Insights into the physical properties of biobased polyurethane/expanded graphite composite foams

The main purpose of this work was to widen the range of applications of the polyurethane foams (PUFs) obtained from renewable resources as higher added value materials by increasing their electrical and thermal conductivities and get a better insight of the parameters governing these properties. The increase of these properties is frequently achieved by filling PUFs with carbon nanofibers (CNFs), carbon nanotubes (CNTs) or graphene layers, however their cost limits their widespread use. In this work, an inexpensive procedure has been developed to prepare electrical conductive PUFs using castor oil (CO) as polyol and expanded graphite (EG). The chemical and structural characteristics of the ensuing composite foams have been evaluated, as well as their morphology and their mechanical, thermal and electrical properties. The DC electrical conductivity results have been fitted to Taherian model. EG loadings between 0.5 and 1.5% (w/w) caused a systematic increase of the thermal and electrical conductivities Moreover, in this fillers' loading range the remaining physical properties namely the glass transition temperature and the Young's modulus are appropriate for standard applications.