Evaluation of the Performance of Bio-Based Rigid Polyurethane Foam with High Amounts of Sunflower Press Cake Particles.

In the current study, rigid polyurethane foam (PUR) was modified with 10-30 wt.% sunflower press cake (SFP) filler, and its effect on performance characteristics-i.e., rheology, characteristic foaming times, apparent density, thermal conductivity, compressive strength parallel and perpendicular to the foaming directions, tensile strength, and short-term water absorption by partial immersion-was evaluated. Microstructural and statistical analyses were implemented as well. During the study, it was determined that 10-20 wt.% SFP filler showed the greatest positive impact. For instance, the thermal conductivity value improved by 9% and 17%, respectively, while mechanical performance, i.e., compressive strength, increased by 11% and 28% in the perpendicular direction and by 43% and 67% in the parallel direction. Moreover, tensile strength showed 49% and 61% increments, respectively, at 10 wt.% and 20 wt.% SFP filler. Most importantly, SFP filler-modified PUR foams were characterised by two times lower water absorption values and improved microstructures with a reduced average cell size and increased content in closed cells.