Despite the fairly advanced technologies used to produce them, adhesives are by no way a recent invention. In fact, evidence of natural adhesives has been found in Mesopotamia, dated to over 200,000 years ago during the Middle Pleistocene era, wherein the bark of the birch tree was used to join flakes of stones. With time and the discovery of synthetic raw materials, a range of artificial adhesives for specific purposes have been designed.
Among the various types of adhesives, those made from silicone, epoxy, and acrylic continue to be the most popular across industries. Acrylic adhesives are made from acrylic, which is also known as poly (methyl methacrylate). Due to their ability to join a wide variety of metals and plastics, often without the need for a primer, and offer immense strength to the bonded parts, they are extensively used in structural applications.
In this capacity, their key applications are building & construction, wherein they are used for ceramic tiles, concrete, flooring underlayment, countertop lamination, drywall lamination, HVAC fixation, cement, pre-finished panels, roofing, resilient flooring, and wall covering. Their usage in buildings over traditional fasteners allows contractors to increase the aesthetic value of the premises and owners to lower their expenses.
Just like acrylic adhesives, those made from epoxy, a class of reactive polymers and prepolymers, offer appreciable strength to metals, glass, ceramics, and a range of other substrates. Additionally, after curing, they experience less shrinkage, which refers to the process of the reduction in their volume and a corresponding increase in density. Moreover, due to their strongly cross-linked structure, they are suitable for rigid surfaces, such as metals, glass, and ceramics, rather than flexible substrates, such as rubber pads, low-density plastic objects, hoses, and piping.
As a result, they witness a high-volume consumption in the building & construction and automotive & transportation industries. In the latter, they are used owing to their resistance to weather and heat, which have become almost imperative for quality and durable automobiles. Moreover, by replacing welds, nuts, and bolts, the vehicle weight can be reduced, which, ultimately, lowers GHG emissions. Further, certain flexible epoxy adhesives allow automakers to decrease noise and vibrations inside the car, thereby making the journey more enjoyable.
Solvent-based adhesives have enjoyed wide popularity in adhesive tapes, packaging, automobiles, graphics, medical sector, and a host of other applications till now as they offer strong resistance to environmental factors, which leads to long-lasting bonds. They are ideal for both non-porous and porous substances, and once the liquid dries, only the actual bonding agent is left on the surface. Additionally, they are easier to apply than water-based variants, which saves application time and effort and, ultimately, cost.
Their key advantages are stability under high temperatures and on exposure to several types of harsh chemicals and water, and fast curing and tact. However, they contain significant amounts of volatile organic compounds, which make them a risk for the environment, animals, and humans. In high concentrations, VOCs can cause irritation in the nose, throat, and eyes, allergic skin reactions, headaches, dyspnea (shortness of breath), nausea, dizziness, and fatigue. Further, prolonged exposure to extremely high amounts of these substances can cause cancer, which is the second-leading cause of death by a chronic disease.
Hence, a host of regulatory agencies, such as the EPA, International Marine Organization, Environmental Protection Department of the Government of Hong Kong, and European Commission, have either completely banned VOCs or strictly regulated their emission limits. This has led to a spurt in the demand for water-based adhesives of late, as their solvent is simply water! Their key advantage is that they are no- or low-VOC adhesives, which is why they are harmless to people and the environment.
The major application of low-VOC adhesives is in the packaging sector, because they offer an eco-friendly option for bonding cases, cartons, and corrugated boxes. Additionally, the biggest reason for their usage in this sector is their compatibility with food packaging. Due to the absence of harmful solvents, such low-VOC adhesives are approved by the FDA for food-grade applications.
Moreover, while most of the adhesives saw a decline in their demand during the pandemic, food-grade packaging adhesives witnessed an unprecedented rise. With people not able to go out, they started ordering packaged food, either processed in factories or cooked in commercial kitchens. The boom in online food orders drove the demand for food-grade packaging massively and, in turn, for water-based adhesives.
Due to the wide applications of bonding agents, from a simple cello tape and furniture to automobiles and even electronics, adhesive consumption is growing continuously. Currently, the Asian region, led by China, India, and Japan, is the largest consumer of such chemicals, as it is home to highly productive construction, automotive, and electronics industries. All this can be, in turn, credited to its huge population, which is increasingly moving to cities.
This is driving the construction of all kinds of infrastructure, as well as people’s disposable income, which is enabling them to purchase automobiles, mobile phones, laptops, houses, and packaged food. Another industry that continues to boom in the APAC region is healthcare and its allied sectors, such as medical devices, cosmetics, and personal care. This is leading to the rising consumption of non-woven adhesives for a range of baby care, adult incontinence, and feminine hygiene products.
Talking of core medical applications, adhesives are required for internal tissue sealing during surgeries, external wound care, dentures, and a range of medical equipment, such as needles, syringes, IV tubing, and even complete imaging systems, including X-ray and MRI scanners. Therefore, while adhesive companies had to deal with a reduced product demand from the automotive, electronics, and construction sectors during the pandemic, they found refuge in the healthcare industry, where the consumption soared in 2020 for the production of face masks, hand gloves, surgical gowns, and several types of PPE.
Since the lifting of the lockdowns and resumption of industrial and construction activities, companies that manufacture or sell adhesives have started to come out of the period of stagnation. The long-pending construction projects are now being executed even more rapidly than originally, which is now driving the consumption of structural adhesives.
Similarly, the resumption of automotive production in an era plagued by carbon emissions is leading to the rising demand for adhesives that can help replace mechanical fasteners, such as nuts, bolts, and welds. Moreover, carbon fiber is being experimented upon to manufacture lightweight automobiles, which further necessitates adhesives over nuts and bolts. Hence, as industrial production and construction activities soar further, the demand for all kinds of adhesives, especially those that are free of VOCs, is bound to increase in the coming time.