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The effect of heating rate on the thermal degradation of polybutadiene
Author(s) -
Brazier David W.,
Schwartz Norman V.
Publication year - 1978
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1978.070220109
Subject(s) - depolymerization , polybutadiene , thermogravimetric analysis , activation energy , yield (engineering) , materials science , polymer chemistry , differential scanning calorimetry , arrhenius equation , degradation (telecommunications) , chemistry , organic chemistry , polymer , composite material , thermodynamics , copolymer , telecommunications , physics , computer science
Using derivative thermogravimetric analysis (DTG), polybutadiene is shown to degrade by two distinct weight loss events when heated dynamically. The volatile products of the first stage are almost exclusively depolymerization products (butadiene and vinylcyclohexene). The residue—cyclized and crosslinked polybutadiene—degrades in the second stage. Increasing the heating rate or sample size results in increased depolymerization; and at a 100°C/min heating rate, up to 50% of the initial sample weight is converted to depolymerization products. Differential scanning calorimetry (DSC) indicates that degradation is exothermic in the temperature range of the first weight loss stage. The determined exothermicity (0.95 kJ/g polybutadiene) is independent of heating rate. Infrared observations show cis—trans isomerization in the same temperature range. Kinetic analysis of the DTG data yields an apparent activation energy of 251 kJ/mole for depolymerization, while for the overall reactions is the first stage, DSC data yield 170 kJ/mole. Why the exothermicity of the degradation is independent of the depolymerization/cyclization ratio is not clear.