Property Improvement of Three-layer LDPE Shrink Film Using LDPE Recycled from Blown Film Production Waste

Abstract

Low-density polyethylene (LDPE) is one of the most used plastics especially in packaging applications. This research attempted to reduce the use of virgin LDPE and effectively recycle industrial LDPE waste by utilizing LDPE scraps from blown film production line (re-LDPE) for property improvement of three-layer LDPE shrink film prepared by blown film co-extrusion. While the skin layers consisted only of virgin LDPE, the middle layer was a blend of virgin LDPE and re-LDPE. The LDPE:re-LDPE ratios in wt% were varied from 100:0, 85:15, 70:30, 55:45, 40:60 to 0:100. It was found that several properties of all shrink films containing re-LDPE in their middle layers were better than those of the film solely made of virgin LDPE. Thermal analysis using DSC revealed an increase in % crystallinity of these films upon increasing re-LDPE content that consequently improved their tensile strengths in both machine and transverse directions despite a slight decrease in their shrink percentages but still within typical range for shrink film applications. In addition to the enhancement of heat-seal ability in both directions, lower gloss and haze values were also observed as re-LDPE content was increased. The results indicated that the film prepared using re-LDPE 100 wt% had highest tensile and seal strengths while the film prepared using re-LDPE 60 wt% exhibited lowest haze with similar gloss to the film prepared without re-LDPE.