A rapid method for determining the degree of crosslinking in elastomers is described which involves measuring equilibrium compression modulus at very small deformations on solvent‐swollen samples. The elastomer used was a polyether urethane vulcanized by an accelerated sulfur recipe. The degree of crosslinking as measured by the compression method agreed with that measured by the extension method within 1–3%. Both methods agreed reasonably well with the theoretical values calculated from the sulfur level, polymer molecular weight, and crosslink structure.

No abstract

No abstract

No abstract

The present work was undertaken to assess the effect of crosslink structure on the properties of an elastic network derived from a linear polyetherurethane elastomer. In order to study this effect, a polyetherurethane was synthesized which contained two types of reactive sites suitable for establishing crosslinks : pendant hydroxyl groups for reaction with diisocyanate curatives and pendant double bonds for vulcanization with sulfur. Incorporation of both types of curing sites within the same linear polymer served to hold constant variables which might otherwise influence vulcanizate properties. Thus, the elastic networks formed by both curing systems were produced from the same polymer, and such factors as polymer molecular weight and molecular weight distribution, interchain forces and cure site distribution remained constant. Furthermore, the curing sites have been placed on pendant groups well removed from the main polymer chain in order to avoid degradation of the polymer by side reactions which may accompany sulfur vulcanization.It is recognized that common elastomers with internal unsaturation, such as SBR and natural rubber, can be crosslinked by more than one method (e.g., with sulfur, peroxides, or high energy radiation), but the extent and nature of side reactions which may occur is not known with certainty. There are possibilities of polymer degradation reactions with all of these curing systems, and the occurence of such degradation reactions would cloud any conclusions concerning the relation between crosslink structure and vulcanizate properties.Polyetherurethane I was synthesized for the present study : n n