Freight transport, passenger rolling stock and rail infrastructure are all in focus as manufacturers search for solutions that can help them to maintain their competitive edge and secure long-term growth, within the context of sustainable mobility in a low-carbon Europe.
Improvements to production processes, weight savings, low maintenance costs, innovative designs and compliance to safety and environmental standards are all key priorities. Huntsman Advanced Materials is finding that its products have an increasingly important role to play in this market shift, when used in composite bonding applications.
This is reflected in the land transport sector’s current 25% share of the European composites market, with the rail industry’s use of composites seeming set to continue its growth at an average rate of 10.5% per annum.
Composites offer a combination of properties – such as high strength, low weight, excellent heat, moisture, corrosion and impact resistance – that are not present in any individual components. Compared with their traditional metal counterparts, composite materials provide lightweight solutions and are now utilised more and more in rail manufacture.
Solutions, such as Araldite FST 40004 / 40005 - a novel resin system that is also well suited for use with its different families of adhesives - illustrate how Huntsman is working to deliver performance and process enhancements to a variety of rail applications.
Offering excellent FST and weight saving properties, Huntsman says Araldite FST 40004 / 40005 allows the production of parts with comparable quality to RTM, infusion and pultrusion processes. Due to its excellent mechanical performance, small parts can be made quickly, large parts can be produced at low temperature injection and a very low exotherm enables the production of high thickness parts.
Huntsman is also modifying its high-performance processing solution for aerospace composites interiors – Araldite FST 40002 / 40003 – to make it suitable for structural and non-structural part production, as a cost effective replacement for low cost phenolic resins.
The advantages of using adhesives with composites are well documented and numerous. As well as allowing the assembly of dissimilar materials and higher weight loads, adhesives improve the uniform distribution of strain and stresses across bonded joints. They maintain material strength and integrity as there are no holes, rivets or fastening elements, facilitating greater design and aesthetic possibilities which are also lighter in weight than mechanical fixings.
For vehicle operation, lighter weight results in improved performance and lower energy consumption - increasingly important criteria for many rail car designs and high-speed railway projects in particular.
Fire safety standards continue to harmonise across the rail industry’s international borders, bringing with them more demanding performance levels for all. Huntsman comments that Araldite 2033 is a new two component gap-filling epoxy with flame retardant properties that has surpassed the HL3 hazard level of fire safety testing under the rigorous unified pan-European EN 45545-2 testing regime.
Classified in the combined R22 Interior and R23 Exterior category, it meets all requirements to achieve the HL3 level, with test parameters that include for instance, evaluation of spread of flame, ignitability, or smoke and toxic gas emissions.
For structural parts such as roofs, doors, floors and semi-structural products such as floor coverings, seat to floor attachments, door frames and hinges, Araldite AW 4859 / HW 4859 is an example of an epoxy adhesive which offers the advantages of ease of application, high strength and shock resistance on multi-material assemblies.
In Italy for example, this adhesive has been used to bond a simple overlap joint aluminium seat fixture in a high-speed train. In this instance, Araldite AW 4859 / HW 4859 was selected for its excellent dynamic load and fatigue resistance.
Araldite AW 4859 / HW 4859 also offers excellent chemical resistance and thermal stability, even in temperatures as high as 140°C, making it particularly beneficial for exterior applications on carriages, where it helps to reduce structural weight and improves fatigue resistance on metal assemblies.
Araldite 2013 is another example of an epoxy adhesive chosen for its superior properties. Offering excellent adhesion, high durability in ambient weather conditions, fatigue resistance and toughness, this adhesive has been used to bond GRP driver cabins. Providing greater design freedom, it supports 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.
For trackside applications such as signal light boxes, traffic control boxes and rail joint construction and repairs, where electrical insulation, very good weathering, thermal resistance and flame retardancy are vital, Huntsman offers a number of products in its epoxy and methacrylate-based adhesives ranges.
Examples include Norwegian manufacturers which attached train detection sensors on the track with Araldite adhesives, Swedish businesses which utilised them to assemble rail shifters and rail companies in the UK, Spain, Romania which used Araldite to bond rail joint assemblies.
Araldite AV 5308 / HV 5309-1 and Araldite AW 106 / HV 997 are two more examples of adhesives from Huntsman which feature on British Rail's Register of Approved Adhesives and are found in application in the UK on fishplate rail line butt joint assemblies.
Laurent Pourcheron, marketing manager adhesives for Huntsman Advanced Materials, comments; “The success of all these projects shows how adhesive bonding continues to grow as the preferred method of assembly for many high performance rail applications. Given the highly valued combination of the superior properties and processing efficiencies they offer, it’s clear to see why both adhesives and composites are rapidly becoming the materials of choice for many rail manufacturers.”