Date

2017

Document Type

Thesis

Degree

Master of Science

Department

Materials Science and Engineering

First Adviser

Pearson, Raymond A.

Abstract

A standard grade diglycidyl ether of bisphenol-A, DGEBA, epoxy resin was evaluated using differential scanning calorimetry, DSC, to determine the optimum stoichiometric balance of a dicyandiamide, DICY, curing agent. The maximum attainable glass transition temperature, Tg, was used as a reference point for the optimal reactivity. The stoichiometric value was found to be 8 epoxy groups to 1 equivalent of dicyandiamide, or an 80% stoichiometric ratio. This value lies within the known literature range of 7-8.5 epoxy groups per dicyandiamide molecule. The optimal blend was then catalyzed with 1, 2 and 3 parts by weight, PBW, of Dyhard UR500, a difunctional urone catalyst. A separate blend was developed for each addition level of Dyhard UR500.Six non-halogenated flame retardants synergies were selected from the literature, and each flame retardant was incorporated at 10 PBW into a separate optimized DGEBA/DICY blend, which contained either 0,1,2 or 3 PBW Dyhard UR500.Cured neat resin and composite samples for each synergy, with each addition level of catalyst, were evaluated to determine the effects of urone catalysis on known non-halogenated flame retardant synergies. The neat resin analysis was performed using thermogravimetric analysis, TGA. The ASTM methods of E1641 and E1877 were used to determine the slope of the thermal endurance graph, or RTI, the slope of the relative thermal index. Composite laminates were prepared using T300B 3K carbon fiber containing 40% resin content, and five samples were evaluated in accordance with the UL-94 test standard.The DSC data showed a reduction in Tg with each increased PBW of urone catalyst. The observed reduction in Tg for these blends is understood to be an accurate representation for the decrease in crosslink density resulting from chain termination during cure. A comparison between the slope of RTI and the UL-94 test data indicate that this reduction in crosslink density has different influences on the flammability and thermal performance of each non-halogenated flame retardant synergy. The effects of the urone catalysis were shown to be highly dependent on the mechanism of decomposition for each flame-retardant synergy. It was also determined that the flame resistance and RTI were dependent on the ability of each flame retardant to synergize with decomposing nitrogen moieties that were contained in the selected urone catalyst.

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