Achieving super-tough high-density polyethylene with promising foamability using silane crosslinked polyolefin elastomer nanofibrils network

This study presents the in-situ rubber nanofibrillation of high-density polyethylene (HDPE), metallocene based polyolefin elastomer (POE) composites employing spunbond technology. The process commenced with the grafting of vinyl trimethoxy silane (VTMS) onto POE chains, a crucial step to preserve the fibrillar structure. Two distinct peroxide initiators, dicumyl peroxide (DCP) and di(t-butyl) peroxide (DTBP), were employed to initiate the grafting reaction. Results from gel content and melt flow index tests demonstrated that DTBP performed more effectively as an initiator than DCP. The grafted elastomers were then incorporated into the HDPE matrix using spunbonding. Subsequently, the fibrillated POE-g-VTMS were crosslinked using moisture to preserve the morphology. Scanning electron microscopy (SEM) images showed the generation of crosslinked nano-scale size POE-g-VTMS fibers in the range of 50–125 nm. Based on the rheological data, drawn crosslinked POE-g-VTMS phase formed an interconnected network, resulting in a remarkable increase in viscosity and storage modulus at the low-frequency range. Additionally, the stretched samples exhibited noticeable strain-hardening behavior at specific extension rates. Notably, this in-situ fibrillation process significantly enhanced HDPE's foaming ability, evident in decreased cell size and increased cell density. Tensile test results conducted at room temperature and subzero temperature (−40 °C) also suggested a substantial enhancement in the elongation at break of the HDPE nanofibrillated composites compared to the unstretched samples.