Radiation-grafted poly

Examples of radiation-grafted PEMs poly(ethylene-flZf-tetrafluoroethylene)-gra/f-poly(sty-rene sulfonic acid) (ETFE-g-PSSA), 30 PVDF-g-PSSA, 31 and poly(tetrafluoroethylene-co-hexafluoropropylene)-g-PSSA (FEP-g-PSSA), 32. 

Hietala, S., Skou, E. and Sundhokn, F. 1999. Gas permeation properties of radiation-grafted and sulfonated poly-(vinylidene fluoride) membranes. Polymer 40 5567-5573. 

Reaction Rates and Physical Properties in the Radiation Graft-Copolymer System Poly(vinyl chloride)—Styrene... 

A similarly poor efficiency in extraction can also be seen in Fig. 11, where the extraction result for the product obtained by the radiation grafting of styrene onto polyethylene terephthalate)(PET) fibers13 is shown. In this case the unreacted PET can be extracted after most of PS homopolymer has been extracted by repeated solution-precipitation of the sample. It should be mentioned here that the solution procedure is also necessary to extract the unreacted PET. Such a solution-precipitation procedure is also necessary for nylon-styrene13 and poly(vinyl chloride)-acrylo-nitrile14 graft products so as to remove the homopolymers to a sufficient extent. 

Film Preparation. Hema and NVP were radiation-grafted onto Silastic to make poly (HEMA)/Silastic and poly (NVP)/Silastic hydrogels as previously described (13). 

The poly (HEM A) sheets were prepared by B. Ratner using a special technique he developed. The HEMA solutions were poured between glass plates, and polymerization was chemically initiated. The chemical and physical properties of this material are very similar to those of radiation-grafted poly (HEMA) insofar as protein adsorption is concerned. Heterogeneous or homogeneous poly (HEMA) films were made by polymerization in solvents in which the poly (HEMA) is insoluble or soluble, respectively the result is a white opaque material in the first case and a transparent material in the second case. The resulting films were washed free of excess monomer and then soaked in the buffer to be used in the fibrinogen adsorption experiment for 10 days at 37 °C prior to the actual experiment. 

Figure 4. Fibrinogen adsorption onto radiation-grafted poly(HEMA)/ Silastic Effect of graft level. Films grafted to the degree depicted were equilibrated at 37°C for 20 hrs in 1 mg/ml fibrinogen solution in 0.01 M HEPES, 0.147M NaCl, 0.02% azide, pH 7.4 and then rinsed by dilution displacement and extensive soaking with buffer at room...

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

Polymer radicals, that have radical centers on the backbone chain to initiate grafting, can also be produced by irradiation of a polymer-monomer mixture with ionizing radiation. Most radiation graft polymerizations are carried out as heterogeneous reactions. The typical reaction system involves equilibration (swelling) of polymer with monomer followed by irradiation of the monomer-swollen polymer while immersed in excess monomer. For example, to produce poly(ethylene-gra/t-styrene),... 

A.M. Dessouki, El-S.A Hegazy, M.M. El-Dessouky and N.M. El-Sawy, Anionic membranes obtained by radiation grafting of 4-vinylpyridine onto poly(vinyl chloride), Radiat. Phys. Chem. 1985, 26, 157-163. 

Also within this category of application is the field of radiation grafting onto pre-existing polymeric substrates. E-beam or gamma sources can be used to initiate grafting onto a range of materials, for example poly(olefin)s, fluoropolymers, and cellulosics. The biocompatibility of poly(olefin)s can be greatly... 

Guimon, C. 1979. Radiation grafting of high density poly-ethylene and polypropylene. Radiat Phys Chem. 14 841-846. 

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