Sealants, neoprene

Filled liquid neoprene sealants are cured at room temperature by the addition of lead oxide, tertiary amines or epoxy resins. Neoprene sealants covered by a top coat of white chlorosulfonated polyethlyene are being used on solar collectors.21 Mixtures of carboxyl terminated acrylonitrile elastomers (CTBN) and liquid epoxy resins cure readily at room temperature in the presence of bis phenol A and amines.22 Coal tar-epoxy resin, two component epoxy resin, and epoxypolyester resin systems have been used as sealants.22... 

Both one-part and two-part neoprene sealants are made most commonly using general purpose neoprenes of the GN and W types. Two-part compositions contain 25-30% neoprene plasticized with materials such as dioctyl sebacate or resinous plasticizers, stabilized with phenolic antioxidants, filled with reinforcing pigments such as carbon black and hard clays, and modified with cure-rate regulators and acid acceptors such as zinc oxide and magnesium oxide. Cure accelerators such as polyamines (i.e., tetraethylene pentamine) are used at 5-10 phr based on neoprene. Heat-reactive phenolic resins are also effective. One such composition is shown in Table 12. 

Hypalon sealants offer good UV, ozone, and chemical resistance. These properties allow them to be used in moderately moving exterior joints around doors and windows or concrete panels. Neoprene sealants exhibit compatibility... 

Formed-in-place gaskets - Silicone RTV sealants are widely used in this application for valve covers, oil pans, thermostats, rear view mirrors. Neoprene sealants have excellent oil and chemical resistance and SBR sealants give good bonding to oily surfaces. Gunnable butyl rubber mastics are used for vibration dampening of panels and as general sealants for frame and body parts. 

Neoprene sealants are available as one or two part systems with good elastomeric properties, modulus, exterior durability and abrasion resistance, but poor color stability and extended cure times when compounded for gunning. Many of their applications, such as chemical plant use, automotive, marine, and concrete pipe seals are due to their excellent oil and chemical resistance. 

Other Uses. Large quantities of hydrocarbon resins are used in mastics, caulks, and sealants (qv). Polymers for these adhesive products include neoprene, butyl mbber, polyisoprene, NR, SBR, polyisobutylene, acryHcs, polyesters, polyamides, amorphous polypropylene, and block copolymers. These adhesives may be solvent or water-borne and usually contain inorganic fillers. 

The use of plasticisers, with other than PVC applications, is extensive. Many polar rubber sealants or caulking materials are plasticised in order to make them more pliable, e.g., polysulfides, polychloroprene (Neoprene ), nitrile rubber. Esters, similar to those employed with PVC, are used to render cellulose diacetate ("Acetate") overhead projection sheets more flexible. 

Neoprene. An elastomer with the repeating structure, -C4H7CI-, that comes in the form of solid, latex, and flexible foam. Used as coatings, sealants, protective garments, adhesive tapes, etc. 

Ozone can also react with components found in air ducts. For example, Morrison et al. (1998) reported that the sealant and neoprene gaskets used in the ducts emitted VOCs into the airstream, but at relatively low levels compared to the typical concentrations found indoors. However, reaction with 03 led to increased emissions of aldehydes, particularly the C5-C10 aldehydes. 

The need to maintain elasticity of rubber is of paramount importance under any serious and severe environmental conditions. The most stable rubbers in radiation environments are polyurethanes and phenyl silaxanes which are usable at well above 108 rads (106 Gy). Butyl rubber liquefies and neoprene evolves hydrochloric acid at similar dose levels. Most polyurethane rubber foams can be used at a dose level of 109 rads (107Gy) in vacuum at temperature levels of between -85°C to +250°C. Silicone and polysulphide sealants are probably less tolerant to ionizing radiation in a nuclear plant where chemical processes are being carried out. A schematic graphical representation of the tolerance of rubbers to ionizing radiation in nuclear plant is shown below in figure 7.4. 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

To furs,her sptcstl the load apply siliconu sealant t heie, Luit neoprene washers and do not tighten the Mrmiv. 

Neoprene. [DiiPont DuPont UK] Poly-chloroprene versatile synthetic rubber fw wire/cable industrial hose and belting automotive gaskets, seals, hose tire sidewalls molded and extruded goods cellular prods. adhesives, sealants, and protective coatings for shoe, home crafts, sporting goods. 

Liquid natural rubber, SBR, acrylonitrile elastomers, neoprene, and chlorosulfonated polyethylene are also used as sealant compositions. Filled depolymerized natural rubber and SBR latex are readily cured at room temperature by the incorporation of ultraaccelerators. 

