Influence of Thermal Ratcheting on the Creep and Mechanical Properties of High-Density Polyethylene

Abstract

Abstract The objective of this research is to describe the consequence of thermal ratcheting on the long-term creep property of the high-density polyethylene (HDPE) material. The thermal ratcheting phenomenon increases significantly the creep strain of HDPE. The magnitude of the creep strain of HDPE increases by 8% after just 20 thermal cycles between 28 and 50 °C. The creep modulus, which is inversely proportional to the creep strain, depletes further under thermal ratcheting. Both the properties change significantly with the number of thermal cycles. The coefficient of thermal expansion (CTE) of HDPE varies with the applied compressive load, with successive thermal cycles, and with the thermal ratcheting temperature. The impact of thermal ratcheting diminishes with an increase in initial steady creep exposure time period, but still the magnitude cumulative deformation induced is noteworthy. The magnitude of growth in creep strain drops from 8% to 2.4% when thermal ratcheting is performed after 1 and 45 days of steady creep, respectively. There is a notable change in the thickness of the material with each heating and cooling cycle even after 45 days of creep; however, the thermal ratcheting strain value drops by 80% in comparison with the thermal ratcheting strain after 1 day of creep and under similar test conditions.