Heat release rate solid polymer flammability

The majority of solids will undergo a chemical decomposition, better known as pyrolysis. Pyrolysis is the chemical decomposition of the solid fuel by the apphcation of a heat source. As the molecular bonds begin to break down, smaller molecules (lower molecular weights) are released in the gaseous form and ignited if released from the solid at a sufficient rate that the flammable limit is reached. Most solids will undergo this process of pyrolysis when exposed to a sufficient heat source some, however, may melt first and vaporize like a liquid. For example, cellulosic materials (i.e., wood, paper) and thermoset polymers will undergo pyrolysis and leave behind a carbonaceous residue (char) in the presence of a sufficient heat source, but thermoplastics (plastic bottles) will melt when exposed to heat and vaporize similar to liquids. 

---