Experimental study of influence injection moulding on shrinkage material sisal-glass fiber biocomposite using response surface methodology (RSM)

Shrinkage is one of the properties of plastic materials, which the greater the shrinkage percentage value can result poor product quality and possible product defects. Therefore, it is important to know the shrinkage value of a material so that the geometry design of a product can be achieved properly. In this final project, shrinkage control is carried out by adjusting injection process parameters, until minimum shrinkage is obtained. The parameters set to control shrinkage values are melting temperature, holding pressure, and injection pressure. According to ASTM D955 to determine the shrinkage value of a material the specimen is made through the injection process. To obtain the minimum shrinkage value, an experimental design was carried out by using response surface method to reach the optimum injection process parameters with Box-Behnken parameter design. As the next step, the injection specimens which made from sisal fiber biocomposite material with composition of 80% Polypropelene, 10% MAPP, and 10% sisal fiber with injection process parameters according to the design. The injection result specimens were measured by calipers, Minitab 18 software was used to process the injection result. This result is used to determine the optimum value of the injection process parameters. Furthermore, with the optimum injection process parameters, the injection process is carried out again with the same material. The specimens obtained were measured to carry out a confirmation test, so that the minimum shrinkage value was obtained. From the statistical response surface analysis using Minitab 18 software, the optimum injection process parameters were obtained at 185⁰ C, holding pressure 35 bar and injection pressure 60 bar with shrinkage values of 1.05%.