摘要:

With a falling ball viscometer, measurements of the viscosity of solutions of GR–S in benzene have been made at very low rates of shear, at concentrations ranging from 10 to 19%, and at temperatures ranging from 10° to 35 °C. Within these limits, the viscosity of a solution of GR–S in benzene is given by the equation. Extrapolation, by means of this equation, to 100% polymer yields a value of 13.0 kcal. per mole for the energy of activation of flow of GR–S; this value, though of dubious antecedence, is yet of interest because it approximates that expected for GR–S on the basis of the behavior of such polymers as natural rubber and polystyrene.

ISSN:1923-4287    

DOI:10.1139/cjr48b-056

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The growth rate of polybutadiene 'popcorn' is essentially the same in butadiene liquid and vapor, is proportional to the initial weight of seed used, and increases with increased active oxygen content of the seed and with increased temperature. Traces of nitric oxide and larger amounts of benzoyl peroxide and of iodine inhibit the growth of popcorn seed. Air also inhibits the growth. Popcorn formation is initiated in butadiene by benzoyl peroxide; the rate of initiation is increased by rusty iron and water and is a function of benzoyl peroxide concentration and temperature. Studies of 'gel' formation in liquid butadiene containing benzoyl peroxide indicate that the polymerization probably proceeds by a free radical mechanism, the rate being proportional to the square root of the benzoyl peroxide concentration. The growth of polybutadiene 'popcorn' appears to take place by relatively slow reaction of monomer with free radicals formed rapidly by decomposition of hydroperoxides in the seed.

ISSN:1923-4287    

DOI:10.1139/cjr48b-057

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

Optimum conditions for the vapor phase conversion of 1,1-diphenylethane to styrene and benzene over activated Morden bentonite have been found to be a temperature of 600 °C., rapid feed rates, and the use of water vapor as diluent. Ethylbenzene has been found in the reaction products as a hydrogenation product. Styrene content has been found to be dependent directly upon vapor velocity while the conversion efficiency was found to be related directly to the use of water vapor as an inhibitor of carbon deposition on the catalyst.

ISSN:1923-4287    

DOI:10.1139/cjr48b-058

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The opalescence of ethylene has been investigated under various conditions in the region of the critical temperature. The opalescence of critical fillings increases as the temperature is lowered and passes through a maximum at the critical dispersion temperatureTs. When the system is heated the value depends upon the thermal history, both below and aboveTs. Two types of time lag curve are observed in the irreversible region, one in which the opalescence passes through a minimum and then a maximum value, and the other through a minimum only. It is believed on the basis of previous qualitative studies that violent shaking would result in reversibility with respect to changes in temperature. Once the apparent phase discontinuity has disappeared the opalescence becomes reversible as long as condensation is prevented. The opalescence of critical fillings depends upon the density and appears to be a maximum when the two phases are present in equal volumes atTs. Air and oleic acid present in small quantities depressTsbut do not appear to change the variation of opalescence with (T−Ts) whenT>Ts. These observations appear to disagree with the classical Einstein–Smoluchowski theory based on light scattering resulting from statistical fluctuations in density. This theory predicts a maximum opalescence at the classical critical temperature, which in the case of ethylene is 0.7 °C. higher thanTs. If, however, the more recent views of the nature of theP−Visotherms near the critical point are taken into account, some of the conflict disappears.

ISSN:1923-4287    

DOI:10.1139/cjr48b-059

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

not available

ISSN:1923-4287    

DOI:10.1139/cjr48b-060

出版商:NRC Research Press    

年代:1948

数据来源: NRC