Category: Blog

As we launch our A2 fire rated epoxy adhesive we at Structural Adhesives ltd are thinking more deeply about the statutes that surround the use of products such as this and how the use is governed.

In the case of A2 rated non-substantial components of a system the rating strictly depends on the application rate of the non-substantial component. A product will have been tested at a stipulated application rate and determined to have limited combustibility. If twice the amount of product were used, the amount of fuel present to burn would be double and hence the reaction to fire would be significantly increased. Using an A2 rated non-substantial component at above the tested application rate is not compliant to regulations.

As the application rate is of paramount importance who is held responsible for ensuring the correct amount is used every time? Simply, all interested parties have some moral responsibility regarding the use of the product. The manufacturers of said A2 non-substantial components have a duty to provide all relevant information and make it clear to their customers that the product is only compliant when used at the correct application rate. Their customers, for example cladding manufacturers, are then responsible for ensuring this application rate is strictly adhered to, making sure all employees using the non-substantial component are aware. The designers and architects of the building should have thoroughly researched and asked questions about the specified products to ensure they are compliant with regulations and measures are in place to ensure that the systems continue to be manufactured accordingly.

In a perfect world this communication should be sufficient to ensure that all materials that end up on high rise buildings are safe and compliant. Unfortunately, this may not always be the case due to error or negligence. For example, a warehouse employee with no knowledge of fire regulations may apply 550 g of a product rather than 500 g thinking it will not matter. There are ways to reduce this risk such as using machines to apply the exact amount of product required, or stressing the importance of the application rate but even this is not fool proof. Also, in every industry there are those that are less than honorable and will cut corners to save time or money or sell a product that may not be entirely fit-for-purpose. Policing is required to make sure that buildings are being constructed to the letter of the law but who carries out this policing?

An enforcement body is needed to monitor regulatory compliance and to administer consequences when there is a lapse. It would be impossible for an enforcement body to monitor every item produced by a manufacturer but it would be possible to carry out surprise audits- a sort of Ofsted for the construction industry.

Morally the responsibility is shared amongst many, but if a building was randomly assessed and deemed non-compliant due to incorrect use of a A2 non-substantial component who would legally be blamed for this? Where does the accountability lie? The UK government is proposing a system of duty holders with responsibilities at certain stages of construction. More clarification of how duty holders are to be appointed is required but this proposal may go some of the way to resolving the seemingly ambiguous nature of responsibility in the construction industry.   

Increased cost is one of the barriers to launching biobased adhesives and this is something the team here at Structural Adhesives Ltd have been discussing recently. Currently, biobased polymers are slightly more expensive than their petrochemical counterparts and so the questions many manufacturers are facing is ‘will my customers be willing to pay a bit more for a product that has a lower carbon footprint?’. For some customers the answer is a quick no. Other customers, usually the ones with sustainability and environmental impact at the very heart of their company policies are more open to consideration.

We are starting to see a shift in tide, the proportion of customers falling into the second category is swiftly rising. With the UK announcing a target of net zero greenhouse gas emissions by 2050 many businesses are following suit and setting targets of their own in-line with the government legislation. Switching to more biobased products is one such way in which business could reduce their carbon emissions and meet their sustainability targets. As well as meeting internal targets it is likely that as we draw closer to 2050 the government will introduce incentives for business to reduce emissions. This could come in one of many forms such as introducing tax relief on ‘greener products’ which would make biobased products more attractive commercially. 

Converting renewable plant matter into biobased polymers for adhesives involves complex processes and has a higher production cost, this is the main reason that petrochemical based adhesives offer a slight cost saving present. However, biopolymer production is still a relatively new industry and advances in efficiency are being made rapidly, thus production cost is beginning to decrease.  Furthermore, the price of petroleum is already subject to sudden and dramatic changes which is of great disadvantage to businesses and this situation will only become worse as the supply of available fossil fuels decreases. Many are predicting that we are nearing the stage where biobased adhesives will be as economically viable as petrochemical adhesives if not more so. 

