Comparison of the curing kinetics of the RTM6 epoxy resin system using differential scanning calorimetry and a microwave‐heated calorimeter

Thermo-physical and mechanical properties of partially and completely cross-linked RTM6 epoxy resin samples in the glassy state have been investigated. A significant dependence of glass transition temperature, density, and modulus on the curing history and the curing degree is found. Density and modulus decrease with increasing curing degree and show a step-like irregularity in the so called transition region, which is related to the transition from rubber to glassy state during cross-linking and the starting of structural relaxation processes. The relationship between the thermo-physical and mechanical properties, which is important for the development of new processing routes for fiber reinforced polymers, is addressed.

Section: Resultssupporting

confidence: 91%

Influence of partial cross‐linking degree on basic physical properties of RTM6 epoxy resin

Moosburger‐Will

Greisel

Sause

et al. 2013

“…This is in agreement with the results obtained using the kinetics models described earlier, although the Kissinger's and Ozawa's methods assumed an n th order kinetic model and the direct fitting assumed an autocatalytic reaction model. A similar effect has been observed during conventional and microwave heating of the RTM6 epoxy–amine system 19…”

Section: Resultssupporting

confidence: 75%

Comparison of the curing kinetics of a DGEBA/acid anhydride epoxy resin system using differential scanning calorimetry and a microwave‐heated calorimeter

Navabpour

Nesbitt

Mann³

et al. 2007

The cure of an epoxy resin system, based upon a diglycidyl ether of bisphenol-A (DGEBA) with HY917 (an acid anhydride hardener) and DY073 (an amine-phenol complex that acted as an accelerator), was investigated using a conventional differential scanning calorimeter and a microwave-heated power-compensated calorimeter. Dynamic cure of the epoxy resin using four different heating rates and isothermal cure using four different temperatures were carried out and the degree of cure and reaction rates were compared. The cure kinetics were analyzed using several kinetics models. The results showed different activation energies for conventional and microwave curing and suggested different reaction mechanisms were responsible for curing using the two heating methods. Resins cured using conventional heating showed higher glass transition temperatures than did those cured using microwave heating. Kinetics analysisThe reactions taking place in an uncatalyzed acid anhydride-cured epoxy system include monoester, diester, and ether formation, as seen in Scheme 1. 12Correspondence to: R. J. Day (richard.day@manchester.ac.uk).

“…The curing process of epoxide resins with amine linkers has been extensively investigated by a number of groups for over 50 years (see Ref. for a brief list of articles that influenced this article). Mooseburger‐Will performed two recent studies describing the properties of partially cured RTM6 which are highly relevant to this work .…”

Section: Resultsmentioning

confidence: 99%

Curing cycle modification for RTM6 to reduce hydrostatic residual tensile stress in 3D woven composites

Gross

Jafari

Tsukrov

et al. 2016

Triaxial residual tensile stresses resulting after cooling a 3D woven composite from the curing temperature cause cracking in the resin pockets for weave architectures that have high through‐the‐thickness constraint. We show how curing cycle modifications can reduce the hydrostatic tensile stress generated by thermal mismatch during cooling of Hexcel RTM6 epoxy resin constrained in a quartz tube which simulates extreme constraint in a composite. The modified curing schedule consists of a high temperature cure to just before the glass transition, a lower temperature hold that takes the resin through the glass transition thereby freezing in the zero stress state, followed by high temperature cure to bring the resin to full conversion. We show that this process is sensitive to heating rates and can reduce the zero stress state of non‐toughened RTM6 resin to a temperature similar to a commercial rubber‐toughened resin, Cycom PR520. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43373.