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Polyvinyl By Martin Batiuk*, C. A. Clarki, A. F. Korneyt, J. R. Russellf, G. A. Smallj and D. E. Witenhafer* One of the most important and diversified poupe of thermoplastics is that made up of vinyl polymers and copolymers. They ve available in a variety of chemical lypee such as polyvinyl chloride (pvcl and ropolymers, chlorinated pvc, polyvinyl acetate used in paint and adhesives, polyvnvbdene chloride used in packaging films and coatings, polvvinylidene fluor ide. polyvinyl alcohol and polyvinyl ^ttyral used as a laminate in safety glass. farlopirwnt C'unsuluni. `Senior D*velopm*nt SciWw. *ml ` I>f\-lfpfnnit >4cientit. B.F. Goodrich Co. fclim Oak Trw Blvd.. CleveUnd. Ohio Some of the newer copolymers, such as ethylene-vinyl-acetate or the olefins as comonomers with vinyl chloride, have attained some commercialization in the past several yean because of their contri butions to ease of processing or impact improvement. The polyvinyl chloride family of homopolymers and copolymers has by far the largest commercial utilization. This is mainly because pvc can be compounded to produce a wide spectrum of physics! properties. Cellular pvc can be rigid or flexible and density can be varied widely. The impact resistance of pvc can be modi fied by compounding and various fillers, processing aids and stabilizen can be added to reduce coBt, increase production speed and to reduce the effects of heat and sunlight. Thus polyvinyl chloride fills a wide va riety of needs from rugged extruded pipe and building products to the demanding and sensitive requirements of very thin, flexible surgeon's inspection gloves. Vinyl chloride polymerizes easily. Rapid polymerization is obtained with many free-radical initiators at 140' P. ni3t>?3*1974 Modem Plastics Encyclopedia PbJvXttAij - Oct*rfa*r 107 c: 33 * URL 14517 (60* C.). The molecular weight can be eming by a multitude of different tech made by these processes are injection varied over a wide Tange by changing the niques. molded. polymerization temperature. Rigid vinyls provide such significant The wire and cable industry' uses large There are three main prowaw for properties as corrosion resistance, thermal volumes of flexible pvc. Excellent electri polymerizing pvc. In the etupenaton and electrical insulation, weather resist cal and physical properties, flame retard- process droplet* of monomer are dispersed ance and a wide range of opaque colors ance, along with low cost and flexibility in water and polymerized to yield porous or outstanding clarity. over a wide temperature range are the particle* about 100 micron* in diameter. For a quarter of a century rigid vinyls primary properties responsible for the In the mats process special agitation is have been successfully employed for in continued growth of this market. New used to polymerize bquid monomer with dustrial pipe, duct systems, fume hoods, resins and other compounding ingredients out water present. `Hus yields particles ranks, water supply and sanitary systems, continue to make new applications for iTnilT to suspension resin. Vinyl chloride many installations of which have been this material possible. polymerizes well in an emulsion system to subjected to a wide range of environ Flexible film and sheet is a well estab yield a colloidal water dispersion, or latex, mental exposure. Based on the experience lished area for pvc. Wall coverings, pack of pvc particles with about % micron gained from these applications, the merits aging film, shower curtains, upholstery diameter. Emulsion polymers can be pur of properly formulated rigid pvc are now and clothing fabrics are typical products. chased as a latex or as a very fine, spray- used in building products, including house These products were made by calendering dried powder resin used mainly in making riding, window sash, building panels, gut but in recent years large volumes have plastisols and organosols. A relatively ters and downspouts, flashing, conduit been made by extrusion. Each application email volume of pvc is polymerized by and electrical raceways requires a compound formulated to meet the costlier solution process to produce s Cellular rigid vinyl has found a ready specific requirements. For example, food- msin with a minims) amount of gel. market for decorative molding and trim grade packaging film for meat and pro Polyvinyl chloride is told as a free- and this is considered a major break duce must be based on FDA-sanctioned flowing resin (without additives), as a through as an economical wood substi ingredients, must have good low- compound (with additives) or as latex. tute. Parts made by extrusion provide t temperature properties and be trans Regardless of end-use or method of close duplicate for prefinished wood in parent. Baby pants formulations must fabrication, compounding ingredients density, feel and appearance. In addition, have excellent soapy water resistance. must be added to pvc resins. These mate its superior toughness, nailability, crack Various types of gasketing and rials can be classified as stabilizers, plas resistance, smoothness, esse of fabrica weatherstripping are made from flexible ticizers, lubricants, fillers, impact modi tion, unlimited lengths end mainte pvc. By the proper choice of plasticizer fiers and processing aidB. All compounds nance-free characteristics have allowed and stabilizer, compounds can be made do not contain all the groups of com cellular vinyl to overcome acceptance for a range of applications from refrig pounding materials. For