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Few would argue that ‘Cyanoacrylate’ is difficult to pronounce, however the elaborate name given to this adhesive type is in stark contrast to its nature.

Quite simply, cyanoacrylate adhesives are super glues – the most commonly used adhesive in the industry.

This blog post explores cyanoacrylates in depth – from the product’s origins to its key attributes and most typical applications.

If you’d rather skip straight to shopping for cyanoacrylate adhesives, click here. 

History

Discovered less than a century ago, cyanoacrylate adhesives are a relatively new product on the market and like many great innovations, were actually invented by accident!

In 1942 whilst attempting to make clear plastic gun sights for the guns of allied soldiers in World War 2, a gentleman named Dr Harry Coover created a formulation that worked extremely well as a quick bonding adhesive. However, so dedicated was Harry to the invention task at hand, it was 9 years later before he reinvigorated his interest in the cyanoacrylate formulation.

Fast-forward to the present day and you will find many variations of the original cyanoacrylate formula – with each kind optimised for specific application requirements.

Typical Applications

Cyanoacrylate adhesives are considered as ‘general-purpose’ due to the wide range of applications to which they are suited.

From metal and wood to rubber, plastic and ceramics, cyanoacrylates will adhere to a host of substrates – even human skin. Because of this versatility, cyanoacrylate adhesives are widely used in the general consumer market – often to repair everyday items which have broken.

Cyanoacrylate adhesives, do however have their place in the industrial sector – particularly for applications that are not exposed to chemicals or physical agents.

Cyanoacrylate adhesives are commonly used for bonding small pieces together since a very small amount of glue will achieve high level of polymerisation and the fast bonding time, benefits more intricate applications.

Furthermore, cyanoacrylates are used for medical applications thanks to their quick cure and high adhesion to skin – making them perfect for closing wounds.

Selecting a Cyanoacrylate

When deciding which cyanoacrylate adhesive to use, users must consider the following specifications:

Temperature: What is the maximum temperature that the cyanoacrylate can be exposed to before its properties are altered?

Viscosity: How resistant does the material need to be to the flow? Viscosity controls the amount of cyanoacrylate adhesive dispensed onto a substrate.

Set Time: The amount of time an adhesive can be applied and repositioned or removed before curing is a major selection consideration, since it will result in the hardening of the bond.

Gap fill: The spacing or gap between the substrate that the cyanoacrylate adhesive can accommodate and still maintain a functional, full strength bond.

Chemical Composition

In their liquid form, cyanoacrylate adhesives consist of monomers of cyanoacrylate molecules.

There are two main kinds of cyanoacrylate – Polyethyl-2-cyanoacrylate and Polymethyl-2-cyancoacrylate.

The monomers within these compounds bind together in polymer chains through a process entitled polymerization and it is this union that gives the substance the power to hold two materials together.

Benefits of Cyanoacrylates

Cyanoacrylate adhesives are considered to be an economical adhesive solution since the best quality cyanoacrylate bonds are achieved by using a minimal quantity of adhesive (just enough to fill the joint). In fact, the thinner the adhesive film, the faster the cure and stronger the bond!

With no need for measuring or mixing, cyanoacrylate adhesives are simple and easy to use. Strength is another key attribute of cyanoacrylate adhesives – with just a tiny amount of cyanoacrylate, an outstanding mechanical strength can be achieved.

Additionally, cyanoacrylate adhesives are known for their rapid cure time. This adhesive type sets almost instantaneously and achieves handling strength in seconds.

Limitations of Cyanoacrylates

As with most adhesive products, as well as a great number of benefits, there are some limitations of cyanoacrylates.

The most notable limitation of this adhesive type is its short shelf life. Once opened, cyanoacrylate adhesives must be used within 6-12 months. Other constraints of cyanoacrylates include the potential for stress cracking and poor resistance to friction.

It is important to remember that for every limitation a specific adhesive has, a solution can usually be found in another adhesive product. If you find that the limitations of cyanoacrylates make them unsuitable for your application and you are unsure where to turn now, don’t hesitate to Ask The Glue Doctor.

Key Cyanoacrylate Brands and Products

As an adhesives distributor, Ellsworth Adhesives Europe supplies a broad range of cyanoacrylate adhesives from major brands, including Henkel Loctite, Permabond, 3M and Resinlab.

A few key cyanoacrylate adhesives worth checking out are: Loctite 406, Permabond 102 and Robnor Resinlab 6503

Shop our full range of Cyanoacrylate adhesives here.

 

 

Adhesive Matters: The importance of surface preparation for effective adhesion

A surface free from contamination is essential to securing a strong adhesive bond – but how can this be achieved?
The answer, quite simply, is through effective surface preparation. Let us take a look at different surface preparation products and techniques; from cleaners and degreasers – to primers and flux removers.

