Flexible water-resistant semi-transparent cotton gin trash/poly (vinyl alcohol) bio-plastic for packaging application: Effect of plasticisers on physicochemical properties

A new cost-effective approach for producing bio-plastic from the combination of poly (vinyl alcohol) (PVA) and cotton gin trash (CGT) is reported in this study intended for probable replacement of non-biodegradable plastics in packaging. The effect of diethylene glycol, glycerol and urea as plasticisers and ethyl cellulose (EC) as coating agent were investigated. The plasticising effect was governed by the synergistic influence of the solubility parameter, molecular weight and the linearity of the plasticisers’ chemical structure. A better plasticising effect reduced the vacant areas at CGT/PVA interfaces, and decreased the crystallinity and tensile strength, while improved the moisture absorption, transmission and thermal stability. Urea, as the plasticiser, showed the best performance among others (modulus 257 MPa, slightly higher than that of commercial LDPE (213.5 MPa), followed by glycerol. With complete flexibility (folding endurance >200), the tensile strength of the composite films was higher than LDPE. The film coated with EC was able to resist water drop penetration at least for 10 min. The films were semi-transparent and have excellent UV resistance. The related cost of electricity and chemicals per gram film production was estimated around 0.02 and 0.18–0.19 AUD, respectively. Overall, this study showed a sensible method of producing water-resistant flexible bio-plastic that could be beneficial in encountering current plastic pollution. [Display omitted] •Flexible cotton gin trash (CGT)/poly(vinyl alcohol) (PVA) plastic was developed.•New method to induce water-resistant property to CGT/PVA plastic was proposed.•CGT/PVA plastics showed relatively similar modulus and higher tensile strength to LDPE.•Thermal stability of PVA enhanced by CGT and complete UV protection achieved.