Tensile, thermal and flammability properties of date palm fiber filled recycled ternary blends and composites

Abstract

High density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) are olefinic thermoplastics polymers that are most commonly found as municipal solid waste in many countries. Their accumulation has become a major concern to world agencies and environmental conservationists due to their harmful effect on environment. The objective of this study is to develop a mechanically strong, and thermally insulating, flame retardant, date palm leaf fibre (DPLE) filled composites based on recycled HDPE, LDPE and PP. Maleated polypropylene (MAPP) and maleated polyethylene (MAPE) were compared as coupling agents for the HDPE/LDPE/PP system. The effects of addition of MAPE and MAPP at 1, 3 and 5 wt% content were investigated. The addition 1 wt% MAPE acted as nucleating agent by increasing the crystallinity of the blends, resulting in improvement of the tensile strength from 20 to 22.7 MPa of the blend. On the other hand addition of 1 wt% MAPP marginally increased the tensile strength of the blend to 21 MPa from 20 MPa. The addition of 5, 10, 20 and 30 wt% DPLF fibre to the 1 wt% MAPE compatibilized ternary blend yielded composites with improved tensile properties. The composites with 10 wt% DPLF content showed the highest tensile strength of 25 MPa. Above 10 wt% DPLF content, agglomeration of the fibre in the matrix was noticed resulting in a decrease in the tensile strength. No improvement in the tensile strength was achieved with addition of 5 wt% DPLF loading in the composite. Additionally, 11% reductions in the effective thermal conductivity of the composites with 10 wt% DPLF was observed. This was attributed to low thermal conductivity of the DPLF compared to the matrix. The flame retardancy of the developed composites was significantly improved with the addition of magnesium hydroxide (Mg (OH)2). However, the tensile strength of the composites was reduced. It was observed that addition of 10 wt% of Mg (OH)2 led to improvement in the limiting oxygen index (LOI) by 22% compared with the composite without Mg (OH)2. The developed composites have potential applications in low heat conducting roofing materials for the building construction industry.