Effects of the Glycerol/Quercetin Ratio on the Structure and Tensile Behavior of PVA-Based Films

Poly(vinyl alcohol) (PVA)-based films containing glycerol and quercetin were prepared by casting as potential active-packaging materials. The effects of the glycerol/quercetin ratio on structural, thermal, mechanical, barrier, and antioxidant properties were investigated. Neat PVA and ternary formulations with PVA/glycerol/quercetin ratios of 70/20/10 (PVA+Gly+Q10) and 70/10/20 (PVA+Gly+Q20) by mass were characterized by FTIR, XRD, SEM, contact angle, TGA/DTG, tensile testing, water vapor permeability (WVP), total phenolic content, and DPPH assays. FTIR indicated changes in hydrogen bonding without new covalent functionalities, while apparent whole-film crystallinity indices were 16.2%, 11.1%, and 10.6%, respectively. Tensile tests included additional glycerol-rich and quercetin-rich endpoint controls to characterize the mechanical range of the formulation series. Neat PVA exhibited the highest maximum stress (15.67±1.49 MPa). PVA+Gly+Q20 showed a strain at break of 256.87±115.68% and an apparent tensile modulus of 26.61±3.40 MPa. The glycerol-rich endpoint exhibited high extensibility, whereas the quercetin-rich endpoint showed a markedly higher apparent tensile modulus (404.69±45.72 MPa). DPPH activity increased from 11.18% for PVA to 35.38% and 44.31% for PVA+Gly+Q10 and PVA+Gly+Q20, respectively. PVA+Gly+Q20 also exhibited approximately 68% lower mean WVP than PVA+Gly+Q10, with no significant formulation effect. These results support further development of PVA+Gly+Q20 for active packaging.