Polymer modification crosslinking

Polyepichlorohydrin (PECH) is well known as a reactive elastomer. Displacement at the carbon-chlorine bond of PECH has been accomplished with a wide variety of nucleophilic reagents, for the purposes of polymer modification, grafting and crosslinking (1, 2). On the other hand, the PECH structure (1) is hardly optimal from the point of view of its reactivity as a substrate for nucleophilic... 

A series of novel styrene- and siloxane-based silanol polymers and copolymers were synthesized by a selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone from corresponding precursor polymers. The conversion of the Si—H to Si—OH in the polymer modification proceeded rapidly and selectively. The silanol polymers obtained in situ showed no tendency for self-condensation to form siloxane crosslinks in solution. Moreover, stable silanol polymers in the solid states were obtained by placing bulky substitute groups bonded directly to the silicon atom. It was found that the properties of these novel silanol polymers and copolymers depended largely on substituents bonded directly to the silicon atom and silanol composition in the copolymers as well. 

The antiplasticization phenomenon is presumably common to all the polymers exhibiting a relatively strong (5 transition, well separated from the a transition. It has been observed for both linear (PVC, polycarbonate, poly-sulphones) and network polymers (amine-crosslinked epoxies). For the case of thermosets, the phenomenon may be a consequence of both internal (change of the network structure) and external (incorporation of miscible additives) modifications of the structure or the composition but it always seems to be a consequence of the plasticization, as shown in Fig. 11.7. 

Luperox. [Atochem N. Am.] Organic peroxide compds. initiator for poly-meiizaticHi, polymer modification, dier-moplastic crosslinking, curing elastomers, high-tenq>. cure ci polyester resins. 

Uses Crosslinker, adhesion promoterfor RTV silicone sealants improves adhesion to PVC and other substrates crosslinker in polymer modification coupling agent for adhesives, coatings, inks, sealants, rubber filler treatment in thermoset/thermoplastic resins fiberglass textiles foundry crude oil extraction ManufJDistrib. ABCR Aldrich Gelest Trade Names Silquest Y-11597... 

Trimethylolpropane trimethacrylate crosslinking agent, moisture-cure polymer modification... 

Synonyms Butanoic acid, 3,3-bis ((1,1-dimethylethyl) dioxy)-, ethyl ester Ethyl 3,3-bis (t-butylperoxy) butyrate Ethyl-3,3-di-(t-butylperoxy) butyrate Classification Org. peroxide Empirical C14H28O6 Properties M.w. 292.36 NFPA Health 2, Flammability 2, Reactivity 2 Uses Polymerization initiator initiator for curing elastomers and for polymer modification thermoplastic crosslinking agent Trade Name Synonyms Aztec EBU-40-G t[Aztec Peroxides] Aztec EBU-40-IC f[Aztec Peroxides]... 

The kinetic descriptions in this chapter are developed for unimolecular scission of an initiator to yield two radicals (Scheme 3.1), the most common means of generating radicals in industrial systems. Thermal initiation of monomers is an additional mechanism capable of forming primary radicals at higher temperatures, as discussed for styrene in Section 3.2.1.3. Photoinitiators that produce radicals by ultraviolet irradiation are often used to initiate crosslinking and curing reactions these polymer modification techniques are not discussed in this chapter. 

Among the polyphenols present in the tree barks, tannins are by far the most interesting oligomers (molecular weights of 1000-4000) in terms of their utilization as macromonomers for the crosslinking of proteins in leather (tanning) and for macromolecular syntheses. The two representative structures of the flavonoid units in tannins are shown in Fig. 1.8. The most salient aspects related to the sources, structures and production of tannins and to their exploitation in polymer modification and manufacture are given in Chapter 8. 

The formation of weak secondary valence gels occurs in poor solvents, which will not prevent all secondary valence bonds between the polymer coils by solvation. The solvation equilibrium is temperature dependent, i.e., it increases at higher temperatures. (ii) The chemical gel is a network structure (crosslinked) formed by covalent hnks between polymer chains. Chemically crosslinked materials are formed by copolymerization, chemical modification, or radiation of linear polymers. The crosslinked network will swell but not dissolve, because the covalent CTossUnks cannot be broken by any solvent and the swelhng depends on the degree of crosslinking. 

---