Photoelastic Studies of Some Polybutadiene Networks

Abstract

ABSTRACT:Two butadiene polymers were used in this investigation, one with 98.5% cis-1,4 units and the other with an approximately equibinary mixture of cis and trans units. Elastomeric networks prepared from these polymers were studied in elongation, in both the swollen and unswollen states over the temperature range -30 to 95°C. There is evidence for crystallization in these networks, particularly as manifested by marked increases in birefringence at relatively low elongations and at temperatures as high as 40°C. As expected, the birefringence and related quantities were found to be more sensitive to crystallization than the force, with the opticalconfiguration parameter and the stress-optical coefficient showing the greatest sensitivity. In the case of the cis-trans copolymer, the crystallization involves trans sequences, which are of relatively high melting point, and thus occurs at a temperature higher than for the lower melting cis sequences in the high-cis networks. The results which were free from the effects of network crystallization were used to calculate values of the temperature coefficient of the unperturbed dimensions of the chains, and values of the optical-configuration parameter. These configuration-dependent properties were found to be in satisfactory agreement with previously published theoretical results based on a rotational isomeric state model of these chain molecules.

Experimental analysis of the molecular theory of rubber elasticity

“…Values of the stress-optical parameter obtained from eq. (7) are given in the last column of Table 11. The average value is 103C = 2.86 f 0.22 (N m r~-~) -' , somewhat lower than earlier published data,7 which gave 103C = 3.35 (N m-')-'.…”

Thermoelastic and strain-birefringence studies on poly(methylphenylsiloxane) networks

“…It was chosen because it is a good solvent for the polymer and has low volatility. Its density (pd = 0.896 g/cm3 at 20 °C) and index of refraction ( = 1.4832 -4.714 X 10~4T, with T in 0 C) were taken from the literature.11, 12 Preparation of the Networks. Two networks were prepared by cross-linking the high molecular weight polymer with dicumyl peroxide (DCP).…”