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Speciality adhesives

Speciality adhesives
Steve Thornton

Published by Steve Thornton - Technical Manager - Wall and Floor

Steve Thornton has almost 30 years of experience in the flooring industry. Starting out as an apprentice floor-layer, Steve acquired a wide range of installation expertise over two decades. He moved on to project management, followed by several years as a National Technical Manager before joining Bostik as a Technical Consultant.

The majority of flooring adhesives out in the marketplace are used on a day-to-day basis. These adhesives are commonplace and the application methods are generally well-known to all that use them.

Circumstances sometimes dictate though that more speciality adhesives are required to provide the correct installation integrity and qualities. Below, I will run through some of these situations and explain why specialist adhesives are required – and how they differ from ‘standard’ solutions.

Pressure Sensitive adhesives – PS. Without doubt, the most commonly used specialist adhesive, and one that I imagine most of you out there would not consider to be a specialist adhesive at all! So why is it here? PS adhesives are both commonly used and commonly misused. When adhering flooring to traditional bases, like smoothing compounds or timber substrates, PS adhesive is used much in the same fashion as most other acrylic adhesives – requiring only a short waiting time before placing the flooring, and allowing a full transfer of adhesive. Allowing a PS adhesive to go fully clear is only needed in quite specific instances. These instances will be when the adhesive is applied to non-absorbent bases such as terrazzo or metal. The application would then usually require the change of the trowel size used (to a smaller notch size). Because non-absorbent bases do not allow the moisture contained within the adhesive to soak in, if you place a resilient floor covering over a semi-wet adhesive, the moisture will become permanently trapped, leading to potential failures. In the case of metal substrates, this can also lead to rusting.

High Temperature adhesives – HT. Perhaps the next most common of the speciality adhesives. HT adhesives are used in environments where the surface temperature of the floor covering is anticipated to fluctuate significantly. These are usually areas where large format windows are present and/or intense sunlight falls onto the floor – traditionally referred to as ‘solar gain’. These adhesives require only a very short waiting time before placing the floor covering. This method gives the flooring the chance to receive the maximum possible transfer of a high strength adhesive, forming a very strong bond. Fluctuations in temperature can cause the floor covering to change dimension multiple times and high temperature adhesives are specifically designed to resist this.

Electro-Static Dissipative adhesives – ESD. A very bespoke adhesive, used in conjunction with ESD flooring and copper tape. The human body carries an electrical charge and just by moving around, friction can cause an imbalance of this – making you electro-statically charged. When you touch a grounded item, this charge escapes (dissipates) – and this is what an electric shock is, just like when you touch a door handle, or car etc. In the vast majority of times, this causes no real issue, but if this happens in a situation when sensitive equipment is being made, or sensitive measuring equipment is used, then these electric shocks can cause significant damage. People who work in these areas wear special conductive shoes, thus any charge generated travels down through their shoes and through the floor covering – this is when the adhesive becomes critical. The adhesive contains conductive fibres, and when applied, these interlink to provide a passage for the charge to follow until it reaches the copper strip (this is stuck to the base substrate under the floor covering). Then the copper strip carries the charge to an earthing point.

High Strength adhesives – MS, PU & Epoxy. There are applications where a much higher strength of bond or more comprehensive qualities are required. These adhesives will provide a much higher sheer resistance and would commonly be used in areas that experience a large volume of traffic – typically warehouses or facilities which use wheeled trollies or pallet trucks. The use of these types of trollies and pallet trucks exerts high dynamic loads onto a floor, the trollies are heavy and the load is spread only through the wheels onto the floor covering. Over time, and especially if they change direction frequently, these loads can destroy the flooring, the adhesive and the smoothing compound. To overcome these issues, environments like these will opt for a high strength smoothing compound in conjunction with high strength adhesives. These are able to withstand these loads exerted and maintain an integral installation.

In general, these adhesives are also likely to have much better heat, moisture and vibration resistance, meaning they are often recommended for areas where large volumes of water are present, fluctuations in temperature are significant, or where the environment may suffer vibration – perhaps from heavy plant movement.

Impact tapes – the last on our list for now. Impact tapes or double-sided tapes have become increasingly popular over the years. Most of us will remember using contact adhesive for flooring installations and let’s be honest, if you stick it with contact adhesive, it stays stuck. But contact adhesive comes with occupational health issues, the fumes can be fatal if managed incorrectly. So, impact tapes were brought in to provide an alternative, and thankfully they have continued to increase in popularity. Yes, it’s true, they don’t provide the same level of bond strength as the traditional contact adhesive, but the benefits far outweigh this.

Impact tapes, if installed and used correctly, provide a bond strength that is good enough and, most importantly, they are not harmful to use.

A vast number of main contractors do not allow contact adhesives onto their sites anymore, and an equally vast number of flooring contractors will simply not use traditional contact adhesives, this is a big step forward for occupational health in the workplace.

Impact tapes also come with the additional benefit that the packaging and removable paper are fully recyclable. And because it comes on an easily storable roll, once you have used what you need, you simply put it back in the van until its needed again, until every bit has been used – there is no wasted adhesive – 100% of the tape is used.