Polyethylene radiation crosslinked

The very first studies with radiation crosslinked polyethylene oxide (PEO) have shown that SAH is able to substantially reduce the sensitivity of plants to water shortage [7], to promote their growth, particularly, under conditions of water deficiency [8], to improve seedling survival and the final crop [9], These results stimulated a more detailed analysis of the effects of SAH in the water balance of... 

In order to investigate the structure of crosslinked polyethylene by, 3C NMR the model compound l,l,2,2-tetra(tridecyl)ethane, i.e. two molecules of n-C27H56 linked at the C-14 atoms, was prepared. The tertiary 13C-14 atoms give rise to a resonance signal at 39.5 ppm. Spectra of long chain n-paraffins eicosane (C20H42) and hexacosane (C26H54) exposed to 5 MGy y-radiation above their respective... 

Crosslinked polyethylene. For additional investigations, LDPE samples were crosslinked by e-beam radiation with a dose of 250 kGy. In order to remove residual soluble components from the cross-linked LDPE samples, a suitable extraction process was developed [16], After being clamped in a frame, the polyethylene foils were extracted in m-xylene for 24 hours at a temperature of 80 °C. The addition of a small amount of BHT (2,6-di-tert-butyl-4-methylphenol), an antioxidant, prevented unwanted oxidation of the LDPE foils. Afterwards the samples were dried carefully at room temperature for 20 hours, and then dried in vacuo (20 mbar, 48 hours at 40 °C) to constant weight. 

Multi-polymer Materials. The literature for multi-polymer materials is extensive but is less than that for blends and grafts composed of two polymers. A ternary graft copolymer, semi-IPN is described by Rogers and Ostler (43, 44) an original crosslinked polyethylene graft-poly-(potassium acrylate) was swelled with styrene and radiation polmerized. The authors comment that most of the grafting of polymer 3 was on polymer 2, the poly (potassium acrylate). This reaction sequence can be described ... 

Mishra, J.K., Chang, Y.W., Lee, B.C., Ryu, S.H. Mechanical properties and heat shrinkability of electron beam crosslinked polyethylene-octene copolymer. Radiat Phys. Chem. 77, 675-679 (2008)... 

Ranogajec, F. Effect of solvent on radiation grafting and crosslinking of polyethylene. Radiat. Phys. Chem. 76, 1381-1384 (2007)... 

Seguchi, T., Hayakawa, N., Yoshida, K., and Tamura, N., Fast neutron irradiation effect. II. Crosslinking of polyethylene, ethylene-propylene copolymer, and tetra-fluoroethylene-propylene copolymer, Radiat. Phys. Chem., 26, 221-225 (1985). Keller, A., and Ungar, G., Radiation effects and crystallinity in polyethylene, Radiat. Phys. Chem., 22, 155-181 (1983). 

XLPE n Abbreviation for Crosslinked Polyethylene. See Radiation Crosslinking. 

Crosslinked polyethylene by gamma-radiation Polyethylene with carbonyl group introduced by oxidation... 

Not all consequences of radiation exposure are deleterious. Crosslinking may be induced by irradiation to improve the mechanical behavior and degradation characteristics. For example, y-radiation is used commercially to crosslink polyethylene to enhance its resistance to softening and flow at elevated temperatmes indeed, this process may be carried out on products that have already been fabricated. 

In polymers there are microregions undergoing reactions different from those occurring in the neighbouring material when exposed to radiation. For example, the crosslinking behaviour In amorphous polyethylene differs from that in the crystalline phase... 

Unlike polyethylene, polypropylene is not crosslinked and deteriorates. The action of high-energy radiation depends in a complex way on the power, dose and wall thickness of polypropylene. Thus, it is often advised to avoid doses greater than 1 kJ/kg (0.1 Mrad). However, special grades are marketed for radiation sterilization but doses of the order of 25kJ/kg (2.5 Mrad) can lead to a certain brittleness after storage of several months. 

No.4, July 2001, p.333-52 INVESTIGATION OF THE RADIATION CROSSLINKED FOAMS PRODUCED FROM METALLOCENE POLYOLEFIN ELASTOMERS/ POLYETHYLENE BLEND Kim D W Kim K S... 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

A second important reaction observed in irradiated polyethylene and certain other polymers as well as paraffins is the formation of trans-vinylene. This product is far less influenced by such factors as temperature or radical scavengers than is crosslinking, and it is therefore often assumed to be formed directly by a molecular process—i.e., molecular detachment of hydrogen. Even this simple explanation cannot be fully sustained. Long after radiation has ceased, the frarw-vinylene concentration continues to rise or fall, whether the specimen is exposed to oxygen or not. This behavior may possibly be correlated with the reaction of trapped alkyl and allylic radicals, which, being slightly mobile, can add to frarw-vinylene or each other over a period of days. 

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