Test EquipmentCreep behavior of high density polyethylene under a constant true stress

We have designed a novel creep apparatus in which the external load is controlled by the transient data of the cross-sectional area of the deformed specimen to ensure that a constant stress level is maintained. The compliance curves of high density polyethylene (HDPE) on the log-time axis at different temperatures were superimposed. The Arrhenius type of time-temperature superposition was applicable to a set of HDPE sheets with different crystallinities, and the activation energy was found to be independent of the crystallinity. The creep behavior of the HDPEs was accelerated by reducing the crystallinity, and the compliance curves were superimposed by shifting the logarithm time axis to give a super-master curve.