Automotive emulsion polymers

Comparing an uncrosslinked emulsion polymer film and a highly cross-linked automotive top coat at temperatures well below their respective glass transition temperatures as an example, both polymeric films have tensile modulus values of approximately 2 x 10 dyncm [8]. Nevertheless, these two polymer systems show very different mechanical properties in the rubbery plateau region. The tensile modulus values are approximately (5-10) x 10 and (2-8) X 10 dyncm for the emulsion polymer and automotive top coat, respectively. Thus, one can certainly improve the physical properties of this latex... 

Table 7-2 shows the emulsion polymers most often used in the various automotive layers. 

Water-borne emulsion polymers are used in formulating automotive coatings for electrocoat, primers and basecoats. Clearcoat polymers are primarily still solvent-borne. A powder dispersed in water (powder slurry) has been developed as a binder for clearcoats [7]. 

EPR and EPDM have been made by either solution or emulsion polymerization processes. More recently a new process involving gas-phase polymerization and metallocene catalysts promises to capture large shares of these markets. These new polymers will be especially attractive in automotive apphcations and wine and cable where theh favorable pricing should be welcome. 

Water-soluble polymers eomprise a major elass of polymerie materials and are used in a wide variety of applieations. Synthetie water-soluble polymers inelude poly(vinyl aleohol), poly(aerylamide), poly(aerylie aeid), poly(ethylene oxide), poly(vinyl pyrrolidone), eellulosies, and many eopolymers of these types. Their end uses are quite varied and their applieations depend mainly on their viseosify-ing, rheologieal, and surfaee-aetive properties (1). For example, poly (vinyl aleohol) is used in adhesives, fibers, textile and paper sizing, paekaging, as a stabilizer for emulsion polymerization, and as a preeursor for the manufaeture of poly(vinyl butyral), whieh is used in automotive windshields. Poly(vinyl aleohol) is also the world s largest volume, eommodity, water-soluble polymer. 

In the 1960s, anionic polymerized solutron SBR (SSBR) began to challenge emulsion SBR in the automotive tire market. Organolithium compounds allow control of the butadiene microstructure, not possible with ESBR. Because this type of chain polymerization takes place without a termination step, an easy synthesis of block polymers is available, whereby glassy (polystyrene) and rubbery (polybutadicnc) segments can be combined in the same molecule. These thermoplastic elastomers (TPE) have found use ill nontire applications. 

Polymer processing can be of several types, including free radical, cationic, anionic, metal complex, or metal oxide catalyzed, as mentioned earlier [5], Polymers can be made by bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization techniques [5], The automotive chemist or design engineer working for an OEM should be aware of these various manufacturing processes, which polymers are made by which process, and what characteristics can be expected from the type of process. 

Uses Intermediate for mfg. of polymers modifying comonomer in prep, of vinyl acetate-based polymer latexes for mfg. of specialty emulsion paints (gloss paints and varnishes, water repellents, anticorrosion paints, coatings for polyolefins), comonomer with acrylates for prod, of emulsion, sol n., and bulk polymers, acid or anhydride-cured acrylic automotive coatings, acrylic powd. coatings... 

Acrylic rubber can be emulsion- and suspension-polymerized from acrylic esters such as ethyl, butyl, and/or methoxyethyl acetate to produce polymers of ethyl acetate and copolymers of ethyl, butyl, and methoxyl acetate. Polyacrylate rubber, such as Acron from Cancarb Ltd., Alberta, Canada, possesses heat resistance and oil resistance between nitrile and silicone rubbers. Acrylic rubbers retain properties in the presence of hot oils and other automotive fluids, and resist softening or cracking when exposed to air up to 392°F (200°C). The copolymers retain flexibility down to -40°F (-40°C). Automotive seals and gaskets comprise a major market. These properties and inherent ozone resistance are largely due to the polymer s saturated backbone (see Table 3.13). 

Chem. Descrip. Emulsion of foam destroying polymers and polysiloxanes Uses Defoamer for aq. systems, gloss and semi-gloss paints, plastic coatings, wood/parquet varnishes, furniture coatings, automotive base coats, and prod, of polymer dispersions... 

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