Toward Compatibility Enhancement of Biodegradable Plasticized Cellulose Acetate and Polyhydroxyalkanoate Blends: Effect of Calcium Carbonate and Maleated Hybrid Blend on Material Performance

ABSTRACT The brittleness of plasticized cellulose acetate (pCA) limits its broader application. Blending with tougher biopolymers is a common strategy to improve toughness, but performance is often restricted by poor compatibility between blend components. In this study, poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P34HB), an amorphous polyhydroxyalkanoate (aPHA), was incorporated into pCA at three blend ratios. Although solubility parameter calculations suggested partial miscibility, glass transition temperature (T g ) analysis and morphological studies confirmed complete immiscibility. To improve the compatibility, a maleic anhydride (MA)‐grafted hybrid blend compatibilizer and CaCO 3 were introduced into the optimized blend formulation. Morphological and surface analyses revealed a droplet‐matrix structure, where the MA‐based compatibilizer reduced the size of dispersed aPHA domains and promoted smoother modulus transitions across the interface. As a result, elongation at break, impact strength, and heat deflection temperature increased by up to 63%, 36%, and 12%, respectively, compared with the neat blend. Rheological properties showed slight improvement, while in terms of thermal stability the onset degradation temperature rose by up to 21°C. No synergistic effect was observed when both additives were combined. The optimized pCA/aPHA blend exhibited a favorable balance of mechanical, thermal, and thermomechanical properties, demonstrating its potential for rigid packaging applications.