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WASTING TIME AND MONEY TRYING TO BOND PLASTICS?
05 September 2006 - Rapra Technology Limited
| Bonding experts had a frequent complaint that joining is not considered until the product design is complete and materials have been specified. Sometimes clients don't even know which plastics they are working with as components are purchased ready-made. This leads to problems in selecting adhesives or the appropriate welding technology. |
Bonding experts had a frequent complaint that joining is not considered until the product design is complete and materials have been specified. Sometimes clients don't even know which plastics they are working with as components are purchased ready-made. This leads to problems in selecting adhesives or the appropriate welding technology. Factors to be considered in the joining method selection include the joint shape, polymer type, process capability, production volume, the strength and seal required, longevity and any standards specified for the product. Different types of adhesives are required depending on the substrates to be bonded, as discussed by Ashland, Henkel Loctite and Dow Corning at the conference. Joint accessibility, application methods and cure times are further considerations in manufacturing. TWI and NPL have helped to develop an adhesive selection protocol, available online at www.adhesivetoolkit.com Plastics welding techniques include infrared, resistance, hot plate, ultrasonic, vibration, heated tool and laser welding. Advantages and limitations of each method were highlighted, with presentations from FFR Ultrasonics, Aachen University, Gentex, Branson Ultrasonics and ProLas. DSM has developed engineering plastics suitable for laser welding, while BASF and Treffert have specialised additives. Many plastics require a pretreatment step before bonding for both surface activation and to remove contaminants such as mould release agents (one cause of failure of bonding). Polypropylene, polyethylene, fluoroplastics, silicone rubber, acetal and PEEK are difficult to bond. The process selection again depends on the polymer, joint design and process capability. Techniques include plasma treatment, corona discharge and chemical primers. Dr Dahm of Loughborough University described detailed studies on fluoroplastics, concluding that sodium in liquid ammonia and sodium naphthalenide are the most effective for pretreatment.
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About: Rapra Technology Limited
Rapra Technology is Europe’s leading independent plastics and rubber consultancy. Rapra provides comprehensive consultancy, technology and information services for the polymer industry and industries using plastics and rubber in any component, product or production process.
Company Statistics: Formerly the Rubber and Plastics Research Association (RAPRA)
Established 1919
5,000 clients worldwide per annum
2,000 technical projects each year
World class Information Centre
2 sites in the UK
130 staff Working for industry. Rapra provides specialist plastics and rubber technical, information and commercial services for the polymer industry and end-user industries including the automotive, construction, electrical, medical, offshore, packaging and polyurethane sectors. Rapra has a unique mix of on-site expertise and facilities enabling the application of an integrated approach to problem solving. Its capabilities lie in the skills and experience of its people, many of whom are recognised as leading experts in their field. Clients can commission individual services,specialist consultancy or participate in multi-client research projects, funded by EC and UK government and/or industry, to progress research and development of polymer technology and applications. Testing, analysis and calibration services. Rapra’s physical testing, analytical and chemical laboratories are UKAS accredited to provide UKAS certification and test to a range of national and international standards. Numerous physical tests assess material properties such as abrasion, fatigue, impact and stress and their performance in products in particular conditions. Rapra’s analytical and chemical laboratories undertake materials identification and characterisation etc. using a range of advanced chromatographic, spectroscopic and thermal techniques. Information services. Rapra’s technical facilities are complemented by an extensive polymer Information Centre. The Polymer Library is the world’s most comprehensive plastics and rubber information database in the public domain. Available either in hardcopy, on CD-ROM or via the internet, it contains over 850,000 references which are updated every two weeks. Rapra produces a range of publications including Journals, Industrial Analysis Reports, Review Reports and global Directories, detailed in a Publications Catalogue. Technology services. Rapra’s plastics and rubber technical services can prevent, identify or solve problems and improve on or ensure continuing quality. Supported by comprehensive testing, analysis and information facilities, technologists can tackle most polymer related projects. Whilst details of specialist services are available, the following represents Rapra’s core technical expertise: Materials selection & application support
Product design & development
Manufacturing process development
Prototyping & small scale production
Engineering & tooling
Fault & failure diagnosis
Testing & Analysis
Conferences
Rapra brings together leading academics and industrialists in an annual programme of national and international conferences. Renowned for their quality coverage of polymer topics, Rapra conferences are of interest to polymer processors and industry-wide users. Technology Training Courses
Rapra runs an extensive programme of short technology-based training courses covering materials, product design, processing techniques and environmental considerations. Recognised by the Institute of Materials Continuing Professional Development scheme, they aim to enhance in-house skills, help in identifying problems and to recognise potential opportunities. |
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