Ethylene-vinyl alcohol surface properties

In the present work we have used, therefore, dextran as the water-soluble macromolecule to be coupled and a film of an ethylene-vinyl alcohol copolymer (EVAL) as the substrate material. This copolymer has hydroxyl groups but is insoluble in water and can be injection-molded to yield a material with good mechanical properties. The coupling reaction of dextran onto the film surface will be achieved by using diisocyanate, since dextran, as well as EVAL, has hydroxyl groups which readily react with isocyanate under formation of urethane linkage. 

FU2 Funke, Z., Hotani, Y., Ougizawa, T., Kressler, J., and Kammer, H.-W., Equation-of-state properties and surface tension of ethylene-vinyl alcohol random copolymers (experimental data by Z. Funke), Eur. Polym. J., 43, 2371, 2007. 

In this chapter we discuss PVT and surface properties of three sets of random copolymers. Monomer units are ethylene, vinyl alcohol, and vinyl acetate, as well as styrene and acrylonitrile. Random copolymers comprising these monomers are used widely. As an example, ethylene-vinyl alcohol random copolymers (EVOHs) have excellent gas barrier properties. They are used for food-packaging films or in fuel tank liners [Takahashi et al., 1999 Alvarez et al., 2003 Ito et al., 2003 Lopez-Rubio et al., 2003 Muramatsu et al. 2003]. 

Several cleaning formulations for specific uses contain unreacted polyamines. Examples include mixtures of ammonium alkylbenzenesulfonate, solvents, and PIP which give good cleaning and shine performance on mirrors and other hard surfaces without rinsing (305), and a hard-surface cleaner composed of a water-soluble vinyl acetate—vinyl alcohol copolymer, EDA, cyclohexanone [108-94-1] dimethyl sulfoxide [67-68-5] a surfactant, and water (306). TEPA, to which an average of 17 moles of ethylene oxide are added, improves the clay sod removal and sod antiredeposition properties of certain hquid laundry detergents (307). 

Ethylene copol nners with vinyl alcohol (PEVA) are derived by saponification of CEVA. Their critical feature is the unique gas barrier property (Table 2.1), which is combined with elasticity, strength, surface hardness, high wear, oil and atmospheric resistance. Thin, strong barrier layers of inhibited films formed from PEVA are impermeable to both Cl and hostile atmospheric vapors and gases [21]. 

The membrane surfaces have also been grafted or coated with polyacrylamide, poly(acrylic acid) [70, 71], poly(vinyl alcohol) and cellulose derivatives [72]. Another possibility for improving the membrane properties is the use of polymer blends. Blends of PVDF/PVP [73, 74], PVDF/poly(ethylene glycol) (PEG) [75], PVDF/sulfonated polystyrene [76], PVDF/poly(vinyl acetate) [77] and PVDF/ poly(methyl methacrylate) [78] have been used in the preparation of micropor-ous membranes. 

Polymers with which we will deal throughout this chapter are water soluble. They can be either ionic or nonionic. Some of them are synthetic, others are of biological origin (proteins, for instance). Both homopolymers and heteropolymers exist. Some polymers own amphiphilic monomers that induce surface-active properties to the whole polymeric structure. Water plays a very important role in determining the polymer properties in solution. The properties are also greatly modified by the addition of salts or by a pH modification. Frequently encountered nonionic polymers in polymer-surfactant interactions and their subsequent adsorption behavior at solid surfaces are poly(ethylene oxide) (PEO), poly(vinyl pyrrolidone) (PVP), polyacrylamide, and poly(vinyl alcohol). 

Another widely used approach is the in situ polymerization of an intractable polymer such as polypyrrole onto a polymer matrix with some degree of processibil-ity. Bjorklund [30] reported the formation of polypyrrole on methylcellulose and studied the kinetics of the in situ polymerization. Likewise, Gregory et al. [31] reported that conductive fabrics can be prepared by the in situ polymerization of either pyrrole or aniline onto textile substrates. The fabrics obtained by this process maintain the mechanical properties of the substrate and have reasonable surface conductivities. In situ polymerization of acetylene within swollen matrices such as polyethylene, polybutadiene, block copolymers of styrene and diene, and ethylene-propylene-diene terpolymers have also been investigated [32,33]. For example, when a stretched polyacetylene-polybutadiene composite prepared by this approach was iodine-doped, it had a conductivity of around 575 S/cm and excellent environmental stability due to the encapsulation of the ICP [34]. Likewise, composites of polypyrrole and polythiophene prepared by in situ polymerization in matrices such as poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidine chloride-( o-trifluoroethylene), and brominated poly(vi-nyl carbazole) have also been reported. The conductivity of these composites can reach up to 60 S/cm when they are doped with appropriate species [10]. 

Surface tension of polymers, related to their electrostatic and hydrophobic properties, is such that certain couples-among which poly(ethylene glycol)/ dextran, poly(vinyl alcohol)/dextran, poly(ethylene glycol)/MgS04, etc.-exhibit mutual incompatibility in water and the mixing of their concentrated... 

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