Effects of liquid crystalline structure formation on the curing kinetics of an epoxy resin

✍ Scribed by Jingping Liu; Chicheng Wang; Gregory A. Campbell; Jim D. Earls; Ralph D. Priester Jr

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 473 KB
• Volume: 35
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19970430)35:6<1105::aid-pola14>3.0.co;2-a

✦ Synopsis

The curing kinetics of a system containing 4,4-diglycidyloxy-a-methylstilbene (DOMS) and different functionality amines, N-ethylaniline (NEA), aniline, benzenesulfonamide (BSA), and sulfanilamide (SAA), have been studied by differential scanning calorimetry (DSC) under isothermal conditions. The phase transformations during curing of the systems have been monitored by a crosspolarized optical microscope equipped with a hot-stage and photo detector. It has been found that the growth of a nematic liquid crystal structure does not cause a discrepancy from the autocatalytic model for the reactions between aniline and epoxy. There is no liquid crystalline structure formed for the systems containing NEA or BSA, which follow the autocatalytic kinetic models within the temperature range of 120-150ЊC. For the curing reactions between DOMS and SAA, there is a big deviation from the autocatalytic model when the liquid crystals transfer from a nematic structure to a smectic structure. Unlike the usual decrease of reaction rate resulting from diffusion in a heterogeneous reaction, the reaction rate is enhanced. A modified kinetic model has been constructed for this reaction system by introducing a pseudoconcentration term caused from the liquid crystalline structure formation.