Abstract: A composition includes a polymethacrylimide polymer which is polymerized in the presence of an epoxy resin and a flame-inhibiting agent. Further, a process is described for making flame-resistant polymethacrylimide, which includes mixing an epoxy resin and a flame-inhibiting agent with a methacrylic acid and methacrylonitrile, and polymerizing. A polymethacrylimide foam so prepared has an LOI value of at least 25 and retains the good mechanical properties that are associated with polymethacrylimide foams.

Abstract: A slab of rigid heat-foamable organic synthetic resin is heated until at least a portion of its surface is at or above the softening temperature of the resin, whereupon a microwave or high frequency field is allowed to act on the slab until foaming occurs.

Abstract: What is disclosed is a method for making a foamed resin sheet from a body of hot foamable synthetic resin containing a blowing agent, which method comprises heating said foamable body to a temperature which initiates foaming, limiting lateral expansion of the resulting foam by contact with a limiting surface while permitting free expansion of the foam thickness, then limiting further expansion of the foam thickness by contact with a limiting surface, and then cooling the foam below the foaming temperature while maintaining said limitations on foam expansion in the lateral and thickness directions by contact with said limiting surfaces.

Abstract: What is disclosed is a method for making a laminate comprising a hard foam layer and a fiber-reinforced synthetic resin layer, which method comprises heating and compressing, in two steps, at least one layer of a high-temperature resistant hard foam and at least one layer of a fiber-containing synthetic resin capable of flowing and of hardening when heated, wherein in a first step, the temperature and pressure employed are sufficient for initiating flow of the synthetic resin and are applied until the synthetic resin has completed flowing, said pressure having a value exceeding the compressive strength of the foam at the temperature employed but not exceeding its compressive strength at room temperature and, wherein in a second step, at a temperature and for a time sufficient to complete hardening of the synthetic resin, pressure is applied which does not exceed the compressive strength of the foam at the temperature used.

Abstract: Laminates comprising at least one reinforcing layer, for example of metal or of fiber-reinforced duroplast resin, bonded to a foamed polyimide layer are disclosed, wherein the particular nature of the polyimide foam imparts high temperature strength properties to the laminates and permits them to be made by methods, also disclosed, employing more extreme conditions of temperature, pressure, and time than are otherwise operable for making conventional laminates.