Polypropylene radiation grafting

Our library synthesis was carried out with a set of 27 tube-shaped solid phase synthesis support, called MicroTubes. These supports are prepared by radiation grafting of polystyrene ( — 350 pmol) onto polypropylene tubes, chemically functionalizing the polystyrene with aminomethyl groups to afford about 55 imol of amine per tube, inserting a reusable Rf ID tag into each tube, and heat-sealing the tube ends to prevent loss of the tag. The chemical conversion of all 36 aminomethyl tubes was carried out simultaneously using standard procedures with rink amide linker, each with —46 pmol of available amine per tube.1 2... 

Consistent with the preceeding acid work, when TMPTA is added to the monomer solutions containing either lithium salt or urea, synergistic effects are observed for the radiation grafting of styrene to polypropylene (Table IV). Again the maximum increase in yield occurs in the monomer solution corresponding to the Trommsdorff peak. 

A theory for this acid effect has been developed essentially from the wool and cellulose work (3,4). Recently, in a brief communication, we reported analogous acid enhancement effects in the radiation grafting of monomers such as styrene in methanol to nonpolar synthetic backbone polymers like polypropylene and polyethylene (5). In the present work, detailed studies of this acid enhancement effect are discussed for the radiation grafting of styrene in various solvents to polyethylene. The results are fundamentally important since most of the experiments reported here have been performed in solvents such as the low molecular weight alcohols which, unlike cellulose and wool systems, do not swell polyethylene. 

The most common material used is cellophane, which is a cellulose film, which acts as a membrane and is capable of resisting zinc penetration. The cycle life of cells utilizing this material is severely limited due to the hydrolysis of the cellophane in alkaline solution. Various methods have been tried to stabilize cellulose materials, such as chemical treatment and radiation grafting to other polymers, but none have, as of now proved economically feasible. The most successful zinc migration barrier material yet developed for the nickel—zinc battery is Celgard microporous polypropylene film. It is inherently hydrophobic so it is typically treated with a wetting agent for aqueous applications. 

Effect of Solvents on Radiation Grafting of Styrene to Polypropylene ... 

Fibrous anion exchangers were prepared from polypropylene staple fibres 22 mcm in diameter by radiation grafting of polystyrene followed by chloromethylation and amination of the grafted polymer. The grafting was... 

In preliminary work (19), divinylbenzene (DVB) has been reported to be a useful additive for enhancing the above grafting reactions. These early data (19) indicate that there are possible common mechanistic pathways between the acid effect and the DVB process. More detailed DVB studies are discussed in this paper for enhancing the radiation grafting yields of styrene in methanol to films of polyethylene and polypropylene. The work has been extended to include the use of other polyfunctional monomers such as tri-methylol propane triacrylate (TMPTA) as additives. The possibility of being able to use these additives for copolymerisation of monomers to naturally occurring trunk polymers such as cellulose will also be considered. 

Table Comparison of Cellulose with Polypropylene as Trunk Polymers for Acid Enhancement in Radiation Grafting of Styrene in Methanol...

The optimum in the copolymerisation process occurs at 50% monomer concentration with both additives. The behaviour of sulfuric acid in these reactions is representative of the most reactive of the mineral acids (12). A comparison of TMPTA with H SO (0.2 M) also indicates that similar trends in enhancement in radiation grafting to polyethylene film are observed with both additives (Table III). Again, when polypropylene film is used as backbone polymer (Table IV), acid and DVB show similar increases in grafting yield with styrene in methanol, however in this system, it is interesting to note that the concentration of monomer at the position of the Trommsdorff peak does not vary for neutral and acidified grafting solutions but changes from 30% to 35% when DVB is additive. 

Styrene in methanol radiation grafted to polypropylene film (0.06 mm) at 4.1x10 rad/hr to dose of 2.4x10 rad in air. 

Copol3nners prepared by radiation grafting styrene in methanol to polypropylene powder. Sulfonation time, 45 min. 