example, rigid problems associated with previous wood erator gasket to outdoor weatherstrip. compounds contain no plasticizers; flexi substitutes. Each year the automotive industry ble compounds contain no impact modi Rigid vinyl sheet and film materials are continues to use larger volumes of flexible fiers; and transparent compounds contain well suited for making shapes that can be pvc. Applications include wire insulation, , no fillers. formed by vacuum, drape, cold forming or injection-molded knobs, upholstery, trim Stabilisers prevent heat degradation by variations of these methods. Bubble or and bumper strips. Besides the usual during processing and for many appli "blister" packaging with dear, thin, rigid properties that make flexible vinyl desira cations extend service life. While they pvc film provides visual appeal and pro ble, its availability in a wide range of have little influence on most structural tection as well as economy. colon makes it especially desirable for use properties, they have a gross effect on Injection-molded vinyl parts are pro in the automotive industry. such properties as electrical and outdoor duced using in-line screw-preplssticizing weathering. (See article on stabilizers on equipment. Products include automotive Melt processing >*42.) Plasticisers impart flexibility to pvc. (See "Plasticizer*," p 264.1 and appliance parts, electrical and pipe fittings, all of which ere well known for their durability, attractive appearance The most common method of convert ing compounded polymer is by the melt process. | Lubricants aid flow during pvc proc and fidelity of surface reproduction. essing. The correct types and amounts of Rigid vinyl's excellent dimensional sta lubricants are important for the best bility, chemical inertness, high impact In extrusion, processing on single-screw 1 extruders is done at basically two melt > viscosity levels. High-viscosity, low- extrusion rate and to prevent plsteout resistance and exceptional clarity permit temperature systems are associated with during calendering. Also, the choice of its use by the packaging industry for low production rates but they maintain lubricant can affect electrical properties, lightweight blow-molded containers. dimensional precision of a product outdoor weathering and other charac Chlorinated pvc extends the many use Low-viscosity, high-temperature melts teristics. ful characteristics of opaque rigid pvc to usually are identified with powder com Fillers reduce the cost of Pvc formula- higher temperatures. As the degree of pound^ because of the high shear rates tions. Fillers in rigid compounds are used chlorination increases, properties such as required to convert powder to a melt on . at low levels. (Fot details on fillers, see p. density and hast distortion temperature a single-screw extruder; these conditions, 216.) are improved, while other properties are however, favor substantially higher out- ( Impact modifiers and processing aids maintained or improved. Products include put rates. Multiple-screw extruders, using improve impact and melt processibility of hot and cold water piping, automotive powder compounds, now claim a large rigid pvc compounds. Typical impact under-the-hood applications, roof ex share of the pipe and architectural msr- | modifiers are methyl methacrylate buta hausts and electrical housings. keta. They can extrude at moderate tern- [ diene styrene, acrylonitrile butadiene sty rene (abs) and chlorinated polyethylene. Common processing aids are methyl methacrylate and etyrene acrylonitrile. Other materials such as color pigments, flam? retardants and fungicides may be added for specific requirements. Flexible vinyls contain plasticizers in sufficient quantity (20 to 100 or more parta/100 of resin) to impart flexibility. Compounds with lower levels of plasti cizer (20 to 40 phr) are often termed semirigids. Flexible compounds find use in wire and cable, insulation, automotive parts, peratures (370 to 390* F.) maintaining ; substantial output rates. The lower ex- j trudate temperatures provide a significant advantage in thermal stability, especially when large inventory dies are used, as in large-diameter, thick-walled pipe. Injection molding of pvc, especially Typos of PVC toys and packaging. rigids, became practical with the advent Flexible compounds can be fabricated of screw injection molding machines Rigid vinyl m a hard, tough thermo by several means. Sheet materials are plastic material. It can be compounded to either calendered or extruded, while tub achieve a wide range of structural prop ing, profiles and wire insulation are ex High-shear screws generate low-viscosity melts that flow more freely into tbe furthermost sections of the mold cavity. erties and it can also be modified for proc- truded. Many other shapes that cannot be In blow molding, programming of tbe Continued on page 1 IS 1973-1974 Modem Plastics Encydopeon 106 Circle 52 for reader service I pifion ii coming into wider uw to reduce costs by providing more uniform wall thickness. There not only i a saving in material, but time cycles also are reduced because thick-wall, slow-cooling sections ie eliminated. In calendering, it is necessary to pro vide a means of fluxing the compound at a rate to match the capacity of the calen der. A Banbury-mill combination is nor mally used. A short-barreled extruder downstream of the mixing equipment is deniable to strain out any foreign mate rials that might damage the costly calen der rolls. Liquid processing Special fine-particle-size pvc resins