Radiation Crosslinking of Polymers

Stable composites of metals and polymers which have a wide range of very interesting mechanical and electrical properties have been obtained recently by radiation crosslinking of polymers and metal powders after cold compaction. Interest is growing very rapidly in this field and industrial plants may well be developed. 

Spenadel, L., Radiation crosslinking of polymer blends. Radiation Physics and... 

Physical entrapment is the simplest, since it only involves radiation polymerization of monomers polymers, or radiation crosslinking of polymers. However, it is very important that either a significant pore structure exist in the final product or that it be in a finely divided form, so as to provide access for other biomolecules to reach the immobilized biomolecule, or vice versa. (The word immobilization refers in a temporal sense to the suddenly lowered mobility of the biological species it may never leach out or it may gradually dissolve into the surrounding medium. In either case, it is considered to have been immobilized .)... 

Henglein, A. Crosslinking of polymers in solution under the influence of y-radiation. J. Phys. Chem. 63, 1852 (1959). 

Pulse radiolysis studies concerning the polymerization as well as the degradation, crosslinking and radiation resistance of polymers are surveyed. Initiation mechanisms of the radiation-induced polymerization of styrene and other monomers are discussed on the basis of the direct measurements of the reaction intermediates. Optical and kinetic data on the short-lived chemical intermediates produced in the solution of polymers and in the rigid polymers are surveyed and discussed with special reference to the degradation mechanism of polymers. 

Dehydrochlorlnatlon measurements of the radiation cured compounds were conducted at 180°C in oxygen (Table IV). Radiation crosslinking of pure CPE reduces the maximum rate of dehydrochlorlnatlon from 0.27 for the uncrosslinked polymer to... 

The rather non-conventional approach to radiation chemistry of polymers leads to conclusions which indicate that the role of multi-ionization spurs in radiation chemistry of polymers cannot be neglected. In spite of low participation of these spurs in radiolysis of low Z materials (ca 20% of total deposited energy), these spurs can explain formation of two basic, different types of crosslinks. Formation of low molecular weight products of radiolysis is also explained, as well as other phenomena. Application of spurs philosophy to polymers is also advantageous in explanation of energy transfer from single ionization spurs and lack of transfer from multi-ionization spurs. 

ZAGORSKI, Z.P., EB — crosslinking of elastomers, how does it compare with radiation crosslinking of other polymers , International Meeting on Radiation Processing Chicago 2003, Sept. 7-12, Book of Abstracts. 

Another method involves the qualitative and quantitative analysis of the trapped intermediates at 77°K. These are supposed to be responsible for the radiolysis when the irradiations are performed at room temperature. This method is, however, very approximate. The yield in volatiles, scission and crosslinking are indeed different whether the irradiation is performed at room temperature or at 77°K. All this indicates that although many quantitative data have been obtained in recent years and information about the behaviour of reactive intermediates is now available, much work is still required to reach a comprehensive understanding of the physico-chemical processes involved in the radiation chemistry of polymers. 

The major industrial applications of this technology in the field of polymers are based on (i) polymerization, (ii) crosslinking, (iii) scission, and (iv) sterilization of medical disposables. Radiation processing of polymer blends can lead to crosslinking or scission of one or more components, or even to inter-phase (inter-polymer) crosslinking. These effects modify the blends properties. 

Low effidency of the radiation crosslinking of polypropylene is a reason why irradiation cannot be used for improving the thermomechanical properties of this polymer as it is commonly practiced with pofyethylene. On the other hand, this fact has stimulated a large amount of research on polyfunctional monomers aimed at a deliberate increase of radiation effidency d"polypropylene crosslinking [76]. 

Jabbari, E. and Nozari, S. 2000. Swelling behavior of acrylic acid hydrogels prepared by y-radiation crosslinking of polyacrylic acid in aqueous solution. Eur Polym J. 36 2685-2692. 

Gamma radiation, frequently used for sterilization in diverse medical applications, and for crosslinking of pol3aners, may cause important modifications in both structure and properties of polypropylene (PP) and related copolymers. It was foimd that the radiation resistance of polymers strongly depends on their amorphous or crystalline structure. 

Bandzierz, K., BieUnski, D. M. (2013). Radiation methods of polymers modification hybrid crosslinking of butadiene - acrylonitrile rubber, 244—247. Abstracts Collection on New Challenges in the European Area Young Scientists, Baku, Azerbaijan. Flory, P. J., Rehner, J. (1943). Statistical Mechanics of CrossUnked Polymer Networks n. Swelling. J. Chem. Pl s, 11(11), 521-526. 

In addition to pore size, the mechanical strength of polymer substrates has an influence on the behaviour of cells, as cells sense their environment through the focal adhesions that attach the cytoskeleton to the scaffold.The mechanical properties of elastomeric poly(l,2-butadiene) (PB) honeycomb patterned films can be controlled by crosslinking the films under UV radiation.Crosslinking of the PB films resulted in a 15-fold increase in the elastic modulus but had no effect on the surface properties of the polymer. Murine fibroblasts exhibited stronger adhesions to the crosslinked PB films. When attached to a growth substrate, cells apply a traction force of 30 nN to the surface. Simulation of this force on the... 

UV stability and radiation-crosslinking of linear low density polyethylene and low density polyethylene for green house applications. Polymer Degradation and Stability, 82 (2003),... 

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