A simplified mathematical model for the pyrolysis of polymers with inert additives

✍ Scribed by J.E.J. Staggs

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 445 KB
• Volume: 32
• Category: Article
• ISSN: 0379-7112
• DOI: 10.1016/s0379-7112(98)00045-9

✦ Synopsis

A mathematical model for the pyrolysis of a solid consisting of a homogeneous mixture of a polymer and an inert, porous filler is discussed. Change of volume of the solid during pyrolysis is modelled and it is assumed that volatile species, formed from the thermal degradation of the polymer, escape as soon as they are formed. The filler and polymer may have different thermal properties. This simplified model represents an upper bound for the early mass loss rate behaviour for the case where the escaping gases diffuse through the filler residue. Although results are presented for the entire mass loss period, for the case of heavily filled materials we expect them only to be valid for the early stages, when the physical effects of the filler residue are negligible. For lightly filled materials, the model should give better results for most of the mass loss period. Change of volume during pyrolysis is shown to have little effect on the initial mass loss rate for moderate external heat fluxes, but has a considerable effect at later times. Furthermore, the model predicts that for increased ignition resistance, optimum filler properties depend on initial filler loading. Low-to-moderate filler loadings require a filler with a similar density to the host polymer, but with higher thermal conductivity and specific heat capacity; highly loaded systems require a filler with high density as well as high thermal conductivity and specific heat capacity.