Optimization of crosslinked poly(vinyl alcohol) nanocomposite films for mechanical properties

The effects of glycerol, bacterial cellulose nanocrystal (BCNC) and boric acid concentrations on the mechanical properties of PVA based films, including ultimate tensile strength (UTS), elongation at break (EAB), tensile Young's modulus (TYM), tensile toughness to break (TT), ultimate puncture strength (UPS), puncture deformation (PD), puncture Young's modulus (PYM) and puncture toughness to break (PT), were scrutinized using a response surface methodology-central composite rotatable design (RSM-CCRD). Second-order polynomial models with high R² values ranging from 0.945 to 0.977 were developed for the studied responses using multiple linear regression analysis. The models showed the maximum UTS (72.84MPa), EAB (293.43%), UPS (4.64MPa) and PD (31.80%) could be achieved at 13.89% glycerol concentration, 5.00% BCNC concentration and a boric acid content of 1.96%. The predicted values for optimum conditions were in good agreement with experimental data. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the formation of intramolecular and intermolecular hydrogen and ether crosslinkages in PVA and/or BCNC chains when boric acid is applied. Results showed that PVA/BCNC nanocomposite films plasticized with glycerol and crosslinked with boric acid showed appropriate mechanical properties that made them suitable as a disposable packaging film.