The coupling effect

In some situations, a hero is needed: Imagine your little daughter’s favorite mug falls off the breakfast table, crashes to the floor, and the handle breaks off. To keep your little angel from crying, you rush to your toolbox, fetch the superglue and within seconds handle and mug are connected again.

In this moment the coupling effect helped you to become your daughter’s hero. The effect turns glue into superglue and is created by an ingredient called silane. In glues these silanes are used as an adhesion promoter. Millions of microscopic silane “bridges” within the glue create a durable bond on a molecular basis between the polymer chains of the glue and the surface of the ceramics. And those bonds on a molecular basis are that strong, that the fixed handle can withstand physical stress, water immersions, and other loads until your little angel is a grown woman.

To understand how the coupling effect is established, let’s focus our imaginary microscope to take a closer look at the appearance of silane coupling agents … You can think of a silane molecule as a railroad car. Basically, a railroad car is a longish structure with a coupler at each end. The couplers are used to connect the railroad car reliably to two other railroad cars.

Now imagine that the couplers of that railroad car are designed to connect to totally different things, for example, to a bus and a trailer. That’s how coupling molecules are designed: They have a coupler at each end of their longish structure, one is designed to connect to organic polymers, the other one is designed to connect to inorganic materials like metal, stone, glass, or the ceramic of your daughter’s mug. Which means that a silane molecule has the talent to connect materials that normally wouldn’t go with each other.

Here are a few examples where the coupling effect of silanes plays a major role:

• Silicone Sealants: The coupling effect of silanes ensures that the silicone polymers of the sealant connect reliably to walls, tiles, or your sink to protect your house from water damage. At the same time, our silanes help the sealant cure faster, so that plumbers can do their work more effectively.
• Fiberglass: A hockey stick, the hull of a yacht, your bathtub, or the wings of wind turbines are most often made of fiberglass, an extremely resilient composite material made of very thin glass fibers in a plastic resin. Our silanes bond the organic polymer chains and the inorganic glass fibers together to one material.
• Cables: Silanes allow the plastic insulation of a cable to embed up to 60 % of halogen-free, mineral-based flame retardants without getting brittle. This coupling of organic insulation and inorganic fire protection does not only improve safety but also prolongs the lifetime of a cable.
• Artificial stone: For artificial stone, polymers are mixed with quartz powder to create surfaces that are both, slick and extremely resilient against scratches. For example, for your next designer table. We think you can already guess which of our chemical products ensures that organic plastic and inorganic quartz can be coupled for ages …
• Thermal management: Silanes are essential when it comes to the management of heat – for example when electronic parts become smaller or when the automotive industry brings in more batteries. Silanes are added to coatings, adhesives, or fillers to help bind components more tightly at a molecular level. This creates better contact between materials, allowing heat to flow more efficiently
• This list could go on and on. But to keep it short we’ll stop here.

If we’ve sparked your interest in silanes, we can recommend our article on the “Mileage Effect.” Here you can learn how a system of silanes and silica in your car tires helps to lower the costs of mobility and to raise the passenger safety.

Silanes bond polymer chains and glass fibers together to a material called fiberglass. It’s even strong enough for the wings of wind turbines.

For more than seven decades, the brand name Dynasylan® has been a synonym for exact specification, extreme purity, and high process stability. Due to continuous innovation, we are now pleased to offer our customers a portfolio of over 150 silane solutions for a wide range of coupling applications. But the stable bond between materials is only one part of the story. The other one is the stable and cooperative bond with our customers which helps us to find solutions that make a difference.

The key to the coupling effect lies in the design of the molecules: Like a bar magnet, coupling silanes are longish structures with two totally different ends. At one end there’s an organofunctional group, designed to build a chemical bridge to all forms of organic polymers: plastics, resins, or rubbers. At the other end there’s a hydrolysable alkoxy group, designed to form covalent bonds with inorganic surfaces of metal, glass, or minerals.

Since this approach of coupling happens on a molecular level it creates one of the strongest and longest-lasting bonds possible. A pleasant side effect of silanes is that they change the molecular structure of polymers: They turn the weak polymer chains into a stable and durable three-dimensional network with improved resistance to mechanical stress, ageing, or UV radiation.

As you can see, Dynasylan® silanes are cutting edge chemistry and no, they are not as cheap as sand or salt. But the investment pays off, because silanes boost productivity in many ways:

• Silanes facilitate manufacturing: Using a coupling agent is often faster and cheaper than screwing, welding, or riveting.
• Silanes facilitate storage and logistics: The quicker an adhesive or coupling agent dries, the faster a product can withstand the mechanical stress of storage or transportation.
• Silanes extend a product’s lifespan: Silanes make surfaces hydrophobic so that your engineered structures – such as bridges, houses, vehicles, ships, wind turbines, or many more – can be used more safely and for longer in humid environments.
• Silanes reduce repairs: Silanes establish extremely durable bonds so that less maintenance costs or repairs can be expected.
• Silanes are extremely effective: In most cases, an addition of less than 1 % is sufficient to achieve the desired effect and to give your product measurably better properties.

To meet all our customer’s wishes in performance and compatibility, we offer a portfolio of more than 150 organofunctional silanes in trading units ranging from 25-kg drums to 20-ton bulk containers. Unfortunately, finding the best silane solution for your product is a complex task. Does your product have to withstand water? How long do you want your product to be used? How fast does the coupling effect have to be achieved? Different answers to these questions require different types of silanes. Additionally, it’s important to check that the silane used is compatible with the other components of the formulation, such as resins, inorganic fillers, pigments, or other additives. But there’s no need to worry: At our Smart Effects department we have a huge team of experienced application engineers. They look forward to assisting you to scout out the most efficient formulation for your use case. Just send us a message.

Silanes from Dynasylan® are strong coupling agents that maintain their performance reliably over years or even decades. This results in very durable products, that do not have to be replaced very often which is a small but important step to conserve our planet’s resources.

Additionally, you will find more direct contributions to environmental protection in our Dynasylan® portfolio. Ask for our solutions to reduce VOC formation to a minimal of <1% in later production or application processes. 

Evonik operates production facilities, service centers, and warehouses from the Americas, across Europe all the way to Asia. Which means, not only do we have decades of experience in the production, application, and further development of silanes. We also have decades of experience in dealing with local regulations in numerous regions of the world.

So, if you have questions about the application, processing, or storage of silanes or if you have questions regarding environmental or toxicological regulations, simply drop us a line at ask-se@evonik.com or press the contact button below. Our experts will get back to you as soon as possible.

You are already an Evonik client? Then you will get support from your regional contact and from our application engineers. We are looking forward to hearing from you.