Time–humidity superposition in some crystalline polymers

Abstract In order to verify precisely the applicability and reasonableness of the time–humidity superposition method to hydrophilic crystalline polymers, stress relaxation measurements were carried out with films of polyvinyl alcohol and nylon 6 by means of a table model Instron Tensile Tester equipped with a special glass cell to control temperature and humidity. In the case of PVA, only the time–humidity superposition is applicable at humidities higher than that at which the transition begins. For nylon 6, on the other hand, time–temperature and time–humidity superposition apply very well in the transition region and fairly well at higher temperatures and humidities. The results obtained by both the superpositions coincide very well, showing the time–humidity superposition is as reasonable as the time–temperature one. The superposed results were also compared with other existing data, and the reasonableness of the time–humidity superposition was confirmed.