The RAI Research Corporation also offers a range of battery separators under the name of Permion (JL). These membranes are made by radiation grafting of a suitably active group onto an inert base film. The active groups include weak acids such as acrylic and substituted acrylic acid and stronger acidic groups such as sulfonated styrene. The base film can be Teflon R, polyethylene or polypropylene. They are thus not strictly perfluorinated membranes as is Nafion, but in chemical inertness and in many physical properties such as electrical conductivity and ion flux are useful as separators in batteries. 

A mobile polymeric surface suitable for peptide synthesis can be radiation grafted to more rigid plastic (polypropylene or polyethylene) pins or small... 

Bucio, E., Aliev, R., and BuriUo, G. 1998. Radiation grafting of dimethylamino ethyhnethacrylate onto polypropylene. Radial Phys Chem. 52 193-196. 

Garcia-Uriostegui, L., Burillo, G., and Bucio, E. 2012. Synthesis and characterization of thermosensitive interpenetrating polymer networks based on N-isopropylacrylamide/N-acryloxysuccinimide, crosslinked with polylysine, grafted onto polypropylene. Radiat Phys Chem. 81 295-300. 

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

Ramtrez-Jimenez, A., Alvarez-Lorenzo, C., Concheiro, A., and E. Bucio. 2012. Radiation-grafting of 2-hydroxyethyhnethacrylate and ohgo (ethylene glycol) methyl ether methacrylate onto polypropylene films by one step method. Radiation Physics and Chemistry 81 27—32. 

Vahdat, A., Bahrami, H., Ansari, N., and F. Ziaie. 2007. Radiation grafting of styrene onto polypropylene fibres by a 10 MeV electron beam. Radiation Physics and Chemistry 76 787-793. 

The first method, although effective, was soon abandoned for safety reasons, while the use of chromic acid has been largely discontinued. The other two have remained the most widely used pre-treatments, not only for LDPE but also for high-density polyethylene (HDPE) and polypropylene (PP). Other methods have been found to be effective, but for reasons of cost, safety or convenience, they have not been widely used. The pre-treatments include fuming nitric acid, potassium permanganate, ammonium peroxydisulphate, ozone, fluorine, peroxides, UV radiation, grafting of polar monomers, plasmas (see Plasma pretreatment), electrochemical oxidation (see Electrochemical pre-treatment of polymers) and the use of solvent vapours. The corona, flame and plasma methods and the use of trichloroethylene are now discussed briefly the latter is included because it involves a different mechanism. 

The pin consists of a radiation-grafted polypropylene crown fitted to an inert polypropylene stem . Graft polymers used with the Multipin system include polystyrene, a methacrylamide copolymer (38), and poly(hydroxyethyl methacrylate) (34) (HEMA). We have found that the HEMA surface is best suited to peptide synthesis. Historically, peptides were prepared in a non-cleavable format on the crown surface for epitope mapping applications (39). Over the past decade, however, most peptides prepared by the Multipin method have been synthesized on cleavable linkers. The linkers used for peptide synthesis are outlined below. 

Fig. 2. Effect of miscellaneous solvents on radiation grafting of styrene to polypropylene film at dose rate of 4.0 x 10 rad/hr to total dose of 0.2 X 10 rad except dioxan (4.5 x 10 and 0.3 X 10 ).

Table 1. Effect of Sulfuric Acid (0.02 M) on Radiation Grafting of Styrene in Low Molecular Weight Alcohols to Polypropylene Film ...

Fig. 1. Acid effect in radiation grafting of styrene to polypropylene film (isotactic, doubly oriented, 0.06 mm) in methanol and ethanol at dose rate of 4.5 x 10" rad/hr to...

The inclusion of divinylbenzene (DVB) enhances the radiation grafting of styrene in methanol to polypropylene (Figure 7) especially at concentrations above 30% monomer where there is generally a 100% increase in yield. Compared with acid and neutral solutions, the Trommsdorff peak in the DVB solution has moved slightly to higher monomer concentration for polypropylene grafting. The acid enhancement is greater than the DVB effect at monomer concentrations lower than 30%, but the reverse holds above this styrene level with polypropylene. 

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