| abstract |
The thermoset, phase-separated polyurethane material of the flexible skin layer is produced from a reactive mixture which is made of one or more isocyanate compounds and isocyanate reactive compounds which comprise one or more polyol compounds, flexibilisers, chain extenders and/or crosslinkers and amine-initiators. Apart from at least one crosslinking amine-initiator, these amine-initiators further comprise at least one extender amine-initiator which has a functionality of 2 and a molecular weight of less than 300 and which corresponds to formula (I) HR 1 N-R 2 -OH (I) wherein: R 1 is H or a cyclic or acyclic hydrocarbon chain, which is substituted or not and which comprises one or more hetero-atoms or not, R 1 being preferably H or a C1 to C6 alkyl group; and R 2 is a hydrocarbon chain which is substituted or not, which comprises a hetero-atom or not and which comprises a backbone linking the amino group with the hydroxyl group and containing at least two carbon atoms. The combination of the flexibiliser and the extender amine-initiator was found to have an increased effect on the flexural modulus and the softening temperature of the polyurethane material whilst maintaining the required mechanical properties at a satisfactory level. |