Developments of biodegradable polymer based on polylactic acid (PLA) with natural color extracts for packaging film applications
Worraphol Nansu, Passarawan CHAIWUT, Sukunya Ross, Gareth M. Ross, Nungruthai Suphrom, Sararat Mahasaranon
Abstract
This research was interested in the use of natural colorants to replace hazardous synthetic pigments in the plastic polymer industry. The natural colors were selected from local plants indigenous to southeast Asia, which were Hibiscus sabdariffa roselle calyx (RS) and Caesapinia sappan Linn heartwood (SP). Natural colorant extracts were used as additives in poly(lactic acid ) (PLA). These were manufactured using a twin screws extruder and blow film extruder to obtain biodegradable thin films for use as packaging materials. Biodegradable films were characterized by color index, light barrier properties, water vapor transmission (WVTR), morphology, mechanical and chemical properties. The results showed high compatibility between PLA and natural color extracts confirmed via SEM morphology. Moreover, the films have the colors associated with the added RS and SP extracts, with a pink tone for the RS film and a yellow-orange tone for the SP film. Films incorporated with the extracts also possessed improved light barrier properties, which were reduced from 98.66% to 78.00% in the UV-A region and 99.33% to 90.00% in the visible region. Water vapor transmission rate was also decreased with incorporation of SP from 4.02 g⋅m-2*day to 2.98 g⋅m-2*day at 7 days and RS 1.66 g⋅m-2*day to 1.59 g⋅m-2*day at 14 days. Moreover, films containing the natural color extracts had higher tensile strength and tensile modulus than pure PLA films. These properties improvement confirm that these extracts are suitable for producing biodegradable packaging thin films.