Adhesives & Sealants

Adhesives are substances that join two or more surfaces (substrates) together, forming a strong bond. Sealants, on the other hand, are materials used to fill gaps, provide a barrier against the passage of fluids (liquids or gases), and often offer flexibility to accommodate movement between joined parts. Both play critical roles in assembly, protection, and structural integrity across countless industries.

Types of adhesives & sealants

Adhesives:

Natural Adhesives: Starch, casein, animal glues (historically significant, less common in industrial applications today).

Synthetic Adhesives:

Epoxy Adhesives: Two-part systems (resin and hardener) offering high strength, excellent chemical resistance, and good temperature performance.

Cyanoacrylate Adhesives (Super Glue): Fast-curing, single-component adhesives activated by surface moisture. Good for small bonds.

Polyurethane Adhesives: Flexible, good impact resistance, strong bonds to various substrates. Often used in construction and automotive.

Acrylic Adhesives: Fast-curing, good for plastics and metals, some are two-part.

Silicone Sealants: Excellent weatherability, flexibility, high temperature resistance, good adhesion to many surfaces.

Polyurethane Sealants: Good flexibility, abrasion resistance, and adhesion, often used in construction.

Acrylic Sealants: Paintable, easy to use, good for general purpose sealing in non-structural applications.

Butly Sealants: Excellent moisture barrier properties, often used for roofing and automotive applications.

Polysulfide Sealants: Good chemical and fuel resistance, used in aerospace and industrial applications.

Hybrid Sealants (e.g., MS Polymer): Combine properties of silicones and polyurethanes, offering good adhesion, flexibility, and paint ability.

Applications in Various Industries

Automotive Industry: Bonding structural components (e.g., body panels), sealing joints (e.g., windshields, sunroofs), thread locking, gasketing, interior trim attachment. Technology involves robotic application, structural adhesives for lightweighting, and noise/vibration damping.

Construction Industry: Sealing windows, doors, expansion joints, curtain walls, roofing, flooring adhesives, structural bonding in prefabricated structures.

Aerospace Industry: Bonding composite structures, interior components, fuel tank sealants, high-temperature adhesives for engine parts. Requires high strength-to-weight ratio and resistance to extreme conditions.

Electronics Industry: Encapsulation of components, bonding heat sinks, conformal coatings, EMI shielding, adhesive attachment of displays. Miniaturization and thermal management are key.

Packaging Industry: Sealing cartons, bags, labels, flexible packaging laminations. High-speed application and food-grade compliance.

Medical Devices: Bonding surgical instruments, disposable medical products, drug delivery systems. Biocompatibility, sterilization resistance, and precision application are critical.

Furniture/Woodworking: Bonding wood panels, laminates, edge banding.

Footwear: Bonding sole to upper, various components.

Manufacturing Technology: Automated dispensing systems, robotics for precise application, UV curing systems, hot melt applicators, surface pre-treatment (cleaning, priming) to optimize adhesion.

Material Selection Considerations

• Substrate Compatibility: Adhesives and sealants must wet out and adhere well to the specific materials being joined (metals, plastics, composites, glass, wood, ceramics).
• Bond Strength/Joint Strength: Required tensile, shear, peel, and impact strength.
• Environmental Resistance: Temperature range, humidity, UV exposure, chemical exposure, water immersion.
• Curing Time and Method: How quickly the adhesive or sealant sets and reaches full strength (room temperature, heat, UV, moisture).
• Flexibility/Rigidity: Whether the bond needs to be rigid (adhesives) or flexible to accommodate movement (sealants).
• Gap Filling Capability: Ability to fill voids and irregular surfaces.
• Application Method: Suitability for dispensing equipment, manual application, spraying, etc.