Polyethylene silane

Vulcanised (cross-linked) polyethylene is being used for cable application where service temperatures up to 90°C are encountered. Typical cross-linking agents for this purpose are peroxides such as dicumyl peroxide. The use of such agents is significantly cheaper than irradiation processes for the cross-linking of the polymer. An alternative process involves the use of vinyl silanes (see Section 10.9). 

Table 9. Effect of silane treatment on the mechanical properties of kaolin-filled polyethylene compositions [276]...

In [276] the properties of kaolin-filled polyethylenes were investigated. The filler was pre-treated with silanes of two kinds, vinyl triethoxysilane (VTES) (I) and gamma-methacryloxypropyl trimethoxysilane (II). The results are presented in Table. 9. 

Multiblock polyethylene-polydimethylsiloxane copolymers were obtained by the reaction of silane terminated PDMS and hydroxyl terminated polyethylene oligomers in the presence of stannous octoate as the catalyst 254). The reactions were conducted in refluxing xylene for 24 hours. PDMS block size was kept constant at 3,200 g/mole, whereas polyethylene segment molecular weights were varied between 1,200 and 6,500 g/mole. Thermal analysis and dynamic mechanical studies of the copolymers showed the formation of two-phase structures with crystalline polyethylene segments. 

Spherilene [Spherical polyethylene] A process for making polyethylene in the form of granules. The catalyst combines a Ziegler-Natta catalyst with a silane. Developed by Montecatini, Italy. The first plant was due for startup by Himont, in Lake Charles, LA, in 1993. 

Rochow, E.G. (1951). An Introduction to the Chemistry of Silane. 2nd, ed.. Chapman Hall. London. Rostami, H., Iskandarni, B. and Kamel, I. (1992). Surface modification of Spectra 900 polyethylene fibers using RE-plasma, Polym. Composites 13, 207-212. 

Describes open cell foamed articles including silane-grafted single-site initiated polyolefin resins. The olefin polymer resin can be a polyethylene, a copolymer of ethylene, a C3-C20 alpha-olefin, or a copolymer of ethylene, a C3-20 alpha-olefin and a C4-C20 diene. The open cell foamed articles have good cushioning properties and can be non-allergenic. 

Electron beam irradiation is one of the methods of cross-linking in fhis process. The other methods use peroxide, multifunctional azide, or an organofunctional silane. Polyethylene resins respond to electron beam irradiation well since the rate of cross-linking exceeds significanfly fhe chain scission. Polypropylene (PP) is prone to P-cleavage, which makes if difficult to cross-link by a free radical process. For fhaf reason, PP resins... 

The vinyl silanized samples from Mr. Robert E. Schultz of J. M. Huber had been prepared as follows liquid vinylmethoxyethoxy silane (Union Carbide A172) was quantitatively added to a known volume of a mixture of 60% de-ionized water and 40% 2-propanol in a polyethylene beaker via a disposable polyethylene syringe. 100 g of ATH (aluminum trihydrate) was stirred into exactly 300 ml of the vinyl silane mixture for 10 min with a polyethylene rod. The resulting slurry was placed in a 100°C oven and allowed to dry for 24 h. 

Keywords Positron annihilation high density polyethylene interphase glass-filled silane coupling agent heat of fusion. 

The interfacial region modified by the silane has properties different from those of the bulk polyethylene. The crystallization in the interphase will be hindered due to the chemical bonds between the azidofunctional group and the polyethylene chains. Figure 6 shows this effect by a decrease of the heat of fusion (AH) with increasing number of silane layers for the composites with 20 and 50 vol% of glass. The AH values in Fig. 6 are in J/g polymer and were calculated from the values... 

Figure 6. Heat of fusion (A W). in J/g of the polymer matrix, of the silane-modified composites against the number of silane layers. The crystallinity scale on the right-hand side was obtained by assumine AH for a polyethylene crystal to be 290 J/g.

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