Glass‐transition temperature based on dynamic mechanical thermal analysis techniques as an indicator of the adhesive performance of vinyl ester resin

Vinyl ester resins are being used extensively as matrices in fiber‐reinforced polymer composite materials, but their use as a structural adhesive has been limited. Initial studies investigating the durability of a vinyl ester as a wood adhesive showed unsatisfactory performance in comparison with other adhesives. In this work, the glass‐transition temperatures (T_g's) of a vinyl ester and a E‐glass/vinyl ester composite material, fabricated by the Composites Pressure Resin Infusion System, were determined with dynamic mechanical thermal analysis. The results indicated that the resin cured under ambient conditions had a much lower T_g (～60°C) than the postcured material (～107°C). This suggested undercuring, that is, incomplete crosslinking, of the resin when it was cured at room temperature. E‐glass/vinyl ester samples, however, showed virtually no difference in T_g between room‐temperature‐cured and postcured samples. The exact reasons for this are not currently known but are thought to be both mechanical and chemical in nature. On the basis of the findings presented in this article, it can be concluded that if this vinyl ester resin is to be used as a structural adhesive, postcuring or formulation to ensure a high degree of crosslinking under ambient conditions is necessary. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2221–2229, 2005