Abstract
A report is given of some investigations of the mechanical behavior of high polymers under deformations of different time function, type, and magnitude. For a plasticized polyvinyl chloride the time‐dependent Young's modulus and the time‐dependent extension compliance were measured in the main relaxation region of the material. The relation between these two characteristic quantities given by the theory of viscoelasticity could be confirmed by using a simple approximation formula. The stress relation behavior of polystyrene under longitudinal and torsional strain was measured. From the corresponding time‐dependent moduli the Poisson ratio was calculated by use of the classical relationship and another one given by Schwarzl. Both calculations agree and give the expected monotonic increase of the Poisson ratio from 0.33 to 0.5 for the transition from the brittle to the rubbery state of the material. The relaxation behavior at larger extensions was investigated on polyethylenes of different crystallinities and on vulcanized rubbers having different filler contents. In the case of the filled rubbers measurements were carried out at strains up to 700%. For both series of materials the effects of strain and time were found to be factorable. In the case of the polyethylenes an appropriate strain function was developed on the basis of the Mooney‐Rivlin theory. For the filled rubbers the stress–strain equations given in literature are insufficient if the whole range of deformations is considered. An appropriate empirical function is given.