New thermosets obtained by the cationic copolymerization of diglycidyl ether of bisphenol A with γ‐caprolactone with an improvement in the shrinkage. I. Study of the chemical processes and physical characteristics |
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Authors: | Servando González Xavier Fernández‐Francos Josep Maria Salla Angels Serra Ana Mantecón Xavier Ramis |
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Institution: | 1. Laboratori de Termodinàmica, Escola Tècnica Superior d'Enginyeria Industrial de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain;2. Departament de Química Analítica i Química Orgànica, Universitat Rovira i Virgili, Marcel·lí Domingo s/n, 43007 Tarragona, Spain;3. Laboratori de Termodinàmica, Escola Tècnica Superior d'Enginyeria Industrial de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, SpainLaboratori de Termodinàmica, Escola Tècnica Superior d'Enginyeria Industrial de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain |
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Abstract: | Diglycidyl ether of bisphenol A was cured with different proportions of γ‐caprolactone with ytterbium triflate as an initiator. The curing was studied by means of differential scanning calorimetry and Fourier transform infrared in the attenuated total reflection mode. The latter was used to monitor the competitive reactive processes and to quantify the conversions of the epoxide, lactone, and intermediate spiroorthoester groups. A partial depolymerization process from the cured material to free γ‐caprolactone was also identified. The formation of a stable carbocation and the coordinative capability of ytterbium triflate were the reasons for this unexpected process. The thermal and dynamic mechanical properties of the cured materials were determined with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. An increase in the proportion of γ‐caprolactone resulted in an increased curing rate, a decrease in the shrinkage after gelation, and a significant decrease in the glass transition temperature. The introduction of ester linkages into the three‐dimensional structure led to more thermally degradable thermosets. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1968–1979, 2007 |
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Keywords: | cationic polymerization epoxy resins infrared spectroscopy lactones thermosets |
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