Effect of storage environment on the crystallinity and compressive load of starch based biodegradable cup

Abstract

The effect of storage environment on the overall crystallinity and compressive load of commercially sold starch based biodegradable cup was determined. Using FTIR and DSC, the components of the cup was identified as starch, polypropylene (PP) and organic acid as compatibilizer. Using TGA, the weight percentage of starch and PP components were 13 and 58%, respectively. The samples were stored 20°C, 80% RH and 40°C, 40% RH for 4 months. Using DSC, the overall crystallinity was evaluated based on the heat of fusion (Hf). Using XRD, the crystalline structure was evaluated based on peaks and full width at maximum height (FWMH). After 4 months, DSC results showed only one endothermic peak with melting point of ≈165°C at both conditions. The Hf was remained ≈50 J/g. Based on XRD results, there were no development of new crystalline peaks and the peak FHWM remained unchanged. Initially, the percentage samples below the set limit of compressive load was ≈20%. The percentage below the set limit was ≈40% for samples stored at 20°C, 80% RH, whereas ≈20% for samples stored at 40°C, 40% RH. The 80% RH at 20°C increased the moisture content from 2% to 3.1%. The overall crystallinity remained unchanged after storage. Water became a plasticizer for the starch component. The increase in moisture content could have decreased the compressive load during storage.