Environmentally friendly alternative to polyester polyol by corn straw on preparation of rigid polyurethane composite

Abstract Corn straw was transferred into straw powders (SPs) by physical treatment in order to prepare rigid polyurethane composite foams by one step method. The obtained foams were evaluated through mechanical properties, thermal properties and cellular structure. It was found that the compression strengths of composite foams sharply decreased compared to pure foam and powder size had no obvious influence on the compression strength in the growth direction. Flexural strengths of rigid polyurethane composite foams with corn straw decreased from 0.34 MPa (pure foams) to 0.22 MPa and 0.26 MPa, which decreased by 35.3% and 23.5%, respectively. The flexural strength of non-growth rigid polyurethane composite foam decreased slightly with the increase of powder size. SEM indicates that cellular foam was combined more tightly due to the addition of SPs. However, there were inhomogeneous distribution and more broken cells in all composite foams. Compared with pure foams, thermal properties of rigid polyurethane composite foams with corn straw were not changed, however, with SPs adding into the matrix, more heat flow was released compared with pure foams. All results indicate that polyol could be possibly replaced by corn straw in polyurethane industry, realizing environmentally friendly alternative to polyester polyol by corn straw in the preparation of rigid polyurethane composites. Rigid polyurethane foams have good thermal insulation effect, and is mainly used in the field of thermal insulation, such as refrigerator insulation filling material, chemical transportation pipeline insulation material, thermal insulation layer of building wall surface, etc.