Degradation of epoxy resins

D.P. Bishop and D.A. Smith, Combined pyrolysis and radiochemical gas chromatography for studying the thermal degradation of epoxy resins and polyimides. I. The degradation of epoxy resins in nitrogen between 400° and 700°C. J. Appl. Polym. Sci., 14, 205 (1970). 

A comprehensive study of the thermal degradation of epoxy resins has been reported by Lee [239]. Their stability was found to be lower than that of polycarbonate, polyphenylene sulphide and teflon (Fig. 64). 

It is generally accepted that degradation of epoxy resins starts by dehydration of secondary alcoholic groups followed by homolytic scission of the formed allylic bond [34, 35]. There have been various studies carried out for the brominated epoxy resin treatment. In the study of Balabanovich [33], brominated epoxy resin produces gases and oil as pyrolysis products at the temperature of about 100 °C. However, these pyrolysis volatiles are contaminated by brominated phenols, brominated alkanes, and HBr, which is a difficult point for pyrolysis of brominated epoxy resin. 

R Original IR spectrum of epoxy resin. b TD Theynal degradation. 

Epoxy resin can have varying amounts of inorganic material remaining in the product after its synthesis. One of these is sodium chloride, which is formed by the reaction of sodium hydroxide with epichlorohydrin molecules, as described in Chap. 2. This is important in electrical applications because the sodium salt can be hydrolyzed and can degrade electrical properties. Some epoxy resin manufacturers will offer special ultrapure electrical grades or low-chlorine grades of epoxy resins for application where this is an important factor. 

Therefore, catalysts merely act as an initiator and promoter of epoxy resins curing reactions. The amounts of catalyst used with epoxy resins are usually determined empirically and are chosen to give the optimum balance of properties under the required processing conditions. Generally, only several parts per hundred of catalyst is used with an epoxy resin. Excess amounts of catalyst can result in poor physical properties and degraded resin. 

Monofunctional epoxy diluents are used primarily with DGEBA epoxy blends. The most common monofunctional diluents are butyl glycidyl ether and phenyl glycidyl ether. The effect of butyl glycidyl ether and other reactive diluents on the viscosity of epoxy resin is shown in Fig. 6.3. Because the monofunctional diluents reduce crosslink density, they are used at relatively low levels to avoid degrading heat and chemical resistance or other properties of the adhesive. 

Suzuki T, Sunose T, Amasaki I, Ozawa T. Chemiluminescence of epoxy resin. Polym Degrad Stabil 2002 77 87-91. 

It seems that the addition of epoxy resin improves wet strength for some MDF cements. It was reported that epoxy resin can harden in the presence of hydroxide ions (OIT) from the cement [19] and as consequence, an epoxy network may form, which may decrease degradation. 

Jin Jin, F.-L., Park, S.-J. Improvement in fracture behaviors of epoxy resins toughened with sulfo-nated poly(ether sulfone). Polym. Degrad. Stab. 92 (2007) 509-514. 

Denq and co-workers [17] applied a variety of techniques in their study of the thermal degradation behaviour of epoxy resins with propyl ester phosphazine ... 

Various other works have discussed the application of MS and other techniques in thermal degradation. Studies have been made on a nnmber of epoxy resins [18-20] based on DGEBA. These inclnde tetraglycidyl ether tetrakis (hydroxyphenol) ethane [17], araldite-epoxy resins [18]. 

In the last years the thermal behavior of carbon fibre reinforced epoxy resins has been investigated by different research groups [50]. Regnier et al. performed a kinetic study on the thermal degradation of carbon fibre/epoxy composites, both in air and in inert atmosphere. The thermal degradation of the composites occurred in three stages [51]. The presence of vapour-grown carbon nanofibres into the epoxy resin matrix did not influence the thermal stability of the resin. The decomposition temperatures in the case of composites were almost the same with the decomposition temperature of epoxy resin [52]. 

Patussi V, Kokelj F, Buttazzi P (1995) Occupational airborne allergic contact dermatitis due to 3-amino-methyl-3,5,5-trimethylcyclo-hexylamine. Contact Dermatitis 32 239 Peltonen K (1986) Thermal degradation of epoxy powder paints (Doctoral dissertation). University of Kuopio, Kuopio, Finland Pigatto PD, Bigardi AS, Cusano F (1995) Contact dermatitis to cocamidopropylbetaine is caused by residual amines relevance, clinical characteristics, and review of the literature. Am J Contact Dermatitis 6 13-16 Potter WG (1975) Uses of epoxy resins. Newnes-Butterworths, London... 

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