Development of a triazole-cure resin system for composites: Evaluation of alkyne curatives

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 c...

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Bibliographic Details
Published in:	Polymer (Guilford) Vol. 53; no. 13; pp. 2548 - 2558
Main Authors:	Gorman, Irene E., Willer, Rodney L., Kemp, Lisa K., Storey, Robson F.
Format:	Journal Article
Language:	English
Published:	Kidlington Elsevier Ltd 07-06-2012 Elsevier
Subjects:	Alkyne Alkynes Applied sciences Azide azides bisphenol A carboxylic acids Chemical properties Crosslinking Curing Cycloaddition diamines differential scanning calorimetry Dynamical systems Dynamics esters ethylene oxide Exact sciences and technology mechanical properties Polymer industry, paints, wood Polymers Properties and testing Resins Technology of polymers temperature Triazole crosslink triazoles Azide Triazole crosslink Alkyne Cyclopolymerization Ester polymer Epoxy resin Ether polymer Curing (plastics) Experimental study Functional polymer Thermosetting resin Alcohol polymer Azides Chemical modification Triazole derivative polymer Polyynic compound Linear polymer Preparation Crosslinked polymer Chemical reactivity Activation energy
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Summary:	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 “out-of-autoclave” 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′,N′-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 kJ/mol versus 82.3–86.4 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 δ peak in 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 resin and composites for traditional mechanical property testing, which will be reported in a subsequent paper. [Display omitted]
Bibliography:	http://dx.doi.org/10.1016/j.polymer.2012.04.002 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0032-3861 1873-2291
DOI:	10.1016/j.polymer.2012.04.002