Acrylic emulsion sealant

Table 5.1 outlines useful properties, products and application areas of acrylic systems. Key market segments are coatings based on methacrylates as well as emulsions and water-based sealants. Acrylic emulsions and redispersible powders as cement modifiers offer many useful products for several end-uses. However, the high cost of acrylic has limited their use as cement modifiers. The use of water-based acrylic systems is increasing because of their non-toxic and environmentally friendly nature. 

Water-based acrylic sealants are also referred to as acrylic emulsion sealants or latex sealants. These are one-component gun-grade material with a solid content ranging from 80%-85%. Curing occurs by evaporation... 

The average shore A hardness of the cured sealant is 20 to 25 but increases with ageing. Resistance to ultraviolet radiation is excellent, but this is not important for indoor applications. The maximum movement accommodation factor (MAF) can be 15% of the total joint width. Joints should be designed so that movement due to shrinkage and thermal changes does not exceed the maximum MAF, related to the joint width. Table 5.4 lists the properties in general for acrylic emulsion sealants. These properties are summarised from the commercial literature of several acrylic emulsion sealant manufacturers and should not be considered as specifications. Table 5.5 lists the standard specifications for these sealants. 

Chem. Descrip. Acrylic prepolymer emulsion Uses Acrylic for interior flat latex paints, primer sealers, exterior masonry, exterior wood stains, caulks, sealants, and mastics Features Prevents paint blistering/peeling soon after applic./before the paint film is leached of its water exiraclables provides alkali resist., pig-... 

Intermediate movement accommodating sealants include solvent-based and emulsion-type acrylic systems, higher quality butyl/PIB blends, neoprene and styrene-butadiene (SBR) based compounds. These have sufficient movement tolerance to be used in joints subject to both settlement and thermally induced movement across the sealant. These intermediate type systems cure by means of solvent evaporation with some auto-oxidation, or a mixture of the two processes. 

The adhesive properties of pol5Tners produced by solvent pol5Tner-ization are better than those produced from emulsion pol5mierization. Acrylic sealants set by solvent evaporation, have good adhesion, excellent flexibility, good heat and chemical and ozone resistance However, they... 

Table 15. Acrylic Emulsion Sealant (Gun Grade, White).

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. 

Bathrooms - Polyvinyl acetate sealants, acrylie emulsion sealants and silieone rubber sealants are all used as bath-tub caulks and for wall tile and wallboard joints. Polyvinyl acetate and acrylic emulsion sealants are easier to apply and clean up, and are lower cost than silicone sealants. The silieone sealants form stronger adhesive bonds and have better long term durability. 

There is a similarly wide range of sealants for the DIY household maihet, varying from oil based putties for glazing polyvinyl acetate and acrylic emulsion sealants, with easy appUcation and clean-up properties and butyl, polyiuethane and silicone sealants for dmable, flexible, long lasting external seals. Again the cost increases progressively from oil based putties to silicone rubber based sealants. 

While silicones, polyurethanes and polysulfides set through a chemical reaction, water based emulsion sealants achieve their functional end state by simple physical drying, i.e. evaporation of the water. The majority of emulsion sealants are composed of acrylic emulsions and to a lesser extent vinylacrylic and other copolymers. 

The total cauUc and sealant market in North America is estimated 500 000 tons of formulated sealants [80], with acrylic emulsion sealants comprising approximately 15 % of the total market, and 23 000 tons dry acrylic resin. Water based sealants, sold primarily in cartridge tubes, are used predominately in construction applications whereas reactive urethanes and silicones are used in more demanding construction and automotive applications. 

Acrylics. There are two principal classes of acrylic sealants latex acrylics and solvent-release actylics. High molecular weight latex acrylic polymers are prepared by emulsion polymerization of alkyl esters of acrylic acid, The emulsion polymers are compounded inlo sealants by adding fillers, plasticizers, freeze-thaw stabilizers, thickeners, and adhesion promoters. As is true of the silicone lalex sealants, die acrylic latex sealants are easy to apply and clean with water. 

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

Emulsions of polyvinyl acetate and polyalkyl acrylates have been used as tub caulking compositions, spackling compounds and as building sealants.22 Acrylic sealants which harden in the presence of powdered iron or copper meet Federal Specifications TT-S-00230C. 27 Liquid monomers, such as polyethylene glycol dimethacrylate and butyl alpha—cyanoacrylate have been used as room temperature curing sealants.22 22. 

Acrylic adhesives first appeared about 1937 the acrylic resins may be considered as belonging to the vinyl family [1, p. 305], Today, acrylic adhesives appear in many forms as both pressure-sensitive and non-pressure sensitive formulations in organic solvent and emulsion forms as monomer and polymer cements as anaerobics as cyanoacrylates as so-called reactive or honeymoon two-part systems and as radiation curing formulations. Commercial production of acrylic polymers began in the late 1920s, but it was not until 1958 that the first aerylie sealant was developed [10, p. 226]. The solvent-based acrylic sealants were first introdueed to the eonstruction industry in about 1960 ... 

