| abstract |
A melt stable, thermoformable polyimide having a melt viscosity measured at a shear rate of 1000 sec⁻¹ of less than 2 kNs/m comprising a polyimide of repeat unit of formulan where Ar is a tetravalent aromatic radical derived from a dianhydride or corresponding derivative, selected from pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, diphenyl sulphone dianhydride and hexafluoropropylidene diahydride and D is a divalent organic radical derived from amines of formulan where A is O or S, the terminal covalent bonds are in meta positions with respect to A and B is -SO₂-, -CO-, or a direct link,n and wherein up to 50 mole % of the radicals D may be replaced by divalent organic radicals derived from other diamines characterised in that the end groups in the polyimide are essentially all unsubstituted aromatic rings. The products are useful for injection moulding, extrusion, for forming films and fibres and as the matrix for reinforced composites. |