Industrial Adhesives & Sealants: Step-by-Step

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Applying industrial adhesives and sealants requires precision and adherence to technological procedures. Even a high-quality product can fail if not applied correctly or if the surface is not prepared according to requirements. In this article, we present a proven procedure that minimizes the risk of defective bonds and ensures optimal performance. We will focus on key steps such as cleaning, surface activation, dosing, and curing, including tips for different types of materials and conditions.

1. Surface Preparation: The Key to Maximum Adhesion

Proper application of industrial adhesives and sealants begins with thorough surface preparation. Regardless of the quality of the product used, the final result will depend on the cleanliness, roughness, and chemical compatibility of the materials being bonded. First, remove all contaminants such as dust, oils, grease, or residues of old coatings. Use suitable cleaning agents for this – acetone or isopropyl alcohol is often sufficient for metal surfaces, while plastics may require special degreasers without aggressive solvents. Important: Always verify the compatibility of the cleaning agent with the material to avoid surface damage or reduced adhesion properties.

Next, check the surface roughness. Smooth surfaces, such as glass or some metals, often require mechanical roughening (e.g., with sandpaper of grit 120–220) or chemical treatment (e.g., acid etching). To achieve optimal adhesion, the surface energy of the material should be higher than the surface tension of the adhesive used. In practice, this means that materials with low surface energy (e.g., polyethylene or polypropylene) may require pretreatment with plasma, corona discharge, or special primers. Remember that even small amounts of contamination can significantly reduce bond strength, so work in a clean environment and use protective gloves to prevent the transfer of grease from the skin.

2. Selecting the Right Adhesive or Sealant: Technical Parameters Matter

Selecting the appropriate adhesive or sealant is a critical step that affects not only the strength of the bond but also its resistance to external factors. Key factors to consider include the type of materials being bonded, required strength, operating temperature, resistance to chemicals, moisture, and UV radiation. For example, two-component epoxy adhesives are often used for bonding metals to plastics, offering high strength and durability. Conversely, flexible bonds, such as seals or vibration-stressed structures, are better suited to polyurethane or silicone sealants.

Another important parameter is the processing time (open time) and curing time. Fast-curing adhesives (e.g., cyanoacrylate) are ideal for small joints and rapid production but require precise application and immediate joining of parts. Conversely, slow-curing adhesives (e.g., anaerobic or some epoxy) allow for longer handling of parts but require fixation during curing. Always check the manufacturer's technical data sheet for optimal application conditions, such as temperature (usually 15–25 °C) and humidity (ideally 40–60 %). At low temperatures, the curing time may be extended, while high humidity can negatively affect certain types of adhesives, such as polyurethane systems.

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3. Application techniques: How to achieve even and precise application

Proper application technique ensures even distribution of the adhesive or sealant and minimizes the risk of air bubbles, which could weaken the bond. For spot joints or small areas, manual application using a syringe or applicator gun is often sufficient. For larger surfaces or mass production, the use of automated systems such as dosing robots or pressure tanks with flow control is recommended. It is important to maintain the recommended layer thickness – a layer that is too thin may result in insufficient strength, while a layer that is too thick increases the risk of incomplete curing and internal stress.

When applying adhesive, ensure that the entire bonded surface is covered, but avoid excess that could overflow and contaminate the surroundings. For some adhesives (e.g., contact adhesives), it is necessary to apply the adhesive to both surfaces and allow it to dry briefly before joining. For anaerobic adhesives, on the other hand, it is crucial that the adhesive is applied to only one surface and the other surface is immediately attached to prevent premature contact with air. After joining the parts, it is often necessary to secure their fixation using clamps, weights, or special fixtures until the adhesive achieves initial strength. The fixation time varies depending on the type of adhesive and can range from a few minutes to several hours.

