Effect of Molding Parameters on Young's Modulus of an Injection Molded Low-Density Polyethylene (LDPE)

Injection molding is a process employed worldwide to manufacture polymer parts. The final properties of the molded part largely depend on the processing conditions used during the manufacturing process. Therefore, it is necessary to develop empirical approaches that help to understand the relationship between the processing conditions and the final properties of the polymer. In this paper we study the effect of the processing conditions of the injection molding process on the Young's modulus of a low-density polyethylene (LDPE). The effect of both the barrel temperature and the mold temperature was investigated using analysis of variance (ANOVA) and the effect of the levels of each parameter was examined using the surface response methodology (SRM). The ANOVA results showed that the mold temperature is the parameter that most significantly impacts the Young's modulus, followed by the barrel temperature, while the combined interaction of both is negligible. SRM showed that the Young's modulus increases with the mold temperature and decreases with the barrel temperature. Based on the SRM, an empirical equation is proposed which can be used to predict the modulus employing only the barrel and mold temperatures. The changes in the microstructure of the injection molded part are discussed in terms of the crystallinity degree. All this was corroborated with X-ray diffraction (XRD) and differential scanning calorimetry (DSC).