TECHNICAL ADVICE

Coming To Terms With Adhesives

PUBLISHED BY: Chris Moore - Northern Division Technical Manager, Bostik

Chris has over 20 years of industry experience. He is passionate about sharing his knowledge of adhesives and most importantly his expertise in Bostik’s professional adhesive systems. Chris wishes to share his skills with flooring professionals to ensure that future installations are completed in the best nature.

Look at any technical datasheet, marketing materials or even the adhesive bucket, and you will find terminology, pictograms and recommendations that can sometimes be confusing. This article is intended to clarify, from a Bostik perspective, what these various terminologies 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 enable initial tack, rib formation, and 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. 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 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 to. Depending on what floor covering is being installed, you may see a different working time for the same adhesive.

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

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Each of these individual times will be quoted based on good ambient conditions. Generally, this will mean an absorbent subfloor at 18°C to 20°C 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 understandable, but manufacturers need to have a starting point for reference until there is an accepted standard site condition (which can never happen until we have sealed buildings, airflow and reasonable temperatures). Some adhesives may perform better than others in cooler, damper conditions, while others are 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 is there for a good reason.

Trowel sizes have also changed significantly over the years. If we look purely at ‘V’ notched trowels, then in Ireland, 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 the trowel is based on what depth and quantity of adhesive are needed for a particular floor covering. A 2mm x 6mm would typically be required for a textile, whereas a 1.5mm x 5mm would be suitable 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 they 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 Ireland. Most manufacturers will quote a range of coverage rates based on using different trowels with specific adhesives. The trowel selection 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 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 critical 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 resources means that everyone should be looking to move away from solvent products wherever possible.

EC1 and EC1 Plus are borne from the German market, where regulation and legislation led to a focus on “cleaner” products long before Ireland. 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 assessment method is quite complex but involves testing the adhesives over the 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 references to phthalate-free and isocyanate-free on packs. This is a requirement in Ireland to conform to indoor air quality standards as part of BREEAM. Although not regulatory, BREEAM certification is increasingly requested by architects and planners to attain maximum sustainability credentials for their buildings. Having an adhesive that is phthalate and isocyanate-free can be beneficial when tendering.

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

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