Curing acrylic sealants

Another class of acrylic sealants arc the solvent-releasing acrylics. Acrylic monomers are polymerized in a solvent. The natural adhesion of most of the solvent-releasing acrylics produces some of the best unprimed adhesion in the sealant industry. However, slow, continual cure generally produces large compression sets and limits their use to low movement applications. Also, the relatively high amounts of solvent and traces of acrylic monomer in these formulations limits their use to outdoor applications, usually in construction,... 

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... 

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. 

Room temperature cured (RTV) silicones are used as potting compounds and as in situ formed gaskets. These compositions are toughened by the addition of styrene or butyl acrylate which form minute strands of fiber in situ when they polymerize.21 Silicone sealants and coatings are being used in the NASA space shuttles.22 Paintable, fast curing-octoate-cured silicone sealants are also available. Simple tests for utility, based on a filled glass tube, have been described.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 ... 

Anaerobic acrylic sealants or cyanoacrylates are known sensitizers, while the modified acrylic structural adhesives that cure in air more rarely cause allergy. Tosti et al. (1993) reported of three carpenters, each of whom became sensitized to wood paints and glues with butyl acrylate, 2-ethoxyethyl methacrylate, or a phth-late. Epoxy resin compounds are another commonly used group of adhesives, which contain resins (generally included in patch-test screening batteries), hardeners, and reactive diluents, as well as many other potentially harmful ingredients, such as tar, fillers, colorants, and other plastics. 

One-part clear acrylic latex sealant formulation, 22 42t One-part manganese dioxide-cured polysulfide formulation, 22 4 It One-part pigmented siliconized acrylic latex sealant, 22 42t One-part RTV silicones, 22 596 One-part silicone cross-linkers, 22 33t One-part silicone sealant formulation, 22 34t... 

Sealants - [ELASTOMERSSYNTHETIC - POLYISOPRENE] (Vol 9) - [SEALANTS] (Vol 21) -acrylics [ACRYLICESTERPOLYMERS - SURVEY] (Voll) -barium compds in [BARIUM COMPOUNDS] (Vol 3) -based on liquid polysulfides [POLYMERS CONTAINING SULFUR - POLYSULFIDES] (Vol 19) -defoamersin [DEFOAMERS] (Vol 7) -fiom fluorosilicones [FLUORINE COMPOUNDS,ORGANIC - POLY(FLUOROSILICONES)] (Volll) -hydrocarbon resins in [HYDROCARBON RESINS] (Vol 13) -lecithin in (LECITHIN] (Vol 15) -organolithiumcmpdsinprdnof [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15) -polysulfide curing [PEROXIDES AND PEROXIDE COMPOUNDS - INORGANIC PEROXIDES] (Vol 18) -propylene oxide in mfg of [PROPYLENE OXIDE] (Vol 20) -PVB m [VINYL POLYMERS - VINYL ACETAL POLYMERS] (Vol 24) -rheological measurements [RHEOLOGICAL MEASUREMENTS] (Vol 21) -from styrenic block copolymers [ELASTOMERS SYNTHETIC - THERMOPLASTIC ELASTOMERS] (Vol 9) -use of dispersants [DISPERSANTS] (Vol 8)... 

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. 

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. 

As previously noted, the primary use for this elastomer has been as solvent-based adhesives and sealants. Solvent-based products are losing market share to water-based poly-chloroprenes, to other polymer types such as acrylics and polyurethanes, and to hot melt adhesives. However, where the processing facility is able to contain the vapor emissions, a solvent-based adhesive or sealant is preferred because of better wetting of surfaces, faster drying, and higher performance of the cured or dried product. Many rubber bonding... 

Chem. Descrip. Epoxy acrylate blended with 40% SR 351 (trimethyloF propane triaciylate), 3800 ppm MEHQ Uses Epoxy for adhesives (anaerobic, binder, pressure sensitive, structural), coatings (glass, metal, optical, paper, plastic, wood, PVC floor), electronics, inks (flexo and gravure, litho, offset, screen), and sealants Features Fast cure response, film hardness, water and abrasion resist. Properties Gardner < 2 clear liq. sp.gr. 1.146 vise. 8200 cps (49 C) 60% oligomer, 40% TMPTA... 

Baccei (21) discloses polymerizable adhesive and sealant compositions having as an important ingredient urethane-acrylate-capped oligomers based on liquid hydroxyl-terminated polybutadiene or polybutadiene/ acrylonitrile copolymers. Properties associated with impact and thermal improvements are noted as well as the ability to cure adequately through the bondline gap. Model systems are largely triethylene glycol dimethacrylate based. Impressive adhesive performance properties are recorded. (Cf. Paper by Malofsky and Baccei in this... 

Anaerobic adhesives and sealants are based on acrylic (usually meth cryXic) functional monomers and cure by a redox-initiated free radical polymerization (see Chain polymerization). They are so named because of the characteristic of requiring a relatively air-free condition to allow curing. Hence, anaerobic adhesives are very suitable for the bonding and sealing of close-fitting metal components. 

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. 

Anaerobic sealants Cyanoacrylates Ultraviolet-cured sealants Methyl methacrylate Metal and glass glues Epoxy diacrylates (vinyl resins) Acrylic dental bonding agents... 

Medium Movement Sealants. These exhibit higher performance properties. The latexes and butyls have a movement capacity of 7.5%. Hypalon, neoprene, and solvent-re-lease acrylics have a movement capacity of 12.5 %. Cure time is about 5 days for latexes, 30 days for Hypalon and neoprene, 120 days for butyls. Service life is 10 years for most me-... 

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