Next post in this series

A Glimpse into the future: biobased adhesives

Defects or irregularities in structural materials such as holes, sharp corners, notches and grooves disrupt the flow of stress and cause areas where the stress is considerably higher than the surrounding areas. [1] These are known as stress concentrations, stress raisers or stress risers. Such irregularities in materials may occur naturally or as a result of manufacturing procedures however, they may also be created intentionally for the purpose of using mechanical fixings such as screws and bolts to join materials together. Fatigue cracks are generally initiated at stress concentrations (such as those from mechanical fixings) when the mechanical stress on the material is not constant but changes in direction and magnitude.[2] After initiation, the fatigue crack will propagate a little with every load cycle. Once the crack has grown to a critical limit the crack will then propagate more quickly and will eventually result in complete failure.[3]

As well as forming at stress concentrations, cracks can also form in structural materials from corrosion, this is known as stress corrosion cracking. Generally mechanical fixings are made of metal or metal alloys and hence can be susceptible to corrosion and stress corrosion cracking. Several mechanisms for initiation of stress corrosion cracking have been suggested. One such mechanism is the rupture of the oxide film which leads to pitting.[4] Pitting initiates crack formation as hydrolysis reactions cause the levels of corrodent in the pits to be significantly higher than the bulk of the material and this creates a climate favourable for crack formation. Furthermore, when metals are joined by metallic mechanical fixings, galvanic corrosion can sometimes occur. Galvanic corrosion occurs when a metal is in contact with a different metal in the presence of an electrolyte.[5] Due to the difference in potential of the two metals current flows between them and consequently corrosion occurs at the metal that is considered the anode.

Joining dissimilar materials improves design flexibility and allows the specific properties of each material to be used in conjunction.[6] However, dissimilar materials expand and contract at different rates with temperature changes. If mechanical fixings are used to join dissimilar materials the clamping force on the materials and the tension in the mechanical fixing will change as the temperature changes.[7] Inappropriate clamping force can lead to breaking of the mechanical fixing or elimination of tension, also known as stress relaxation can occur.

Some manufacturers are taking precautions to limit the risks of failure occurring by the previously discussed methods. One such measure that is becoming popular is combining mechanical fixings with adhesive bonding. Using two or more joining techniques is known as hybrid bonding and there are studies to suggest that this can lead to improved fatigue, strength and stiffness.[8]^,[9] In hybrid joining, adhesives are particularly used at stress concentrations to enhance joints and reduce fatigue cracking.[10]

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[1] P G Forrest, Fatigue of metals, Pergamon Press Ltd., Oxford, 1, 1962, Chp. 1, pp 1-2

[2] G.A. Lange, in Encyclopedia of Materials: Science and Technology, ed. K.H. Jürgen Buschow, Robert W. Cahn, Merton C. Flemings, Bernhard Ilschner, Edward J. Kramer, Subhash Mahajan and Patrick Veyssière, , Elsevier, Amsterdam, 2^nd edn, 2001, pp 3265-3270,

[3] J.K. Lim, in Stress Corrosion Cracking; Woodhead publishing series in metals and surface engineering, ed. V.S. Raja and T. Shoji, Woodhead Publishing, Cambridge, 2011, pp. 485-536

[4] B.F. Brown, Stress-corrosion cracking in high strength steels and in titanium and aluminium alloys,Naval research laboratory; [for sale by the Supt. Of Docs., U.S. Govt. Print. Off.], Washington, 1972

[5] X.G. Zhang, in Uhlig’s Corrosion Handbook, e.d R. Winston Revie, John Wiley & Sons, Hobken, 3^rd edn., 2011, ch.10, pp 123-143

[6] P. Kah, R. Suoranta, J. Martikainen and C. Magnus, Rev. Adv. Mater. Sci., 2014, 36, 152-164

[7] J. Bickford, An introduction to the design and behaviour of bolted joints, Revised and Expanded, Routledge, Boca Raton, 1995

[8] F.M.De Wit and J.A. Poulis, in Advanced materials in Automotive engineering, ed. J. Rowe, Woodhead Publishging, Cambridge, 2012, ch. 12, pp 315-329

[9] R. Matsuzaki, M. Shibata and A. Todoroki, Composites part A: Applied science and manufacturing, 2008, 39 (2), 154-163

[10] I. Ashcroft and P. Briskham, in Advances in Structural Adhesive Bonding; in Woodhead Publishing series in Welding and other joining technologies, ed. D.A. Dillard, Woodhead Publishing, Cambridge, 2010, ch. 16, pp 469-515

The sea change in worldwide attitudes towards how we impact on our surrounding community and the environment and has never been more relevant.  Manufacturing and in particular, the Chemicals Industries, have their part to play redressing the issue. Structural Adhesives Ltd is committed to sustainability, the environment and always seeking better solutions and this drives our business values. With the United Nations sustainable achievement goals in mind, for the past few years and months our team have been taking measures to improve our social impact.

