Effects of Stone Powder on Water Absorption and Biodegradability of Low Density Polyethylene/Palm Pressed Fibre Composite Film

Abstract

This study was aimed to develop semi-biodegradable low density polyethylene (LDPE)/oil palm pressed fibre (PPF) composite film for agriculture applications such as nursery bag and plastic mulch. Biodegradability and water absorbency are among the properties need to be considered. Biocomposite plastic that rich with cellulose normally takes faster time to biodegrade as the fibres become the food source of microbes in soil. It also absorbs water easily due to hydrogen bonding formation between the cellulose and the water molecules. To have a balance between these properties is important to determine the service life of the film. Inorganic filler, stone powder with particle size of 37 micron was incorporated at 5, 10 and 15 phr into a mixture of LDPE/PPF, in order to improve both properties. The stone has undergone a catalytic transmuted process to produce fine powder using technology patented by Blapol Sdn Bhd. The mixture was compounded using twin screw extruder and palletized prior to blown into a sheet of film. The effects of stone powder onto water absorption and biodegradability were studied. The percentage of water absorption was decreased about 13 % with addition of 15 phr stone powder, which is thought due to the ability of stone powder to interfere the formation of hydrogen bonding between hydroxyl groups of cellulose and water molecules. Meanwhile, the weight loss in biodegradability test has been slow down, probably due to inorganic nature of stone powder that takes longer time to be digested by microbes in soil.