Glass-reinforced thermoplastic moulding compositions

A mouldable thermoplastic material comprising from 20% to 90% by weight polypropylene, polyethylene or polyamide as thermoplastic matrix, from 80 to 10% by weight of glass fibre and from 0.05 to 15% by weight based on the total weight of the glass fibre and thermoplastic matrix of an additive capable of coupling with the glass at a temperature within the range from 180.degree. C to 300.degree. C and incapable of forming a homopolymer at said temperature, said additive being selected from the groups consisting of oxalic acid and organic compounds containing the grouping ##STR4## in which X may be a hydrogen atom, an alkyl group, a carboxyl group, or a group of the formula ---CO-R.sub.3, R.sub.3 being selected from alkyl groups, and aromatic groups with or without carbonyl containing substitutents, Y may be a hydrogen atom, an alkyl or a carboxyl group or a group of the formula ---COR.sub.4, R.sub.4 being selected from alkyl groups and aromatic groups with or without carbonyl containing substituents, or

• X and Y may together constitute an anhydride grouping thus forming a cyclic anhydride,
• R.sub.1 and R.sub.2 may be selected from hydroxyl groups, aromatic groups or --COR.sub.1 and --COR.sub.2 may together constitute an anhydride group thus forming a cyclic anhydride.