Curing, composite resins crosslinking

An example for the polymer network characterization by the 13C CP MAS NMR is shown in Fig. 35. The chemical structure of the cured polystyrylpyridine resins (PSP), synthesized from terephthalic aldehyde and collidine (2,4,6-trimethylpyridine), is determined from CP-MAS spectra by comparison with the solution state spectra of the model compounds and supported by selective DD observations. The CH and CH2 of the crosslinking points, as deduced from the model BP2, give rise to a composite line at about 45 ppm the assignment of other signals is indicated in the figure 239). 

Heat resistant IPN systems were obtained by simultaneous radical polymerization of divinylbenzene with benzoyl peroxide as an initiator and Zn acetate as cyclotri-merization catalyst [122], Hot-curing composition contains BPA/DC, BMI, epoxide resin, Zn acetate and divinylbenzene [123]. Crosslinked compositions consisting of BPA/DC and BPA bis(vinylbenzyl) ether show Tg values above 240 °C [124]. 

Naphthalate polyester articles can be coated with polymerizable and crosslinkable compositions. The composition is made from the matrix and a large amount of benzotriazole derivatives. This class of compounds absorbs UV light. The cured compositions help protect the naphthalate polyester from UV exposure and other weathering effects [78]. The matrix consists of acrylic resins and methacrylic resins. The compositions are photopolymerizable. 

Phthalic anhydride and its hydrogenated derivatives are among the more common anhydride curatives. They provide more rigidity to the cured epoxy resins than linear anhydrides because of the cyclic structures and the ability to crosslink multifunctional epoxy resins. Tetrahydrophthalic anhydride (56) and it derivatives, such as methyltetrahydrophthalic anhydride have been described in coating and adhesive compositions... 

Similar to the vinyl ester resins, the cured epoxyfumarate resins are distinguished by enhanced chemical resistance (e.g. in aqueous 20% NaOH at 60 °C), heat deflection temperature and flexibility. The chemical composition of the R group (methyl, ethyl, n-butyl, benzyl, cyclohexyl) influences the properties of the crosslinked epoxyfumarate resins [6]. If the R group contains bromine (e.g. tribromoneopentyl or 2,3-dibromopropyl), the cured resins are fire retardant [7]. Moreover, the brominated resins are distinguished by increased Martens heat deformation temperature and low water absorption. 

Heat resistant resin compositions based on BMI/aminophenol-Epoxy blends are achieved by reacting a BMI/p-aminophenol 1 1 adduct with epoxy resin (62). Both the secondary amine and phenol functionality may react with the epoxy resin and subsequently cure through an imidazole catalyst. Imidazole catalysts promote both the epoxy/phenol reaction and the anionic maleimide crosslinking. The formation of a 1 2 BMI/aminophenol adduct, as in Fig. 20, is claimed in a patent (63). The hydroxy terminated BMI/aminophenol adduct is an advantageous curing agent for epoxy resins when high temperature performance is desired. 

Throughout this chapter the chemical concepts employed to synthesize and cure addition poly(imides) have been discussed and their use as matrix resins for fiber composites has frequently been mentioned. The most important property of the imide backbone structure is the inherent thermal stability. The target of achieving the temperature performance of linear poly(imide) has not been reached, because of the aliphatic nature of the reactive endgroups, and because of the low molecular weight of the imide backbone required for processing. Future developments of addition polyimides will, as in the past, focus on the requirement of high thermal and thermal oxidative stability of the crosslinked... 

The formulated adhesives are generally available as films or solvent solutions. They are commonly used as laminating adhesives for film or metallic foil because of their high peel strength. A composition consisting of a plasticized polyvinyl chloride copolymer and an epoxy resin can be cured with an aliphatic polyamine, which will crosslink by reacting with both resins. This adhesive possesses excellent adhesion to metals. 

In Sect. 5, the macroscopic extension at break of the glassy networks considered was shown to be s, 4-6% and only weakly dependent on the network s chemical composition. However, local plasticity markedly depends on the chemical composition of the network. L( in the samples with an excexs of amine (P = 1.3) is about 10 times larger than in the samples with an excess of epoxy groups (P = 0.8). This is an additional argument in favour of the assumption of the keyrole of 3-linked chemical crosslinks in network plasticity (see Sect. 5 and Fig. 20). It is evident that the excess of amine in the initial mixture leads to a relatively high concentration of 3-type crosslinks in cured resins. 

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