PRODUCTS & APPLICATIONS FASTENINGS & ADHESIVES THREAD LOCKER AND SEALANT BENEFITS PIPE FITTING MANUFACTURER
HUOT is a century-old French company that specialises in the manufacture of products and components for drinking water supply. It produces in the region of one million brass pipe fittings per year, and the EN805 standard to which they conform requires them to have a service life of more than 50 years. However, the average lifespan of a HUOT product is actually 70 years. The company, however, had
been using an adhesive to seal its
threaded products but, when cured, it became brittle, resulting in the seal breaking if the fitting was accidentally dropped. Even the impact of the fitting being thrown into a steel storage box could result in the seal fracturing. Several alternative adhesives were therefore trialled and the WRAS-approved LOCTITE 2400 thread locker and sealant proved superior for three reasons: when cured it could absorb any shock, the resultant bond was extremely durable and, most importantly, it was also hazard label free. LOCTITE 2400 now ensures the brass pipe fittings will continue to meet the
company’s high standards when they leave the production line. The product is dispensed both manually and automatically onto the male threads and its thixotropic nature reduces the migration of the adhesive after application to the substrate. The adhesive cures when it is confined in the absence of air between the close-
fitting metal surfaces when the joint is tightened. As the adhesive fills all gaps between the threads there is no scope for any micromovement of the joint, the major cause of self-loosening. It is designed for locking and sealing threaded fasteners which require normal disassembly with standard hand tools. This one-part adhesive was one of the founding products in Henkel’s Health and
Safety range and has recently been further developed for use on zinc-coated products. For HUOT, a key specification for the replacement thread locker was that it
should be hazard label free but, by switching to LOCTITE 2400, the company has also drastically reduced customer returns, ensured the long term service quality of products and underpinned its brand image.
Henkel
PREVENTING CA BLOOMING
Cyanoacrylate adhesives (CAs) are prone to blooming – a chalky, white residue on the surface of a part. Although it won’t affect bond integrity, it is undesirable if aesthetics are important or if the presence of blooming might imply a quality problem to your customer. Several cyanoacrylate monomers are used to
formulate CAs. Ethyl (ECA) monomers are the most common, but their volatility means they also more prone to both blooming and a harsh odour. Cyanoacrylate adhesives based on methoxyethyl (MECA) monomers are often marketed as ‘low odour, low bloom’ formulations, but they can compare poorly in terms of cure speed, strength and cost. The new Born2Bond Ultra CAs offers another option as it combines the fast cure associated with ECA-based CAs with the low blooming characteristics of MECA-based CAs. Their inherently low volatility means less odour, and they are less irritating. Another way of reducing blooming is to
minimise the size of adhesive fillets. Excess adhesive squeezed out into fillets around the bondline will cure more slowly and will provide
12 FEBRUARY 2021 | DESIGN SOLUTIONS
www.henkel-adhesives.co.uk STAINLESS STEEL BALL LOCKS
Ball locks are regularly specified by end user fixture designers aiming to improve or secure OEM-supplied machinery, as well as machine builders using the fastening devices at source. Now, a stainless steel version of its ball lock mechanism has now been introduced by WDS Component Parts. This provides extra durability and rust-free use for the accurate locating and locking of fixture plates and subplates to machines. The ball lock mounting system ensures repeatable
positioning, reducing set-up time and making secure installation of plates to machinery both fast and simple. Accuracy of positioning means the installer doesn’t have to make an extended check of fitting, reducing overall installation time. The advantage of the ball lock is a result of its location and pull-down fastening mechanism, providing greater accuracy and security. The device consists of a
locating shank as well as liner and receiver bushings, which are installed into the machine or subplate with the liner bushing inserted into the fixture plate. The locating shank is then inserted through the liner and into the receiver where tightening the shank’s grub screw establishes the required holding force. Stainless steel ball lock mechanisms have resistance to
corrosion, even in aggressive environments. Stainless steel ball lock shanks and bushes will remain rust-free over prolonged use with corrosive media, ensuring longer machine life and improved maintenance procedures. The ball lock shanks, which are removed and act as
installation tools, are available in 12 sizes, while the liner bushes are available in 33 sizes. Reverse-mount bushes are also available as well as a version with recesses, which can be bolted to the plates. The ball lock shank also has an optional repair kit available, consisting of replacement bearings and an O-ring, which helps keep down maintenance costs.
WDS Components
exposed surfaces. Where joint size or configuration means that fillets are inescapable, a low bloom, fast cure, formulation allows a wider dispensing tolerance. Slowing down the cure will allow
more time for volatile monomers to be released; but making the cure faster will generate a higher exotherm in the adhesive, encouraging the release of volatiles. Controlling the speed of cure can minimise blooming. If exposed fillets are unavoidable,
accelerating cure should restrict blooming. One method is to use an activator, but application might need to be carefully controlled. Another approach is to use a light cure cyanoacrylate adhesive, like Born2Bond Light Lock. Any interfacial adhesive is cured by the normal cyanoacrylate mechanism, but exposed fillets are cured tack-free by exposure to low intensity UV light. The light cure of only a few seconds eliminates the possibility of blooming because the volatiles never have a chance to become mobile. Cyanoacrylate adhesives, however, will become slower with age, and so more prone to blooming. Simple local ventilation and increased airflow will help to blow the volatilised monomers away
www.wdscomponents.com
from the parts before they can settle on the surface. Blooming will also occur if the bonded parts are placed too quickly into a sealed environment such as a bag or shipping container, where any volatility is trapped with the parts. Higher ambient temperatures encourage
the volatility of the CA monomers, leading to a higher likelihood of blooming. Conversely, lower temperatures slow the reaction mechanism, causing prolonged cure time and opportunity for volatiles to be released into the air. Because CAs usually cure by a reaction
with surface moisture, relative humidity (RH) can be important. Best practice would
suggest keeping the relative humidity to 40% to 60% and the temperature at around 21˚C; consistency of environmental conditions will inform consistency of process times and outcomes. Acidic surfaces like wood or leather will cause
cyanoacrylate adhesives to cure more slowly, increasing the risk of blooming. In these cases, it is recommended that a ‘surface insensitive’ CA is used. Alternatively, Born2Bond Ultra offers a fixture time on leather of 5-10 seconds, with a low odour, low bloom formulation.
Intertronics
www.intertronics.co.uk / DESIGNSOLUTIONS
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