Journal
INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES
Volume 116, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ijadhadh.2022.103153
Keywords
Cellulose acetate; Castor oil; Green chemistry; Solvent-free synthesis; Bio-sourced adhesive
Funding
- MINECO-FEDER [CTQ2014-56038-C3-1R]
- Junta de Andalucia programme [TEP-1499]
- Ministerio de Educacion [FPU13/01114]
- Universidad de Huelva/CBUA
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This study evaluated the effect of traditional solvent-based and simplified solvent-free methods on the synthesis of bio-based polyurethane adhesives, and compared their performance with commercial adhesives. The results showed that the inclusion of cellulose acetate improved the performance of polyurethanes, and solvent-free synthesis exhibited good adhesion performance.
During the last decades, the replacement of the traditionally petro-based raw materials by eco-friendly substances in polyurethane production has become a great challenge. The synthesis of polyurethanes is mainly conducted by means of a selective reaction between active isocyanate and hydroxyl groups, yielding a characteristic segmented chemical structure. In this study, the traditional solvent-based polycondensation reaction for the synthesis of bio-based polyurethane adhesives, involving first cellulose acetate modification with 1,6-hexamethylene diisocyanate and subsequent crosslinking with castor oil, was evaluated and compared with a simpler solvent-free single-step protocol. The impact of the preparation procedure and reagent proportions, on the chemical structure, thermo-rheological behaviour and ultimate adhesion performance were evaluated. The rheological response and adhesion performance of these bio-inspired polyurethanes were also compared to those found in some commercial adhesives. This research highlights the reinforcing and stabilizing effect of cellulose acetate on bio-polyurethane performance. Particularly, the inclusion of cellulose acetate into the adhesive manufacture allowed a reduction in the maximum curing time under room conditions to almost one week, while yielding a higher thermal stability and a fourfold increase in elastic modulus in comparison to the cellulose acetate-free counterpart. Moreover, the proposed solvent-free synthetic route enhanced the microphase mixing of the ensuing bio-based polyurethanes, exhibiting an adhesion performance comparable to the considered commercial benchmarks, but with failure occurring primarily within the substrate material - the preferred locus of failure.
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