A Study on the Characteristics at Low Temperature of Welded Polyethlene

Abstract

This paper describes an experimental study on the characteristics at low temperature of welded low density polyethylene. The results of some measurements on the mechanical properties, fracture surfaces, X-ray diffraction patterns and electron spin resonance spectra are reported and discussed.
This study intends to clarify the low temperature characteristics of weld comparing with those of base material, and to discuss the change in mechanical properties from room temperature down to the neighborhood of -70°C and fracture in low temperature experiment from a microscopic view point. Nothc and load velocity effects on the brittle fracture tendency are also discussed. Testing materials were low density polyethylene board of 2mm. in thickness, and tests were carried out at low temperature of methyl alchohol and dry ice. A heat plate welding apparatus, with which specimens could be secured under fixed contact force, was made in order to carry out the experiment of welding.
The following summary can be made of the experimental results. Tendency of low temperature characteristics of the welded material is generally similar to that of the base material, except that a change occurs at -60°C.
Effect of load evlocity is observed both on the base and the welded materials, and this effect becomes great when the temperature is low and load velocity is high. Notch effect is also obsrved both on the base and the welded materials, and this effect appears great with the welded material under the temperature of below -40°C. Correlations are observed between fractured surface and mechanical testing results, as well as between X-ray diffraction pattern and mechanical testing results. No formation of non-coupling electron by welding is observed from electron spin resonance spectrogram.