Definitions of Plastic Resins; Part 4
Polyvinyl Acetate (PVAc) & Other Vinyls
Polyvinyl acetate is a thermoplastic resin produced by the polymerization of vinyl acetate monomer [CH3COOCHCH2] in water producing an emulsion with a solids content of 50-55%. Most polyvinyl acetate emulsions contain co-monomers such as n-butyl acrylate, 2-ethyl hexyl acrylate, ethylene, dibutyl maleate and dibutyl fumarate. Polymerization of vinyl acetate with ethylene also can be used to produce solid vinyl acetate/ethylene copolymers with more than 50% vinyl acetate content. Polyvinyl alcohol (PVOH) is produced by methanolysis or hydrolysis of polyvinyl acetates. The reaction can be controlled to produce any degree of replacement of acetate groups. Co-polymers of replaced acetate groupings and other monomers such as ethylene and acrylate esters are commercially important. Polyvinyl butyral (PVB) is made by reacting PVOH with butyraldehyde [CH3(CH2)2CHO]. Polyvinyl formal is made by condensing formaldehyde [HCHO] in presence of PVOH or by the simultaneous hydrolysis and acetylization of PVAc. Polyvinylidene chloride is made by the polymerization of 1,1-dichloroethylene [CH2CCL2]. Typical applications for the above resins are found in adhesives, paints, coatings and finishes, and packaging.
Polyvinyl Chloride
Thermoplastic resins produced by the polymerization of the gas vinyl chloride [CH2CHCl]. Under pressure, vinyl chloride becomes liquefied and is polymerized by one of four basic processes: suspension, emulsion, bulk, or solution polymerization. The pure polymer is hard, brittle and difficult to process, but it becomes flexible when plasticizers are added. A special class of PVC resin of fine particle size, often called dispersion grade resin, can be dispersed in liquid plasticizers to form plastisols. The addition of a volatile diluent or a solvent to the plastisol produces an organosol. Copolymers with vinyl acetate, vinylidene chloride, and maleate and fumarate esters find commercial application. Major markets for PVC are in building/construction, packaging, consumer and institutional products, and electrical/electronic uses. This material bonds effectively using solvents. Plasma treatments can enhance the adhesion of this material if solvents are not used.
Styrene Acrylonitrile
Thermoplastic copolymers of styrene [C6H5CHCH2] and acrylonitrile [CH2CHCN]. SAN resins are random, amorphous copolymers produced by emulsion, suspension, or continuous mass polymerization. Typical uses include automobile instrument lenses and housewares. Typically, this material does not have adhesion issues.
Styrene Butadiene Latexes & Other Styrene Copolymers
Styrene butadiene latexes usually have a resin content of about 50%. The styrene/butadiene ratio varies from 54:46 to 80:20. Most are carboxylated by the use of such acids as maleic [HOOCCHCHCOO], fumaric [HOOCCHCHCOOH], acrylic [CH2CHCOOH], or methacrylic [CH2C(CH3)COOH]. Two types of styrene-maleic anhydride (SMA) [(COCH)2O] are available: SMA copolymers, with and without rubber impact modifier (e.g., DYLARK¨) and SMA terpolymer alloys (e.g., CADON¨). K-Resin¨ is a solid styrenebutadiene copolymer resin. Acrylic monomers are also used in conjunction with styrene (or styrene plus other monomers) to produce specialty resins. For example, there are transparent terpolymers of methyl methacrylate, butadiene, and styrene (MBS), and others of acrylonitrile, an acrylic monomer, and styrene (AAS). Ion-exchange resins or divinylbenzene-modified polystyrene are another variation. SB latexes are used in carpet backing and paper coatings. The other styrenics are used in paints, coatings, and floor polishes, plus many other uses. Typically this material can be bonded using solvents. Moreover, these materials are enhanced after plasma treatment using other adhesives.
Sulfone Polymers
A family of engineering thermoplastic resins characterized by the sulfone [SO2] group. Polysulfone is made by the reaction of the disodium salt of bisphenol A[(CH3)2C(C6H4OH)2] with 4,4′- dichlorodiphenyl sulfone 4,4′-DCDPS [(C6H4Cl)2SO2]. Polyethersulfone is made by the reaction of 4,4′-DCDPS with potassium hydroxide [KOH]. Polyphenylsulfone is similar to the other sulfone polymers. Typical applications for sulfone polymers are found in electrical/electronic uses and automotive parts. Plasma treatments often enhance the adhesion of this material significantly using epoxies.
Thermoplastic Polyester (Saturated)
A family of polyesters in which the polyester backbones are saturated and hence nonreactive. The most common commercial types are: PET (polyethylene terephthalate) produced by polycondensation of ethylene glycol [CH2OHCH2OH] with either dimethyl terephthalate (DMT) [C6H4(COOCH3)2] or terephthalic acid (TPA) [C6H4(COOH)2]; and PBT (polybutylene terephthalate) produced by the reaction of DMT with 1,4 butanediol [HO(CH2)4OH]. Typical applications are found in packaging, automotive, electrical, and consumer markets. Plasma treatments enhance this material when using epoxy.
Unsaturated Polyester
Thermosetting resins made by the condensation reaction between difunctional acids and glycols. The resulting polymer is then dissolved in styrene [C6H5CHCH2] or other vinyl unsaturated monomer. The structures of the acids and glycols used and their proportions, especially the ratio of the unsaturated versus the saturated acid, and the type and amount of monomer used, are all tailored for each resin to balance economy, processing characteristics, and performance properties. One common formulation is the reaction of maleic anhydride [(COCH)2O], phthalic anhydride [C6H4(CO)2O], and propylene glycol [CH3CHOHCH2OH]. Both dicyclopentadiene [C10H12] and isophthalic acid [C6H4(COOH)2] can be substituted for phthalic anhydride. Vinyl ester resins are linear reaction products of bisphenol A [(CH3)2C(C6H4OH)2] and epichlorohydrin [CH2OCHCH2Cl] that are terminated with an unsaturated acid such as methacrylic acid [CH2C(CH3)COOH]. Typical applications are found in transportation, appliances, electrical, and construction markets. As in the above material, plasma treatments enhance this material when using epoxy.
Urea-Formaldehyde
Formed by the condensation reaction of formaldehyde [HCHO] and urea [CO(NH2)2]. These thermoset resins are clear water-white syrups or white powered materials which can be dispersed in water to form colorless syrups. They cure at elevated temperatures with appropriate catalysts. Molding powders are made by adding fillers to the uncured syrups, forming a consistency suitable for compression and transfer molding. The liquid and dried resins find extensive uses in laminates and chemically resistant coatings. The molding compounds are formed into rigid electrical and decorative products.
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January 13th, 2010 at 9:08 AM
On sub-heading Styrene Butadiene Latexes & Other Styrene Copolymers. A note on the two SMA types which are named. Dylark is no longer available as Nova chemicals seized production in July 2009, Cadon does no longer exist since the sale of Solutia to Hercules. Today there are therefore only two major commercial producers of SMA, Sartomer with exclusively low Moleculaire weight products typically below 20.000, and Polyscope who provides SMA copolymers with a Moleculaire weight between 5000 and 180.000, and a Maleic anhydride content between 8 and 42%, including post-impact modified grades (Comparable to former Dylark resins).