All manner of business areas can have an impact on the wider community. A particularly relevant area for our business is the use of energy and resources in the manufacture of our products and the impact of this on the climate. There is a carbon footprint for all manufactured items and this is inescapable. As well as the energy used in the production of a product itself, energy is used to extract, mine, grind and transport the raw materials. Structural Adhesives Ltd understands the processes involved in the manufacture and distribution of fillers and additives and chooses raw materials carefully when formulating to bear this in mind. Minimising our carbon footprint is of high priority at Structural Adhesives Ltd and we source locally where possible. As well as considering the environmental factors of our supply chain Structural Adhesives Ltd are also conscious of only working with suppliers that have first rate ethics policies.

Often the raw materials that go into adhesives are from unsustainable resources such as fossil fuels, Structural Adhesives Ltd have been developing and formulating products with reduced amounts of these raw materials and are investigating alternatives such as biobased raw materials. Also, regular readers of the blog will already be aware of our constant research into reduction of plastic packaging and waste. In addition to actively reducing the impact of our processes on the environment, the technical team at Structural Adhesives Ltd are always looking for area’s in which we can use our knowledge to have a positive impact. This includes research into areas such as renewable energy and more environmentally friendly transportation that may require the use of adhesives.

Alongside our environmental policies Structural Adhesives Ltd are starting to try to use our position to improve the community in our local area and also the wider scientific community.  Structural Adhesives Ltd is a female lead company that is very diverse and inclusive and we are seeking to improve opportunities for all and to promote STEM wherever possible. As part of the chemicals industry, we are well aware of the issues surrounding gender imbalance and diversity. Many of the industries we service including Aerospace, Engineering and Construction are heavily male dominated. Additionally, our MD has come from a teaching background and absolutely believes in the necessity of redressing the imbalance that currently exists in STEM. As a result, our MD and the all-female technical have all become Women in Construction Ambassadors and helped support and drive diversity and equality across the built environment. Furthermore, the technical team have spoken to both students and teachers at exhibitions about the vast range of career prospects in STEM particularly opportunities with small businesses like ours. Structural Adhesives Ltd have plans to participate in more outreach and community involvement programmes in the future.

The adhesives industry is far from stagnant, like in any other industry the popularity of different technologies rises and falls. Some technologies stick around for a prolonged period of time where as others are merely the ‘flavour of the month’ before fading into obscurity, finding use in only very niche applications.

From the first recorded use of adhesives in 70,000 BC, all the way up until the 18^th century, glue was typically produced for only personal use. Adhesives were made from animal products such as bone, blood, skin or casein (a milk-based protein). Adhesives made from plant matter such as tree resin or starch were also used. In 1700 the first commercial glue plant started operating, producing glue from horses’ hooves. An industry was born.

In 1841 rubber vulcanization was discovered and marked a turning point for the Adhesive industry. The beginning of synthetic adhesives. Phenolic adhesives were the first commercial synthetic adhesives and sales begun in 1902. Phenolic adhesives were a revelation and use began for many applications such as a binder for plywood. There are still many cases of phenolic adhesives being used today, however, in recent years there has been a significant movement to the use alternatives due to the hazards associated with phenol formaldehyde.

The onset of the second world war created a demand for more durable adhesives that could withstand very harsh conditions. Chemists eagerly took up the challenge and structural adhesive technologies such as epoxy and polyurethane were quickly developed. Such technologies have since found use in a wide variety of industries such as aerospace, construction and electronics, in many cases replacing mechanical fixings. These technologies have been immensely popular due to good mechanical properties, good heat resistance and resistance to chemicals and it is likely that their popularity will continue far into the future.  

It’s interesting to look back at the development of adhesive technologies over time and the factors that drove these developments. We can find some indication of the future of the adhesives industry by considering the challenges of today. With the outset of REACH the spotlight has become even more firmly set on the health and safety of products. We are already beginning to see a change in the adhesives market towards products with less hazards and it seems this will become more pronounced in the years to come. Structural Adhesives Ltd are conscious of this and have recently developed an STP adhesive for the construction industry that is significantly less hazardous than typical construction adhesives. Additionally, society is becoming more aware of the safety materials from a fire point of view and we are likely to see a shift to adhesives that are less combustible, for this reason Structural Adhesives Ltd have ongoing development projects for A1 and A2 rated adhesives. Furthermore, the ever-pressing matter of dwindling resources and the volatility of petrochemical prices promises a shift to more biobased adhesives and adhesives made from recycled materials. On the subject of recycling, the amount of material salvaged from products at the end of their lives would be much higher if the products could be easily de-bonded. We could see possibilities of a future where adhesives could be turned on or off on demand.

