Epoxy systems, bisphenol

Polynuclear Phenol—Glycidyl Ether-Derived Resins. This is one of the first commercially available polyfunctional products. Its polyfunctionahty permits upgrading of thermal stabiUty, chemical resistance, and electrical and mechanical properties of bisphenol A—epoxy systems. It is used in mol ding compounds and adhesives. 

In addition to electrical uses, epoxy casting resins are utilized in the manufacture of tools, ie, contact and match molds, stretch blocks, vacuum-forrning tools, and foundry patterns, as weU as bench tops and kitchen sinks. Systems consist of a gel-coat formulation designed to form a thin coating over the pattern which provides a perfect reproduction of the pattern detail. This is backed by a heavily filled epoxy system which also incorporates fiber reinforcements to give the tool its strength. For moderate temperature service, a Hquid bisphenol A epoxy resin with an aHphatic amine is used. For higher temperature service, a modified system based on an epoxy phenol novolak and an aromatic diamine hardener may be used. 

The/flc-ClRe(CO)3(4,7-Ph2-phen) complex has been demonstrated to be a useful spectroscopic probe in the curing of photosensitive epoxy-based materials [100], Emission spectra obtained from a 0.05-mm thickness film of a mixed epoxy system of bisphenol-A/novalac resin (Interz, SU8) and diglycidyl ether of bisphenol-A (DGEBA) containing cation-generating triarylsulfonium hexafluo-roantimonate salts as photoinitiators (Union Carbide, Cryacure UVI-6974) and... 

Figure 25 (a) Emission spectra at 293 K of/ac-ClRe(CO)3(4.7-Ph2-phcn) in the mixed epoxy system of bisphenol-A/novalac and DGEBA resin (0.05-mm thin film) containing a triarylsulfonium hexafluoroantimonate photoinitiator as a function of UV-irradiation time (A) 0 s, (B) 15 s, (C) 30 s, and (D) 60 s. The emission spectra are uncorrected for photomultiplier response and vertically displaced for clarity. Excitation wavelength is 420 nm in each case, (b) Plot of emission intensity at the MLCT band maximum of /ac-ClRe(CO)3(4,7-Ph2-phen) as a function of UV-irradiation time. (From Ref. 100.)... 

Acitelli, M. A., Prime, R. B., Sacher, E. Kinetic of epoxy cure (1) the system Bisphenol-A diglycidyl ether/m-phenylenediamine, Polymer, 12, 335 (1971)... 

We conclude from our morphology observations and the properties listed in Table VI that at low bisphenol A content the system shows the same appearance and therefore the same properties as the CTBN-epoxy system. As the bisphenol A is increased to an optimum of 24 phr, the particles decrease in size, a two-particle size population develops, and multiple failure sites appear. An example of the bisphenol A modified system is shown in Figure 2 in which the fractograph shows one family of small particles < 0.1 pin diameter and another family of larger particles 1-5 pm diameter. Another feature shown in this micrograph are multiple... 

Table VII. Thermal—Mechanical Properties of Bisphenol A Modified CTBN—Epoxy System...

Figure 4. Schematic reaction steps in bisphenol A modified CTBN-epoxy systems...

Next we looked at the microvoid situation in a bisphenol A modified CTBN-epoxy system. This sample had the highest toughening properties that we developed in the epoxy system because of a two-particle size rubber population that uniquely gives a combination of shear deformation and tensile crazing. Only some of the large particles had microvoid development. Consequently the whitening was much less than when only crazing occurs. The multiple failure sites were still evident. 

The IPNs prepared were composed of a rubbery polyurethane and a glassy epoxy component. For the polyurethane portion, a carbodiimide-modified diphenyl-methane diisocyanate (Isonate 143L) was used with a polycaprolactone glycol (TONE polyol 0230) and a dibutyltin dilaurate catalyst (T-12). For the epoxy, a bisphenol-A epichlorohydrin (DER 330) was used with a Lewis acid catalyst system (BF -etherate). The catalysts crosslink via a ring-opening mechanism and were intentionally selected to provide minimum grafting with any of the polyurethane components. The urethane/epoxy ratio was maintained constant at 50/50. A number of fillers were included in the IPN formulations. The materials used are shown in Table I. 

Epoxy resins produced by the reaction of bisphenol A and epichloro-hydrin are versatile polymers with several useful properties (subsection 2.2.2.1). However, one significant weakness is their brittle nature. Incorporation of plasticisers is not very useful. Dibutyl phthalate is an exception, showing good compatibility but offering only limited ability to flexibilise the resin. Moreover, plasticisers affect the mechanical properties and chemical resistance of the cured system. With polyurethanes it is possible to complement the flexibility of the epoxy system. Numerous attempts have been made to combine the two types to achieve beneficial modifications (Lee and Nivelle, 1967). These modifications proved successful under high-temperature cure but inferior results were obtained for ambient cures. 

The curing behavior of an epoxy system was investigated by dynamic differential scanning calorimetry (DSC). The epoxy resin (R) was a blend of bisphenol-A-diglycidylether (90%) and a monoepoxide (10%). The hardener (H) was a triethylene-tetramine-phenol-formaldehyde adduct containing 2% free phenol. 

In some epoxy systems ( 1, ), it has been shown that, as expected, creep and stress relaxation depend on the stoichiometry and degree of cure. The time-temperature superposition principle ( 3) has been applied successfully to creep and relaxation behavior in some epoxies (4-6)as well as to other mechanical properties (5-7). More recently, Kitoh and Suzuki ( ) showed that the Williams-Landel-Ferry (WLF) equation (3 ) was applicable to networks (with equivalence of functional groups) based on nineteen-carbon aliphatic segments between crosslinks but not to tighter networks such as those based on bisphenol-A-type prepolymers cured with m-phenylene diamine. Relaxation in the latter resin followed an Arrhenius-type equation. 

Another case confirms the suspected role of conducting nanoparticles in increased conductivity during and after the reaction in a similar epoxy system. Martin et al. (2005) dispersed CNTs into a bisphenol-A based epoxy resin and reacted it with an amine hardener at SO C. After about 600 s. 

Generally, a vinyl ester could be classified as methyl acrylic acid extended bisphenol A epoxy, acrylic acid bisphenol E epoxy, a bisphenol F novolac epoxy, or a urethane modified ester. Each will provide a different degree of resistance. Vinyl ester lining systems have been successfully applied to provide protection to stack liners, ducting, scrubbers, thickener tanks, and other vessels in FGD plants, stacks and ducts, electrostatic precipitators, and bag house environments. 

Sue Sue, H.-J., Puckett, P. M., Bertram, J. L., Walker, L. L., Garcia-Meitin, E. 1. Structure and property relationships in model diglycidyl ether of bisphenol-A and diglycidyl ether of tetra-methyl bisphenol-A epoxy systems. I. Mechanical property characterizations. J. Polym. Sci. Part B - Polym. Phys. 37 (1999) 2137-2149. 

To date only few dielectric relaxation studies have been reported on thermosetting nanocomposite systems. Kanapitsas et al. [109] reported isothermal dielectric relaxation studies of epoxy nanocomposite systems based upon three different clay modifications, a low viscosity epoxy resin based on the diglycidyl ether of bisphenol-A type (Araldite LY556, CIBA) and an amine hardener in a temperature range of 30-140 °C. Whilst details on the epoxy system investigated and the nanocomposite morphology were vague, it was reported that the overall mobility is reduced in the nanocomposite compared to the neat matrix resin. 

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