Poly(lactic acid)-based Composites Incorporated with Spent Coffee Ground and Tea Leave for Food Packaging Application: A Waste to Wealth

Abstract

Polymer composites of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) incorporated with spent coffee grounds (SCG) and tea leave (TL) were prepared by two-roll mill mixer. 4,4-methylene diphenyl diisocyanate (MDI), toluene 2,4-diisocyanate (TDI), and bis[3-(triethoxysilyl) propyl] tetrasulfide (TESPT) were used as coupling agents. The influences of coupling agent types, coupling agent content, and weight ratios of polymer to filler on the mechanical properties, melt flow index, and overall migration (OM) of the composites were studied. The results showed that MDI and TDI had better performance compared to TESPT for both tensile and elongation at break. The tensile strength and elongation at break of PLA+PBAT/SCG composites with weight ratio of polymer to filler = 70/30 increased from 19.6 MPa to ∼23.0 to 25.0 MPa, and 6.6 to ∼10.0%, respectively when using these coupling agents (MDI and TDI) of 3 g/100 g polymers. Moreover, the addition of MDI and TDI greatly increased the viscosity of the melted composites (4-fold), while TESPT made the viscosity decrease. However, the mechanical properties of the composites decreased drastically with increasing SCG proportion. Compared to PLA+PBAT/SCG, interfacial adhesion of PLA+PBAT/TL was higher confirming by tensile strength and SEM images. However, there was no significant difference between PLA+PBAT/TL and PLA+PBAT/SCG composites in terms of elongation at break, impact strength and melt flow index. The OM of PLA+PBAT/SCG and PLA+PBAT/TL composites with coupling agents were in the range of ∼0.03–0.28 mg/dm2 when using 3% acetic acid and 10% ethanol as food simulants, which not excess the migration limit (10 mg/dm2) according to Food Contact Materials EU No. 10/2011 legislation. It means that they might be safe for use as food contact materials for packaging and containers.

Torrefaction of Coffee Husk Flour for the Development of Injection-Molded Green Composite Pieces of Polylactide with High Sustainability

“…The described decrease of the mechanical properties was ascribed to the low aspect ratio of the CSS particles as well as their poor adhesion to the biopolymer matrix. In this regard, the use of coupling agents has improved both the tensile strength and ductility of PLA composites prepared with SCG, though the improvements achieved were relatively low and their overall and specific migration limits (OML and SML) should also be carefully determined [59].…”

A Review of the Applications and Biodegradation of Polyhydroxyalkanoates and Poly(lactic acid) and Its Composites

“…Songtipya et al [ 101 ] explored the food packaging application of PLA/polybutylene adipate terephthalate (PBAT), which employed spent coffee ground and tea leaves as fillers. The study indicates that the overall migration values from all composite samples in all food stimulants did not exceed the maximum migration limit (10 mg/dm 2 ), which comply with EU regulations.…”

“…It is not possible for the chemicals to be diffused easily into food stimulants through the polymer composites. Therefore, PLA/PBAT composites used as food contact materials for packaging and containers have a minimum effect on food security [ 101 ].…”

“…Songtipya et al [101] explored the food packaging application of PLA/polybutylene adipate terephthalate (PBAT), which employed spent coffee ground and tea leaves as fillers.…”

“…The food-packaging industry has gone through some considerable transformations in the 20th century. Many advancements in packaging technology appeared, such as intelligent or smart packaging (IOSP; time-temperature indicators (TTIs), gas indicators, microwave doneness indicators, radiofrequency identification (RFID), and others), and active packaging (such as oxygen scavengers, moisture absorbers, additives and antimicrobials) [101,135,[141][142][143]. These innovations act by prolonging the shelf-life, preserving desirable food quality, providing indications about and regulating the freshness of food products.…”