectively. The crystallization rate is significantly decreased by stretching and the rate is slower, the greater is the molecular chain orientation in the fibre.
