Vinyl polymers, chemical resistance

Poly(vinyl chloride). PVC is one of the most important and versatile commodity polymers (Table 4). It is inherently flame retardant and chemically resistant and has found numerous and varied appHcations, principally because of its low price and capacity for being modified. Without modification, processibiUty, heat stabiUty, impact strength, and appearance all are poor. Thermal stabilizers, lubricants, plasticizers, impact modifiers, and other additives transform PVC into a very versatile polymer (257,258). 

The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. The polymer is an excellent adhesive and possesses solvent-, oil-, and grease-resistant properties matched by few other polymers. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which, under dry conditions, are superior to those of any other known polymer. The polymer s low surface tension provides for excellent emulsification and protective coUoid properties. 

Vinyl ester resins generally offer mechanical properties superior to those of polyester matrices but at an increased cost. Vinyl esters are chemically similar to epoxy resins but are manufactured via a cold-curing process similar to that used in the manufacture of polyester resins. Vinyl esters offer superior resistance to water and chemical attack and are used in such appHcations as underground pipes, tank liners, and storage tanks (see Vinyl polymers). 

Vinyls Vinyl chloride co-polymer resins were developed in the USA in the late 1930s. They have better weather and slightly more chemical resistance than chlorinated rubber paints. They are generally resistant to crude oil but application is more critical. For example, they are particularly sensitive to moisture present on a surface during painting and this can lead to adhesion failure. They are also more prone to solvent entrapment than chlorinated rubber paints. 

Modified alkyd resins In this group one finds styrenated alkyds, vinyl toluenated alkyds, oil-modified vinyl resins, acrylic alkyds, silicone alkyds and polyurethane alkyds. The modifying component usually has a number of effects. It always increases the molecular weight of the alkyd polymer, and may impart hardness, durability, or chemical resistance. It also affects the solubility of the polymer in solvents. 

We report here plasma etch rate data for a series of vinyl resist polymers with a wide range of side chain substituents. The results of this study are valuable because they provide, when combined with other radiation chemical test data. Improved design criteria for making improved high performance radiation resists. Structural fomulae and chemical nomenclature plus acronyms for the vinyl polymer systems studied are compiled below ... 

Acrylic fibers are vinyl polymers valued for resistance to chemical and biological degradation. Acrylonitrile (or vinyl cyanide) forms a homopolymer that is used in filters and artificial wool, which is widely used in sweaters. 

Epoxy resins may be blended with certain vinyl polymers to improve the impact strength and peel strength of the adhesive. Polyvinyl acetals, such as polyvinyl butyral and polyvinyl formal, and polyvinyl esters are compatible with DGEBA epoxy resins when added at concentrations of 10 to 20% by weight. The addition improves the resulting impact resistance and peel strength of the cured adhesive. However, temperature and chemical resistance are sacrificed by the addition of the low-glass-transition-temperature vinyl resins. 

Vinyl lacquers are used mainly where a high degree of chemical resistance is required these lacquers are based on vinyl chlorides and vinyl acetates. Acrylic lacquers are based on methyl methacrylate and methyl acrylate polymers and copolymers. Other esters of acrylic and methacrylic acid also may be used to make nonconvertible film formers. Judicious selection of these acrylic acid or methacrylic acid esters allows one to produce film formers with specifically designed properties such as hardness, flexibility, gloss, durability, heat, and chemical resistance. Acrylic lacquers, however, are not noted for their water resistance. The principal uses of acrylic-type lacquers are fluorescent and metallic paints, car refinish applications, clear lacquers and sealers for metals, and protective coatings for aircraft components and for vacuum-deposited metals, as well as uses in pigmented coatings for cabinets and appliances. 

The mechanisms of the thermal and photochemical degradation of poly(vinyl chloride) (PVC) continue to be active areas of research in polymer chemistry mainly because its high chemical resistance, comparatively low cost and wide variety of application m e PVC one of the most widely used thermoplastic materials. The wide variety of forms which the material can take includes pastes, lattices, solutions, films, boards and moulded and extruded pieces and depends to a very large extent on the good electrical and mechanical properties of the polymer. In spite of these advantages the even wider application of the material has been restricted by its low thermal and photochemical stability. Thermal instability is a problem since processing of the polymer is carried out at about 200 C and the photochemical instability places a limit on the extent of the outdoor applications which can be developed. 

As shown in Table 2.7, the coefficient of chemical resistance of RubCon is 1.0 for water, 0.81-0.95 for all mineral acids (exception is KCI = 0.69 for 36% solution of hydrochloric acid), 0.82-0.95 for organic acids, 0.82-0.91 for alkalis, 0.88 for solvents and petroleum products, and 0.84-0.86 for solution of salts. The analysis of experimental data has shown that RubCon offers universal chemical resistance many times higher than ordinary Portland cement concrete and surpasses the chemical resistance of polyester, polyepoxy, and vinyl ester polymer concrete. It is worth noting that penetration depths of 5% nitric and 36% solution of hydrochloric acids into RubCon sample bodies were 3, 4, and 5.1 mm, respectively the penetration ability of these acids is higher as compared with other corrosive environments. 

RubCon offers universal chemical resistance many times higher than ordinary Portland cement concrete and surpasses the chemical resistance of polyester, polyepoxy, and vinyl ester polymer concretes. 

PE/Other Commodity Polymer Blends PE s are frequently used as impact modifiers for a variety of other thermoplastics. For example, addition of either PE, CPE, or CSR to PVC improved its moldability, stability, impact strength and chemical resistance [Matsuda et al, I960]. Blends of PO/PVAl were developed to improve the antistatic properties [Minekawa et al, 1969]. LDPE was blended with poly(2-ethyl-2-oxazoline) (PEOX) for improved adhesion, e.g., to PET [Hoenig et al, 1984]. Blends of PE, PP, PS or their copolymers with ethylene-fluorinated vinyl ether copolymer... 

Poly(vinyl fluoride) is a highly crystalline polymer available commercially as a tough, flexible film sold under the trade name Tedlar by DuPont. It has excellent chemical resistance like other fluoropoly-mers, excellent outdoor weatherability, and good thermal stability, abrasion, and stain resistance. It maintains useful properties between -180°C to 150°C. It is used as protective coatings for materials like plywood, vinyl, hardboard, metals, and reinforced polyesters. These laminated materials find applications in aircraft interior panels, in wall covering, and in the building industry. 

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