 

Abrasion

Mechanical abrasion is one of the most commonly used surface preparation methods and is suited to most materials.

The main objective of mechanical abrasion is to remove weak boundary layers, however this approach will also change the topography of the adherent, consequently increasing the bondable surface area. In addition, mechanical abrasion will enhance the adhesive’s ability to fully wet the surface.

Popular abrasion methods include sandblasting, vapour honing and the use of abrasives or cleaning and finishing materials.

Sandblasting with fine sand can only be used on substrates sufficiently thick to prevent distortion while vapour honing is satisfactory when minimum reduction is desired in metal thickness.

 

Cleaners and Degreasers

As the product name would suggest, cleaners and degreasers have been created to remove greases, oils, lubrication fluids, metal cuttings and fines from the surface that is to be bonded.

Cleaners and degreasers are highly effective and are available in both aqueous and solvent-based formulations.

Loctite 7063 is an example of a solvent based formulation. As a final pre-assembly cleaning treatment, this hydrocarbon-based, non-CFC solvent is designed to be used as a spray or in immersion cleaning processes. On the other hand, Microcare MCC-BGA is an aqueous formulation. This stencil cleaner will remove all types of solder paste as well as uncured chip bonder and inks. Safe for use on webbing, frames and misprinted boards, MCC-BGA provides fast and thorough cleaning – even inside stencil apertures.

When choosing a cleaner or degreaser, the major factors to consider are dry time, residue, odour and substrate compatibility. Residue is a particularly important concern because if there is any secondary processing of the part, e.g., painting or bonding, a residue could interfere with that process. Substrate compatibility is another common concern when dealing with plastics and solvent-based cleaners.

For precious metals and jewels, degreasing will generally be entirely satisfactory, with the possible exception of silver where the tarnish should be removed with medium grit emery paper. A stabilised Trichlorethylene vapour phase degreaser is recommended.

 

Primers

Primers are designed to enhance the bonding quality of adhesives. When applied as a surface coating, they will change the base of a surface to enable more effective adhesion.

The requirement for a primer is dependent on the material – for example a primer will be required when adhering to any porous substrate. This is because a pourous substrate will eventually absorb the adhesive that would normally create a long lasting bond. By using a primer, the adhesive’s ability to wet out the surface is significantly increased, thus solving the problem.

Plastic is another material requiring a primer – though the type of primer needed for this material can be very specific. For example, polyolefin requires a special polyolefin primer. Amongst a range of other primers, Henkel manufactures Loctite 770, a primer that has been designed to prepare the surface of difficult to bond plastics just like polyolefin and other low energy surfaces.

Another key priming product is Dow Corning PR-1200. Dispersed in naptha, PR-1200 is a one part primer available in clear or red that can be used on most metals, glass, ceramics and masonry to enhance adhesion. Typically applied in a thin layer, PR-1200 and indeed other Dow Corning primers, are dilute solutions of silane coupling agents and other active ingredients. These products should be applied in a very light, even coat by dipping or spraying and excess material should be wiped off to avoid over application.

 

Accelerators and Activators

Both adhesive accelerators and activators are applied ahead of the adhesive act as catalysts. While both product types are designed to increase cure time, activators also improve the quality of adhesion.

One of the most commonly used adhesive activators is Loctite 7455 – used for applications requiring an increased cure speed. While this activator can be applied before or after the bond, it is particularly suited to post-application on cyanoacrylate adhesives, since it ensures rapid fixture between close fitting parts. Typical applications for activators include securing wires or coils to PCB’s, tamper proofing adjustable components and mounting stand off’s, edge guides and board stiffeners.

Moving onto accelerators, while this product type is used to speed up cure time, users should be aware of the ‘trade off’ in the bond strength. For example, when bonding a very porous material with a cyanoacrylate, the application of an accelerator may increase adhesion by causing the cure before the adhesive is fully absorbed. Where possible it is therefore better to use an activator than an accelerator.

 

Flux Removers (or defluxers as they are sometimes known)

Flux removers are designed to remove flux residues and other contaminants that may be found on printed circuit boards due to rework, repair or manufacture.

Used before the application of an encapsulant or conformal coating, flux removers play a critical part in ensuring reliable circuitry.

Microcare MCC-PW2101 Power Clean is a flux remover that promises to deflux high temperature lead-free solder residues. Fast drying and non-flammable, this PowerClean product will even clean oils and inks.

Another popular Flux Remover is Microcare MCC-UFR107 Universal Flux Remover which is designed to safely remove contamination and soils that can impact the functionality and reliability of electronics. The fast drying and low aroma properties make it ideal for cleaning electronics during rework and repair, spot cleaning or in-field service repairs.

