Engineering Commons^™

The chemorheology of cross-linked polyethylene disulfide, polyethylene tetrasulfide, and mixtures of these polymers with elemental sulfur is investigated. It is shown that stress decay in the disulfide polymer occurs by scission of the small quantities of higher poly­sulfide linkages present in the network. It is also shown that elemental sulfur decreases the chemical relaxation time in cross-linked polyethylene disulfide in a predictable manner.

A study of network cleavage in a crosslinked poJ.yurethane elastomer was ma.de using the technique of stress relaxation. 

It was found that the data could be well represented by a sum 

of two exponential decay terms, and a theoretical explanation for this is presented. stress relaxation in the. polyurethane sample investigated is discussed in terms of the reversible cleavage 

of various linkages formed by isocyanate reactions. It is possible to identify two different decay processes and obtain activation energies for these processes. These are identified with cleavage of two different linkages. It is not possible at present to give a …