Types of Rubber Adhesives and Sealants

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

• 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.

Product Types

• Aerosols
• Films
• Gels
• Liquids
• Slurries
• Solids
• Pastes

• Powders

• Putties

Applications

Compatible Surfaces for Rubber Adhesives

• Ceramics and glass
• Concrete and masonry
• Paper and paperboard
• Rubbers and elastomers
• Leather
• Textiles
• Metal
• Plastic
• Wood

• Porous surfaces

• Composite materials

Industries Served

• Aerospace
• Automotive
• Electrical
• Electronic
• Marine
• Medical
• Military

Rubber adhesives and sealants are also used in abrasives, optics, photonics, and semiconductors.

Curing Technologies

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.

Specifications

• Viscosity
• Full cure or set time
• Ultimate tensile strength
• Elongation
• Shear strength
• 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.

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.

Standards

A-A-1936 - Adhesives, contact, neoprene rubber.

ASTM C1085 - Specification for butyl rubber-based solvent-release sealants.

IEC 60454-3-2 - Pressure-sensitive adhesive tapes for electrical purposes - part 3: specifications for individual materials - sheet 2: polyester film tapes with rubber thermosetting or acrylic crosslinked adhesives.

SAE AS5127/1 - Aerospace standard test methods for aerospace sealants two- component synthetic rubber compounds.

References

Image Credits:

Hapco, Inc. | Master Bond, Inc. | Berry Plastics Corporation - Engineered Materials Division