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There Isn’t One Glue That Fits All

Martin Cummins on targetting the range

OVER the years I have been working in technical services, product development and technical training I have become a bit immune to the fact that product ranges can sometimes be confusing to contractors and retailers.
It can be a bit of a challenge trying to fathom which adhesive is needed for a particular job, so why do we have different products for different applications?
Surely a ‘one glue fits all’ policy would be better, wouldn’t it?
In theory yes it would, but in practice this isn’t going to happen anytime soon.
In any case, if we did happen to formulate an all-encompassing product thats fits all the technical requirements, meets all the handling needs, and is suitable for all the conditions and applications then you can be assured that it would cost a pretty penny.
So how does offering a product range help to meet these demands?
Let’s start by looking at handling needs. What I mean by this is that the product needs to be applied in a way that delivers the right amount of adhesive in the right manner to give the correct level of adhesion.
Probably the most straight forward method of applying a product is when it needs only to be a very thin film, for example when a tackier bond is required for carpet tiles. This is because the design of carpet tiles means they generally lay flat, are stable and can be uplifted and replaced if damaged, stained, soiled etc.
In order to get a thin coat of adhesive we can apply by roller or by a soft brush if desired but to enable the adhesive to spread thinly it needs to be low viscosity, meaning it is thin and relatively runny.
Similarly when applying contact adhesive you want to apply a thin film onto two surfaces, although you may need to apply onto a vertical surface so it is necessary to give the adhesive a false body. That is something we refer to as being thixotropic. This basically means it is of a gel like consistency but when brushed or rollered this consistency is broken down to enable a thin film to be applied.
When it comes to applying adhesives to bond down a carpet, which may have an embossed backing or may be woven, you need to ensure the adhesive stands proud off the floor and so penetrate into the profiled texture on the underside of the carpet.
To get an adhesive to stand proud we need it to be applied by a notch trowel and for it to retain the trowel ribs. The rib height will be determined by the trowel notch selected and the selection of notch will depend mainly on the depth of the profile and texture. To enable an adhesive to retain these ridges it needs to be made to more of a paste like viscosity, not a runny viscosity. To do this the products generally need to incorporate materials which bulk up the consistency, often referred to as fillers.
The fillers generally have little adhesive effect so it is necessary to make sure the polymers and resins used to adhere the carpet are balanced to give the adhesion required.
Also, if applying by ribs it is sometimes necessary to leave the adhesive to rest on the floor (open time) before placing the carpet otherwise the adhesive may simply be flattened and not serve its purpose.
When it comes to vinyl floorcoverings then there is a need to utilise polymers that do not get affected by the plasticisers (materials in the vinyl that make it flexible). Most vinyl products are relatively smooth backed so the adhesive does not need the level of viscosity to give the ribs, as would be required with carpet.
However, you can’t make the adhesive too runny otherwise you will not get enough on the floor to give a bond strong enough to resist movement of the vinyl under load and temperature changes.
So the best adhesives would be viscous enough to apply by a small notch trowel, but also suitably low on viscosity to enable the trowel ribs to be rollered flat if desired.
With resilient flooring such as vinyl and rubber it is important to try and get as close to 100% contact between adhesive and backing of the floorcoverings. This is not so critical with textiles.
When it comes to bonding materials such as timber, where the floorcovering cannot be manipulated to ‘mould’ with the floor then it is necessary to develop adhesives that can be applied using larger notch trowels and can retain their adhesive peaks.
If the adhesive slumps then the timber may bridge across when a floor has any slight undulations and not make contact. No contact, no adhesion. Obviously this will result in a hollowness and a point from which the timber can begin to debond from the floor.
If the floor preparation is particularly good, say to an SR1 level, then there is not such a concern, but we have to develop products to work under ‘normal’ conditions rather than just in ‘perfect’ conditions. So this means that a higher viscosity for a more treacle like consistency is needed.
And finally, where adhesives need to be applied as a spray, such as in aerosols, you have to develop them so they can exit through a small nozzle. They cannot therefore have any large filler particles as it will clog up the spray equipment.
You may have to incorporate different raw materials that keep the adhesive in a ‘web’ sort of spray rather than simply coming out as dots of adhesive spread over the surface.
It is easy to see that even without considerations like the types of resins, polymers or carriers that purely from a point of view of applying the adhesive there is a large variation in what is needed. Hence why we have product ranges for different applications.
This ensures the contractor can get an adhesive ideal for his application rather than one that is ‘sort of OK’.
An analogy that comes to mind would be selecting an appropriate bicycle. They all have two wheels, handlebars and pedals but would you really use a mountain bike on an Olympic time trial, or would you try to go up a steep dirt track on a racing bike? Of course not – it’s horses (or bikes) for courses.
Martin Cummins is UK technical support manager at Bostik.

www.bostik.co.uk
T: 01785 272625

This article has been reproduced from the Contract Flooring Journal. You can find them at www.contractflooringjournal.co.uk.