| 摘要 |
Polyester-based molding compositions containing certain polyurethanes having utility as low profile additives, a method of preparing polyester-based molding compositions containing such polyurethane low profile additives, and thermoset articles made with the method. The polyurethane low profile additives comprise the reaction product of: (a) a polyisocyanate; (b) a polyol or polyol blend having an average functionality of 2 to 3 hydroxyl groups per molecule and an average molecular weight of at least 500; and (c) a diol chain extender having a molecular weight of less than about 500. A polyester-based molding composition of the invention comprises: (a) an unsaturated polyester; (b) an ethylenically unsaturated monomer which is copolymerizable with the unsaturated polyester; (c) a polyurethane low profile additive of this invention as described above; (d) fiber reinforcement; and (e) a chemical thickener. A method of preparing thermoset polyester compositions comprises the steps of mixing a polymerization initiator with the polyester-based molding composition of the invention described above, forming the resulting mixture into a desired shape, and heating the shaped composition to cure it. |
