Development of a triazole-cure resin system for composites: Evaluation of alkyne curatives
- 作者：Irene E. Gorman ; Rodney L. Willer ; Lisa K. Kemp ; Robson F. Storey ; Robson.Storey@usm.edu
- 关键词：Triazole crosslink ; Alkyne ; Azide
- 刊名：Polymer
- 出版年：2012
- 期刊代码：83_00323861
- 类别：ms
- 出版时间：7 June, 2012
- 卷：53
- 期：13
- 页码：2548-2558
- 文件大小：873 K
摘要
We are developing a resin system that cures via triazole ring formation (cycloaddition reaction of azides with terminal alkynes) instead of the traditional oxirane/amine reaction. The high exothermicity of the azido/alkyne reaction is expected to yield higher extents of reaction under ambient-cure conditions, making the resin system potentially suitable for 鈥渙ut-of-autoclave鈥?curing processes. The difunctional azide-terminated resin, di(3-azido-2-hydroxypropyl) ether of bisphenol-A, was selected as the baseline diazide. A number of alkyne crosslinkers were synthesized and characterized, including propiolate esters of di- and trifunctional alcohols, propargyl esters of di- and trifunctional carboxylic acids, propargyl ethers of di- and trifunctional alcohols, and N,N,N鈥?N鈥?tetrapropargyl derivatives of primary diamines. Commercially available tripropargyl amine was also studied. Those systems employing a propiolate-based alkyne were found to be much more reactive toward the Huisgen 1,3-dipolar cycloaddition than the propargyl species. Curing energetics as a function of alkyne type, investigated through a dynamic differential scanning calorimetry approach, showed a distinct divide between the averaged activation energies of the propiolate and propargyl-type crosslinkers, 69.2-73.6聽kJ/mol versus 82.3-86.4聽kJ/mol, respectively. Cured network properties were readily manipulated through the incorporation of varying amounts of di- versus tri- and tetra-functional alkynes or through incorporation of soft alkylene and alkyleneoxy versus rigid aromatic polyalkynes. As expected, mechanical properties, e.g., the temperature of the tan聽未 peak in聽dynamic mechanical analysis, were found to increase with increasing crosslink density. These results have allowed us to select the most promising systems for scale-up and fabrication of samples of both pure聽resin and composites for traditional mechanical property testing, which will be reported in a subsequent paper.