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).
Al-43.5Zn-1.5Si (wt%) alloys are widely used as coatings on steel substrates. This kind of coatings is manufactured by hot-dip process, in which Si is added as solid particles or master alloy. The role of Si during formation of the coating is to control the metallurgical reactions between solid steel and liquid Al-Zn-Si alloy initially forming an AlZnFeSi intermetallic layer and next the excess of Si forms intermetallic compounds, which grows over this alloy layer, segregates into the Zn rich interdendritic regions, and solidifies as eutectic reaction product as massive particles with needle like morphology. Therefore, during the experimental procedure is very difficult to control the final morphology and distribution of the silicon phase. The acicular morphology of this phase greatly affects the mechanical properties of the alloy because it acts as stress concentrators. When the coated steel sheet is subjected to bending, the coating presents huge cracks due to the presence of silicon phase. Therefore, the aim of the paper was to propose a new methodology to control the silicon phase through its addition to Al-Zn alloy as nanocomposite and additionally determine the effect of cooling rate (between 10 and 50°Cs−1) on the solidification microstructure and mechanical properties of Al-Zn alloy.
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