Morphology and mechanical properties of silicate filled polyurethane elastomers based on castor oil and polymeric MDI

Elastomers of castor oil and polymeric 4,4′‐diphenylmethane diisocyanate (PMDI; functionality 2.7) filled with clay, wollastonite, silica, talc, and calcium carbonate were prepared and their properties compared with the unfilled elastomer. It was found that clay and wollastonite fillers can be used for cost reduction without any detrimental effects on the mechanical properties. Scanning electron micrograph studies of freshly cut surfaces of the silicate filled elastomers showed that clay and wollastonite are much more compatible with the elastomer than silica, talc, and calcium carbonate. Results of gel time measurements in the castor oil — PMDI reaction are also presented as a help for the selection of processing parameters in the manufacture of the filled and unfilled elastomer.