new , flexible intumescent protection sheeting of unusually uniform thickness have been prepared from epoxy - polysulfide compositions containing microfibers and the ammonium salt of 1 , 4 - nitroaniline - 2 - sulfonic acid , as disclosed in u . s . pat . no . 3 , 663 , 464 , except that an ammonium salt particle size in the order of 5 to 8 microns and a fiber size of about 1 / 128th inch in length and 3 to 5 microns in diameter have been found critical to obtain the required density of 1 . 46 to 1 . 50 g / cc . the insulation sheeting is prepared by a continuous process involving vacuum mixing , calendering , and curing under very strict conditions which depend to some extent upon the thickness of the sheet produced . the resulting flexible sheet can be wrapped easily and tightly around small diameter missiles , thus affording them for the first time , protection from fire for at least 5 minutes . the material is also suited for the protection of other articles with convoluted or contoured surfaces , which require covering of highly uniform thickness .