VISIOMER® Specialty Methacrylates

 
Adhesives have become increasingly important as lightweight construction allows vehicle designers to improve efficiency, reduce CO₂ emissions, and increase sustainability. Structural adhesives are used to permanently join critical components of the vehicle and to replace less effective bonding methods such as welding and mechanical fasteners. They provide stiffness, strength, and durability. Methacrylate adhesives in particular are valued for their nearly instant cure and proven durability.

 
Evonik’s specialty methacrylates like VISIOMER® BNMA were developed to meet higher health and safety standards, enabling formulators to increase the safety of their products while maintaining the long-term durability of these critical adhesives.

Because the vehicle assembly directly affects passenger safety, automotive structural adhesives must pass a gauntlet of rigorous testing before they can be qualified for use. Adhesives must be fast-curing, tough, and resist impact both in the winter cold and during high temperature manufacturing processes. Adhesives should not shrink, require an acceptable odor, and should protect the substrate from corrosion to ensure a long-lasting bond. Because most adhesives are applied robotically, adhesives must have a pumpable viscosity and rheology. The adhesive should not react too fast while curing to avoid warping parts from the high exotherm.

 
The materials used to build vehicles is changing as manufacturers reduce weight to improve efficiency & driving range. This places new demands on formulators for adhesion to a wide variety of substrates. Modern passenger vehicles are built with stamped aluminum frame components which are bonded together with adhesive. The adhesive allows manufacturers increase strength while employing lighter frames and thinner metal stampings. Body panels made of aluminum, epoxy composite, or steel are glued to the frame. Polymers like PET, nylon, PPE, and PP are used to produce parts and interior components which are assembled with methacrylate adhesives. Electric vehicles introduce further complexity, requiring adhesion to polymer composite battery enclosures, copper, and nickel. Many parts, including metal frame components, are delivered unclean and are bonded unprepared, with a coating of process oil or lubricant remaining on the surface. Despite the contamination, the adhesive must provide a tough and long-lasting bond.

 
Choosing the right mix of methacrylate monomers is key. Formulators must balance the physical properties of the monomers to achieve the right strength and flexibility. Monomers including VISIOMER® BNMA or VISIOMER® c-HMA may be selected for their dimensional stability or high heat resistance. Reactivity must be balanced to provide a rapid cure without damaging the part. VISIOMER® HEMA-P may be selected to improve adhesion and corrosion resistance, while proven monomers like VISIOMER® MEEU are chosen for their solvent-like ability to adhere to oily metals and soften polymer matrixes. Diluent monomers have a low viscosity, making mixtures pumpable and enabling increased filler loading. These benefits extend beyond automotive adhesives, making VISIOMER® Specialty Methacrylates broadly used in adhesive and anchoring applications.

The automotive structural adhesives market keeps evolving. Sustainable methacrylate monomers, based on bio-sourced and recycled raw materials, are being developed to meet the growing need for monomers with reduced global warming potential. Vehicle manufacturers demand formulas which are even safer & easier to handle, and the list of substrates requiring strong bonds keeps growing as new materials are introduced. The ongoing electrification of the vehicle fleet and persistent demand for lightweight, efficient construction means that methacrylate structural adhesives are likely to becoming increasingly important.