Chemical copolymers Ethylene-vinyl alcohol copolymer

Chemical Resistance - Ethylene Vinyl Alcohol Copolymer... 

Table 4.19 Ethylene-vinyl alcohol copolymers examples of chemical behaviour at room temperature...

With the growing demand for coextruded products, barrier plastics have shown significant growth in the last several years. Historically, the high barrier resins market has been dominated by three leading materials — vinylidene chloride (VDC) copolymers, ethylene vinyl alcohol (EVOH) copolymers, and nitrile resins. Since 1985, however, there has been a lot of interest worldwide in the development of moderate to intermediate barrier resins, as apparent from the introduction of a number of such resins, notably, aromatic nylon MXD-6 from Mitsubishi Gas Chemical Company, amorphous nylons SELAR PA by Du Pont and NovamidX21 by Mitsubishi Chemical Industries, polyacrylic-imide copolymer EXL (introduced earlier as XHTA) by Rohm and Haas and copolyester B010 by Mitsui/Owens-Illinois. 

Levasint. Payer] Saponified ethylene vinyl alcohol copolymer, used as corrosion protection for metal parts used in construction and chemical industry, traffic, transport offshcxe, coastal arid drinking water supply installations, sports facilities, coitsumer and Indus trial goods. 

Tsai, B.C. and Wachtel, J.A. (1990) Barrier properties of ethylene-vinyl alcohol copolymer in retorted plastic food containers. In Barrier Polymers and Structures, (ed. Koros, W.J.) American Chemical Society, Washington DC, pp. 192-202. 

The disc-shaped plastic micoreactors, termed microcapillary films (MCFs), contain 19 parallel microchannels, each with a mean internal diameter of 142 10 pm. The material was prepared using a melt extrusion process from an ethylene-vinyl alcohol copolymer (EVOH) [28]. Immobilization of palladium(0) on the wall surface inside the MCFs was performed by simple chemical deposition techniques (Scheme 7.3). The palladium-coated capillaries were used for transfer hydrt enation of ketones, imines, nitro compounds, alkenes, and alkynes with triethylsilane under flow conditions [29]. Microcapillaries whose inside surfaces were coated with copper or gold were also utilized for the continuous-flow reactions [30]. 

Barres [113] used NIRS to monitor the chemical modification (catalyzed esterification) of a molten ethylene-vinyl alcohol copolymer by octanoic acid in a twin screw extruder. Extrusion samples were characterized off-line, for calibration purposes, with the use of H-NMR and residual free acid titration. Multivariate PLS calibration was performed successfully to predict the analyte concentrations. 

As an example the characterization of surface grafting onto an ethylene-vinyl alcohol (33 67) random copolymer (EVA) film33 is described here. Since this water-insoluble film has hydroxyl groups on the surface, surface grafting may occur, for instance, with the so-called dialdehyde starch (DAS), whose chemical structure is given by... 

In copolymerization of ethylene with different class monomers, all the foregoing aspects are superimposed various chemical comonomer sequences can be generated, with various mutual stereospecific placements. Chemical comonomer sequences can be analyzed by statistical methods completely analogous to those described in Section IV (Tables 3 and 4), but practical analysis may be complicated by superposition of stereosequence statistics. Short-chain branching in longer polyethylene sequences is an additional factor to be considered. All these aspects can be demonstrated on the example of the ethylene-vinyl alcohol E/V copolymer prepared by a high pressure, free radical process, which has been characterized in great detail by modern NMR methods. 

Figure 9 Chemical structure of ethylene-co-vinyl alcohol copolymer.

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