Graft polyolefins techniques

Dow has prepared a compatibilized blend of PC and linear PE. The compati-bilizer used was EPDM grafted with SAN. The product has high impact strength and good melt processability. Polymer alloys with S-AMS copolymer and PP with styrene-grafted polyolefin copolymer have been reported. Triax 1000 of Monsanto is a blend of nylon and ABS compatibilized with styrene-acrylonitrile and glycidyl methacrylate terpolymer. The compatibilizer often improves the property balance of an immiscible blend. Reactive compatibilization is an emerging technique. 

Qiu, W, Endo, T., and Hirotsu, T. (2005). A novel technique for preparing of maleic anhydride grafted polyolefins. European Polymer Journal 41(9), 1979 1984. 

Radical induced grafting may be carried out in solution, in the melt phase,292 29 or as a solid state process.296 This section will focus on melt phase grafting to polyolefin substrates but many of the considerations are generic. The direct grafting of monomers onto polymers, in particular polyolefins, in the melt phase by reactive extrusion has been widely studied. Most recently, the subject has been reviewed by Moad1 9 and by Russell.292 More details on reactive extrusion as a technique can be found in volumes edited by Xanthos," A1 Malaika and Baker et a 21 7 The process most often involves combining a frcc-radical initiator (most commonly a peroxide) and a monomer or macromonomer with the polyolefin as they are conveyed through the extruder. Monomers commonly used in this context include MAII (Section 7.6.4.1), maleimidc derivatives and malcate esters (Section 7.6.4.2), (meth)acrylic acid and (meth)acrylate esters (Section 7.6.43), S, AMS and derivatives (Section 7.6.4.4), vinylsilancs (Section 7.6.4.5) and vinyl oxazolines (Section 7.6.4.6). 

Radiation grafting is an extremely valuable one-step method for directly modifying the properties of polymers (y,2). The technique has been used with a wide variety of naturally occurring macromolecules such as wool (3) and cellulose (4) and also with many synthetic polymers, particularly the polyolefins (2, 5, 6) ... 

This problem has also been more durably addressed by modifying the surface properties of the polyolefin materials used to form polymeric sheets, by graft-copolymerizing to those surfaces a monomeric substance which, after copolymerization, confers hydrophilic properties and, in some cases, ion exchange properties. This technique has been found to be practical when the porous substrate is formed from PE, which has been found to lend itself well to a graft-copolymerization reaction of this kind. However, it has been found that when such a reaction is... 

As films are used e.g. the polymerization product of ethylbenzene and divinylbenzene (33) the copolymer of styrene and butadiene (755) the copolymer of styrene and butadiene mixed with polyethylene (157) a vulcanized or cyclized copolymer of an aromatic vinylcompound and an aliphatic conjugated polyene (2). As a crack resisting matrix is mentioned the copolymer of styrene, divinylbenzene and butadiene with e.g. dioctylphthalate as a plasticizer (176). Other examples are the copolymers of unsaturated aromatic compounds and unsaturated aliphatic compounds (77) and the reaction products of polyolefines and partially polymerized styrene (174). Primary groups can be introduced also with the help of Friedel-Crafts catalyst. Ts. Kuwata and co-workers treated a film of a copolymer of styrene and butadiene with an aluminium-ether complex and ethylenedichloride (79). Afterwards they allowed the film to react with trimethylamine. Another technique is the grafting of e.g. a polyethylene film with styrene (28). 

The same technique can be used to dye a material that is otherwise difficult to dye. An ethylene-propylene copolymer rubber was reacted first with maleic anhydride, then with an aromatic amine dye in an extruder to produce a dyed rubber.81 Dye sites can also be inserted into polyolefins by grafting them with dimethylaminoethyl methacrylate, using azo or peroxide catalysts in an extruder.82 jV-Vinylimidazole has been grafted to polyethylene in an extruder with the help of dicumylperoxide.83 The product was mixed with an acrylic acid-modified polypropylene and used to compatibilize polyethylene and polypropylene. This could be helpful in the recycling of mixed polyolefins from municipal solid waste. Recycling of cross-linked (thermoset) polymers is more of a problem because they cannot be remelted in an extruder. However, they can be if... 

Heterogeneous composite materials made from waste or recycled components such as polyolefin polymers and wood fibers were shown to be made compatible by T. Czvikovszky through the use of small amounts of monomers that graft onto the two normally incompatible phases of said mixtures. These compositions demonstrated sufficient material properties to be used in the construction of truck and automotive components, such as door and side panels. To exploit the use of such recycled resources, process techniques in mixing and compounding had to be developed. 

Examples in these and other categories could be multiplied indefinitely, but these few will suffice. The fields of compounding, additives, blends, grafts, and composites all see continual small advances that eventually add up to major gains and will undoubtedly continue to do so. Similarly, new applications and new shaping techniques will continue to be developed (e.g., rotational molding is old hat but not exhausted, solid-phase forming has yet to come into its own, and polyolefin foams have enormous potentials that have scarcely been tapped). 

Instead of polybutadiene, polyolefins may be used as substrate upon which styrene and acrylonitrile can be grafted. This, however, is difficult by conventional techniques because no double bonds are available for the grafting... 

The grafting of succinic anhydride onto PPs was evaluated quantitatively by FTIR spectroscopy. The relative absorbance values obtained from the IR spectra were correlated with grafting levels of the sample as determined by an improved traditional hot titration method. The results obtained appeared to be valid for either atactic or isotactic modified PPs and suggested that a careful review should be conducted of the use of this technique in the quantification of polar groups grafted onto polyolefins. 37 refs. 

LRP is a powerful tool for the synthesis of complex polymer architectures as was shown above. However, in some cases it is desirable to combine structures that are hardly or not at all accessible via radical polymerization techniques. In such cases it may be beneficial to combine LRP with another polymerization mechanism. Many examples have been reported so far. A few examples will be listed here. Polystyrene-6-pol3risobutylene-6-polystyrene was synthesized via a combination of living cationic polymerization and ATRP (98). Polyolefin Graft Copolymers (qv) were synthesized by first polymerizing alkoxyamine-substituted olefins via metallocene catalysis, and subsequent polymerization of vinyl monomers via... 

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