Adhesives are widely used bonding agents in manufacturing. They are polymeric materials that are applied to the surfaces of materials—often two different materials—to bind them together and create a molecular attachment. Common examples of adhesives include glues, pastes, epoxies and silicones. Adhesives work through mechanical interlocking and/or chemical reactions between polymer chains at the interface of the materials being joined.
Properties of Adhesives
Adhesives demonstrate a variety of properties depending on their specific chemistry and intended application. Some key properties of adhesives include: bond strength, cure speed, heat resistance, moisture resistance and chemical resistance. Bond strength refers to how strongly the adhesive binds the materials together. Cure speed is how quickly the adhesive sets and reaches maximum bond strength. Heat, moisture and chemical resistance determine how well the bond withstands related environmental exposures. Adhesives are engineered with different combinations of these properties for applications across diverse manufacturing industries.
Major Adhesive Types
There are several major categories of adhesives based on their chemistry and curing mechanisms:
- Pressure sensitive adhesives: Adhesives And Sealants adhere instantly upon application of light pressure and include products like tapes and labels. Acrylics are commonly used pressure sensitive adhesives.
- Reactive adhesives: They chemically react or crosslink during curing and form very strong bonds. Epoxies, polyurethanes and silicones fall under this category. Reactive adhesives are ideal for structural and temperature/chemical resistant applications.
- Hot melt adhesives: As the name suggests, these are heated and then used to bond materials together upon cooling and solidification. Ethylene-vinyl acetate is a popular hot melt adhesive polymer.
- Water-based adhesives: Comprised of water-soluble polymers, these adhesives are environmentally friendlier than solvent-based types. Examples include latex and casein.
- Solvent-based adhesives: They utilize organic solvents as vehicles or carriers for the adhesive resin. Contact adhesives commonly use petroleum distillate solvents which evaporate after application.
Introduction to Sealants
Sealants are construction sealers applied between joined surfaces, interfaces or around the peripheries of assemblies to fill gaps and prevent passage of air, water, dust or noise. Elastomeric polymers within sealants allow them to flex with expansion/contraction of materials while securely bonding and sealing gaps over long service periods. Common applications of sealants include sealing buildings, vehicles, aircrafts, boats and devices. They also protect components during extreme weathering or harsh chemical/physical exposures.
Types of Sealants
Similar to adhesives, sealants demonstrate diversity based on chemistry:
- Silicone sealants: Renowned for their flexibility and adherence properties, silicone sealants work well up to 500°F temperatures. They have high weatherability.
- Polyurethane sealants: Considered all-purpose sealants, polyurethanes bond to most surfaces and cure quickly. Some withstand continuous water immersion.
- Acrylic latex sealants: Water-based and popular for indoor/residential applications, they dry fast with little odor. However, not ideal for prolonged water exposure.
- Butyl rubber sealants: Highly effective for sealing against moisture/gas/vapor penetration, butyl rubbers have great flexibility in cold temperatures down to -40°F.
- Polysulfide sealants: Capable of bonding to various materials, they offer good chemical resistance and are suitable for civil engineering and marine applications.
Adhesives and Sealants in Manufacturing
Adhesives and sealants play a crucial role across manufacturing industries by facilitating production processes and performances of finished products. Key applications areas include:
- Automotive: Assembly of vehicle bodies/parts, bonding electronics/components. Sealants weatherproof cars.
- Aerospace: Assembly and bonding of aircraft components, sealing airframes and engines.
- Building/construction: Structural bonding, sealing gaps/joints in building envelopes for insulation/weather resistance.
- Packaging: Bonding cartons/containers, attaching labels. Heat sealing plastic films.
- Electronics/appliances: Assembly, attaching circuit boards/displays. Encapsulating components for protection.
- Furniture: Structural bonding of panels/frames, edgebanding, laminating veneers.
- Footwear/apparel: Bonding/laminating layers, seam sealing, attaching accessories.
- Renewable energy: Bonding wind turbine/solar panel components, potting electronics. Sealing cable entries.
Quality control testing ensures consistent performances of adhesives and sealants during mass manufacturing. Their special properties enable modern design and production innovations across industries.
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