Epoxy thermoplastics crystallization

As a class, epoxy thermoplastics generally resist crystallization, but incorporation of biphenylene, p-phenylene or a-methylstilbene segments into backbones that are sufficiently mobile to allow ordered chain packing (i.e. Tg < 100 C) can in a few... 

Much work has been reported on studying the structure of thermoset resins via SAXS, especially focussing on interpenetrating network polymers (IPNs), thermoset nanocomposites, rubber-modified thermosets and thermoset-thermoplastic blends. Most recently Guo et al, (2003) have examined the use of SAXS to monitor the nanostructure and crystalline phase structure of epoxy-poly(ethylene-ethylene oxide) thermoset-thermoplastic blends. This work proposes novel controlled crystallization due to nanoscale confinements. 

Injection molding ABS, acetal, acrylic, alkyd, allyl, amino, cellulosics, epoxy fluorocarbons, liquid crystal polymer, nylon, phenolic, polycarbonate, polyester (thermoplastic), polyester (thermoset), polyethylene, polyphenylene oxide, polypropylene, polystyrene, polysulfone, polyurethane (thermoplastic), PVC, SAN... 

Synthetic thermosetting polymers used in the construction industry are polyester, vinylester and epoxies these materials are generally used to manufacture parts of the machines that produce sustainable energy generators. In addition, thermoplastic resins, such as polyetheretherketone (PEEK), polyethersulphone (PES) and various liquid crystal polymers (LCP) are also used. The latter high performance polymers also meet stringent out-gassing (relevant to space environments) and flammability requirements. 

Figure 1 Cost-related (specific) flexural strength of major thermoplastics, versus cost-related (specific) thermal tolerance. The unit cost is the market price in US cents (1992) of 1 cm plastics. The thermal tolerance is the temperature difference (AT) over room temperature (AT — T - room T), by which temperature (7 ) the flexural modulus is equal to 1 GPa. Designations, abbreviations WFRP-S, wood fiber reinforced PP (S type) of AECL, Canada (See Table 1) PMMA, polymethylmethacrylate PVC, pol)winyl chloride PS, polystyrene PP, polypropylene UP, unsaturated polyesters PA-GF, glass fiber (35%) reinforced polyamide PHR, phenolic resin EP, epoxy resin ABS, acrylonitrile/butadiene/styrene copolymer UF, urea/formaldehyde LDPE, low density polyethylene PC, polycarbonate POM, polyoxymethylene CAB, cellulose acetate butyrate LCP, liquid crystal polymers PEEK, polyether-etherketone PTFE, polytetrafluorethylene.

Dow Chemical developed liquid crystalline polymers (LCP) based on diglycidyl ether of 4-4 -dihydroxy-o -methylstilbene in the 1980s (62,63). Liquid crystal thermoplastics and thermosets based on this novel chemistry showed excellent combinations of thermal, mechanical, and chemical properties, imachievable with traditional epoxies. However, commercialization of these products has not materialized. 

A related application requiring a two-phase treatment is that of polymer dispersed liquid crystals. The optical properties of these films may be electrically modulated and their potential for application is quite high (189). By controlled cooling, the size of the liquid crystal droplets in the polymer matrix may be varied between 1 and 30 )um or larger. Three commercial liquid crystals were dispersed in two thermoplastics [poly(vinylpyrrolidone) and poly(methyl methacrylate)] and epoxy. These were studied by infrared microspectroscopy, both polarized... 

The combustion of the LDH nanocomposites leads to the formation of an intercalated nanostructure of mixed metal oxides (produced by thermal degradation of LDH) and char. This hypothesis is supported by XRD, due to the presence of a peak at 1.28 nm in the epoxy-LDHl and epoxy-LDH2 after the UL-94 test. It is interesting to note that Gilman et al. reported an intercalated structure of char from montmorillonite nanocomposites, with the same interlayer spacing of the chars, 1.3 nm, independent of the chemical structure of the polymer (thermoplastic or thermosetting) or nanostructure (delaminated or intercalated). The same value observed in an LDH-based nanocomposite (1.28 nm) shows that the interlayer spacing in the char may be independent of the nature of the layered crystal. 

Su WFA (1993) Thermoplastic and thermoset main-chain liquid-crystal polymers prepared from biphenyl mesogen. J Polym Sci Polym Chem 31 3251-3256 Su WFA, Chuang CM (2002) Effects of chemical structure changes on curing reactions and thermal properties of cyanate ester-cured rigid-rod epoxy resins. J Appl Polym Sci 85 2419-2422... 

Goossens S, Groeninckx G. High melting thermoplastic/epoxy resin blends influence of the curing reaction on the crystallization and melting behavior. J Polym Sci B Polym Phys 2007 45 2456-69. 

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