termed dispersion resins are dispersed in plasticizers, usually by low shear, stir-in techniques, to produce remarkably versa tile liquid systems. The plasticizers have little effect on the resin at room tempera ture, providing liquids with viscosity sta bility over a long period of time. Heating the system to about 177* C. (350* F.) causes fusion (mutual solubilization of resin and plasticizer) to occur. Cooling the melt to below 60* C. (140* F.) provides a tough, flexible vinyl product. In ease of formability vinyl dispersions are the quintessential plastics material, sface the force of gravity alone is often sufficient to produce the desired shape and surface contour. Plastisola are vinyl dispersions contain ing little or no volatile liquids and thus are essentially 100% solids. Organosols are rimilar in composition to plastisola except for the presence of volatile liquids used to extend the liquid phase and thus reduce viscosity. Heat, without pressure or shear, is all that ia required to convert these dispersions to flexible solid materials quite similar in physical and chemical proper ties to vinyl products prepared by melt processing of solid compounds. Polyvinyl chloride for plaatisola and organosols is polymerized in emulsion systems that provide colloidal water dis persions containing ultimate particles of approximately 0.2 to 2.0 microns in size. Spray drying of the water dispersion pro duces the commercial product, a dry pow der of approximately 2 microns average particle size, with some particles as large as 15 to 20 microns. About 10% of the pvc used in the U.S. is dispersion grade. Formulating vinyl dispersion resins is similar to that of melt processed vinyl resins, except that the compounding in gredients must be selected to keep the rheological properties of the liquid system within the limits imposed by the process ing method. In addition to the com pounding ingredients mentioned, certain large particle size, suspension polymerized pvc resins, designated blending resins, are often used to replace part of the disper sion resin to reduce cost or adjust flow properties. Most vinyl dispersion resins find use in the two broad areas of coating and mold ings, Roll coating, spraying and dipping are all employed to coat a variety of sub strates, Fabrics, coil metal, paper and roll goods flooring are usually processed by knife or roll costing. Spray coating ia often used on stamped metal and dipped coatings may be applied to racks as well as to formed metal parte. Rotational casting of plastisols is used to mold open or closed hollow objects such as dolls, balls and automotive up holstery parts such as arm resta. Open hollow parts such as boots and traffic cones can be efficiently produced by slush molding plastisola. Cloth supported and unsupported gloves are typical examples of dip molded products. Organosols are used to produce thin films of higher hardness than can gener ally be obtained from plastisols. Greater hardness is made possible through the use of volatile dispersants and diluents and low concentrations of plasticizer. Dispers ants are polar ketones and esters that aid in dispersion and fusion of the resin, while diluents are nonpolar solvents that adjust flow properties and reduce the solvating effect of the dispersant. Vinyl solutions. Polyvinyl chloride and copolymers with vinyl acetate and vinylidene chloride can be dissolved by electron-donorsolvents. Viscosity depends upon composition and molecular weight of the polymer and the total solids of the solution. A wide range can be obtained, which allows the procewor to deposit polymer films by most common methods. Some of the copolymers contain carboxyl and hydroxyl groups for improved adhe sion and reactivity with isocyanate, methylol and epoxy resins. Solution tech nology allows deposition of hard, highmolecular-weight polymer* at room tem perature or thin films of 1 mil or less. Latex liquid systems of vinyl chloride homopolymers and copolymers are also available. These systems are colloidal dis persions in water. The average particle nie ia usually less than 0.3 micron. Poly vinyl chloride latexes form film as a result of the enormous capillary forces that are exerted as the last amounts of water volatilize from the wet film. Latexes are effectively used to coat, impregnate or saturate fabrics, paper and leather with polymeric dispersions of lower viscosity than most plastisols. La texes are also used as tie coats on fabric or paper to bond plastisols, organosols or calendered film to these substrates. In end uses where flame retardancy is a require ment, latexes can be used in conjunction with antimony oxide, phosphates or chlo rinated paraffins. Latexes are applied by most of the common coating methods including knife, roll, spray and curtain. Vinyls are an established plastics family with broad uses throughout industry and in consumer products. At the same time, new varieties of vinyl materials and im proved processing methods and com pounding ingredients are continually de veloping. These advances account for the steady expansion of the uses of vinyl ma terials. Additional information related to vinyls may bt found as followt: Charts in the Data Bank (p. 533) give technical infor mation. Processing methods appear in two sections: Primary Processing (p. 273) and Fabricating and Finishing (p. 479). Index of Classified Advertisers (p. 839) lists advertiser page references. Free product literature available from suppliers appears on p. 377. And for additional sources ofsupply, see p. 773. URL 4518