RUBBER & PLASTICS
CYANOACRYLATE MYTH BUSTING
Cyanoacrylate adhesives (CAs) - also known as superglues or instant adhesives - are fast curing adhesives suitable for bonding a wide variety of substrates including metals, plastics, elastomers, and porous materials. Because these materials have traditionally come with many compromises, there are several myths around their use. Here Paul Whitehead, strategic accounts manager at adhesives specialist Intertronics, busts cyanoacrylate adhesive myths.
typically water, resulting in polymerisation into a long chain polymer. CAs can be based on various monomers but are most commonly formed from ethyl cyanoacrylate (ECA) or methoxyethyl cyanoacrylate (MECA) monomers.
A
MYTH 1. ALL CAs ARE THE SAME
While it is possible to walk into your local hardware store and purchase a consumer CA, these are not indicative of the capabilities of all CA materials. Newer entries to the market aimed at industrial and technical markets have been formulated to overcome some of the historic challenges and broaden the applications in which CAs are used.
t the molecular level, cyanoacrylates are composed of acrylic monomers stabilised by a weak acid. Cure is initiated when the acidic stabiliser is neutralised by a weak base,
Cyanoacrylates are produced in a variety of
formulations, each exhibiting distinctive attributes of viscosity, thixotropy, cure time, bond strength, and more. There are materials available for everything from hobbyist woodworkers to electronics manufacturing to medical-grade skin bonding materials for wound closure.
MYTH 2. THEY ARE BRITTLE While CAs are generically brittle, some, like the Born2Bond Ultra range, are less brittle than conventional products. Rubber toughened formulations can offer better impact resistance. adhere ADH9480 Cyanoacrylate Adhesive, for example, when compared with other grades, offers improved shock resistance and peel strength and has a longer setting time than other grades, while being specially formulated to achieve the strongest possible bond between well-mated, non-porous surfaces. Alternatively, ADH9105 offers higher impact, humidity, and temperature resistance than similar materials, resulting in a more flexible bond. Recent innovations have seen the launch of
CAs that are inherently flexible. For example, Born2Bond Flex offers >200 per cent elongation, absorbs impact and vibration and copes with bonding substrates with different thermal expansion coefficients.
MYTH 3. THEY HAVE A MAXIMUM OPERATING TEMPERATURE OF 80°C While 80°C is the maximum recommended operating temperature for a lot of CAs, there are several products available that offer improved temperature resistance. Born2Bond Structural, for example, can withstand temperatures up to 120°C, while ADH9480 can withstand up to 125°C.
MYTH 4. THEY ALWAYS CAUSE BLOOMING A side effect of CA’s volatility, blooming is the name given to the chalky white
residue that appears on the surface of the part. While it does not affect bond integrity, blooming can be aesthetically undesirable. Because CAs based on MECA monomers are less volatile than ECA products, they are less susceptible to blooming; manufacturers looking for a low bloom material could consider ADH9408, ADH9640 or ADH9403. Recent advances have seen the introduction of
low blooming MECA materials with fewer compromises, for example Born2Bond Light Lock, which has an additional light curing mechanism, or Born2Bond Ultra, which combines the fast curing associated with ECA- based CAs with the low-blooming characteristics of MECA-based ones.
MYTH 5. THEY HAVE AN UNPLEASANT ODOUR Almost anyone who has used superglue at home will have noticed its distinct smell. When working with traditional CAs, it is important to work in a well-ventilated area and with the correct protective equipment. A suitable dispensing methodology can reduce the need for handling and improve health and safety. However, not all CAs smell - low bloom
formulations are also low odour. Born2Bond Ultra, for example has inherently low volatility, which means less odour, less irritation and no CLP hazard symbols on the label.
MYTH 6. THEY MUST BE DISPENSED MANUALLY There is no requirement to apply a CA directly from the tube or bottle. Depending on the level of accuracy and repeatability required, as well as the throughput of the application, CAs can be dispensed as part of a manual, semi-automated or fully automated process. For example, you can combine a pressure pot or reservoir with a suitable diaphragm dispensing valve for a semi-automated, precise dispensing technique. Mounting this equipment onto a robot to automate fully will result in a methodology that requires very little operator intervention. The trick to establishing a successful dispensing methodology is finding an adhesives supplier that is also experienced with the relevant dispensing and automation equipment.
18
Spring 2023 UKManufacturing
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