Phase change materials based on polyethylene, paraffin wax and wood flour
Mngomezulu, Mfiso Emmanuel
MetadataShow full item record
Phase change material (PCM) composites based on high-density polyethylene (HDPE) with soft (M3) and hard (H1) Fischer-Tropsch paraffin waxes and alkali-treated wood flour (WF) were investigated in this study. Both the blends and composites were prepared using a meltmixing method with a Brabender-Plastograph. SEM, DSC, TGA, DMA, tensile testing and water absorption were used to characterize the structure and properties of the blends and composites. The HDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (HDPE) is a necessary property for effective energy storage. M3 wax blends were immiscible, whereas H1 wax blends seemed to be partially miscible and cocrystallized with the polymer matrix. In the presence of WF, the wax seems to crystallize around and in the pores of the WF particles, thus reducing co-crystallization with the HDPE and improving the energy storage capacity. TGA results showed a reduction in the thermal stabilities of the blends and composites in the presence of both WF and waxes. The storage modulus was reduced in the presence of wax, but improved when both WF and wax are present, although the improvement was less significant in the case of the M3 wax. Depending on the type of wax, the γ- and α-transitions were influenced differently, and there was an emergence of a β-relaxation in the case of the M3 wax blends. Both waxes had different influences on the tensile modulus and strength of the blends, with H1 increasing and M3 decreasing these properties. The PCM composites, on the other hand, had high moduli. High content of WF in the composites showed high water absorption. However, in the wax containing composites, there was a general decrease in water uptake.