Mechanical and Linear Viscoelastic Properties of High Density Polyethylene Obtained from Tensile and Dead-Load Creep Tests.

摘要

Three grades of high density polyethylene (HDPE) are tested for tensile, creep and creep recovery, and creep properties determination. As a result of tensile tests, the materials were found to strain uniformly under constant strain rate to about 3% at 20 deg C which is well below the 12% yield point (YP). With creep tests, an attempt was made to explain and predict the effects of low loads and temperature on linear viscoelasticity (LVE) in these materials. When a creep curve plateaus (zero creep strain after a transient primary creep strain), strain recovery from the plateau is 100%. This combination of creep plateau and full recovery as another manifestation and definition of linear viscoelasticity is presented. The effort presented was only partially successful for HDPE as the creep apparatus has an error zone producing uncertain data precisely in the region where HDPE linear viscoelasticity is expected. However, from past research on the same creep apparatus, it was found that amorphous polycarbonate (PC) produces plateaus outside and above this error zone, from which full recovery occurs at strains up to 1% and stresses up to approximately 3300 psi (22.75 MPa). Keywords: Polyethylene, Mechanical properties, Linear viscoelasticity. (JES)