Low density polyethylene tapioca starch degradable biofilms with palm oil based processing aid for blown film extrusion

Abstract

In this study, tapioca starch-based polyethylene biofilms with various starch contents, ranging from 5 to 40 wt%, were prepared with added plasticizers and polyethylene-grafted-maleic anhydride (PE-g-MA) as compatibilizer by a one-step process. The pellets of tapioca starch-based low density polyethylene (LDPE/TS) were first produced using a twin-screw extrusion process, followed by film blowing extrusion process to produce biofilm samples. Two types of plasticizers, commercial glycerol and palm oil based olein, were added to produce the best formulation for the film blowing process. Palm oil based olein influenced the processing of biocomposites by inducing lower viscosity, better dispersion and flowability. The biocomposites with addition of fixed amount of palm oil based olein displayed excellent film blowing ability compared to glycerol. Scanning electron micrograph of this biofilm with incorporation of starch up to 30 wt% showed good dispersion of starch granular in the polymer matrix. Adding compatibilizer increased the compatibility of the blends, and thus the mechanical properties of tapioca starchbased biofilms were improved. Optical properties, such as haze and gloss of biofilms, decreased as the starch contents increased, coinciding with the starch particle size in the polymer matrix. The barrier properties of tapioca starch-based biofilms, such as water uptake, moisture content and water vapour transmission rate were higher than pure LDPE, due to the hydrophilic characteristics of starch. Biofilms exposed to outdoor weathering, fungi, enzyme and controlled soil burial test demonstrated significant changes on weight loss and surface structure due to photodegradation by sunlight and microorganism activities. Biofilms with starch contents 10 to 40 wt% were determined safe to be used as food plastics packaging for aqueous, non-acidic and acidic foods, oils and processed dry food containing fat and alcoholic ingredients.