Accession Number : AD0652218
Title : THE RELATIONSHIPS BETWEEN POLYMERS AND GLASS TRANSITION TEMPERATURES.
Descriptive Note : Final rept., Apr 66-Sep 66,
Corporate Author : AMERICAN CYANAMID CO STAMFORD CONN
Personal Author(s) : Lewis,O. G. ; Gallacher,L. V.
Report Date : SEP 1967
Pagination or Media Count : 34
Abstract : The Gibbs-DiMarzio theory of the glass transition in ploymers is formulated in such a way that interdependent rotations may be taken into account. Using an empirically estimated value of 0.025 for the free volume fraction at the transition temperature, the Gibbs-DiMarzio theory was fitted to empirically estimated transition temperatures for the n-alkanes, hexane to eicosane. A good fit was obtained with Epsilon-1 = 768 cal/mole for the energy difference between trans and gauche states, and gauche rotations of opposite sign excluded. The Adam-Gibbs theory of relaxation processes links the viscosity or relaxation time of a polymer to an energy barrier independent of temperature, and an independently rearranging region containing z* segments, where z* varies inversely with temperature. Values of z* calculated from the viscosity data, assuming a minimum value of k ln 2 for the configurational entropy of the critical region, were unreasonably small: one to four segments. A theory is presented by means of which z* may be calculated from (d ln tau/dP) sub T, avoiding the need for the k ln 2 assumption. The average number of backbone bonds in a single chain through the critical region may be calculated. Chains were generated on a diamond lattice using a Monte Carlo technique, and the computed chain lengths for the three polymers ranged from 10 to 17. (Author)
Descriptors : (*POLYMERS, TRANSITION TEMPERATURE), (*EPOXY RESINS, PHASE STUDIES), (*VINYL PLASTICS, PHASE STUDIES), GLASS, CHEMICAL BONDS, STEREOCHEMISTRY, THERMOCHEMISTRY, VISCOSITY, ENTROPY, MOLECULAR STRUCTURE, FREE ENERGY, POLYETHYLENE PLASTICS, HALOCARBON PLASTICS, STYRENE PLASTICS
Subject Categories : Plastics
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE