Polyacrylic sealants

From the DLTMA curves, the authors reported that besides the likely relaxation effect observed at -50°C (see Fig. 8), the silicone rubber behaves as an ideal rubber-elastic solid over the whole temperature range. The polysulfide and polyurethane sealants, on the other hand, exhibit viscous flow at temperatures higher than 150°C. The polyacrylate sealant will soften above 50°C indicating a pseudoplastic behavior. 

Bisphenols is a broad term that includes many chemicals with the common chemical structure of two phenolic rings joined together by a bridging carbon. Bisphenol A is a monomer widely used in the manufacture of epoxy and phenolic resins, polycarbonates, polyacrylates and corrosion-resistant unsaturated polyester-styrene resins. It can be found in a diverse range of products, including the interior coatings of food cans and filters, water containers, dental composites and sealants. [4]. BPA and BP-5 were selected for testing by the whole... 

Acrylic acid and its salts are raw materials for an important range of esters, including methyl, ethyl, butyl, and 2-ethylhexyl acrylates. The acid and its esters are used in polyacrylic acid and salts (32%, including superabsorbent polymers, detergents, water treatment chemicals, and dispersants), surface coatings (18%), adhesives and sealants (15%), textiles and non-wovens (12%), plastic modifiers (5%), and paper coating (3%). 

Latekoll . [BASF AG] Polyacrylic derivs. diidceners fm polymer dispersions latexes for paints and textured finishes, adh ves, sealants, prod, (d fiber webs. 

The above criteria were employed to select several commercially supplied Class PS elastomers for laboratory screening by employing selected tests taken from National Bureau of Standards NBSIR 77-1437(j4) and ANSI/ASTM D-3667-78 specifications for "Rubber Seals Used in Flat-Plate Solar Collectors". Four silicone, three EPDM, two fluorocarbon, three epichlorohydrin, one ethylene-acrylic, one polyacrylic, one chlorosulfonated polyethylene, one bromobutyl and two butyl rubbers were studied in these screening tests. These materials are identified in Table I and those compositions which were revealed by their manufacturers are shown in Table II. Undoubtedly some materials which should have been included were omitted however, we hope that this sampling will provide an indication of the applicability of a wide range of materials for use as sealants in thermal solar collectors. 

Their work on adhesives was not a major effort. Some anaerobic adhesives were developed by the Institute, and later produced by the Oriental Scientific Instruments Import Export Corporation in Guangzhou. Two of the series are GY-340 anaerobic adhesive-sealant and GY-168 anaerobic flexible sealant. Both have a polyacrylate-base, with a shelf-life of one year. The curetime for GY-340 was 2 to 6 hours at room temperature the curetime for GY-168 was 12 to 24 hours. 

Polyacrylics. Polyacrylic adhesives and sealants are formulated from functional acrylic monomers, which achieve excellent bonding upon polymerization.Alkyl esters of acrylic or methacrylic acids up to 80,000 molecular weight constitute the main bonds of acrylic sealants. 

As early as 1982, Riesen and Bartelst ] demonstrated the usefulness of dynamic load thermomechanical analysis (DLTMA) for the characterization of commercial joint sealants for building construction. They used DLTMA to study the viscoelastic behavior of four different sealant types polysulfide, polyurethane, silicone, and polyacrylate. The difference in viscoelastic behavior of the sealants can be seen from Fig. 8. 

A typical gun-grade acrylic emulsion sealant (Table 15) contains about 18% acrylic polymer solids and 9-10% of a polymeric plasticizer. Sodium polymetaphosphate is a primary pigment dispersant aided by a water-soluble polyacrylate. A nonionic surfactant acts as a wetting agent and emulsifier. Often small amounts (up to 2%) of glycols are included for additional freeze-thaw stability. Mineral spirits (about 2%) retards skin formation. Acrylic emulsion caulks are used indoors as bathtub caulks, baseboard and trim seams, and outdoors for glazing, masonry joints, and roof and siding joints. 

Current inventions show improvements in solvent utilization, as follows. PVC-based adhesive for PVC pipes, typically containing solution of PVC in tetrahydrofuran, was replaced by solution of chlorinated PVC in 1,3-dioxolane and/or its derivatives whieh are far less toxic than THF. Ethanol is used in polyimide adhesive and dental adhesive. Monomer solvent mixture is used in crosslinkable acrylate adhesive, which permits formulation of VOC-free composition. Polyurethane hot-melt adhesive produced from polyacrylates and polyesters does not need solvents for its production and cure which occurs under the effect of moisture. Similar observations can be made for sealants. For example, sealing agent for semiconductor light emitting elements have been made from acrylic monomers without application of solvent. Material for production of printed wiring board was produced and cured without solvent from polymethacrylate. It is clear from these examples that new processes are consciously directed towards less toxic solutions. 

Acrylic acid is an important chemical building block used in the manufacture of polyacrylates and commodity acrylates. Commodity acrylates, such as methyl, ethyl, n-butyl, and 2-ethylhexyl acrylate, are utilized in various industrial applications, including coatings, adhesives and sealants, textiles and fibers, polymer additives/impact modifiers, and films. Polyacrylates are extensively used as super absorbent polymers. Bio-based acrylic acid can be obtained through the fermentation of carbohydrates to 3-hydroxypropionic acid (3-HPA), and further dehydration of 3-HPA gives acrylic acid. 3-HPA could also be used as a precursor to other important chemical building blocks, such as PDO, acrylonitrile, and acrylamide. Via another route, glycerol can be chemically converted to acrylic acid, either by dehydration to acrolein followed by oxidation to the final product or in a one-step oxydehydration. 

Modem reactive sealants are mainly made from synthetic products (silicone, polyurethane, polyacrylics and polysulfides). There are, however, a series of specialty products based on - resins, natural, wax, rubber, glue and starch. 

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