Influence of strain rate, temperature and humidity on the tensile yield behaviour of aliphatic polyketone

The tensile yield behaviour of an aliphatic polyketone is studied in relati on to the molecular relaxation processes present in the polymer. Dynamic me chanical thermal analysis reveals the presence of three molecular relaxatio n mechanisms; the crystalline alpha-, and the amorphous beta- and, gamma-pr ocess. The tensile yield behaviour, measured over a large range of temperat ure and strain rate, also gives evidence of these three relaxation mechanis ms. The increase of the water content from 0.5 to 2.3 wt% leads to a select ive change in the beta-contribution, whereas the alpha- and gamma-processes show little to no change. With respect to the tensile yield behaviour this leads to a reduction of the yield stress at high strain rates and/or low t emperatures. (C) 1999 Elsevier Science Ltd. All rights reserved.