Process for forming a fire retardant intumescent material having two stages of expansion

摘要

An intumescent material and a process for forming of an intumescent material is disclosed including a two stage intumescent expansion characteristic. The composition includes an intumescent material having a primary expansion ingredient such as expanding graphite in combination with a pre-expansion material adapted to provide intumescent expansion at a temperature less than that of the primary expansion material. The pre-expansion material preferably is a liquid isobutane encapsulated within microspheres of any latex material or polyvinylidene. The pre-expansion step allows for a low density mass having fairly uniform dimensions relative to the original proportions of the specimen. A novel process for forming same allows heating to a temperature greater than the pre-expansion temperature within a closed mold to prevent pre-expansion by containment therein and still allow heat fusing of the fire barrier form.