Chlorosulfonated polyethylene (Hypalon) has been used as a roofing composition and blends of this polymer and neoprene have been used as sealants. Block copolymers of styrene and butadiene (Kraton) have also been used as sealants.2 ... 

Synthetic rubber, a dimethylbutadiene, was developed as a substitute for natural rubber in Germany during World War I and saw limited use as an adhesive. In the early 1930s, neoprene rubber (then called Duprene) became available to adhesive manufacturers in the United States, and shortly thereafter in Great Britain. Today, neoprene rubber adhesives are available as both thermoplastic and cross-linking systems in both solvent and emulsion formulations. Neoprene rubber is the major base resin for contact adhesives. A limited amount of neoprene rubber is also used in sealants. 

Uses Tackifier resin for water-based adhesives and sealants based on acrylic, S/B, nat. rubber, neoprene, and PVAc, esp. for pressure-sensitive adhesives, and for coatings Features Solv.-free... 

Uses Coupling agent esp. for polyolefins and polyolefin elastomers, min.-and glass-filled formulations, sealants (acrylic, SBR), rubbers (butyl, neoprene, isoprene, fluorocarbon), as primer coal for metals in insert molding... 

Neoprene TRT Neoprene TW Neoprene W Neoprene WB Neoprene WD Neoprene WHV Neoprene WHV-100 Neoprene WHVA Neoprene WRT polychloroprene, sealants Neoprene Series Neoprene AC Neoprene AD Neoprene AG Neoprene GNA Neoprene GRT Neoprene GW ... 

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. 

Within solvent release type thermosetting sealants, there are Neoprene, hutadiene-styrene, chlorosulfonated polyethylene, EPDM, and silicones. Solvent release types constitute the largest variety of sealants and are composed of three parts (1) the liquid portion of the compound which is the basic non-volatile polymer/elastomeric vehicle, (2) the pigment component, and a (3) solvent or thinner component used to ease the process and to control the thickness. The sealant is cured and its required viscosity is controlled by the evaporation of solvent. 

Fluid neoprene is the primary component in such products as adhesives, coatings and paints, sealants, caulks, and fiber binders. 

The main reasons for the use of methyl chloroform in formulations for urethane and neoprene/phenolic contact adhesives, mastics, sealants, and natural mbber tire repair cements are its ability to substantially reduce flammability, its non-photochemical reactivity, and the favorable characteristics of the resulting adhesive formulation. 

Megill, R.W., Adhesives Based on Neoprene AG, Adhesives and Sealant Council—Spring Meeting 1968. 

Extruded Tapes. These are preformed ribbons or profiles of butyl rubber, neoprene, or polyvinyl chloride, and may be either solid or expanded. They may be supplied as composite structures with rubber cores, rubber rod spacer, or aluminum shims surrounded or embedded in an adhesive or sealant. 

Other types of neoprene-containing sealants include a neoprene/Hypalon gun-grade caulk and a pressure-sensitive neoprene foam tape for mounting molding and trim on autos, boats, and trailers. 

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-... 

Rubber tubing made of neoprene, EPDM, or butyl is an excellent but expensive backup material. In essence, the tubing acts as a duad system with the sealant, since the partly compressed tubing will also act as a water barrier in case the sealant suffers a loss of adhesion. 

Concrete pipe seals - Butyl sealant tapes and neoprene rubber are frequently used as concrete pipe seals. The neoprene seals have very good chemical resistance. 

Roadways, parking decks, and bridges - Neoprene, two part polymethane and two part polysulfide sealants are excellent sealants for concrete expansion and paving joints. They offer excellent weatherability and 20 year life e ectancy. Neoprene is especially resistant to oil and chemical attack and is... 

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 somce of the halogen can be from the base polymer (e g. neoprene, PVC) of the adhesive or sealant, or organic halogen compoimds, especially long chain halogenated aliphatic compounds which can decompose readily to release reactive halogen. 

Statt, B.K. et al, 1992, "Precipitated Silicas in Adhesives and Sealants", Supplier Short Course on Additives, Adhesive and Sealant Council, Washington, DC, April, pp IV, 1-30. Steinfmk, M., 1977, "Neoprene Adhesives Solvent and Latex", Handbook of Adhesives, 2nd ed., 1. Skeist(ed.), Van Nostrand Reinhold, New York, pp 343-367. 

In general, polysulfide sealants resist attack from fuels and water and have good chemical resistance. Polyurethane sealants are especially resistant to alkali exposure. Polyurethane, acrylic, and polychloroprene (neoprene) are all moisture resistant. Both polychloroprene and butyl rubber sealants have good general chemical resistance. Silicones, although expensive, are often the sealant of choice, because they are strongly resistant to moisture and all chemicals. Silicones are also the most resistant sealants to UV and solar radiation. 

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