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Factors influencing the kinetics of the alkaline depolymerisation of poly(ethylene terephthalate). I: The effect of solvent
Author(s) -
Ramsden M. John,
Phillips Julia A.
Publication year - 1996
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/(sici)1097-4660(199610)67:2<131::aid-jctb538>3.0.co;2-f
Subject(s) - solvent , chemistry , hydroxide , activation energy , kinetics , dissolution , solvent effects , potassium hydroxide , alkaline hydrolysis , diffusion , hydrolysis , ethylene , inorganic chemistry , organic chemistry , catalysis , thermodynamics , physics , quantum mechanics
The effect of solvent on the kinetics of the alkaline depolymerisation of poly(ethylene terephthalate) (PET) has been investigated. The process was found to be first‐order with respect to hydroxide ion concentration, and the activation energy for the reaction in water was found to be 69 ± 13 kJ mol −1 (95% confidence limits). This is higher than the reported activation energy in the homogeneous molten state depolymerisation, but lower than the reported activation energies for the neutral solid‐state heterogeneous hydrolysis. The choice of solvent plays an important role in the alkaline depolymerisation process; strong solvent–polymer interactions can facilitate the depolymerisation by causing swelling to mitigate diffusion constraints, and strong solvent–solvent interaction can enhance the nucleophilicity of the hydroxide ion. However, the first‐order kinetic behaviour with respect to [NaOH] has been shown to be applicable over a limited range in some solvent systems, the limitation being due to ion‐pairing which leads to reduced activity of the hydroxide ion.