Page 15 - Industrial Technology EXTRA - 6th April 2020

ADHESIVES... Intertronics

it’s important that the adhesive receives the correct
dose of UV light, as well as the right wavelengths.
Most UV curing adhesives start curing once exposed
to the correct light, and will stop if the light is
removed, so it is important to ensure a full cure is
achieved in the exposure process
Manufacturers should test their process to
determine the minimum light dose to achieve optimal
cure for their application; dose is a combination of
light intensity or power, and exposure time. Once the
process. So, what can manufacturers do to get the minimum dose is empirically established, best
most out of their process? practice suggests that a safety factor (perhaps 25%) is
added to arrive at a robust process. High performance
Broad versus narrow spectrum lamps UV curing adhesives designed for use in industrial
There are two types of lamp available, broad- applications will require a minimum activation energy
spectrum mercury arc UV lamps and LED-based UV level of 50 mW/cm in order to properly establish
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curing lamps. LED-based UV lamps will have a quite cross-linking and effect a good cure.
narrow spectral output based around a single Higher intensity lights will result in faster cures
wavelength (e.g. 365nm, 385nm). The traditional and process efficiency; more energy will help to give
broad-spectrum lamp has been the workhorse of the a better cure, improving performance. Manufacturers
industry for many decades, but does have some can use a radiometer to check the light intensity and
shortcomings that manufacturers have to compensate your technical contact at your adhesives supplier can
for, such as the operational life of the bulb and recommend a radiometer for your application.
intensity that degrades over time. In contrast, LED UV
curing lamps have a consistent output, no bulbs to Keep safe
replace and no warm-up time, amongst other UV light is hazardous. However, protecting operators
advantages. from the light using integral shielding or by equipment
For best results, remember that your adhesive design is straightforward. For manual, hand-held
must be matched to the output of the curing lamp — curing operations, a common sense approach would
not all adhesives will cure optimally with narrow be to consider how you would look after yourself on a
spectrum light from an LED lamp, requiring a broader sunny day at the beach — cover up exposed skin and
range of light energy to achieve tack free and best protect eyes. A good supplier will deliver safety
cured properties. Matching the spectral output of the eyewear with each lamp and will help with any
lamp to the light responsiveness of the adhesive is a further PPE needed, as well as the risk assessment.
crucial step in getting the process right. Training is recommended for everyone involved in the
process. A radiometer can be used to check levels of
What’s the dose? UV light near the equipment, and to give
An advantage of UV is that complete cure is achieved colleagues better understanding of any hazard.
in the bondline in seconds. In order for this to happen, www.intertronics.co.uk

6 April 2020 • INDUSTRIAL TECHNOLOGY EXTRA! • p15