The effect of strain rate, temperature, and molecular mass on the tensile deformation of polyethylene

Abstract

Conventional tensile testing applied to high density polyethylene can lead to erroneous impressions of the tensile response of the material due to a local reduction in cross section of the sample. Several workers have developed novel tensile testing techniques to measure the response of a small element as it deforms. The true stress true strain curve that results describes tensile deformation of the material in a geometry‐independent manner. Here, results from previous workers, together with some of our own, are interpreted in terms of the Haward‐Thackray spring‐dashpot model, in which the spring defines a strain hardening process according to the theories of high elasticity and the dashpot describes a strain‐independent viscous process. The effects that temperature, strain rate, and molecular mass have on each process are investigated. For a pipe‐grade, modified high density ethylene copolymer, sufficient data have been measured to interpret the effects of strain rate and temperature in accordance with an Eyring flow process, where the parameters for the two mechanisms are found to be similar.

Comparative study on the deformation behavior, structural evolution, and properties of biaxially stretched high‐density polyethylene/carbon nanofiller (carbon nanotubes, graphene nanoplatelets, and carbon black) composites

“…Although both the experimental and theoretical results demonstrate that the sheet temperature increases by a few degrees during biaxial stretching, this slight increase in temperature is unlikely to influence the relaxation of polymer chains. where is the effective thermal plastic work conversion factor ( ∼ 1) , is the differential of strain , is the heat capacity of the carbon nanofiller reinforced composite, which are 2,184, 2,188, and 2,188 J/(kg K) for the HDPE/MWCNT, HDPE/GNP, and HDPE/CB composites from the mixture rule .…”

High Strain Rate Mechanics of Polymers: A Review

“…Although the strain rate at which an experiment may be considered adiabatic depends on both material properties and specimen size, for typical tests on polymers it may be of the order 0.01-1 s -1 [94]. Important studies involving the temperature rise in specimens during high rate deformation have been conducted by a number of authors [95][96][97][98][99][100][101]. A notable achievement was by Chou et al [95], who showed that the temperature rise in specimens increases significantly after yield.…”

“…Good agreement was observed between the experimentally measured temperature rise and the ''theoretical'' rise obtained by assuming that 100 % of the mechanical work is converted to heat and adiabatic conditions prevail. Hillmansen et al [98,99] studied plastic work being converted to heat by studying high density polyethylene (HDPE) and found, similarly, that the plastic work at large strains was approximately 100 % converted to heat.…”

Characterization of volume strain at large deformation under uniaxial tension in high-density polyethylene

“…Only a few workers [8][9][10][11][12] have overcome this problem by measuring in real time the cross-section area at the center of the neck by means of mechanical or optical transducers. As such, under the assumption of constant density, they were capable of deriving the response of the material within a very small representative volume element (RVE) in which stresses and strains are supposed to be nearly homogeneous.…”