 

Conclusion

Surface preparation is undoubtedly an important process for effective adhesion, however the approach to this process, cannot be considered as ‘one size fits all’.

Important factors to be considered include the application in question, material type and the form of contamination. The key surface preparation products and techniques have been outlined above, along with an explanation of their suitability for certain materials and applications.

If you have any further questions on this topic please don’t hesitate to Ask The Glue Doctor – who will be happy to answer all of your technical questions.

At Ellsworth Adhesives Europe, we can proudly say that we supply adhesive solutions to almost all of the industrial markets including aerospace, military, construction, white goods and LED and lighting, however there is one market that we know more intimately than most and that is the electronics market.

As a distributor of adhesives and adhesive dispensing equipment, we represent a number of key manufacturers within the industry – and many of these manufacturers have product ranges specifically designed for the electronics sector such as Henkel Loctite, Dow Corning and Robnor Resins.

Henkel is the world’s leading and most progressive manufacturer of qualified materials for the electronics industry, including semiconductor packaging, printed circuit board (PCB) assembly and advanced soldering solutions. There are hundreds of different ways in which Henkel electronic adhesives can enhance the quality and efficiency of electronic components.d

The Technomelt range from Henkel, for example, provides protective encapsulation for electronic components, making it the perfect adhesive for low-pressure moulding applications. Henkel Technomelt, available from Ellsworth Adhesives Europe, is an innovative hot melt adhesive that both bonds and protects. In the low-pressure moulding process, the components are placed without a housing in a mould and encapsulated with the hotmelt. Once the moulding has cooled and solidified, the components – now provided with a protective outer shell – are ready for further processing. Hotmelt moulding uses one-part adhesives, resulting in a simple, very fast and clean production process. The low application pressure ensures that the process is gentle and therefore suitable for encapsulating even the most small and delicate components with a hotmelt adhesive.

Like Henkel, Dow Corning has a portfolio of adhesives tailored to suit the specific requirements of the electronics market. Dow Corning is a globally integrated provider of materials, application technology and services. A key benefit of Dow Corning adhesives is their potential to significantly increase reliability of the electronic module or component because of their stress-relieving properties. Dow Corning adhesives have a “rubbery”, elastomeric nature and are not traditional, highly rigid adhesives. This low stress environment can reduce damage to module components and interconnections.

Dow Corning manufactures a variety of noncorrosive, thermally conductive silicone adhesives that are ideally suited for use in bonding hybrid circuit substrates, power semiconductor components and devices to heat sinks as well as for use in other bonding applications where flexibility and thermal conductivity are major concerns. The flowable versions are also perfect for use as thermally conductive potting materials for transformers, power supplies, coils and other electronic devices that require improved thermal dissipation.

Launched last year, TC-2030 from Dow Corning offers outstanding thermal conductivity and excellent elastomeric properties after aging, providing long-term reliability. Good adhesion to various substrates, such as anodized or cast aluminium, tin-plated copper and printed circuit boards, make this material well suited for use across a wide variety of electronics markets. TC-2030‘s thermal conductivity of 2.7 W/mK is higher than traditional thermally conductive adhesives and with a viscosity of 190 Pa.s, it also offers good dispensing characteristics and can be easily applied by a dispenser once the two-part formulation is mixed. The electronics market has shown a need for improved heat dissipation in printed circuit board applications with high power components and Dow Corning’s high thermal conductivity TC-2030 provides manufacturers with a viable option to address this need.

Moving from silicone adhesives to polyurethanes, for our final application focus we turn to Europe’s leading formulator of epoxy and polyurethane resin systems, Robnor ResinLab.

Robnor’s electrical and electronic polyurethane range offers a comprehensive choice for users who have a variety of requirements for their application. Robnor polyurethanes are used in applications demanding economy, toughness, high insulation and thermal impact resistance. Furthermore, this range of polyurethanes can be used as an alternative to epoxy and silicone materials and offers lower unit costs and faster production while providing excellent general performance.

One of the most common applications for Robnor polyurethanes is potting for electronic devices. Robnor EL199HP is used by a smart metering solutions provider for potting its electronic RFID transmitting data devices in mechanical water metering systems. EL199HP provides a low cost integral solution with resin and dispensing equipment thanks to its low viscosity, low hardness and high flexibility. EL199HP offers good adhesion to ABS & FR4 and is also UL94-VO compliant.

Our Sales Engineers could fill a whole series of books with their knowledge of adhesives and industrial applications – this small snapshot of their experience in the electronics industry is just the tip of the iceberg. Please contact the Ellsworth team with any technical questions you may have on your own specific application and our Sales Engineers will be happy to assist.