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A spreading model for the oxidation of polypropylene
Author(s) -
George Graeme A.,
Celina Mathias,
Lerf Claude,
Cash Gregory,
Weddell David
Publication year - 1997
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19971150107
Subject(s) - polypropylene , materials science , composite material , chemical engineering , engineering
A model for the heterogeneous oxidation of polypropylene (PP) is proposed in which it is considered that there is a small initial fraction, p o , of oxidizing centres which have a high local rate of oxidation. Within these zones there is a free radical chain reaction producing secondary oxidation products, volatiles and chemiluminescence (CL) from peroxy radical termination reactions. These zones progressively spread (rate coefficient b/s −1 ) and the free radical reactions die away within the volume of the original zones, producing a measurable concentration of oxidation products (rate coefficient α/s −1 ). Analysis of the CL‐time curve as representing the instantaneous infectious , fraction, p i , in the spreading model enables the parameters p o , b and α to be determined and profiles of the remaining fraction (p r ) and dead or oxidized fraction (p d ) constructed. Analysis of CL curves from 120°C to 150°C gives an activation energy for spreading in PP particles of 96kJ/mol. Both single particles and groups of particles of different types of PP have been examined and evidence is presented of rapid surface spreading of oxidation from particle to particle.