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Adhesive terminology explained

Adhesive terminology explained
Martin Cummins

Published by Martin Cummins - UK Technical Support Manager, Bostik

Martin has been involved in the industry for over 20 years. He’s passionate about flooring in all its guises, with his particular expertise being in subfloor preparation products and adhesives. Martin is an active member of the CFA manufacturers committee and he sits on the CFA council. He aims to keep abreast of all the changes in the industry and feeds this knowledge back to installers to make sure when floors are laid they perform to their maximum potential.

Look at any technical datasheet, marketing materials or even the adhesive bucket and you will find terminology, pictograms and recommendations that can often be confusing. This article is intended to clarify, from a Bostik perspective, what these various terminologies actually mean.

Waiting time: Sometimes referred to as “airing” time. This is the length of time after the adhesive has been applied to the substrate that you must wait before even considering applying any flooring products. This may be to enable initial tack, rib formation and also evaporation of some of the carrier (usually water, but can also be solvent) to take place. The waiting time will be less for certain coverings than others. This is because a “wet” adhesion is necessary to achieve a high integral bond. For some coverings, it may be recommended that a long waiting time is required, especially on impervious substrates.

Working time: This is the period of time after the waiting time has elapsed that you have available to install your floor covering. It is related to the bond strength required to ensure the particular flooring remains fully adhered. You may see a different working time for the same adhesive depending on what floor covering is being installed.

Open time: This is generally an accumulation of the waiting time plus the working time. It is an indication of the time-frame available to you from applying adhesive to completion of the flooring installation. However, it won’t include suggested times for the re-rolling of floor coverings.

Walk on time: This is the recommended time that a floor covering bonded with a specific adhesive needs to be left before allowing people to walk on it. There may also be recommendations relating to heavy trafficking, such as bringing in office equipment, racking and shelving, as well as the time needed before welding on sheet vinyl and linoleum can be carried out.

All of the above will be quoted based on good ambient conditions. Generally this will mean on an absorbent subfloor at 18oC to 20oC with an air humidity of 50-65%RH. This is often a bone of contention with contractors as it doesn’t always tally with the conditions experienced on site. This is totally understandable, but until there becomes an accepted standard site condition (which can never happen until we have sealed buildings, air flow and reasonable temperatures) then manufacturers need to have a starting point for reference. Some adhesives may perform better than others in cooler, damper conditions, whilst others will be ideal in higher temperatures. It is horses for courses but bear in mind that floor covering manufacturers have their recommended conditions for fitting flooring, which are there for good reason.

Trowel sizes have also changed significantly over the years. If we look purely at “v” notched trowels, then in the UK we have described them in terms of how deep the notches are and how close they are to each other. A 1.5mm x 5mm notched trowel will have V notches (cut at 60 degrees) that are 1.5mm deep and 5mm from each other. Similarly, a 2mm x 6mm will have a deeper notch of 2mm, with the notches being placed 6mm apart. The choice of trowel is based on what depth and quantity of adhesive is needed for a particular floor covering. A 2mm x 6mm would typically be needed for a textile, whereas a 1.5mm x 5mm would be fine for vinyl.

With influence from Europe, the terminology for trowels has changed somewhat too. You will now find references to A1, A4, B2 etc. These don’t offer much insight into what size the trowel is, how deep the ridges are and how much adhesive it will apply.  The basic understanding is that ‘A’ trowels will generally have shallower notches more closely spaced, so are ideal for floor coverings where a nice smooth subfloor is in place. The trowels referenced ‘B’ tend to be more like the trowels traditionally used in the UK. Most manufacturers will quote a range of coverage rates based on using different trowels with specific adhesives. The selection of trowel will depend on the expected bond strength, which can vary from floor covering to floor covering and from situation to situation.

Other information you may also see on products includes terms such as solvent-free, EC1, phthalate free etc. These are an aside as to how the products should be used and what they are for, but they are becoming much more important with regard to getting adhesives specified. Historically, the difference between adhesives was simply whether a product was solvent based or water based. As time progressed, the differentials became more akin to whether the product was solvented, low solvent or solvent-free. Ask any of the older fitters working today and they would rate the solvent based adhesives very highly with regard to performance. There are reasons why this would be the case but the impact on health, environment and also resources means that everyone should be looking to move away from solvented products wherever possible.

EC1 and EC1 Plus are borne from the German market, where regulation and to some degree legislation led to a focus on “cleaner” products long before the UK. The system introduced enables products to be rated and approved, particularly in government funded buildings. There is a cost to this which includes site and factory audits to maintain accreditations. The method of assessment is quite complex but basically involves testing the adhesives over long term and monitoring the release of the various components. If components are such that they can cause discomfort or worse, then the products will not be approved.

You may have also seen reference to phthalate free and isocyanate free on pack. This is a requirement in the UK in order to conform to indoor air quality standards as part of BREEAM. Although not regulatory, BREEAM certification is increasingly requested by architects and planners to enable them to attain maximum sustainability credentials for their buildings. Having an adhesive that is phthalate free and isocyanate free can therefore be beneficial when tendering.

Solvent-free is another common term. The misconception is often that a product is safe and clean just because it is solvent-free, but this cannot be determined. The aforementioned criteria are your best guide to the real safety and cleanliness of a product. Unlike ‘solvent-free’, they all link to the nature of the product with regard to hazardous components and more specifically to the emissions released after application.

I hope this has been helpful in explaining what the various terms you will see on Bostik packaging and other flooring products in general mean, but please feel free to contact me if you’d like any further clarification.