Poly peroxide crosslinking

Fig. 8. Gel formation of peroxide crosslinked poly(HAMCL), based on coconut fatty acids (COFA), oleic acid (OA), tall oil fatty acids (TOFA) or linseed oil fatty acids (LOFA)...

Peroxide, crosslinking Peroxide, decomposer Peroxide, degradation Peroxy free radicals PES (Poly-ether sulfone) PES blends... 

Blending methyl methacrylate-butadiene-styrene copolymer with poly(vinyl chloride) for instance was shown to decelerate the dehydrochlorination (leading to discoloration). The gel content, surface energy, and the spectroscopic characteristics of the blend was altered by the presence of the seccHid polymer [158]. In ethylene-propylene-diene rubber EPDM where the third monomer is ethylene-2-norbomene (NB), the photo-oxidation rate as measured by the accumulation of typical products such as hydroperoxides, varied linearly with the NB content [159]. The same held true for peroxide-crosslinked compounds of the same EPDM except that the linear relationship was found between the relative carbonyl absorbance on photoxidation and the amoiuit of peroxide used to crosslink the material... 

L.H. Palys, P.A. Callais, M.F. Novits, and M.G. Moskal, New Peroxide Crosslinking Formulations for Metallocene Based Poly (ethylene octene) Copolymer, Paper No. 88 presented at a meeting of the Rubber Division ACS (Oct. 8-11, 1996). 

Two types of networks were prepared (i) randomly crosslinked polybutadiene, and (ii) model urethane networks, (a) polybutadiene based, and (b) poly(e-caprolactone) based. The randomly crosslinked networks were prepared from polybutadiene (Duragen 1203 obtained from General Tire and Rubber Co.) crosslinked with di-cumyl peroxide. Specifications of the as obtained polybutadiene are given in Table I. Polybutadiene was purified by dissolving in benzene and precipitating in methanol. Precipitated polybutadiene was redissolved in benzene. Seven different weights of dicumyl... 

Oil-Based SINs. The SINs produced were based on a castor oil polyester-urethane and styrene crosslinked with 1 mole percent of technical grade (55%) divinyl benzene (DVB) (7). This structure may be written poly[(castor oil, sebacic acid, TDI)-SIN-(Styfene, DVB)], poly[(CO,SA,TDI)-SIN-(S,DVB)]. Benzoyl peroxide (BP) (0.48%) was used as the free radical initiator for the styrene and 1,4-tolylene-diisocyanate (TDI) was used as the crosslinker for the polyester prepolymer. A 500 ml resin kettle equipped with a N inlet, condenser, thermometer, and high torque stirrer was used as the polymerization reactor. 

Because of its chemical inertness, no direct way of curing poly(thiocarbonyl fluoride) has been found. However, creep has been reduced and strength at elevated temperatures improved by milling into the polymer a free-radical generator, such as dicumyl peroxide or azobisisobutyronitrile, and a free-radical acceptor, such as N,N -m-phenylenebismaleimide or triacryloylhexahydro-s-triazine, and curing with heat and pressure (65). A better method is to mill in divinylbenzene and a small amount of benzoyl peroxide and cure with heat and pressure (66). The divinylbenzene forms a crosslinked matrix that mechanically traps poly(thio-carbonyl fluoride) molecules. Since the elastomer is in effect filled with poly(di-vinyl benzene), the final composition is less resilient than untreated poly(thio-carbonyl fluoride). 

The catalytic or initiated reaction involves heating the poly(diene) in an aromatic solvent to temperatures between 120-150 °C in the presence of free radical initiators such as peroxides, hydroperoxides and azo compounds. The ensuing reaction involves addition of maleic anhydride to a polymeric radical which was formed by abstraction of an allylic hydrogen by initiator radicals. Four modes of addition are possible leading to partial structures such as (175)-(178) illustrated with poly(isoprene). It can readily be seen that some crosslinking is an inherent problem because of structures (177) and (178). The amount of gel formed, however, is found to be largely dependent on the initiator employed and can be minimized, especially with hydroperoxide initiators. 

Such graft polymers, which virtually contain all the poly (vinyl chloride) in a grafted condition, can be crosslinked easily with peroxides via the EVA copolymer chains. This corresponds to an indirect statement on the degree of grafting of the products. 

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