10 Common Mistakes in the Application of Industrial Adhesives and Sealants That Cost Time and Money

Photo: Khang Nguyen / Unsplash

Industrial adhesives and sealants are crucial for reliable bonds in automotive, construction, electronics, and mechanical engineering. However, even experienced technicians often make mistakes that lead to weakened bonds, longer curing times, or even complete application failure. Many of these issues can be prevented by adhering to basic technical principles—from proper surface preparation to optimizing curing conditions. In this article, we will explore ten of the most common mistakes that cost manufacturing companies time, materials, and money, and show how to effectively eliminate them.

1. Insufficient surface preparation before bonding

The first and often underestimated step when working with industrial adhesives and sealants is thorough surface preparation. Contamination, grease, dust, or residues of old coatings significantly reduce adhesion and can lead to joint failure. According to applicable technical standards, it is essential to first mechanically clean the surface (e.g., by grinding or sandblasting) and then degrease it with a suitable solvent or cleaning agent. For certain materials, such as metals or plastics, chemical pretreatments, such as etching or the application of a primer, are also recommended to improve wettability and long-term joint stability.

A common mistake is underestimating the impact of surface moisture or temperature. A damp or excessively cold material can cause water vapor condensation, creating a barrier between the adhesive and the substrate. The ideal temperature for adhesive application is usually between 18–25 °C, with relative humidity not exceeding 60%. For sensitive applications, such as in the aerospace or automotive industries, it is recommended to monitor these parameters with measuring instruments and work in climate-controlled environments.

2. Incorrect dosing and mixing of two-component adhesives

Two-component adhesives and sealants require precise adherence to the component ratio and thorough mixing. An error in dosing, such as adding too much hardener, can lead to insufficient curing, joint brittleness, or a shortened processing time. Conversely, a lack of hardener will cause the adhesive to remain soft and fail to achieve the required strength. Always follow the ratio specified by the manufacturer, which is usually indicated on the packaging or in the technical data sheet, and use calibrated dosing equipment.

Another critical point is the homogeneity of the mixture. Insufficient mixing leads to local concentrations of one component, causing uneven curing and weakening of the bond. For mixing, use a mechanical stirrer with low speed (approx. 300–500 rpm) to minimize air entrainment in the mixture. For larger volumes, it is advisable to use static mixing nozzles, which ensure consistent mixture quality without manual intervention. After mixing, always check that the mixture has no streaks or inhomogeneities.

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3. Ignoring the working life and open time

Every industrial adhesive has a defined pot life and open time that must be respected. Pot life indicates how long the adhesive can be used after mixing or opening the container before it begins to lose its properties. Exceeding this time leads to premature curing in the container or on the application equipment, resulting in material loss and the need for cleaning. Open time then determines how long the adhesive can be applied to the surface before joining the parts without compromising adhesion.

A common mistake is underestimating the effect of temperature on these parameters. Higher temperatures accelerate chemical reactions, thereby shortening both the pot life and open time. For example, with epoxy adhesives, a 10 °C increase in temperature can reduce the pot life by up to half. Conversely, low temperatures slow down reactions, which can lead to insufficient curing. Always work within the recommended temperature range and adjust the amount of adhesive prepared according to current conditions to minimize losses.

4. Incorrect Storage and Handling of Adhesives and Sealants

Storing industrial adhesives and sealants requires adherence to specific conditions to prevent material degradation. Most adhesives are sensitive to moisture, temperature, and light, so they must be stored in dry, cool, and dark spaces. For example, cyanoacrylate adhesives (so-called instant adhesives) degrade quickly at high humidity, while polyurethane sealants can react with water vapor in the air and cure prematurely. The ideal storage temperature typically ranges between 5–25 °C, although some materials require refrigeration (e.g., anaerobic adhesives).

Another common issue is improper handling of containers. After opening, it is important to reseal the container immediately to minimize contact with air and moisture. For two-component adhesives, the components must be stored separately and contamination must be prevented. When handling adhesives, use protective equipment such as gloves and goggles, and follow the safe handling instructions in accordance with REACH and CLP/GHS regulations. Regularly check the expiration date and do not use materials that have exceeded their shelf life, as their properties may become unpredictable.

Photo: Khang Nguyen / Unsplash

5. Underestimating the impact of temperature and humidity during application

Temperature and humidity are critical factors that significantly influence the final strength and quality of a bonded joint. Many users underestimate that even minor deviations from recommended conditions can lead to insufficient adhesion, prolonged curing time, or even complete joint failure. For example, epoxy adhesives require an ambient temperature of at least 15 °C – at lower temperatures, the chemical reaction slows down, which prolongs curing time and reduces final strength. Conversely, excessively high temperatures can cause premature curing of the adhesive before application, especially in fast-setting systems.

Air humidity is equally important, particularly for polyurethane and cyanoacrylate adhesives. High humidity can accelerate curing, leading to the formation of brittle joints or bubbles in the adhesive. Conversely, an overly dry environment can slow down polymerization, especially in water-based adhesives. It is therefore always recommended to check the manufacturer’s technical data sheet and adjust the application conditions – ideally using air conditioning, heaters, or dehumidifiers. For sensitive applications, it is advisable to measure temperature and humidity directly at the workplace and adjust process parameters accordingly.

6. Using an unsuitable adhesive type for the given material

Choosing the wrong type of adhesive is a common cause of joint failure, which can lead to financial losses and safety risks. Each material has specific surface properties that affect adhesion – for example, low-surface-energy plastics (PP, PE) require pretreatment or special adhesives with adhesion promoters, while metals often need adhesives with high tensile strength and resistance to temperature fluctuations. Using a universal adhesive regardless of the material can result in insufficient strength or long-term degradation of the joint.

When selecting an adhesive, it is necessary to consider not only the type of material but also the requirements for mechanical properties (strength, flexibility, resistance to vibrations), chemical resistance (to oils, solvents, water), and operating conditions (temperature, UV radiation, humidity). For example, for bonding rubber, it is advisable to choose a flexible adhesive that can withstand dynamic stress, whereas for metal structures, high strength and temperature stability are key. It is always necessary to consult the adhesive's technical data sheet and, in case of uncertainty, conduct tests on samples before final application.

7. Neglecting Safety Measures and Occupational Health Protection

Working with industrial adhesives and sealants often involves handling chemicals that may pose health risks—whether through irritating fumes, allergenic components, or toxic effects from long-term exposure. Neglecting safety measures not only increases the risk of workplace accidents but can also lead to long-term health issues, such as dermatitis, respiratory problems, or damage to the nervous system. According to REACH and CLP regulations, all chemicals must be properly labeled, and users must be informed of their risks.

Basic safety measures include the use of personal protective equipment (PPE)—gloves, safety goggles, and respirators with appropriate filters. It is also important to ensure adequate workplace ventilation, especially when applying adhesives with a high content of volatile organic compounds (VOCs). For some adhesives (e.g., cyanoacrylates), skin contact must be avoided, as they can cause immediate bonding or chemical burns. Workers should be trained in first aid for accidents and should have access to safety data sheets (SDS) for all products used. Adhering to these principles not only protects health but also minimizes the risk of material contamination and defects.

The right choice of raw material is key

Every adhesive or sealant has specific properties and application requirements. GCG Group provides detailed technical data sheets and safety data sheets (SDS) for every raw material supplied, which include recommended procedures and conditions of use. If you are unsure about the selection or application, contact our experts – we will advise you on the choice and optimisation of the process. Get in touch – or browse our catalogue of over 1,300 products right away.