Measuring the conversion of epoxy-amines cured with homopolymerizer via near-infrared spectroscopy and dynamic scanning calorimetry Francis Gurman 1 , Andrew Parnell 1 , Anthony Ryan 2 , Anthony Wright 3 , John Wood 3 1 Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, U.K. 2 Department of Chemistry, The University of Sheffield, Sheffield, S3 7hf, U.K. 3 AkzoNobel, International Paint Ltd, Gateshead, NE10 0JY, U.K. Epoxy-amine coatings are used as protective coatings on ships in order to prevent corrosion. They are used due to having good chemical, moisture and corrosion resistance; good mechanical strength and toughness; and being adhesive. These beneficial properties are maximised with increased conversion. Homopolymerizing agents can be used to raise this conversion in formulations of excess epoxy. In this investigation, glass transition temperatures of samples of epoxy-amine, of stoichiometric ratio and excess epoxy, with and without homopolymerizer, were measured via DSC. Near-infrared spectroscopy was used to measure conversion during cure. Commerical liquid epoxy resin (DER331) was used, MXDA the amine and DMP-30 the homopolymerizer. Formulations without DMP-30 decreased in Tg as level of excess epoxy increased. With DMP-30, Tg remained similar to that of stoichiometric ratio without DMP-30, regardless of level of excess epoxy. The Tg of stoichiometric ratio was lower samples of stoichiometric ratio with DMP-30, believed to be due to excess amine. Tg was greater for samples cured with only DER331 and DMP-30, possibly due to a different network from homopolymerization. Conversion via near-IR showed that although adding DMP-30 allowed for complete conversion of epoxy, after the 60C cure, conversion was lower for samples with DMP-30. Upon heating to 100C, the conversion in samples with DMP-30 increased. It is believed that DMP-30 starts to act above 60C. At 60C and below, DMP-30 induces very little homopolymerization. Furthermore, the presence of DMP-30 inhibits the epoxy-amine reaction. More work need to be done looking into the differences in homopolymerization in the presence of amine curing agent and when alone. Furthermore, the influence of DMP-30 on epoxy-amine reactions needs to be investigated. References 1. E. Duemichen et al. “Analyzing the network formation and curing kinetics of epoxy resins by in situ near-infrared measurements with variable heating rates”. In: Ther-mochimica Acta 616 (2015), 49–60. DOI: 10.1016/j.tca.2015.08.008. 2. Fred Meyer et al. “The effect of stoichiometry and thermal history during cure on structure and properties of epoxy networks”. In: Polymer 36.7 (1995), 1407–1414. DOI: 10.1016/0032-3861(95)95918-q 3. John D. McCoy et al. “Cure mechanisms of diglycidyl ether of bisphenol A (DGEBA)epoxy with diethanolamine”. In: Polymer 105 (2016), 243–254. DOI: 10 . 1016 / j.polymer.2016.10.028. 4. S. Mortimer, A. J. Ryan, and J. L. Stanford. “Rheological behavior and gel-point deter-mination for a model lewis acid- initiated chain growth epoxy resin”. In: Macromolecules 34.9 (2001), 2973–2980. DOI: 10.1021/ma001835x
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