Otimização do processo de moldagem por injeção do ABS via metodos estatisticos

Abstract

Injection molding is one of the most versatile and widely used processes in the manufacture of polymers. However, there is an incidence of so many factors that tend to influence the process, to the point that strict control of the process parameters is necessary to obtain pieces with adequate quality level. In this study, the relationships between process conditions, microstructure and properties for acrylonitrile-butadiene-styrene (ABS) polymer were evaluated. To do this, ABS was injected under 9 conditions, varying important injection parameters: melt temperature (between 210 and 240 ºC), mold temperature (45-65 ºC), compression pressure (150-250 bar) and injection rate (50-110 cm 3 / s). From the results of the mechanical properties obtained (Resistance under Traction, Impact Resistance, Elastic Modulus and Maximum Force under Impact), 3 prediction models were developed, determined by the Taguchi Method, Response Surface and Linear Regression, with the Taguchi Method was more effective. From the prediction models four different injection conditions of the orthogonal matrix were chosen, in order to verify the accuracy of the models created. The microstructure was evaluated by Scanning Electron Microscopy (SEM) of fractured samples by instrumented impact and by the measurement of the elastomeric domains (distribution of the polybutadiene size) through image analysis. Finally, the thermal treatment of stress relief was applied, the mechanical properties were determined and finally compared between the presence and absence of heat treatment, where it was observed that no considerable effect was observed.