This specification covers one type of quartz cloth impregnated with a heat-reactive, thermosetting, hot-melt, addition-type, polyimide resin system, furnished in continuous rolls of full width material. This cloth has been used typically for structural laminates requiring high strength, excellent electrical resistance, and heat resistance for long-term service up to 230 degrees C (446 degrees F) and short-time service up to 260 degrees C (500 degrees F), but usage is not limited to such applications.