Poly , coatings

For very difficult to adhere bag substrates, such as poly-coated bags, or where extreme chemical resistance is needed, polyamide hot melts are used. These adhesives are very lightly formulated if at all. They provide soft adhesives with outstanding heat and chemical resistance, but at roughly double the price. 

U.S. Pat. No. 5,952,105 [67] describes a thermoplastic composition comprising sheared poly-coated paper (50-70% by weight) and polyethylene (30-50%). An example provided in the patent describes making an 80-g batch of a compression-molded composite comprising HDPE (39%), a poly-coated paper (scrap milk cartons, 59%), and a conpling agent (Polybond 3009, 2%). 

Level 4 Poly coated made from SMS PP or spunlace PET/wood pulp material coated with polyethylene (PE). PP is hght and comfortable, and PE gives a strong barrier to fluids. Used when high contact with blood and bodily fluids is expected. 

Resins formed from the reaction of poly(vinyl alcohol) with aldehydes. The formal derivative (from methanal) is used in wire coatings and adhesives and the bulyral (from butanal) is used in metal paints, wood-sealers, adhesives and in safety glass interlayers. 

Solid-phase microextractions also have been developed. In one approach, a fused silica fiber is placed inside a syringe needle. The fiber, which is coated with a thin organic film, such as poly(dimethyl siloxane), is lowered into the sample by depressing a plunger and exposed to the sample for a predetermined time. The fiber is then withdrawn into the needle and transferred to a gas chromatograph for analysis. 

Capillary Tubes Figure 12.42 shows a cross section of a typical capillary tube. Most capillary tubes are made from fused silica coated with a 20-35-)J,m layer of poly-imide to give it mechanical strength. The inner diameter is typically 25-75 )J,m, which is smaller than that for a capillary GC column, with an outer diameter of 200-375 )J,m. 

Poly(vinyl cinnamate) Resists. Dichromated resists exhibit numerous shortcomings which include lot-to-lot variabiUty of the components, aging of the formulated resists in solution and in coated form, poor process stabiUty (due to a sensitivity to variations in temperature and humidity), and intrinsically low photosensitivity requiring long exposure times for adequate insolubilization. 

The linear polymer of PX, poly(p-xylylene) (PPX) (2), is formed as a VDP coating in the parylene process. The energetics of the polymerization set it apart from all other known polymerizations and enable it to proceed as a vapor deposition polymerization. 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Acrolein is highly toxic by skin absorption. Brief contact may result in the absorption of harmful and possibly fatal amounts of material. Skin contact causes severe local irritation and chemical bums. Poly(vinyl chloride) coated protective gloves should be used (99). 

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

Poly(vinyhdene chloride) (PVDC) film has exceUent barrier properties, among the best of the common films (see Barrier polymers). It is formulated and processed into a flexible film with cling and tacky properties that make it a useful wrap for leftovers and other household uses. As a component in coatings or laminates it provides barrier properties to other film stmctures. The vinyUdene chloride is copolymerized with vinyl chloride, alkyl acrylates, and acrylonitrile to get the optimum processibUity and end use properties (see Vinylidene chloride monomer and polymers). 

The Fe, Co, and Ni deposits are extremely fine grained at high current density and pH. Electroless nickel, cobalt, and nickel—cobalt alloy plating from fluoroborate-containing baths yields a deposit of superior corrosion resistance, low stress, and excellent hardenabiUty (114). Lead is plated alone or ia combination with tin, iadium, and antimony (115). Sound iasulators are made as lead—plastic laminates by electrolyticaHy coating Pb from a fluoroborate bath to 0.5 mm on a copper-coated nylon or polypropylene film (116) (see Insulation, acoustic). Steel plates can be simultaneously electrocoated with lead and poly(tetrafluoroethylene) (117). Solder is plated ia solutioas containing Pb(Bp4)2 and Sn(Bp4)2 thus the lustrous solder-plated object is coated with a Pb—Sn alloy (118). 

Polyester. Poly(ethylene terephthalate) [25038-59-9] (PET) polyester film has intermediate gas- and water- vapor barrier properties, very high tensile and impact strengths, and high temperature resistance (see Polyesters, thermoplastic). AppHcations include use as an outer web in laminations to protect aluminum foil. It is coated with PVDC to function as the flat or sealing web for vacuum/gas flush packaged processed meat, cheese, or fresh pasta. 

Poly(vinylidene chloride). Poly(viayHdene chloride) [9002-85-1] (PVDC), most of which is produced by Dow Chemical, is best known in its saran or PVC-copolymerized form (see Vinylidene chloride and poly(VINYLIDENE chloride)). As solvent or emulsion coating, PVDC imparts high oxygen, fat, aroma, and water-vapor resistance to substrates such as ceUophane, oriented polypropylene, polyester, and nylon. 

A viscous solution of poly(amic acid) can be processed into films, fibers, and coatings, and the final product undergoes thermal cyclo dehydration. 

Vinyl fluoride (fluoroethene), is manufactured from the cataly2ed addition of hydrogen fluoride to acetylene. It is used to prepare poly(vinyl fluoride) which has found use in highly weather-resistant films (Tedlar film, Du Pont). Poly(vinyhdene fluoride) also is used in weather-resistant coatings (see Eluorine compounds, organic). The monomer can be prepared from acetylene, hydrogen fluoride, and chlorine but other nonacetylenic routes are available. 

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

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