Enhancing the mechanical strength and tuning the optical properties of reinforced PVA films: The effects of graphene oxide, cellulose nanocrystals, and PVA molecular weight

This study investigates the synergy of varying concentrations of graphene oxide (GO) and cellulose nanocrystals (CNCs), and poly(vinyl alcohol) (PVA) molecular weight (MW) on the UV protection, transparency, and tensile strength (TS) of PVA/GO/CNC films. GO and CNCs were sustainably synthesized from graphite and office waste paper. PVA MW ranged from 20 to 130 kDa for broad applicability. The maximum percent of TS improvement (POTSI) reached 40% under 65% relative humidity, influenced more by CNC and GO concentrations than PVA MW. GO significantly impacted the films' optical properties. For low PVA MW (20 kDa), the optimized film (1.00 wt% GO, 3.52 wt% CNC) achieved excellent UVA (82.3%) and UVB (91.7%) barriers, acceptable transparency (43.9%), and a POTSI of 33.5%. For high PVA MW (130 kDa), the optimized film (0.6 wt% GO, 1.86 wt% CNC) exhibited higher transparency (50.8%) but reduced UVA (69.2%) and UVB (77.9%) barriers, and a POTSI of 36.5%. UV barriers can be controllably improved by increasing GO concentration, followed by CNC adjustment to preserve TS. Conversely, transparency can be enhanced by reducing GO and CNC concentrations, with some compromise in UV protection. These findings guide the optimization of PVA/GO/CNC films for enhanced performance in the composite industry.