A Study on the Characteristics at Low Temperature of Polyamide

Abstract

This paper describes an experimental study on the characteristics at low temperature of welded polyamide (Nylon-6). The results of some measurements on the mechanical properties, fracture surfaces and X-ray diffraction pattern 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 viewpoint.
Notch and load velocity effects on the brittle fracture tendency are also discussed. Testing materials were polyamide board of 2 mm in thickness, and tests were carried out at low temperature of methylalcohol 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.
(1) Welded parts of polyamide must be used very carefully in low temperature atmosphere.
(2) Low temperature characteristics of welded parts are different from those of parents in polyamide.
(3) Effects of load velocity and notch are observed both on the basic and welded parts of polyamide in low temperature atmosphere, and brittleness becomes great.
(4) Low temperature characteristics on welded parts of polyamide are considerably refined if welding is conducted under the condition below 2.0% water contents.
(5) Correlations are observed between fractured surface and mechanical testing results, as well as between X-ray diffraction pattern and mechanical testing results.