Uses Monomer for emulsion polymerization of acrylic and vinyl-acrylic, latex paints, adhesives, caulks, sealants wet adhesion promoter scrub resist, aid in paint films... 

Uses Plasticizer for PVC, cellulosic, acrylate resins, syn. rubber, adhesives, sealants, emulsion paints, food pkg. syn. lubricant basestock in food-pkg. adhesives... 

Uses Acrylic resin comonomer anaerobic adhesives and sealants printed circuit boards cosmetics artificial finger nails modifier for hard rubber rolls wire and cable coatings screen printing inks emulsion polymerization plastic modifier EB-curable coatings reactive diluent for hot-melt prepregs and adhesives... 

Properties M.w. 170.21 dens. 1.044 b.p. 52 C (0.4 mm) flash pt. 90 C ref. index 1.4580 Uses Acrylic resin comonomer anaerobic adhesives and sealants printed circuit boards cosmetics artificial finger nails modifier for hard rubber rolls wire and cable coatings screen printing inks emulsion polymerization plastic modifier EB-curable coatings reactive diluent for hot-melt prepregs and adhesives Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, CPS Monomer-Polymer 8i Dajac Labs Polysciences... 

Fifteen papers are presented at this two day international annual conference on latex and latex based products. Both synthetic and natural latices are covered including natural rubber latex, high volume synthetic emulsions and speciality products such as acrylics. Application markets addressed include adhesive and sealants, paper coatings, construction, fabrics, foamed articles, medical gloves, medical devices, textile threads and condoms. 

This paper reports on the synthesis, characterisation, and applications of novel flame retardant dibromostyrene-based latexes. They are copolymers of dibromostyrene with butadiene, alkyl acrylates and methacrylates, vinyl acetate, styrene and unsaturated carboxylic acids, which form a wide variety of flame retardant latexes via an emulsion polymerisation technique. Choice of monomer or monomer blend is based upon the final glass transition temperature of the copolymer desired. Other criteria include desired physical properties and chemical resistance. Dibromostyrene-based butadiene and acryUc latexes are shown to possess the desired physical properties for use in coatings, adhesives and sealants, and the bromine content of the latexes has enabled the material to pass six different flammability requirements for the end uses such as textile backcoating, latex-based paint, contact adhesive, latex sealant, nonwoven binder, and carpet backing. 18 refs. 

Chapter 2 Acrylic Dispersion Adhesives and Sealants, by Dr Urban, scientist at BASF, Germany, the world leader for acrylic polymers and emulsions it will... 

Sealants and caulks based on vinyl acetate homo- and copolymers have been on the market since the late 1950s. Use of these lower-performance materials has been mostly in residential areas—bathtub caulking, wall tile joints, wallboard joints, etc. Latex caulks based on polyvinyl acetate plasticized with dibutyl phthalate, or on one of the newer vinyl acetate-acrylic emulsion copolymers, have the same ease of application as the acrylic emulsion caulks but are less flexible, harden on aging, and have inferior exterior durability. ... 

Glazing - Linseed oil based putties were extensively used in the past for glazing applications. Newer glazing sealants include polysulfide, silieone, and acrylic emulsion. Butyl tape, polysulfide and silicone sealants are used in the manufacture of insulated glass. Safety glass door and window panels ean be made by sandwiching a layer of polyvinyl butyral film between two layers of glass. 

Bentonite thickening agents are used in various water based adhesives, caulks and sealants including those based on proteins and starch, polyvinyl acetate emulsions, natural rubber latexes, acrylic emulsions, neoprene emulsions, butyl emulsions, nitrile emulsions, and SBR emulsions. 

The base polymer for this t5q>e of sealant exists in the form of an emulsion of micron- and submicron-sized partides of the polymer suspended in water. The base polymer formed by free radical polymerization may be a homopolymer of an acrylic monomer but is more likely to be a copolymer of a number of different monomers chosen to provide the correct balance of properties. The polymer latex has to be made more permanent and therefore a nonionic surfactant such as a nonyl phenol/ polyethylene oxide is added to help stabilize the emulsion. Other additives to the sealant formulation include plastid-zers, fillers, solvents, and silanes. A plasticizer is added to the formulation in order to improve upon or maintain the flexibility of the sealant. Solvents (usually a small amount) are added to improve the tooling of the sealant after it is applied. In addition, a solvent could be a material such as ethylene or propylene glycol which can improve the resistance of the packaged sealant to temperatures below freezing. The most widely used filler for this type of sealant is calcium carbonate. Silanes are often added to acrylics to improve the wet adhesion of the sealant to glass. Other additives include antimildew agents (for tub and tile applications) and clay for rheological control. 

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