Abstract: Methods of converting essentially unpolymerized precursors into polyimides in which the precursors are exposed to microwave radiation. Preheating, thermal post-curing, and other techniques may be employed to promote the development of optimum properties; and reinforcements can be employed to impart strength and rigidity to the final product. Also disclosed are processes for making various composite artifacts in which non-polymeric precursors are converted to polyimides by using the techniques described above.

Abstract: This invention provides cross-linked, flame retarded poly(p-methylstyrene) foam insulation. It also provides a method for preparing it, that comprises incorporating a flame retarding amount of flame retardant material into poly(p-methylstyrene), foaming the resultant composition, and cross-linking.

Abstract: A crosslinked, soft, flexible, closed-cell foam of chlorinated high density polyethylene and a process for the preparation thereof, comprising admixing a high density chlorinated polyethylene with a thermally decomposable chemical foaming agent at a temperature below the decomposition temperature of said foaming agent, molding the chlorinated high density polyethylene into desired form at a temperature below the decomposition temperature of the foaming agent, subjecting the molded chlorinated high density polyethylene to irradiation cross-linking at a temperature below the decomposition temperature of said foaming agent and contacting, in a substantially oxygen-free environment, the crosslinked chlorinated high density polyethylene with a heat transfer medium maintained at a temperature of from about 150.degree. C. to about 350.degree. C. for a period sufficient to form the desired product.

Abstract: A crosslinked, soft, flexible, closed-cell foam of suspension chlorinated high density polyethylene and a process for the preparation thereof, comprising admixing a high density suspension chlorinated polyethylene with a thermally decomposable chemical foaming agent at a temperature below the decomposition temperature of said foaming agent, molding the chlorinated high density polyethylene into desired form at a temperature below the decomposition temperature of the foaming agent, subjecting the molded chlorinated high density polyethylene to irradiation crosslinking at a temperature below the decomposition temperature of said foaming agent and contacting, in a substantially oxygen-free environment, the crosslinked chlorinated high density polyethylene with a heat transfer medium maintained at a temperature of from about 150.degree. C. to about 350.degree. C. for a period sufficient to form the desired product.

Abstract: There are provided shaped articles, such as trays and food containers, thermoformed from oriented poly (p-methylstyrene) sheet, oriented foamed poly (p-methylstyrene) film with oriented poly (p-methylstyrene) foam or polystyrene foam, that have been cross-linked by exposure to radiation. Such articles are resistant to fats and fatty foods contained therein can be placed in microwave ovens without destruction by hot, melted fats. The articles can also withstand conventional oven temperatures.

Abstract: Crosslinked polyvinyl chloride foams are formed by first expanding a polyvinyl chloride containing plastisol comprising a blowing agent, and a reactive crosslinking plasticizer to form a foamed composition and then subjecting the foamed composition to irradiation to crosslink the foamed composition via the crosslinking plasticizer.

Abstract: Foamed radiation-crosslinked high density polyethylenes having substantially closed cells and uniform structure are made from radiation-crosslinked high density polyethylene compositions comprising thermosensitive foaming agents by heating such compositions while excluding molecular oxygen from contact therewith during that heating and foaming step. Oxygen is excluded by providing an oxygen-free inert gas atmosphere or by submerging the foamable material beneath the surface of a body of liquid heat transfer medium during the heating and foaming step.

Abstract: A crosslinked, soft, flexible, closed-cell foam of chlorinated high density polyethylene and a process for the preparation thereof, comprising admixing a high density chlorinated polyethylene with a thermally decomposable chemical foaming agent at a temperature below the decomposition temperature of said foaming agent, molding the chlorinated high density polyethylene into desired form at a temperature below the decomposition temperature of the foaming agent, subjecting the molded chlorinated high density polyethylene to irradiation crosslinking at a temperature below the decomposition temperature of said foaming agent and contacting, in a substantially oxygen-free environment, the crosslinked chlorinated high density polyethylene with a heat transfer medium maintained at a temperature of from about 150.degree. C. to about 350.degree. C. for a period sufficient to form the desired product.

Abstract: A process for producing a photodegradable rubber foamed products of excellent softness, which comprises mixing 1,2-polybutadiene with 0.1 to 3.0% of a photosensitizer and with a thermally decomposable foaming agent, irradiating with ultraviolet ray of a wavelength of 240 to 400 m.mu. for 10 minutes or less to form a cross-linked material having a gel fraction of 30 to 80% (in boiling toluene; 7 hours), and heating to 150 to 230.degree. C. to form a foamed product. In particularly preferred embodiments of this invention, the foaming agent is p,p'-oxybis (benzenesulfonylhydrazide).

Abstract: A process for producing an open cell foam by irradiating a composition comprising (a) a thermoplastic resin polymer blend including 1,2-polybutadiene as one component, (b) a photosensitizing agent and (c) a thermally decomposable foaming agent, with ultraviolet light having a wavelength ranging from about 254 to about 400 m.mu. to thereby cross-link mainly the 1,2-polybutadiene, and subsequently foaming the composition at a temperature higher than the softening point of the 1,2-polybutadiene and that of the thermoplastic resin polymer blended therewith and higher than the decomposition temperature of the foaming agent.

Abstract: Methods involving the use of high frequency heating means and temperature-compensating means to expand hollow, thermoplastic resinous microbeads in a controllable manner. The heat-expanded microbeads are suitable for use, for example, in providing viscous, flowable, pressure-compensating fitting materials or compositions.