Investigating the Thermal Characteristics and Water Absorption Capacity of Post-consumer Recycled Low Density Polyethylene Hybrid Composite

Abstract

The ability of a roofing material to resist heat, fire and moisture due to human and environmental factor is a critical requirement of a roofing tile or sheet. This work is focused on the thermal properties and water absorption capacity of Hybrid polymer composites (HPC). Durable HPCs of varying filler and polymer matrix formulation content were produced from Eucalyptus globulus sawdust ash (EGSA), locust bean pod ash (LBPA) kaolin clay and post-consumer low density polyethylene -LDPE (water sachet). Process-mixture experiment design was used to generate 12 runs for the formulation mix. Recycled LDPE and virgin LDPE matrices were also produced and used as control samples for the analysis. The thermal properties of the HPC samples with the best and optimum tested mechanical property (HPC2 and HPC7) was analyzed to determine the thermal properties which is responsible for their resistive capacity to heat and fire, using differential scanning calorimeter (DSC). Similarly, the water absorption capacity (WAC) of the HPCs was also determined. Result from the thermal analysis shows that HPC7 recorded the lowest enthalpy (∆H) value of 92.13 J/g. On the other hand, HPC2 recorded the highest melting temperature (Tm) of 138.39 oC, glass transition temperature (Tg) of 63 oC, degree of crystallization (Xc) of 96.28 % and oxidation onset temperature (OOT) of 59.61oC. These recorded values are due to the strong covalent bond, initiated by the crosslinking effect of the double cycle of heat of polymer extrusion, and the reinforcing effects of the fillers. The values are in comparison with the control samples.  Furthermore, HPC 4 recorded the lowest water absorption capacity of 0.50% with good dimensional stability. This value is within the acceptable WAC limit, proposed for nonporous roofing tile by ASTM C373 -2018. The crosslinking effect of recycled LDPE matrix is also responsible for this good resistance to moisture. By extension, the WAC value is 20 times lower than the permissible standard value for general purpose roofing tiles. This HPC is recommended to be suitable for roofing purpose.