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Sorbitol arises to be a strong candidate for renewably sourced polyol synthesis. Moreover, processes for extracting sorbitol directly from cellulosic materials are effective, and materials such as agroforestry residues could be used as green sorbitol sources. Rigid polyurethane foams were successfully synthesized by using mixtures of a sorbitol based high functionality polyol and a corn based diol. Microstructure and properties of the rigid polyurethane foams were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, thermal conductivity measurements, compression tests, and dynamic mechanical analysis. Results showed that the cross-linking density of the formed polymer network was directly modified by polyol mixture ratio, and microstructure and properties also changed in consonance. The incorporation of different amounts of a diol with longer chain length between hydroxyl groups allowed fixing the rigidity of the foams, opening the door to the possibility of designing rigid polyurethane foams with tailored properties.

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Different types of phosphorus containing halogen-free flame retardants (FRs) were added to an epoxy-dicyandiamide resin formulation in order to study to which extent they affect its glass transition temperature (T g), tensile properties, thermal stability and burning behavior of the resin. For this purpose, an additive-type FR (ammonium polyphosphate encapsulated in melamine resin, MAPP) and two reactive-type FRs i) a commercial epoxy resin pre-reacted with 9,10-dihydro-oxa-10phosphaphenanthrene-10-oxide, (DOPO), and ii) a phosphorus containing hardener (poly(m-phenylene methylphosphonate), (PMP) were used. It was observed that the addition of additive-type FR did not affect in great extent the T g and provided a V-0 rating in UL94 test at low loadings. The addition of reactive-type FRs (DOPO and/or PMP), however, modified the structure of the chain network resulting in lower crosslink density as a consequence of their higher equivalent mass, but achieving also with low PMP content V-0 rating.