Next post in this series :

Adhesives for vehicles of the future

The raw materials that make up almost all classes of structural adhesives including epoxies and polyurethanes are derived from fossil fuels. Fossil fuels are not going to last forever and it’s up to us as a community to find sustainable alternatives before it’s too late. Plants present a renewable source of aromatic hydrocarbons that can be converted into a variety of chemicals so its inferable that these will be a source of adhesive raw materials in the future.

The conversion of crops such as corn and sugar cane into the necessary raw materials is the cheapest and easiest way to produce biobased adhesives. However, with a growing population there’s billions of hungry mouths to feed and the use of food stuff in applications such as these is ethically questionable. Using trees as a renewable resource rather than agriculture may be a more suitable option, but even this is not without complications. Firstly, deforestation is already a huge contributor to climate change and the level of deforestation would only increase if wood was also required for the production of petrochemical alternatives. In addition to climate change, we must consider the effect deforestation has on the prevalence of precious habitats and endangered species.

Of the trees that are already harvested for existing purposes not 100% of the material is currently utilised, there is some waste. Lignin makes up approximately a quarter to a third of the mass of vascular plants. In the paper-making process the paper is delignified as lignin weakens the paper, is coloured and yellows in air. Lignin is an unwanted by-product and almost all the lignin produced from paper making is burnt. Therefore, in lignin there is an abundance of material that can be used as a substitute for petroleum based aromatic chemicals, that would otherwise have been wasted.

For lignin based raw materials to compete commercially with petrochemical based chemicals more research and development is required. The structure of lignin is complex and hence the downstream processing is significant and energy costs are high. However, work is being carried out and the process is becoming steadily more efficient. The cost of producing aromatic fine chemicals is steadily decreasing and the cost of petrochemicals will start to increase due to lack of availability in the not too distant future. It is likely lignin-based bio adhesives will be common place before too long.

The technical team at Structural Adhesives Ltd are researching into biobased raw materials currently on the market and keeping a keen eye on developments in this sector.

Recent bouts of unseasonal weather got me thinking about the effect of atmospheric conditions on the use of adhesives. Over the past few years the UK has seen snow in April and a heatwave in October both of which would have an effect on adhesives that may have been unexpected.

The industry accepted temperature for epoxy adhesive use is above 10°C. At temperatures below this the reaction becomes slow or may not proceed at all. A general rule for many epoxies is that for every 8-10°C increase in temperature the cure rate is halved and for every 8-10°C decrease in temperature the cure rate is doubled. For example, if an adhesive has a pot life of 10 minutes and a cure time of an hour at 23°C, at 33°C the pot life would be just 5 minutes and the cure time 30 minutes. This could cause practical issues on site as a short pot-life may result in material going off before it can be used, resulting in waste. Equally low temperatures may also cause a practical issue. Taking the previous example, if the temperature was 13°C the pot-life would be 20 minutes and the cure time 2 hours, which would mean the bond would have to be left longer before it could be moved which would decrease productivity. Epoxy adhesives that cure at low temperatures are available and should be considered by those looking to use adhesives outdoors or in poorly heated warehouses.

Another climate factor that effects the use of adhesives (particularly epoxies) in the construction industry is rainfall. Generally, contamination of adhesives with water will have a detrimental effect on the cure rate and degree of cure. Therefore, most adhesives cannot be used outside whilst there is precipitation. Furthermore, some adhesives are intolerable of damp substrates, in these cases materials that are outside during wet weather must be left until completely dry before they can be bonded, which will hold up construction significantly. In extreme or prolonged cases of bad weather construction output overall decreases and this has a profound effect on the use of adhesives.

We’ve all seen the devastating images of beaches covered with rubbish, not an inch of sand or sea visible. A spotlight is being shone on waste, particularly plastic waste, and its effect on the environment. Here at Structural Adhesives Ltd we are actively researching ways in which we can reduce our plastic waste.

