Synthesis of Rigid Polyurethane Foam from Modified Castor Oil and Sugar to Enhance Thermal Insulating Properties and Degradability

In this study, rigid polyurethane foams were synthesized using modified castor oil polyol and varying amounts of sugar to enhance thermal insulating properties and degradability. Castor oil was first converted into polyol and subsequently polymerized with polymeric diphenyl methane diisocyanate (PMDI). The weight ratio of castor oil polyol to sugar was systematically varied to assess its effect on foam properties. The experimental results showed that the 1:3 ratio yielded the highest hydroxyl value of 905.75 mg KOH/g, providing more reactive sites for cross-linking. However, the foam synthesized with a 1:1 weight ratio exhibited the most suitable overall properties, including a thermal conductivity of 0.0356 W/m·K, a bulk density of 44.84 kg/m³, and a compressive strength of 0.1528 MPa. Although the addition of sugar contributed to improved degradability, it also increased thermal conductivity, bulk density, and compressive strength, exceeding typical industrial and production standards. Group 1 foams (ratios 1:0 and 1:1) had smaller, closed-cell structures that limited heat transfer, while Group 2 foams (ratios 1:2 and 1:3) exhibited larger cell size, leading to increased heat conduction. These findings suggest that while sugar enhances biodegradability, excessive amounts may compromise thermal performance and mechanical stability.