Properties and characterization of low density polyethylene/modified cockle shells composite films

Abstract

The objective of this research was to study the mechanical, thermal and morphological properties of low-density polyethylene (LDPE)/cockle shell (CS) composite films. Untreated cockle shells (UCS) and treated cockle shells (TCS) were used as fillers in the composite system with filler loadings of 10 – 50 phr. Stearic acid (SA) was used as a coupling agent to produce the TCS. The composite films were prepared using a co-rotary twin screw extruder machine at temperature 160ºC and screw speed 64 rpm followed by blown film machine. It was found that the increasing of UCS loading reduced the tensile strength and elongation at break for all LDPE/UCS composite films. However, the incorporation of SA coupling agent slightly increased the tensile strength of LDPE/TCS composite films compared to pure LDPE film and LDPE/UCS composite films. Scanning electron microscopy micrographs showed presence of agglomeration at the higher filler loading which probably caused the reduction on the tensile strength of LDPE/40UCS films compared to LDPE/40TCS films. Differential scanning calorimetry results showed that degree of crystallinity (Xc) and melting enthalpy (?Hm) of the films slightly increased with the presence of CS loading while melting temperature (Tm) and crystallization temperature (Tc) only showed slight changes for LDPE/UCS and LDPE/TCS formulations. Reduction of Xc and ?Hm was observed in LDPE/TCS composite. Thermogravimetry analysis showed that the thermal degradation temperature slightly increased with the incorporation of CS and the higher char residue was observed at 50 phr filler loading for both UCS and TCS. The overall result showed that the incorporation of TCS into LDPE/TCS composite films showed better properties, especially in the tensile strength.