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Adhesives: Building a strong bond to last long



With car makers opting for lighter materials such as polymer and aluminium (which are not suitable for welding), the demand for high-performance adhesives or bonders is on the rise. Besides, water based adhesives market is also expected to witness an upswing with growing awareness about the environment.

The automotive industry has seen changes in requirements of raw materials (used to make components) with the shift toward lightweighting. This, in turn, has impacted the technologies which help create newer and better suited products. In the automotive industry, adhesives are one such indispensable component. “Cars are built to last. Keeping individual components firmly bonded for the lifetime of the vehicle requires adhesives that will provide strong, long-lasting bonds. Adhesives are used throughout the car with different formulas needed to match each component type, from glass, rubber and electronics to chassis, powertrain and bodywork. To cover all the automotive adhesive requirements, you need support from a broad portfolio of high quality industrial bonding adhesives,” inform Barun Bharadwaj, Business Director, Transport and Metal, Henkel Adhesives Technologies India Pvt Ltd, which provides solutions for over 150 applications in a car, utilising more than 40 technologies. Henkel’s offering includes structural, instant and magnet bonding, thread locking and sealing, interior lamination solutions and more. Among them are urethane adhesives, epoxy glues, and tape and foam adhesives.

Consumer or environment-driven factors are major reasons due to which adhesives are extensively gaining a foothold in the automotive industry. They are not just required for interior applications but are also put to use in body shops. The major driver for growth of adhesives market is increase in production of passenger cars and light commercial vehicles. The automotive adhesive industry in India is directly affected by emerging trends. The dynamics are steered by factors such as increased use of plastics and lightweight materials in automotive applications and rise in usage of water based adhesives.

The reliability factor
Cars which are glued with adhesives are likely to be safer and more economical. In Europe, around 9 per cent of the total adhesive production goes into automobile manufacturing and a car today contains between 12 and 18 kg of adhesive, the reason being that glued cars have displayed a higher resistance than welded designs in crash tests.

"The automotive use of adhesives is nearly as old as the industry itself. The early wood and canvas bonding agents have been replaced by formulations capable of holding metal, glass, plastics, rubber, and a variety of fabrics to themselves, to each other and to painted surfaces. They are routinely used in structural, holding, and sealing applications. In India, PU, acrylic, hot melt elastomer based adhesive applications have been present for a while now. However, the use of structural adhesives has gained traction in the last five to seven years,” informs DS Bhattacharya, General Manager, R&D, Automotive & Automotive Aftermarket, 3M India.

Structural adhesives (SA) are chosen for a multitude of assembly operations. “They can join dissimilar materials without galvanic corrosion, are amenable to a number of different geometries, don’t concentrate stress at a few localised spots (thus increasing fatigue resistance) and don’t require refinishing steps or leave protrusions (aesthetically more pleasing),” explains Rajesh Balakrishnan, CEO, Industrial Products Division, Pidilite Industries.

Bharadwaj adds, “Structural adhesives can join dissimilar materials, while distributing stress more evenly across the joint - compared to fasteners and spot welding. Structural adhesives enable designers to specify thinner, lighter materials while meeting strength requirements.”

Structural adhesives also play an important role in the move to composite materials, which allow for significant weight reduction with comparable stiffness, compared to metals. Adhesives bond a wide array of automotive assemblies, including windshields, structure, interior components, brakes, wire harnesses and exterior trim etc.

Balakrishnan reveals, “Lighter, thinner materials can often be used without sacrificing strength. Costs can be lowered by reducing material requirements and weight through eliminating drilling, welding, screwing, and similar operations. Common examples of structural adhesives include epoxies, cyanoacrylates, and certain urethanes and acrylic adhesives.”

Meeting multiple purposes
Acrylics are structural adhesive that is widely used in automobiles. Available in both (one and two-component) formulations, acrylics bond well to many substrates, including plastics, glass, composites and stainless steel. A two-component acrylic bonds magnets in stereo speakers.

When it comes to structural bonding, OEMs primarily focus on safety and durability. The applications of sealants and adhesives are different in terms of light and heavy vehicles, since the two are differently constructed. Like heavy trucks and MHCVs, light passenger vehicles do not have a separate frame-on-frame structure. They are usually built as unibodies, which then carry the passengers. This is the area which will contain the most weight and will have to be stiffer, safer, more durable and will also have to experience the most amount of impact in the event of a crash.

Cyanoacrylates are another type widely used in the automobile industry which are solvent-free, one-component, room-temperature curing adhesives. “When pressed into a thin film between two surfaces, cyanoacrylates cure rapidly to form rigid thermoplastics with excellent adhesion to most materials. Epoxies find their way into automobiles primarily through electrical and electronic assemblies. Epoxies pot or encapsulate printed circuit board assemblies, switches and sensors,” informs Balakrishnan.

Thread lockers represent another way that adhesives can complement mechanical fasteners in an assembly. Once tightened, a threaded fastener stays in place mostly through friction. Thread lockers provide 100 per cent contact between the two parts. As the material cures, it completely fills the tiny gaps between the interfacing threads, locking the fasteners in place. Liquid gaskets are adhesives that take the place of die-cut or moulded solid gaskets made of cork, rubber and other materials. They have many automotive applications, including oil pans, oil seals, transmission pans, crankcases, axle covers, oil and air filters, fuel tanks and constant velocity joints.

