| Summary: | Rigid polyurethane (PUR) foams produced from walnut shellsderived polyol (20 wt.%) were successfully reinforced with 2 wt.% of nontreated, acetylated, and silanized walnut shells (WS). The impact of nontreated and chemicallytreated WS on the morphology, mechanical, and thermal characteristics of PUR composites was determined. The morphological analysis confirmed that the addition of WS fillers promoted a reduction in cell size, compared to pure PUR foams. Among all the modified PUR foams, the greatest improvement of mechanical characteristics was observed for PUR foams with the addition of silanized WS—the compressive, flexural, and impact strength were enhanced by 21, 16, and 13%, respectively. The addition of nontreated and chemicallytreated WS improved the thermomechanical stability of PUR foams. The results of the dynamic mechanical analysis confirmed an increase in glass transition temperature and storage modulus of PUR foams after the incorporation of chemicallytreated WS. The addition of nontreated and chemicallytreated WS did not affect the insulating properties of PUR foams, and the thermal conductivity value did not show any significant improvement and deterioration due to the addition of WS fillers.
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