Rotational polymerization molding

A method of forming rigid cross-linked polymeric solid articles having one or more chambers therein from a liquid monomer solution comprising:

• (a) providing a liquid monomer solution, and rotational molding means, said molding means having an inner chamber wall defining an inner chamber, said liquid monomer solution comprising tantalum catalyst, dicyclopentadiene, and activator of a metathesis-catalyst system, said tantalum catalyst comprising tantalum said solution not comprising an amount of moderator effective to delay substantial polymerization ten seconds or more, said solution being effective to allow distribution of said liquid monomer within said rotational molding means to substantially the shape of the article being formed in from ten seconds to one minute and prior to any substantial rise in viscosity of said liquid monomer due to polymerization;
• (b) conveying said solution into said rotational molding means, the amount of said solution within said molding means being insufficient to fill said inner chamber;
• (c) rotating said rotational molding means, the rate of rotation being at least sufficient to substantially evenly distribute said solution along said inner chamber wall prior to a substantial increase in viscosity of said solution due to polymerization;
• thereby forming at least one chamber in said solution;
• (d) continuing said rotation while said solution polymerizes to form a rigid solid article of cross-linked polymer comprising polymerized units of dicyclopentadiene, said article having at least one chamber therein.