Bharadwaj of Henkel Adhesives explains that there is growing demand for high-performance adhesives or bonders, since OEMs opt for lighter materials such as polymer composites and aluminium which are not suitable for welding. “These modern adhesives not only fill small gaps in various car body sections but are also used to hold together and stiffen load-bearing parts,” he added.

Spurring adhesives demand
Industrial adhesives are increasingly replacing conventional fasteners in packaging, construction and automotive industries owing to superior product characteristics. The future of adhesives in the Indian automotive industry looks promising with opportunities in the passenger cars and commercial vehicle segments. Higher disposable income and with the rise of the millennials, there is a significant rise in the auto manufacturing units in the APAC region. “Because of this, we anticipate a surge in the demand for industrial adhesives for automotive applications in developing nations like India and China where major adhesive manufacturers and auto makers have already set up base to meet the customer demand locally,” states Bhattacharya of 3M India.

Unlike the established markets in Europe and America, in India, everything boils down to the system cost. Despite the relatively lower cost of labour, for the adhesive market to gain traction – it will require some amount of cost-innovation on the automation front. “It could start with localised semi-automated dispensing units to fully-automated end to end assembly lines thereby increasing productivity, improving quality and reducing costs in the long run,” suggests Bhattacharya.

Adhesives in the Indian automotive industry are expected to grow at a CAGR of 8.4 per cent by value from 2019 to 2022. Within the adhesives in the Indian automotive industry, the polyurethane adhesives segment has the largest market. “It has better mechanical properties, and an increase in automotive production is expected to drive adhesives consumption, which would spur growth for this segment over the forecast period,” says Balakrishnan.

Lighter is more brighter
As sustainability continues to become a critical issue for the automotive sector, it motivates manufacturers to work towards significant reductions to the overall environmental impact of vehicles. This has led to a focused outlook towards light-weighting. The basic idea of light-weighting is simple. Essentially, it means the reduction of weight (actually the mass) of a product without compromising its functionality and structural integrity.

“Maximising efficiency of resources and reducing carbon dioxide emissions are among the biggest global megatrends today and one of the chief proponents of lightweighting and sustainability. Leading automakers are constantly scouting and researching for innovative lightweighting solutions including the use of high-performing, modern adhesives. Lightweighting also poses challenges challenges which now involves different substrates. To be integrated in the car body seamlessly without adding weight to the car, with traditional techniques, is a big hurdle. The biggest challenge for OEMs in India is how to strike the right balance between weight savings and costs. As sustainability becomes an increasingly important factor in the manufacturing industry, the elimination of heavy metals, reduction in energy and waste water consumption of priority,” opines Bharadwaj.
Lightweight materials have become a crucial element for product design across several industries. The automotive industry - along with aerospace – is a forerunner when it comes to the use of new lightweight materials.

Structural adhesive plays a major role in reducing the weight of the vehicle which in turn increases fuel efficiency. Pidilite has developed acrylic structural adhesive which would help in bonding plastic parts. A significant contributor towards light-weighting is the need for more fuel-efficient vehicles on the road. “At the same time with the Corporate Average Fuel Economy (CAFE) norms coming into play, which requires cars to be 30 per cent or more fuel efficient from 2022 and 10 per cent or more between 2018 and 2021, it is imperative to meet this rising demand,” opines Bhattacharya. Adhesives, when compared to the conventional methods of bonding or joining, have proven to be superior in performance while at the same time simplify the assembly process (thereby improving the manufacturing productivity) in many cases.

In future, the majority of innovations in vehicles will come from electronic systems, providing a key differentiator to car manufacturers around the world. Adhesives will surely play a role in these demanding applications.

Light-weighting propelling adhesives market
A significant contributor towards light-weighting is the need for more fuel-efficient vehicles on the road. This is a boon for plastics and composites because the benefits that these materials offer in the face of an upward trend in metal prices, are exactly what the automotive industry needs, says Bhattacharya of 3M. The key benefit includes reduced mass for improved fuel economy. An adhesive based system has the following benefits:

  • Enables installation of different components with minimal sheet metal redesign and tooling cost.
  •  Helps reduce warranty costs, removes rattling, wind noise or rust concerns and bonds and seals to prevent water intrusion.
  • Use of tape helps solve problems enabling fixes throughout vehicle processing, including near time of vehicle launch.
  •  Enables the use of dissimilar materials facilitating design flexibility.
  • Helps in weight reduction through the elimination of mechanical attachments and extra components

To cite a unique application, 3M engineers have successfully minimised the vibration concerns faced in the BIW while significantly contributing to the light-weighting to the car. “As the trend shifts from mild steel to UHSS to aluminium and other lightweight materials, joining dissimilar metals will be a challenge and that’s where 3M has a wide portfolio of products to meet the customer needs,” observes Bhattacharya.

When pressed into a thin film between two surfaces, cyanoacrylates cure rapidly to form rigid thermoplastics with excellent adhesion to most materials. Epoxies find their way into automobiles primarily through electrical and electronic assemblies.
Rajesh Balakrishnan, CEO, Industrial Products Division, Pidilite Industries

In India, PU, acrylic, hot melt elastomer based adhesive applications have been present for a while now. However, the use of structural adhesives has gained traction in the last five to seven years.
DS Bhattacharya, GM, R&D, Automotive & Automotive Aftermarket, 3M India

There is growing demand for high-performance adhesives or bonders, since OEMs opt for lighter materials such as polymer composites and aluminium which are not suitable for welding.
Barun Bharadwaj, Business Director, Transport and Metal, Henkel Adhesives Technologies India

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