Influence of Tannic Acid and Glycolic Acid on Adhesion, Curing Behavior, and Mechanical Performance of Polyester/Polyacrylic Acid Composites

Abstract

The present study explores the formulation and performance evaluation of polyester/polyacrylic acid (PAA)-based composite films modified with tannic acid, glycolic acid, and petroleum-derived additives. In-situ polymerized composite systems were prepared to investigate the influence of additive chemistry on film morphology, adhesion strength, drying efficiency, moisture retention, flexibility, brittleness, and curing stability. Significant formulation-dependent variations were observed in both physicochemical and mechanical properties. The tannic acid-containing formulation exhibited superior adhesion strength (92%) and flexibility (86%), attributable to enhanced intermolecular hydrogen bonding and improved polymer network compatibility. Conversely, glycolic acid incorporation increased hydrophilicity, resulting in elevated moisture retention, incomplete curing, and reduced structural stability. Petroleum-modified composites demonstrated rapid drying (90%) and low moisture retention (18%) due to increased hydrophobicity; however, excessive rigidification led to severe brittleness and diminished adhesion performance. Surface morphology analysis confirmed that additive chemistry strongly influenced film continuity, phase compatibility, and defect formation. The findings highlight the critical role of hydrophilic–hydrophobic balance and intermolecular interactions in governing the overall performance of polyester/PAA composite systems. Tannic acid emerged as the most effective modifier for achieving an optimal combination of adhesion, flexibility, and structural integrity, while further optimization of crosslinking density and curing conditions is required to simultaneously enhance drying efficiency and mechanical durability.