Hydrolytic kinetic model predicting embrittlement in thermoplastic elastomers

• Published in: Polymer degradation and stability 2020-01, Vol.171, p.109002-12, Article 109002
• Main Authors: Bardin, Antoine, Le Gac, Pierre-Yves, Cérantola, Stéphane, Simon, Gaëlle, Bindi, Hervé, Fayolle, Bruno
• Format: Article
• Language: English
• Subjects: Carboxylic acids; Catalysts; Chain scission; Cleavage; Deactivation; Elastomers; Elongated structure; Embrittlement; Engineering Sciences; Hydrolysis; Kinetic model; Kinetics; Materials; Polyurethane; Polyurethane resins; Reaction kinetics; Relative humidity; Structure-property relationships; Submerging; Thermoplastic composites; Thermoplastic elastomer; Thermoplastic elastomers; Urethane thermoplastic elastomers
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2019.109002

A hydrolytic kinetic model predicting chains scissions of a polyurethane elastomer (TPU) containing an anti-hydrolysis agent (stabilization via carbodiimide) was developed. This model is based on four components: uncatalysed hydrolysis, acid-catalysed hydrolysis, carboxylic acid dissociation and competitive carbodiimide-based deactivation of acid. Protons were considered as the key catalyst responsible for the hydrolysis. Model parameters were determined by fitting experimental data measured on unstabilized and stabilized TPUs, aged in immersion from 40 to 90 °C. Scission kinetics were predicted for immersion and 50% relative humidity conditions, from 10 to 100 °C. Structure-failure property relationships were also investigated, between molar mass and elongation at break. A master curve was established for elongation at break with molar mass, including both TPUs at four ageing temperatures. By combining predictions for scission kinetics with the molar mass-elongation at break master curve and an embrittlement molar mass as the end-of-life criterion, non-Arrhenian lifetime predictions are proposed for all exposure conditions considered. •Hydrolysis of ester group was highlighted with NMR.•A hydrolytic kinetic model describing chains scissions was successfully developed.•Molar mass-elongation at break has been identified as a suitable structure-property relationship for TPU.•TPUs Lifetime prediction in immersion and at 50% RH was realized.