Structure cross-linking reaction

The effect of specific chemicals on molecular structure, particularly in so far as they lead to degradation and cross-linking reactions. 

The cross-linking reaction is carried out after the resin has been applied to the glass fibre. In practice the curing is carried out either at elevated temperatures of about 100°C where press mouldings are being produced, or at room temperature in the case of large hand lay-up structures. 

In some cases, diene polymers (for instance polychloroprene rubbers) can add to the growing polymer chain by 1,2 addition (also called vinyl addition). This creates labile hydrogen or reactive halogen on tertiary carbon atoms. A few percent of this type of structure in the rubber will assist cross-linking reactions. 

Temperature dependence (related to the temperature dependence of the conformational structure and the morphology of polymers) of the radiation effect on various fluoropolymers e.g., poly (tetrafluoroethylene-co-hexafluoropropylene), poly(tetrafluoroethylene-co-perfluoroalkylvinylether), and poly(tetrafluoroethylene-co-ethylene) copolymers has been reported by Tabata [419]. Hill et al. [420] have investigated the effect of environment and temperature on the radiolysis of FEP. While the irradiation is carried out at temperatures above the glass transition temperature of FEP, cross-linking reactions predominate over chain scission or degradation. Forsythe et al. [421]... 

Contents Structure and reactivity of monomeric, molecular tin(ll) compounds / M. Veith, O. Recktenwald — Chirality, static and dynamic stereochemistry of organotin compounds / M. Gielen — Coordination effects in formation and cross-linking reactions of organotin macromolecules / Z. M. O. Rzaev. 1. Organotin compounds — Addresses, essays, lectures. I. Gielen, M. (Marcel), 1938 — II. Series. 

A thermosetting resin converts to an infusible, cross-linked plastic which is insoluble in any solvent after curing. Because of this irreversible cross-linking reaction, excellent physical properties such as heat resistance, creep resistance, mechanical strength, etc., are obtainable through design of the polymer structure. 

GA is exclusively monomeric — a mixture of several monomeric structures which are in fast equilibrium with each other — at the starting point of the cross- linking reaction. The content of a, y3 - unsaturated polymeric structure is quite negligible, which has been believed, by many biochemists, to be the principal species in GA solution and to play the central role in the cross- linking reaction. 

The structure of a segment of the peptidoglycan before and after the final cross-linking reaction. 

Figure 17 Protein cross-linking reactions done using homobifunctional reagents can result in large polymeric complexes of multiple sizes and indefinite structure.

Glutaraldehyde is the most popular bis-aldehyde homobifunctional cross-linker in use today. However, a glance at glutaraldehyde s structure is not indicative of the complexity of its possible reaction mechanisms. Reactions with proteins and other amine-containing molecules would be expected to proceed through the formation of Schiff bases. Subsequent reduction with sodium cyanoborohydride or another suitable re-ductant would yield stable secondary amine linkages (Chapter 2, Section 5.3, and Chapter 3, Section 4). This reaction sequence certainly is possible, but other cross-linking reactions also are feasible. 

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