Improvement of Mechanical and Thermal Properties of Semirigid Polyurethane Foam by the Addition of Cellulose Sulfate

The demand for sustainable resources in production and improvement of various properties of polymer materials is increasing. In this study, cellulose sulfate (CS) was synthesized from microcrystalline cellulose and used as an additive at different ratios (5% and 10%) in the production of semirigid polyurethane foam (SrPUF). The effects of the CS additive on the mechanical properties, combustion behavior, and thermal stability of SrPUF were extensively investigated by rigorous tests such as tensile strength, flexural strength, UL 94 vertical burn test, and thermogravimetric analysis (TGA). The findings indicate that incorporating a 10% CS additive contributed to a considerable advancement in tensile strength, with an increase of 51.39%. Additionally, the flexural strength of SrPUF improved markedly, rising from 47 kPa to an impressive 147 kPa. The UL 94 vertical combustion test showed that the flame spread rate of SrPUF containing 10% CS experienced a substantial decrease, while the maximum degradation temperature (Tdmax) of SrPUF increased from 384 degrees C to 405 degrees C. The char yields of 0%, 5%, and 10% CS added to the foam were 5.61%, 6.84%, and 13.01%, respectively. In conclusion, this study demonstrates that doping SrPU foam with CS significantly enhances its durability in both mechanical and thermal aspects.