Abstract: A process for preparing formed articles made of polyurethane foams, which comprises reacting at least a polyisocyanate with at least a compound containing end activated hydrogens in the presence of an expanding medium, selected from at least a hydrofluoroalkane and/or perfluoroalkane, and of a product, containing at least a structural unit of the aminic type, chemically bound or present in free form in one of the two polyurethane reagents, said expanding medium being dissolved in said one of the two polyurethane reagents.

Abstract: Flexible polyurethane foams having densities lower than 25 kg/m.sup.3 and a load bearing capacity, at a 40% compression, higher than 150N, prepared by reacting a modified polyiso=cyanate with a compound containing active end hydrogens and wherein high levels of water are used as foaming agent, without risk of self-ignition.

Abstract: A process for preparing low-density flexible polyurethane foams obtained, in the absence of expanding agents of chlorofluoroalkane type, by the polycondensation of an organic polyisocyanate with at least one polyol of equivalent weight exceeding 50 and functionality equal to or greater than 2, in the presence of an expanding system comprising water and dimethyl carbonate (DMC).

Abstract: Flexible polyurethane foams having bulk densities within the range of from 15 to 60 kg/cm.sup.3 and a load bearing capacity, under a compression rate of 40%, higher than 50 N, obtained by the reaction of a modified polyisocyanate with a compound containing activated hydrogen atoms in chain-end position, and wherein agents different from chloro-fluoroalkanes are used as the foaming agent.

Abstract: Polyisocyanate compositions comprising:(a) from 90 to 50% by weight of the reaction product between an organic diisocyanate and a polyether-polyol of functionality of at least 2, and wherein said reaction product has a content of free NCO radicals within the range of from 26.5 to 33% by weight; and(b) from 10 to 50% by weight of polymethylene-polyphenyl-polyisocyanates.

Abstract: A thermoplastic polyurethane endowed with improved heat distortion resistance, which comprises the product of reaction ofat least one polyisocyanate, preferably an organic diisocyanate;at least one polyol material reactive with the isocyanate and having a molecular weight higher than 400;a chain extender having a molecular weight lower than 400; andan aromatic anhydride having the formula (I): ##STR1## wherein A is a possibly substituted (C.sub.6 -C.sub.30) aromatic radical, m may be 0 or an integer from 1 to 3, and n is an integer equal to 1 or 2.

Abstract: The invention concerns a process for the manufacture of thermoplastic polyurethanes wherein an organic polyisocyanate is made to polymerize with a polyol (reactive with same isocyanate) in the presence of a chain extending agent having a molecular weight lower than 400, under continuous stirring, at a temperature higher than 150.degree. C. and for a time sufficient to obtain a product having a melt flow index lower than 25 g/10'.