Micro fibrillated cellulose reinforced bio-based rigid high-density polyurethane foams

Rigid polyurethane foams (RPUF) are the most consumed cellular polymer in the world. Bio-based polyols are sometimes used as raw material for RPUF but with a detrimental effect on mechanical properties. In this paper, micro fibrillated cellulose (MFC) was used as a reinforcement to enhance the mechanical, thermal and dynamic mechanical properties of bio-based RPUF. A bleached Eucalyptus sp. pulp was dispersed in glycerine and then subjected to mechanical defibrillation to extract the MFC, a route that does not require dispersants or drying, which is advantageous for the MCF incorporation. The RPUF were manufactured in a closed mould in a way to obtain overpacking. The higher the overpacking degree, the higher the apparent density and stiffness of the RPUF. Also, expansion under confinement yielded more rounded polymer cells with decreased anisotropy. The MFC and overpacking acted synergistically, improving strength, stiffness, thermal stability and dynamic mechanical properties of the RPUF. Thermal conductivity of the RPUF, on the other hand, was unaffected by those factors.