Investigating the role of chemical additives in injection molding of high-density polyethylene: mechanical, thermal, optical, and energy considerations

Abstract This study investigates the effect of three chemical additives on energy consumption during the injection molding of high-density polyethylene (HDPE). Simultaneously, the mechanical, thermal, and optical characteristics of the produced polymer molds were explored. Besides a blank HDPE sample, polymer mixtures containing anti-block masterbatch (ABM), slip masterbatch (SM), or polymer processing aid (PPA) (0.5, 1, 1.5, 1.75 and 2 wt%) were prepared. The maximum energy saving was $$\cong$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>≅</mml:mo> </mml:math> 10% (by ABM at 1.5% concentration), while SM and PPA made 8.8% and 8.5% energy saving at 1.75 wt% and 2 wt%, respectively. To evaluate the mechanical behaviors of blank and molded samples, elongation (%B), tensile strength at yield (σY), and tensile strength at break (σB) were measured. %B of the polymer was enhanced to reach its highest value (799%) by PPA 0.5 wt%. For σY, it remained relatively consistent across all samples; however, samples with the SM and ABM had lower σB than the blank sample. DSC analysis indicated that the degree of crystallinity, melting temperatures, and crystallization temperatures of the blank polymer were not affected by adding the chemical additives. When PPA was used, the whiteness index was improved. Nevertheless, the molds' optical appearance was negatively affected by ABM and SM. According to our findings, using chemical additives in the injection molding process can minimize energy consumption without degrading the polymer properties.