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Synthesis and characterization of PVA?fumaric acid cross?linked biodegradable films.Polyvinyl alcohol (PVA) is a widely used polymer that is biocompatible, nontoxic, and water?soluble due to the presence of hydroxyl groups in its domain. This study aims to investigate the effects of fumaric acid (FA) cross?linking and thermal cross?linking (TC) on the PVA's mechanical and thermal properties. When the FA is mixed with PVA, it was found in the chemical reaction that the OH groups of PVA are condensing with the carboxylic acid units of FA to yield new ester linkages and water as a by?product, which further results in the reduction of the water absorption capacity. Quantitatively, the addition of 8 (wt. /wt. %) FA resulted in a minimum of 65% water absorption rate, as compared with 117% for pure PVA. The mechanical and thermal properties of PVA also enhanced with the addition of 2% to 8% FA by weight. For the TC case, the % increase in ultimate tensile strength was 30.9% and 42.5% with and without TC, respectively. As the wt. % of FA increased from 2 to 10%, the % elongation value decreased for both with and without TC films relative to pure PVA. The thermogravimetric analysis revealed the change in degradation temperature of FA?PVA blended film in comparison with pure PVA. Dynamic mechanical analysis was utilized to analyze the viscoelastic nature and temperature variation at the glass transition temperature. The current fabricated film is a potential candidate for the food packaging films application; moreover, the results reported in this investigation will accelerate the industrial applications of biodegradable PVA.HighlightsIncreasing the weight percentage of fumaric acid leads to an enhancement in mechanical and thermal properties of the film.Esterification is the usual reaction between fumaric acid and polyvinyl alcohol (PVA), in which ester linkages are formed when the carboxyl groups (?COOH) of fumaric acid and the hydroxyl groups (?OH) of PVA combine.Water absorption characteristics of the film reduces as the wt. % of fumaric acid increases.Thermal cross?linking of the film leads to further improvements in mechanical and thermal properties.The overall effect of increasing the wt. % of fumaric acid is negative on the glass transition temperature of the film.The developed film is a potential candidate for the food packaging films application.