With the increasing technical development of the automobile, applications of seals, adhesives and potting materials to various components are becoming increasingly relevant. Foam seals and potting are used, for example, to protect automotive electronics from corrosion caused by moisture. Adhesives are indispensable for lightweight construction and electromobility.
Requirements of the automotive industry
In the automobiles produced today, sealing, potting and adhesive applications based on polyurethane or silicone can be found in many places, e.g. for engine and interior components, for lighting, bodywork and electronics. They serve as dust, chemical and moisture protection as well as vibration damping.
The requirements for the different material systems are divers. These are often laid down in a separate OEM specification, e.g. DBL 5450/5452 or TL 848/577-A. The resistance of the seal to the various media always depends on the contact duration, temperature and concentration of the medium. Both polyurethane and silicone gaskets achieve high IP protection classes in combination with the respective overall construction. The IP (International Protection) class tests provide information on how protected electrical equipment and products are against various environmental influences. In the area of media resistance and at high temperatures, however, silicone shows better behavior. In some cases, damage to the seal can also be prevented by changing the design of the component. Simple storage tests of the sealing material in the respective contact medium therefore allow only limited conclusions to be drawn; the sealing behavior must always be tested and evaluated on the overall construction.
For applications in the temperature range from -40 °C to +80 °C, polyurethane seals are suitable for sealing against dust and moisture. Silicone systems are used in areas with a permanently higher temperature load up to + 250 °C or for sealing against more aggressive media. High temperature resistance is generally required for motor applications. Here, however, it must also be critically questioned whether the seal is actually permanently exposed to an increased temperature, since the use of silicone seals is associated with significantly higher costs.
At Henkel a consistently high quality of sealing, bonding and potting of components is already decided by the correct selection of raw materials for the formulation of the material systems. The safety, accuracy and ease of operation of SONDERHOFF mixing and dosing systems are also very important for a precise and trouble-free application process of the materials to the components. The exact interaction of different setting parameters and additional functions of the dosing machine is also responsible for this. These machines also enable flexible adaptation to different production situations in the automotive industry, such as changing batch sizes, increasing variant diversity and component complexity.
High process reliability with FIPFG sealing technology
Due to the high level of automation in automotive production, material application must also be highly automated. In recent decades, foamed seals made of polyurethane, but also silicone, have become the standard. These gaskets are applied directly to the component to be sealed using FIPFG (Formed-In-Place-Foam-Gasket) technology with the aid of modern mixing and dosing systems. The polyurethane foam then hardens at room temperature to form an elastic soft foam seal. Two- and three-dimensional parts are dosed with the same precision as components with and without grooves. With FIPFG technology, much better sealing results are usually achieved than with conventional, manually inserted seals, while at the same time saving costs due to automation. All machine, material and process data relevant for quality assurance are automatically recorded by the mixing and dosing systems and can therefore be called up at any time. The FIPFG technology together with the traceability of the previous processing sequences of the system ensures reproducible production quality of the foamed components. This supports the zero-error tolerance aimed for in automotive engineering. The high process reliability of the FIPFG technology in turn enables trouble-free production speeds and thus higher productivity.
Low-emission foam seals for clean air in the car
Increasingly, the use of plastics in car interiors to protect vehicle occupants requires compliance with emission values, i.e. the lowest possible release of substances into the environment. Even at very high temperatures in the car, the plastic components must not emit any harmful substances. However, the limit values required vary depending on the manufacturer's standard. In general, however, they can be described as very demanding. After all, the aim is to protect the occupants of the vehicle from harmful substances.
The minimization of emissions is achieved through the selection of raw materials. In the case of sealing foams, this means that volatile components such as blowing agents, oils or plasticizers must not be used. The SONDERHOFF FERMAPOR K31 low-emission polyurethane foams meet the strict limit value requirements of all major automobile manufacturers. For example, they meet the target values of Daimler's own specification DBL 5452-13. Here, the target values for VOC emissions are 100 µg and for fogging behavior 250 µg per gram of polyurethane. This significantly reduces a high level of VOC in the air inside the vehicle. Irritations of the eyes, nose, throat, skin or allergic effects are thus avoided. VOC refers to volatile organic compounds that are not always firmly integrated into the molecular structure of plastics or adhesives.
This low-emission sealing foam seals filter housings for fresh air intake in the driver's cab, for example. It ensures that the filter is positioned at the air intake duct in the air conditioning systems of cars so that no unfiltered air can get past the filter into the passenger compartment.
Too much VOC in the air often causes fogging. VOC components move in the air from warm to colder zones and are separated there. In a car, this can lead to fogging of the windscreen or the inside of the headlights. In extreme cases, this could impair drivers' road safety. The low-emission sealing products, which are particularly in demand among car manufacturers and their suppliers, make a decisive contribution to reducing the fogging effect and VOC pollution of the air inside the car.