We have focused on considering how our adhesives are packaged in the future. It is common practice for adhesives and sealants to be packed in cartridges or buckets which are generally made of plastic. Suitable alternatives to plastic are not easy to come by for products such as ours. Any packaging we use must be impervious to the chemicals in our products, which narrows down the choices significantly. Furthermore, as many of our products are liquid, materials such as fibre-based packaging are not suitable. Some of our adhesives are already packaged in tin or steel pails, and switching over to packaging more adhesives in this way is a possibility. However, it is heavily debated whether they would be any better for the environment than plastic buckets. For example, plastic is much lighter than metal and leads to better fuel economy. Although there is no obvious replacement at present, research and development is being carried out all over the world to find more alternatives to plastic so I’m keeping my ear to the ground.

If we were to continue using plastic packaging there are still ways to reduce the impact of said packaging on the environment. One such way of doing this is using plastic packaging that is produced from recycled material. As part of the chemical industry the packaging we use must meet certain standards. A quick internet search for adhesive cartridges made from recycled plastic resulted in no relevant hits but this doesn’t mean we’ll give up. Using plastic packaging that can be easily recycled at the end of its use is another option we are investigating for decreasing plastic waste. At present the UK only recycles approximately 30% of its plastic waste. The primary challenge for recycling in the UK is sorting plastic by type so that it can be recycled effectively which can be a costly process. The colour of plastic often presents an issue for recycling as well because machines at some recycling plants cannot recognise black or dark items. Thankfully solutions are immerging for these problems and the rate of plastic recycling in the UK is set to increase in the near future.

Recycling of plastic doesn’t necessarily have to mean producing new plastic products from the old ones, plastic can be converted into oil. If the same oil could then be converted into materials to produce our adhesives, we would really be on to something. A truly circular economy.  

The United Kingdom is currently experiencing a period of great change. From Brexit to the fourth industrial revolution, businesses of all kinds are in the process of adapting for the future. Construction is facing a monumental change that may be little known to those outside the industry. In the wake of the Grenfell tower fire the government has introduced building regulations to ban the use of combustible materials above 18 m. This ban affects new high-rise buildings such as flats. Some organisations and individuals are calling for the ban to be extended further to cover buildings that are not high rise. It is possible the affect of the new regulations will be even wider reaching than first anticipated. As Assistant Chemist at Structural Adhesives Ltd I have been keeping a close eye on advancements in the governments fire safety inquiries since long before the ban was announced. I alongside the Senior Chemist have attended a number of lectures on the new construction fire regulations and what this will mean for the industry. Many construction companies that supply materials, for instance cladding or insulation, to projects such as these are now unable to do so without making substantial changes to their products. Corporations are pooling time and money into developing new materials that are able to pass the stringent fire tests to gain A1 or A2-s1d0 fire ratings and be classified as non-combustible or of limited combustibility. Not only must construction companies assess the combustibility of their products they must also evaluate how they designed to be are fixed in or onto buildings. 

The research and development team at Structural Adhesives Ltd are working tirelessly to develop A1 and A2-s1d0 rated adhesives that can be used for bonding substrates in buildings above 18 m. The vast majority of adhesives inherently contain a high level of carbon which is combustible but is also heavily involved in the bonding mechanism. 30 years’ experience at Structural Adhesives Ltd is being used alongside knowledge from degree level qualifications in chemistry to develop innovative technologies that overcome the challenge of drastically reducing the combustibility, whilst still maintaining the adhesives ability to form a durable bond. As well as being of limited combustibility any adhesives used on the exterior of high-rise buildings must be equipped to tolerate harsh weather conditions such as frost, rain, high winds and UV light. Part of the A1/A2 adhesive development process at Structural Adhesives Ltd includes rigorous testing of potential products against factors such as these, giving customers peace of mind. Structural Adhesives Ltd are also striving to ensure that the A1/A2 adhesives developed look, feel and behave similarly to those currently being used for such applications, with the aim to provide a welcome sense of continuity to the industry.

The availability of an A1 or A2 adhesive would be a breath of fresh air for architects giving greater flexibility of design for high-rise buildings. Designers would benefit from the advantages of an adhesive, such as aesthetics and bonding dissimilar substrates, whilst being assured of fire safety and regulatory compliance.

Next post in this series

Will modular housing be the next big thing for the glue industry?