Dynamic mechanical properties of supported polymers. II. Application of the torsional braid technique to the study of the curing and stability of resins

Abstract

Abstract Transformations, physical and chemical, which occur in polymeric systems are usually accompanied by changes in rigidity. In the present method, a modified torsional pendulum is employed such that the vertical specimen shaft consists of a fabric braid which is impregnated with the polymeric material under investigation. Therefore, in principle, any changes in the mechanical properties of the composite will be reflected by changes in frequency of free oscillation of the system. This dynamic mechanical technique provides a very sensitive tool for following nondestructively, the liquid to solid transitions accompanying the curing of polymers. In this communication the utility of the torsional braid technique in the study of heat resistant polymers is emphasized. Curing and thermal softening behavior, as well as pyrolytic and oxidative degradations are monitored with precision. A comparative study between three thermosetting resins, i.e., a phenolic, an unsaturated polyester and a phosphonitrilic, is presented.