Styrene-butadiene rubber sealants

All grades of regular butyl rubber are tacky, rubbery and contain less unsaturation than natural rubber or styrene-butadiene rubber. On the other hand, low molecular weight grades of polyisobutylene are permanently tacky and are clear white semi-liquids, so they can be used as permanent tackifiers for cements, PSAs, hot-melt adhesives and sealants. Low molecular weight polyisobutylenes also provide softness and flexibility, and act as an adhesion promoter for difficult to adhere surfaces (e.g. polyolefins). 

Styrene butadiene rubber (SBR) adhesives, used to replace natural rubber adhesives, saw limited use during World War II, but commercialization took place during the 1950s. Today, in terms of monetary value, SBR adhesives are the most important adhesives in the United States. Their use in sealants is minor. 

MAJOR APPLICATIONS Poly(propylene sulfide) is an elastic material that compares with styrene-butadiene rubbers. However, this polymer has not yet achieved commercial production, although the PPS elastomer offers a combination of good solvent and weather resistance. Low molecular weight functional PPS is suitable for use in sealants, adhesive, etc. ... 

The inherent properties of polymers of the poly isobutylene family, particularly the chemical inertness, age and heat resistance, long-lasting tack, flexibility at low temperatures, and the favorable FDA position on selected grades, make these products commercially attractive in a variety of pressure-sensitive and other adhesives, in automotive and architectural sealants, and in coatings. An added dimension is achieved in the blendability of the polyisobutylene polymers with each other and with other adhesive polymers such as natural rubber, styrene-butadiene rubber, EVA, low molecular weight polyethylene, and amorphous polypropylene to achieve specific properties. They can, for example, be blended with the highly unsaturated elastomers to enhance age and chemical resistance. A description of poly isobutylene polymer family use in adhesive and sealant applications follows. 

Elastomers used to a minor extent as the principal binder in sealants include styrene-butadiene rubber (SBR), nitrile rubber, and reclaim rubber. 

Styrene-butadiene-styrene (SBS) rubbers are either pure or oil-modified block copolymers. They are most suitable as performance modifiers in blends with thermoplastics or as a base rubber for adhesive, sealant, or coating formulations. SBS compoimds are formulations containing block copolymer rubber and other suitable ingredients. These compounds have a wide range of properties and provide the benefits of rubberiness and easy processing on standard thermoplastic processing equipment. 

Chem. Descrip. Bis-(3-[triethoxisily0 propyl)-tetrasulfane CAS 40372-72-3 EINECS/ELINCS 254-896-5 Uses Coupling agent for polysulfide and styrene-butadiene polymers, butyl polymers, for adhesives, coatings, filler treatment, foundry, inks, rubber, sealants, and textile applies. 

Thermoplastic rubber is a relatively new class of polymer. It has the solubility and thermoplasticity of polystyrene, while at ambient temperatures it has the toughness and resilience of vulcanized natural rubber or polybutadiene. These rubbers are actually block copolymers. The simplest form consists of a rubbery mid-block with two plastic end blocks (A-B-A), as shown in Figure 5.7. Examples of commercial products are Kraton and Solprene . These materials are often compounded with plasticizers to decrease hardness and modulus, eliminate drawing, enhance pressure-sensitive tack, improve low-temperature flexibility, reduce melt and solution viscosity, decrease cohesive strength or increase plasticity if desired, and substantially lower material costs. Low levels of thermoplastic rubbers are sometimes added to other rubber adhesives. These materials are used as components in the following applications PSAs, hot-melt adhesives, heat-activated-assembly adhesives, contact adhesives, reactive contact adhesives, building construction adhesives, sealants, and binders. Two common varieties of thermoplastic rubber adhesives are styrene-butadiene-styrene (S-B-S) and styrene-isoprene-styrene (S-I-S). ... 

Butyl rubber Butadiene-styrene copolymer Polychloroprene Sealants... 

Acrylic sealants are water-based but they may also contain ethylene and propylene glycols, mineral spirits and mineral oil. There are also solvent-based aerylie sealants whieh eontain substantial amounts of solvents such as mineral spirits, toluene and xylene. Polysulfide sealants usually contain toluene but methyl ethyl ketone is also used. The group of class B sealants contains substantially more solvents (up to 40% by volume) but there are some exeeptions. PVC sealants are based on plastisols and they can be made without solvents. Butyl rubber based sealants usually contain hydrocarbons (C -C 2). Styrene-butadiene-styrene based sealants usually have a large amount of solvents selected from a group including toluene, heptane, hexane, methyl ethyl ketone, isobutyl isobutyrate, n-amyl aeetate, n-amyl ketone. They are usually proeessed in solvent mixtures. Polychloroprene is usually dissolved in a mixture of solvents ineluding ketones or esters, and aromatic and aliphatic hydrocarbons. The list ineludes naphtha, hexane, aeetone, methyl ethyl ketone, benzene, and toluene. 

Produced by a solution polymerization process, this material exhibited an ordered molecular structure with the styrene monomer located at the ends of the butadiene monomer chain. In addition, other monomers such as isoprene, ethylene, butylene, and others, could be added to the polymer chain, which further modified basic properties. These materials possess a continuous rubber phase for resilience and toughness, and a discontinuous plastic phase for solubility and thermoplasticity. A variety of different grades are also available for this type of SBR, with differences in molecular weight, differences in the types of monomers used, differences in structural configuration, and differences in the ratio of endblock to midblock. Both emulsion and solution polymerized grades of SBR are available as solvent-based and water-based adhesives and sealants. Block copolymers are extensively used for hot melt formulations and both water-based and solvent-based pressure sensitive adhesive applications. Today, SBR elastomers are the most popular elastomers used for the manufacture of adhesives and sealants. 

---