Monomers graft

If polyvinyl alcohol is used as the reducing agent and the oxidation is conducted in the presence of vinyl monomer, grafting occurs. This method of grafting yields substantially pure graft copolymers since the free radicals are formed exclusively on the polymer backbone. 

Based on the ESR studies of Ce(IV) ion-BzyAcAc-MNP, Ce(IV) ion BzAc-MNP systems as mentioned before, the grafting reaction of P(St-CH2-AcAc) will take place on the methene carbon of 1,3-dikeone via the abstraction of hydrogen by the Ce(I V) ion to form radicals and then initiate monomer graft copolymerization. The initiation mechanism of graft copolymerization is proposed in Scheme (10). 

An alternative to the direct use of peroxides in monomer grafting is to first functionalize the polymer with initiator or transfer agent functionality. 

Various (meth)acrylic monomers have been successfully grafted onto polyolefins. Most studies deal with functional monomers. Grafting yields obtained with PP are usually low (<20%) and are dependent on the particular monomer. Liu et al.jM carried out a comparative study on the grafting of various functional methacrylates onto PP. The experiments were performed in a batch mixer at 180 °C with 7 wt% monomer and 0.05 wt% 22 as an initiator. Grafting levels (wt%) obtained under these conditions were as follows HPMA (I), TBAEMA (1), GMA (0.8), IIEMA (0.4), DMAEMA (0.3), 32 (0.2). Grafting yields to PE appear generally higher. 

Graft copolymers are those in which a homopolymer backbone has a number of branches, which are themselves homopolymers of another monomer, grafted on ... 

Prior irradiation of the backbone polymer in the presence of oxygen and subsequent monomer grafting by polymeric peroxides... 

Flexible polyurethane foam pre-irradiated with ionizing radiation in the presence of air can be readily grafted with vinyl monomers. Relatively low radiation doses (3 to 10 megarads) are required to graft various polar vinyl monomers. Grafting of as little as 2% by weight of acrylamide, methacrylamide, or acrylic acid converts the normally hydro-phobic polyurethane foam into a water-wettable sjjonge. 

If the reaction takes place in the presence of monomer, grafting occurs in the usual manner. The fact that some homopolymerization also occurs in the redox-catalyzed grafting system can be explained by a chain-transfer mechanism (Reaction 10). The growing polymer radicals can abstract hydrogen atoms from the monomer, forming monomer radicals and thereby initiating homopolymerization. 

Dose, Monomer Graft, Tensile, Elonga- sion Set, Rebound,... 

Random copolymers are characterized by the statistical placement of comonomer repeating units along the backbone chain. Alternating copolymers, as the name suggests, are characterized by the alternate placement of monomers. Graft copolymers are made of chemically linked pairs of homopolymers and resemble a comb. Block copolymers are composed of terminally connected structures. 

Graft reactions and functionalization reactions Graft copolymer of polystyrene and maleic anhydride graft copolymer of polyolefines and vinylsilanes graft copolymers of polyolefines and (meth)acrylic monomers, graft copolymer of EVA with acrylic acid graft copolymer of polyolefines and maleic anhydride halogenation of polyolefines or EVA... 

Waak14) successfully copolymerized co-allylpolystyrene macromonomers with acrylonitrile and several other monomers. Graft copolymers resulted in spite of the fact that allylic double bonds are not very suitable for free-radical copolymerization. However, a detailed characterization of these copolymers has not been given. 

However, since free radicals generally lack selectivity in attacking substrates or vinyl monomers, grafting efficiencies lower than 100% are to be expected. 

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