THE EXAMINATION OF WELD LINE PROPERTIES IN INJECTION MOLDED PP AND PP COMPOSITES

Abstract

In this study, the effect of weld lines occurred in injection moulded components on mechanical behaviours of PP and PP with 30% glass fiber (GF) materials has been investigated. Two types of specimens were produced; with and without weld line by using single gate and double gate moulds. The range of process temperatures was varied depending on the type of material. The mold was designed to achieve homogenous cooling with the help of Moldflow software. The bending and tensile tests were carried out on the specimens. Tensile strength of the PP and PP+30%GF specimens with weld line decreased by 11.04 and 52.81 % respectively compared to those without weld line. Bending strength of the specimens with weld line decreased by 23.88 and 41.14% for PP and PP+30%GF samples respectively. It was seen that the process temperature is an important parameter affecting weld line property and low temperatures should not be preferred. PP+30%GF samples with weld line is of higher strength than the unreinforced PP counterpart. The tensile and bending strength of PP+30%GF samples with weld line increased 40.65 % and 102.65 % respectively.