Grafting peroxidation procedure

The peroxidation procedure, which is the least often used of all the irradiation techniques, involves irradiation of the substrate in the presence of air or oxygen. This produces diperoxides and hydroperoxides on the surface of fhe subsfrafe, which are stable, and the substrate can be stored until the combination with a monomer is possible. Monomer, with or without solvent, is then reacted with the activated peroxy trunk polymer in air or under vacuum at elevated temperatures to form the graft copolymer. The advantage of this method is the relatively long shelf life of fhe infermediate peroxy trunk polymers before the final grafting step. ... 

The introduction of functional groups is suitable to control the chemical and physical properties of the polymer. However, the introduction of functional groups may cause a reaction of the unshared electron pairs of the functional groups with the active catalytic sites. Thus, the active sites of the catalyst are destroyed. In order to overcome this problem, a procedure has been developed, where the functionalized monomers, such as maleic acid, nadic acid or their anhydrides are grafted after the polymerization reaction (4,37). Grafting takes place as a radical reaction, using e.g., dicumyl peroxide. Other attempts use excessive amounts of catalysts. 

Craft Copolymers with Low Backbone-Polymer Content. The procedure for preparing this kind of graft copolymer is based on the dissolution of the backbone polymer in the monomer, dispersion of this solution in water, and polymerization by means of an organic peroxide. It applies only to soluble backbone polymers, such as most EPR s. As the handling of a too-viscous vinyl chloride/backbone polymer solution is impractical, this procedure is normally used for preparing end products of the type VC/backbone polymer (95-5) or (90-10). 

Styrene and butadiene also form copolymers known as high impact polystyrene, or rubber-modified polystyrene, when the content of butadiene is 10%. This type of material has excellent mechanical properties, and it is widely used in practice for the manufacturing of numerous objects, including parts for household appliances, furniture, etc. Rubber-modified polystyrene is commonly used as wood replacement and also for packaging. The synthesis of this material typically is done by dissolving polybutadiene in styrene monomer, followed by free radical polymerization achieved using a peroxide catalyst. This procedure leads to block or graft type copolymers. 

The analysis— by titration procedures and IR spectroscopy—of each of the separated phases showed that MAH becomes mostly grafted to EPR chains, and a small portion of the monomer combines with the PR No differences have been detected in the effect of peroxide initiators that show solubility values close to that of EPR or PR... 

There are three predominant methods for radiation grafting These include (i) the pre-irradiation process, (ii) the peroxidation technique and (iii) the mutual or simultaneous procedure. In preirradiation, the backbone polymer is irradiated in vacuo or in the presence of an inert gas prior to exposure to the monomer which may... 

Grafting polymer by irradiation procedure has been used for the modihcation of biomaterial surfaces (Stannett, 1990). As irradiation sources, EB (Yamada et al., 1990), plasma (Pan, Wesley, Luginbuhl, Denton, Ratner, 2001), gamma ray (Biazar et al., 2010), and ultraviolet (UV) (Biazar, Khorasani, Daliri, 2011 Morra Cassinelli, 1997) are often used for preparing TRCS. These irradiation procedures can be subcategorized into (1) mutual radiation (Pan et al., 2001 Yamada et al., 1990), (2) preirradiation (Biazar et al., 2010, 2011 Della Volpe et al., 1998), and (3) peroxide (Chen, Ito, Imanishi, 1997 Rayatpisheh, Li, Chan-Park, 2012) formation approaches. Mutual radiation includes grafting polymer by EB, plasma, and UV irradiation. In the... 

In simultaneous radiation grafting, the polymer and the monomer are exposed to radiation at the same time. A chemical reaction of the monomer with the polymer backbone radical initiates the grafting reaction [177]. Alternatively, a two-step grafting procedure may be adapted, hi the first step, the polymer is exposed to radiation which leads to the formation of radicals on the macromolecular chain. If the irradiation is carried out in air, radicals react with oxygen, leading to the formation of peroxides and hydroperoxides (hydroperoxide method). When in contact with a monomer, the irradiated polymer initiates grafting by thermal decomposition of the hydroperoxides. 

---