Sticking together � adhesives in industry

Mon, 15 Feb 2010 00:00:00 +0200

Adhesives and sealant manufacturers are overcoming the challenges posed by environmentally stringent legislation with new formulations and products. Rachel Connolly investigates.

The ability to adapt and be innovative in the face of economic, environmental and technological pressures was the focus of discussion at an event on ‘Future Directions for Adhesives and Sealants’ on 10 December 2009, in London, UK. Hosted by the IOM3 Society of Adhesion and Adhesives (SAA) and the British Adhesives and Sealants Association (BASA), the event gave attendees an insight into the challenges confronting the industries.

Lorna Williams, Sealants Chairman for BASA, told Materials World after the event that ‘Health and hygiene and environmental restrictions, along with CE markings, may cause a barrier to genuine innovation’.

Dr Luc Peeters of Kaneka, a chemical production company based in Westerlo-Oevel, Belgium, echoed this view. He said, ‘One of the biggest challenges in the future for adhesives will be compliance with upcoming restrictions on the use of raw materials. ‘From one side it is positive that, for instance, with the introduction of REACH, chemicals have to be checked on toxicity and their effect on the environment, but on the other side it makes it very challenging for adhesive formulators’.

In order for more environmentally friendly products to be developed, new processes will have to be devised. Kaneka has recently introduced a blending technology to mix high viscosity bitumen with low viscosity solvent-free polymers, removing the use of solvents in construction applications to comply with volatile organic compounds limits.

Peeters says, ‘With more focus on the idea of “green” adhesives, the trends are likely to shift to renewable sources. “Green” adhesives still, however, need a lot of research and development to replace traditional adhesive applications. Environmental resistance, process requirements and specific application are some of the challenges faced’.

Lighter vehicles, tougher adhesives

Dr James Broughton, Principal Lecturer at the Joining Technology Research Centre at Oxford Brookes University, UK, is researching adhesively bonded composite truss structures thatwill reduce the weight of vehicles in a project named Advanced Composites Truss Structures (ACTS). The team is evaluating different adhesive routes such as co-bonded, co-cured and secondary bonding. Broughton says, ‘To date, there are limitations to the weight savings that can be gained from using space-frame structures due to an inability to match the performance of existingisotropic metallic connectors, which transmit multiple and multidirectional forces acting at the joints, known as nodes. The ACTS project focuses on all-composite nodes for truss and space-frame structures’.

The team is working with industrial partners Bentley Ltd to develop lightweight aluminium space-frames that use fibre-reinforced polymer (FRP) composite nodes. While secondary bonding is envisaged with this type of application, there are challenges with the joint design. The mixed metallic to FRP substrate joint must withstand impact loadings that do not affect the nodes’ integrity, but supports the deformation of the aluminium strut, and facilitate repair rather than complete replacement or scrappage.

Design for disassembly

In consumer electronics, legislation such as The Waste Electrical and Electronic Equipment Directive is increasingly driving the design of materials and products. With the constant demand for more compact and easy-to-recycle products, it would seem the role of mechanical fixings is fast becoming obsolete.

Norman Stockham from TWI, Great Abington, UK, says, ‘Environmental legislation will also increasingly drive the design of materials and products. Initially in terms of removing lead in solder and bromine compounds from polymers, then in terms of design for disassembly and recycling. In the latter case it would be very beneficial to have adhesives that come apart on command to allow reuse and disassembly of products. Additionally it would be advantageous to have one adhesive for all assembly joints, thereby providing lower cost processing and end of life disassembly'.

Stockham explained that the use of adhesives is expected to increase with the general need to reduce costs. This will be accelerated by adhesive science and technology developments in terms of materials dispensing, placement techniques and cure characteristics. His organisation is researching adhesives that are loaded with metallic fillers such as silver loading epoxins or carbon/polymer particulates. The aim is to improve heat removal from high power electronics. It is also looking to replace solder with carbon nanotubes suspended by adhesives.

Alternative solutions

Developments to achieve higher yielding alternative energy sources are also looking to the adhesives and sealants markets. Peeters says, ‘In solar or photovoltaic cells, different substrates will have to be adhered, the electronics will have to be sealed off, and in windmill applications, adhesives and sealants will be needed that are able to withstand abrasive conditions from the high velocity of the blades and weather conditions’. Overall, there will still be many challenging opportunities for adhesive formulators to be successful in a fast changing and environmentally focused future.

Author : Rachel Connolly
Materials World Magazine,
01 Feb 2010

Kaneka Belgium N.V. LPD Press

Sticking together � adhesives in industry