Processing of Plastic Film from Potato Starch: Effect of Drying Methods

Abstract

Starch- based plastics are biodegradable, compostable compounds made of starch and plasticizers from natural sources. Th eir fabrication involves the starch- plasticizer reaction at 70–100°C followed by cooling and drying. Th e most common drying method is air drying (natural convection), which is eff ective but slow. Th e objective of this work is to study the eff ect of fast drying (forced convection) on the quality of the plastic fi lm. Th is work compares the eff ects of drying conditions and drying rate on warpage, shrinkage rate, and presence of bubbles. Five drying methods are studied: (1) natural convection with uncovered petri dish, (2) natural convection while hanging, (3) forced convection with covered petri dish, (4) forced convection with uncovered petri dish, and (5) hybrid natural and forced convection. A standardized composition of starch- based plastic is prepared. Samples of 20 g of plastic deposited on 10- cm- diameter petri dishes are prepared. Drying and shrinkage rates are determined by recording the mass and diameter at multiple time intervals. A digital microscope is used to observe air bubbles. Th e most favorable drying method was forced convection with a covered petri dish, which displayed a drying rate of 0.765 g/h, no signifi cant shrinkage rate (< 0.00 mm/h), no warping, and almost no bubbles.