Publication: Effect of benzoyl peroxide on the morphological, thermal, and mechanical properties of recycled high density polyethylene / recycled polyproplene blends
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Date
2025-08-04
Authors
Soh, Jee Von
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Abstract
The recycled High-Density Polyethylene (rHDPE) and recycled Polypropylene (rPP) are challenging due to their inherent immiscibility, which leads to poor interfacial adhesion. This study explores the use of benzoyl peroxide (BPO) as an in situ reactive compatibilizer to enhance these recycled blends. The primary objectives were to evaluate the effect of BPO on the blend's phase morphology, thermal properties, and mechanical performance. Scanning Electron Microscopy (DSC) analysis shows that BPO refined the phase structure by reducing dispersed domain sizes and improving interfacial adhesion, with 0.5 wt.% BPO generally provides the most homogeneous morphology for most blends. Differential Scanning Calorimetry analysis shows the blend's immiscibility, with distinct melting peaks for rHDPE and rPP across all compositions. Thermogravimetric Analysis (TGA) revealed that while BPO could enhance stability in some blends, it significantly decreased the thermal stability of PP-rich blends, indicating that peroxide-induced chain scission of the rPP matrix was a dominant and detrimental effect. In HDPE-rich blends, BPO induced
extensive cross-linking, causing a dramatic increase in ductility. Conversely, in PP- rich blends, BPO-induced matrix degradation caused tensile strength to decrease before recovering. Impact strength showed the most significant improvement in PP- rich blends, increasing steadily with BPO concentration. The final properties depend on the balance between grafting at the interface, cross-linking of HDPE, and degradation of PP. So, the best blend depends on the HDPE and PP ratio and which property to improve.