Investigation on Foaming Mechanism of Polylactide-Based Rigid Polyurethane Foams with Uniform Cell Structures and Enhanced Properties

The strategic incorporation of renewable resources in polyurethane foam synthesis emerges as an innovative approach to minimize carbon footprint. Recent advancements in bio-based lactide production and the molecular architecture of polylactide have facilitated the development of high-performance polyurethane foams through the integration of renewable resource. In this study, polylactide (PLA)-based polyols with molecular weights ranging from 500 to 1500 g/mol and functionalities of 2 and 3 were synthesized via the ring-opening polymerization of L-lactide, and were subsequently employed as the sole polyol component in the preparation of bio-based rigid polyurethane foams (RPUFs). The physicochemical properties of the polyols, foaming behavior, as well as the mechanical performance, cellular structure, and thermal properties of the bio-based RPUFs were thoroughly characterized. Results indicated that the reactivity of PLA-based polyols exhibited a positive correlation with their functionality while demonstrating an inverse relationship with their molecular weight. Notably, tPLA500 exhibited optimal reactivity with a viscosity of 1107 mPa·s. The elevated reactivity facilitates the gelling reaction during the foaming process, while the lower viscosity enhances foam expansion. This synergistic effect improves cellular uniformity and the curing process, yielding a bio-based RPUF with intact cellular structure. This optimized morphology enables the bio-based RPUF to achieve a compressive strength of 384 kPa and a thermal conductivity of 0.036 W/(m·K), demonstrating its potential as a high-performance biobased thermal insulation material.