Graft polymerization processes

Another variation for both pseudopolyrotoxanes and polyrotoxanes is the placement of the cyclic component on linear side chains during a graft polymerization process. 

The chain transfer to polymer process that produces long-chain branching is also a graft polymerization process (Sec. 3-6d). 

Methods for detecting whether peroxy compound have been used for cross-linking elastomers have been reviewed. An important application of dialkyl peroxides is as initiators of cross-linking and graft polymerization processes. The success of both processes depends on the ability of the peroxide to produce free radicals and the ability of the free radicals for H-abstraction from a relevant donor substrate. A method for evaluating this ability consists of inducing thermal decomposition of the peroxide dissolved in a mixture of cyclohexane and MSD (225). The free radical X" derived from the... 

Salsbury, J. M., S. Kaizerman, and G. Mino, American Cyanamid Company Graft polymerization process, U. S. 3,046,078 (July 24, 1962). 

Characteristics of the Graft Polymerization Process. Under certain polymerization conditions such as when the vinyl chloride/polyethylene ratio is high, heterogeneous products are obtained in the sense that, beside the polyethylene grains gorged with PVC, independent suspension PVC particles are formed. Since the optimum conditions for production of PVC and graft copolymers are not necessarily identical, it is advantageous to avoid the formation of these independent PVC particles. 

Our work on vinyl chloride graft copolymers has led to the development of a graft polymerization process for the production of homogeneous VC/PE graft copolymers with high backbone-polymer content. This process is now being tested on a pilot-plant scale, and industrial applications are being considered. 

The graft polymerization process also applies to other backbone polymers, such as rubbery ethylene-propylene copolymers and amorphous epichlorohydrin polymers. Further work is necessary to bring the resulting products to industrial maturity and to develop their applications. 

Kollicoat IR is a unique polymer for pharmaceutical applications prepared by a graft polymerization process of polyethylene glycol (25%) with polyvinyl alcohol (75%). Kollicoat IR dissolves quickly in water and aqueous solutions of acid and alkali and reduces the surface tension of aqueous solutions to allow the solutions to have high spray rates. The polymer film is very flexible, not tacky, and easily colored. The polymer can be used as instant release coating, pore former, binder, protective colloid, etc. 

The polymer substrate activated this way in plasma (by attachment of the siuface peroxide groups) is able to initiate the graft polymerization of gas-phase or liquid-phase monomers. To initiate the graft polymerization process, the substrate should first be heated up to dissociate the organic peroxide on the strrface (9.76) and (9.77) and to form active organic radicals ... 

This method of surface graft polymerization usually includes two steps surface activation and graft polymerization. Sites on the nanoparticle surface are first activated by high-energy electrons, plasma treatment, chemical reactions, etc. and, subsequently, the graft polymerization process is generated. 

Y.W. Chen, W.C. Wang, W.H. Yu, E.T. Kang, K.G. Neoh, R.H. Vora, C.K. Ong, L.F. Chen, Ulfra-low-K materials based on nanoporous fluorinated polyimide with well-defined pores via the RAFT-moderated graft polymerization process, J. Mater. Chem. 14 (9) (2004) 1406-1412. 

Due to their physical and chemical inertness, fluoropolymers are resistant to UV irradiation in the wavelength range of 100-400 nm. It is difficult to directly activate the fluoropolymer membrane surface via UV initiation due to its inert property. A photo-initiator, such as benzophenon, is usually needed to initiate the photo graft polymerization process from the fluoropolymer membrane surfaces [130]. Benzophenon was decomposed into radicals. The free radicals are transferred to the fluoropolymer membrane and hydrogen abstraction leads to the generation of initiating radicals. Benzophenon can be coated onto the membrane surface by dipping the membrane in benzophenon solution in an adsorption process [130,131]. This method could... 

Some polymers are lacking in the reactive functional groups necessary to take advantage of the silane mechanisms outlined above. Polypropylene and other polyolefins are prime examples. They are therefore modified by a graft polymerization process so as to attach functional molecules to the polymers. Maleic anhydride is widely promoted as a suitable agent for use with polypropylene. 

Emulsion graft polymerization processes can be used to obtain coreshell modifiers, in which the core consists of crosslinked poly B (Tg = -6 to -85) or NBR (Tg -45). The latex particle size is very crucial for effective toughening of the diverse matrices styrenic polymers require larger particles (d > 0.2 pm) than engineering polymers id < 0.2 pm), due to their different toughening mechanisms. The ABS composition and properties are affected by the following polymerization variables (1) monomer amount (2) initiator type and amount (3) emulsifier concentration (4) reaction temperature and time (5) chain transfer agents. 

---