Abstract
Novel thermosetting polyphenol-based polyurethane (PU) films were prepared using condensed tannin (CTs) and hydroxypropyl tannin derivatives (HPTs) from Pinus pinaster bark and diisocyanates. Four HPTs with a degree of substitution (DS) rising stepwise from 1 to 4 were crosslinked with either an aromatic (polymeric methylene diphenyl diisocyanate (pMDI)) or an aliphatic isocyanate (hexamethylene diisocyanate (HDI)). Chemical structure, moisture sorption, thermal, and morphological properties of the films were studied. Properties varies with NCO:OH ratio (0.5–4.0), DS, diisocyanate type, and cross-link density (CD). Partial tannin hydroxypropylation (DS 2, 3) based/films showed a flexible-type character in term of Young’s modulus, elongation and tensile strain. Significant relationships were established between CD and physicochemical properties. HPTs constitute suitable macro building-block polyols for urethane chemistry.
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