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

Abstract

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).

Chemical, Thermal and Physical Characterization of Inulin for its Technological Application Based on the Degree of Polymerization

“…Evidently, this was a crystallization effect caused by the amount of adsorbed water. The presence of these melting endotherms observed for both inulin powders is related with the presence of crystals differing in perfection, where crystals with different morphology and size show a different thermal behavior (Dan et al 2009;Ronkart et al 2009a,b;Leyva-Porras et al 2013;Hijo et al 2014). This suggested the melting (T m1 ) of the secondary small crystal entities (developed at higher water activities), and the melting (T m2 ) of the primary large crystal entities (developed at low water activities).…”

“…Now, when high DP inulin adsorbed more water from the environment reaching a water activity of 0.69, the moisture content increased to a value of about 10 g of water while the T g lowered to 219C. Despite the storage room temperature, at these conditions, inulin was already crystallized and some undesired characteristics such as stickiness, agglomeration and change in color may occur in the inulin powder (Leyva-Porras et al 2015). Unlike the high DP inulin, low DP inulin presented a moderated phase change.…”

“…Nowadays inulin is widely employed as an ingredient in commercial products where its presence is commonly unnoticed (Franco et al 2015): it is used as excipient in tablets, adjuvant in vaccines and encapsulating material for a variety of bioactive products in the pharmaceutical industry, as chelating agent and in the prevention of scales formation in pipes and equipment in the chemical industry, and as an ingredient in the development of healthy products in food industry (Pintor et al 2014;S anchez-S aenz et al 2010). The range of potential applications has increased due to the good acceptance of the functional products in the market, these products offer additional benefits such as natural prebiotic, dietary fiber, stabilizer, fat substitute and as texture modifier (Mancilla-Margalli and L opez 2006;Robert et al 2006;Pop et al 2015). The application field of inulin largely depends on the initial physical properties such as crystallinity, water adsorption and degree of polymerization (DP).…”

“…Several authors have reported different state diagrams for sugar-rich systems such as dehydrated fruits and fruit powders: Bai et al (2001); Fabra et al (2009);Jaya and Das (2009);Khalloufi et al (2000); Moraga et al (2004Moraga et al ( , 2006; S a and Sereno (1994); Sobral et al (1994); Sobral (2009, 2001); Tonon et al (1989); Wang et al (1999); Welti-Chanes et al (2008). Recently, Leyva-Porras et al (2015) reported the state diagrams for inulin and inulin-orange juice, including other aspects such as water content, microstructure and particle morphology. They proposed the use of these diagrams for the prediction of the optimal storage conditions of inulin-based systems.…”

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

“…Hence, a smaller P ‐value leads to a larger confidence in the data . According to Leyva‐Porras et al ., data obtained from DSC experiment may show small difference, however it can be confirmed by XRD results. It can then be concluded that increasing the molding temperature and pressure, while decreasing the cooling rates, leads to higher melting points.…”