4. Curing and Aftercare: How to Ensure Long-Term Bond Durability

The curing process is crucial for achieving the final mechanical properties of the bond. Different types of adhesives require different conditions – some cure at room temperature, while others need elevated temperatures (e.g., 60–120 °C) or UV radiation. Curing time ranges from a few minutes (cyanoacrylates) to several days (some epoxies). During this period, it is important to maintain stable conditions, particularly temperature and humidity, to prevent bond deformation or the development of internal stress. For heat-cured adhesives, it is essential to follow the exact temperature profile, including the heating rate and dwell time at the target temperature.

After curing, it is advisable to perform a joint quality check, both visual (checking for the presence of adhesive across the entire joint, absence of bubbles or cracks) and mechanical (e.g., tensile or shear strength tests according to applicable standards). If necessary, non-destructive tests such as ultrasonic inspection can also be carried out. For long-term joint durability, it is important to protect it from extreme conditions such as high temperatures, chemicals, or mechanical stress. In some cases, applying a protective coating or sealant may be appropriate to prevent moisture or corrosive substances from penetrating. Regular maintenance and inspection of joints will help prevent premature failure and extend the lifespan of the entire structure.

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Environmental conditions check: Why temperature and humidity affect the outcome

The application of industrial adhesives and sealants is not an isolated process – its success also depends on surrounding conditions. Temperature and air humidity are among the critical factors that influence both the workability of the material and the quality of the final bond. Most adhesives and sealants require a temperature range between 15 and 25 °C for optimal viscosity and adhesion. At lower temperatures, the product thickens, making even application difficult and prolonging the curing time. Conversely, excessively high temperatures can cause premature evaporation of solvents or accelerate polymerisation, leading to insufficient bonding.

Air humidity is equally important, especially for polyurethane and silicone sealants, which react with water vapour. An overly dry environment slows down curing, while high humidity can cause bubble formation or insufficient bond strength. It is recommended to measure conditions using a hygrometer and thermometer and, if necessary, adjust the environment (e.g., using air conditioning or dehumidifiers). For sensitive applications, such as bonding metals or composites, working in a controlled environment with defined parameters is advisable.

Workplace Safety: How to Minimise Risks When Handling Chemical Products

Industrial adhesives and sealants often contain substances with irritant, toxic, or flammable properties, making workplace safety an essential part of every application process. The foundation is compliance with the instructions provided in the Safety Data Sheet (SDS) under REACH and CLP/GHS regulations. Workers should use personal protective equipment (PPE), such as nitrile or butyl gloves, safety goggles with side shields, and, if necessary, respirators with appropriate filters (e.g., for organic solvents or isocyanates).

Ventilation of the workspace is also important – ideally, local extraction of fumes directly at the application site. When working with flammable products, it is necessary to eliminate sources of sparks and open flames. In case of skin contact, the affected area should be immediately washed with water and soap; for eye contact, rinse for at least 15 minutes and seek medical assistance. Adhesives and sealants should be stored in dry, cool, and well-ventilated areas, separately from food and feed, with clear labelling according to CLP.

Solving Common Problems: How to Identify and Eliminate Joint Defects

Even with careful preparation and application, joint defects may occur, compromising functionality. The most common issues include insufficient adhesion, bubble formation, uneven curing, or cracks. The cause is often improper surface preparation, unsuitable application conditions, or incorrect adhesive selection. For example, grease or dust on the surface prevents perfect contact, while excessive humidity can cause foaming in polyurethane sealants.

To identify the problem, visual inspection is key, and mechanical tests (e.g., tensile testing according to standard methods) may be necessary. If a defect is detected before curing, the adhesive or sealant can often be removed and the application repeated. For cured joints, the solution involves mechanically removing the defective part and repairing it with a compatible material. Prevention includes following technological procedures, regularly checking environmental conditions, and training personnel. For critical applications, it is recommended to perform test joints and verify their quality before starting mass production.

Need help selecting the right adhesive or sealant?

Every material and application requires an individual approach. GCG Group provides detailed technical data sheets and safety data sheets (SDS) for supplied raw materials and assists in selecting the optimal solution for your specific needs. Contact us – or browse our catalog of over 1,300 products.