Reaction Injection Molding and Foaming of Smart Biodegradable Polyurethane Based on Chemorheological Investigation

Growing environmental concerns and increasingly stringent regulations have accelerated the development of biodegradable polymer systems. Polyurethanes (PUs), widely used in diverse industrial applications due to their robust mechanical performance, are increasingly being explored in biodegradable forms. Among PU processing techniques, reaction injection molding (RIM) and foaming are extensively employed; however, both processes are highly sensitive to the initial viscosity and curing behavior of the reactive mixture. Despite this practical dependence, the chemorheological characteristics of biodegradable PU systems have not been sufficiently connected to process stability and final performance. In this study, a biodegradable PU based on a biopolyol, i.e., polycaprolactonediol (PCL), was synthesized and processed into molded parts and foams via RIM and chemical foaming. Rheological measurements and cure kinetic analysis were conducted to characterize viscosity evolution, gelation behavior, and processing windows under reactive conditions. The obtained chemorheological parameters were incorporated into process simulation based on finite-element-method (FEM) to evaluate mold filling behavior and curing progression, supporting the identification of stable processing conditions. The molded specimens were evaluated in terms of mechanical and shape-memory performance, while the foamed samples were characterized with respect to mechanical properties, sound absorption, and cellular morphology. The influence of isocyanate composition on rheological behavior, processing characteristics, and final properties was systematically analyzed. Through an integrated experimental and simulation approach, optimized processing conditions were established for the RIM process, while the foaming system was systematically analyzed to elucidate formulation dependent property relationships, providing practical insights into the processing of biobased PU systems. This integrated strategy establishes a quantitative formulation-processing-property relationship that informs the rational engineering of biodegradable polyurethane materials across diverse manufacturing routes.