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영어

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.