Huntsman steering adhesives toward rail interiors

Citing an adhesive's ability to save weight, combined with the European Commission's €1 billion Shift2Rail initiative, Huntsman says now is the time to emphasize the utility of a variety of adhesive types in rail applications.

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Huntsman Advanced Material (The Woodlands, Texas, USA and Basel, Switzerland) reported on May 15 that its Araldite adhesives are being positioned to serve the European rail interiors market for the next several years.

Laurent Pourcheron, marketing manager for adhesives at Huntsman Advanced Materials, says rail is among the most efficient and climate-friendly forms of transport, yet currently it only carries approximately 10 percent of European cargo and 6 percent of passengers each year. 

The need to develop rail as a key mode of transportation is reflected in the establishment of the European Commission’s Shift2Rail initiative. This new public-private partnership has been set up to invest just less than €1 billion in research and innovation to support better rail services and encourage more passengers and freight onto Europe’s railways.

Among the key areas identified for investment, the Shift2Rail initiative highlights production process improvements, new designs, weight savings, compliance to stringent safety and environmental standards and low maintenance costs as being vital to success.

Adhesive bonding, Pourcheron notes, enables the most efficient method of assembly, optimizing manufacturing methods with easy handling and simplified assembly procedures, which speed up cycle times and reduce costs in parts production.

Adhesives, he says, form a continuous bond, providing more uniform stress distribution within a leak proof solution that is also said to be less prone to corrosion and therefore well placed to provide a longer service life under load in a range of applications. A bonded structure is often cited as a safer structure as the occurrence of fatigue cracks are reduced through the uniform distribution of stress concentration. Bond lines are also frequently described as crack formation stoppers.

As there are no holes, rivets or fastening elements to weaken structures, adhesives also facilitate the integrity and strength of materials, giving a smooth appearance to designs with improved aesthetics on finished parts and greater design flexibility.

For complex assemblies, such as composite sandwich structures, adhesives tend to be the only fastening technique that can successfully bond them together. They can also join dissimilar materials together and compensate for differences in the coefficients of thermal expansion, helping to reduce ongoing maintenance costs.

Huntsman emphasizes the effectiveness of epoxy, polyurethane, methacrylate and phenolic-base-based adhesive systems:

  • Epoxy adhesives offer excellent adhesion to metals and thermoset composites, providing excellent durability, chemical and temperature resistance (up to 190°C/374°F) with low shrinkage
  • Polyurethanes are more suitable for bonding thermoplastics, offering good long-term durability, strength and flexibility
  • Methacrylates offer good adhesion on metals, thermoset composites and most thermoplastics, providing both rigid and flexible mechanical properties and minimum surface preparation requirements
  • Phenolics are well suited to metals and friction materials. They offer outstanding temperature and chemical resistance, ease of application and a virtually infinite open time once applied.

In Italy, Huntsman's AW 4859/HW 4859 adhesive is being used to bond a simple overlap joint aluminium seat fixture within a high-speed train. Araldite 2013 is used to bond GRP driver cabins because it offers excellent adhesion, high durability in ambient weather conditions, fatigue resistance and toughness. It also is said to enable greater design freedom, supporting the structural strength and integrity of the more complex and ergonomic shapes of driver cabins now seen on the latest generation of high-speed trains.

In Germany, another epoxy adhesive from Huntsman, Araldite 2015 is replacing the welding process used to assemble aluminium substrates on the driver compartments of regional train units. As a result of weld distortions, this process was found to be time intensive and costly, often requiring the need for re-working and further sealing techniques on the compartment door leaves. By contrast, adhesive bonding \maximises process and performance benefits by minimising the steps in production, reducing costs and improving the design ergonomics whilst helping to extend the compartment’s service life, thanks to its superior strength.

Because it forms joints with elastomeric type behaviour that are water tight and durable, Araldite 2015 is also used in Italy to bond an antivibration damper to a train body. In addition, in Germany and Austria it is used to bond aluminium driver door profiles on trams and trains.

The methacrylate adhesives, such as Araldite 2021, tend to be used for bonding metal hinges to GRP interior panels and on a range of interior furnishings such as fold tables, luggage racks and ceiling liners, where their fast curing properties provide significant time saving advantages.

In Spain and Sweden, manufacturers are benefitting from this adhesive’s s rapid assembly and peel resistance on a range of rolling stock interior components, bonding doors to lockers, reinforcing train roofs and constructing WC modules.