Injection molding is extensively used for mass production of plastic products. Over the years, the plastic products have been manufactured in a variety of colors, materials and mechanical properties to fulfill the market demand. The purpose of this study is to identify the relation between the color of resin and the product quality. To proceed this study, different colored PBT specimens have injection molded, and mechanical properties were compared. Tensile tests and bending tests have carried out to study mechanical properties of the specimens, and differentials have occurred in tensile strength, bending strength and tensile elongation by their respective color. And the red specimens were broken during the bending test. The experimental results reveal that the color of the resin influences the mechanical strength of the injection molded product. As a result, the color of resin should be considered when setting parameters for injection molding in order to improve the product quality.

Due to the development of plastic materials, injection molding products are limitlessly used. The colours of the plastic material also, have been developed to meet the needs of customers. The purpose of the present study is to verify the shrinkage of the injection-molded PC and PBT specimens in different colours. In this study, red, white, black and transparent colours were selected for PC resin. Also blue, red and black colours were selected for PBT resin. 50 specimens were produced per each colour, and measured after cooling-off. The P-value, the test statistic of the measurements in every direction of PC and PBT specimens were below 0.05 except the PBT specimen’s thickness. The rate of shrinkage for the length and thickness of PC specimens were 0.48% and 3.9% that obtained 4.4 times as big as the gap those between those two rates. The shrinkage in PBT were about 1.45% for the length and 5.08% for the thickness which had 3.6 times as big as the gap. This experimental results obtained that the colour of the resin (PC and PBT) effects its shrinkage. Consequently, the colour of the resin must be concerned in the event of injection-molding.