Fast-Cure foam seals for high cycle process manufacturing
When applying a seal to a component, the cycle time with which the components are fed to the mixing and dosing system and subsequently processed is of great importance. Modern mixing and dosing systems have therefore always worked very quickly and with high precision. However, components with a foam seal that has just been applied generally require a certain amount of time before they can be further processed. The reason for this is the cross-linking reaction of the material components polyol and hardener. It must first be completed before the seal surface is tack-free and parts can be handled. The parts can only be installed once the seal has completely cured. As a rule, the foam seal cures in 25 to 120 minutes.
However, in automotive engineering with high cycle process manufacturing, rapid part handling is required after just a few minutes. For this purpose, the tack-free time can be significantly reduced by using so-called polyurethane-based fast-cure systems. The surface of the SONDERHOFF FERMAPOR K31 FAST-CURE foam seal is tack-free at room temperature after approx. 120 to 180 seconds, depending on the formulation. The foamed components can thus be quickly further processed in subsequent manufacturing processes and thus assembled earlier. This saves energy costs, possible costs for intermediate storage of components, investments in temper furnaces or transfer belts for long curing lines. Faster further processing and thus earlier final assembly of the components lead to considerable time savings in the entire manufacturing process, lower unit costs and more efficient production.
Special SONDERHOFF FERMAPOR K31 FAST-CURE foam seals also meet the technical requirements of the manufacturer's own automotive industry standards, from Daimler DBL 5452-13 to VW standard TL848 to Chrysler/Fiat standard MY 560. Fast reacting Fast-Cure sealing foams generally have good adhesion, but on certain substrates only after prior pretreatment, e.g. by primer or plasma activation as an adhesion promoter. The viscosity of Fast-Cure foams can be flexibly adapted to the respective component geometry from liquid to pasty. and can be easily installed thanks to different shore hardness.
Typical applications in the automotive industry
Foamed gaskets based on polyurethane or silicone are used in vehicles, for example in the interior or engine compartment, as well as for parts of the body, lighting and automotive electronics. Typical applications for foam gaskets include door modules, which have been fitted with directly applied FIPFG gaskets as standard for years. The door modules accommodate loudspeakers and electric windows whose electronics must be protected from moisture and dust. Further standard applications are the sealing of plastic housings, e.g. for electronic components or "third brake lights", for which red-coloured seals are often required. Polyurethane and silicone seals can also be adjusted in other colours. An example of a sealing application with increased requirements is the timing belt cover. It is located in the engine compartment and is fitted with a silicone seal due to the temperature load there.
Polyurethane adhesives for lightweight automotive construction
Thanks to new materials and material combinations, the design possibilities in lightweight car construction have become more versatile. Mounting and attachment parts in cars made of thermoplastic or duroplastic plastics (partly fibre-reinforced) or plastic components with metallic components are increasingly being bonded with 2-component polyurethane adhesives. In vehicle construction, this is a multitude of components, such as GRP sandwich structures, KTL coated metal frames for sliding glass roofs, parts made of PMMA or PC with scratch-resistant coatings, roof panels, trim strips and spoilers as well as ABS- or PP-based tailgates.
The automotive industry has access to Henkel's extensive adhesive portfolio. The 2K polyurethane adhesives enable optimum adhesive results for components made of different materials. They also meet the high mechanical and climatic requirements. The perfect gluing process requires precise mixing and dosing of the adhesive components and the adherence to a precisely defined mixing ratio. The SONDERHOFF mixing and dosing systems enable exactly this, namely through process-continuous dosing accuracy and systematic process monitoring.
Conclusion for the automotive industry
The Formed-In-Place (FIP) sealing technology for the fully automated application of liquid to pasty 2-component material systems made of polyurethane or silicone directly onto the components has established itself as the manufacturing standard in highly automated vehicle construction. The SONDERHOFF mixing and dosing systems used for this purpose can be very easily integrated into existing production lines and concepts.
With the FIP sealing technology, a large number of very different component geometries can be precisely dosed with soft foam seals, adhesives or pottting compounds in reproducible quality. The raw materials used are almost 100 % utilized. The application possibilities for foamed gaskets are particularly diverse and can be perfectly adapted to the requirements of the automotive industry. In addition to emission behavior, temperature and contact media resistance, this includes the good resetting ability of a foam seal, suitable for repeated opening and closing of the part for maintenance purposes, as well as flexible hardness adjustment and other mechanical properties such as tensile strength and elongation at break. The requirements of the various automotive standards must be taken into account as well as the requirements resulting from the specific application.
