Rubber adhesives and sealants are highly flexible, natural or synthetic materials that are used to join components or fill gaps between seams or on surfaces. Natural rubber is based on polyisoprene. Synthetic rubbers and elastomers include silicone, polyurethane, polysulfide, styrene-butadiene rubber (SBR), butyl, acrylic or polyacrylate, isoprene, polyisobutylene, ethylene-vinyl acetate (EVA), vinyl and nitrile compounds. Pressure sensitive adhesives (PSAs) are often based on non-crosslinked rubber adhesives in a latex emulsion or solvent-borne form. Rubber adhesives and sealants are also available as aerosols, films, gels, liquids, slurries, solids, pastes, powders, and putties. They are compatible with substrates made from ceramics and glass, concrete and masonry, paper and paperboard, rubbers and elastomers, leather, textiles, metal, plastic, wood, porous surfaces, and composite materials. Rubber adhesives and sealants are used in a variety of aerospace, automotive, electrical, electronic, marine, medical, and military applications. They are also used in abrasives, optics, photonics, and semiconductors.
Rubber adhesives and sealants use several curing technologies. Air setting or film drying forms bonds by evaporating water or organic solvents. Anaerobic adhesives cure in the absence of air or oxygen. Thermoplastic or hot melt adhesives can be repeatedly softened by heat and then hardened or set by cooling. Thermoset adhesives are crosslinked polymeric resins that are cured with heat or heat and pressure. Single component rubber adhesives and sealants consist of a resin that hardens by reaction with surface moisture or the application of heat. Two or multi-component systems consist of two or more resins or a resin and hardener, crosslinker, activator or catalyst that, when combined, react and cure into a polymerized component or bond. Some abrasives use ultraviolet (UV) light, visible light, or electron beam (EB) irradiation to initiate curing. Reactive resins such as polyurethane reactives (PUR) are single component adhesives that react with moisture to crosslink and polymerize.
Important specifications for rubber adhesives and sealants include viscosity, full cure or set time, ultimate tensile strength, elongation, shear strength, and maximum use temperature. Viscosity, a measurement of a fluid’s resistance to flow, determines the amount of adhesive dispensed on a substrate. Full cure or set time depends upon the curing temperature and varies among thermosetting systems. Ultimate tensile strength (UTS) is the amount of applied stress required to cause failure in a control specimen under tensile load conditions. Elongation is the amount of permanent deformation after a controlled tensile test. Shear strength is the maximum shear load per unit cross-section that an adhesive joint can withstand before mechanical failure or breakage occurs. Maximum use temperature is the temperature range to which rubber adhesives and sealants can be exposed without degradation of structural of other required end-use properties.
Rubber adhesives and sealants are available with a variety of features. Products that are designed for electrical and electronics applications are often provide protection against electrostatic discharge (ESD), electromagnetic interference (EMI), or radio frequency interference (RFI). Thermal compounds that use a phase change are able to absorb additional heat from electronic devices or electrical components. Retaining adhesives position cylindrical mating parts such as bearings, pulleys, rotors, and gears. Transfer adhesives are coated onto single or double-sided liner. Threadlocking products protect transverse and axial loads against vibrational loosening. Removable adhesives can be repositioned without de-laminating a substrate or leaving a residue. Flexible adhesives and sealants form a layer that can bend or flex without cracking. Dampening products reduce sound, shock, or vibration. Chemically resistant products can withstand acids, alkalis, oils and fuels. Weatherproof or weather resistant materials are designed to withstand wind environmental variables. Non-toxic, low-odor, colorless, and transparent rubber adhesives and sealants are also available.
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Conductive compounds provide an electrically and/or thermally conductive path between components.
Conformal coatings encapsulate circuit boards and their electronic components in order to prevent the ingress of moisture, fungus, dust and other environmental contaminants.
Epoxy adhesives are chemical compounds for joining components. They require clean surfaces and are valued for their toughness and resistance to chemical and environmental damage.
Gel elastomers are highly viscoelastic polymer gel materials that have excellent shock absorption and damping characteristics. They are available in a variety of material types and grades.
Pressure Sensitive Adhesives (PSA) and Contact Adhesives
Pressure sensitive adhesives (PSA) and contact adhesives adhere to most surfaces with very slight pressure. They are available in solvent and latex or water-based forms.
Silicone Adhesives and Sealants
Silicone adhesives and sealants have a high degree of flexibility and a very high temperature resistance (up to 600° F), but lack the strength of other epoxy or acrylic resins.
Thermoplastics and Thermoplastic Materials
Thermoplastics and thermoplastic materials soften when heated and harden when cooled. They can withstand many heating and cooling cycles and are often suitable for recycling.