TWI provides a number of services relating to the welding of polymers, including training, equipment and expert advice.
We have built up an extensive knowledge base covering the more widely used processes for welding plastics, including thermoplastic elastomers, and pioneered the development of innovative techniques that provide improved quality and greater productivity.
We can offer impartial advice on the most appropriate joining technique for any application or thermoplastic material.
Expertise and equipment
TWI's expertise and equipment is made available to Members in the following ways:
- Welding equipment and expertise for all processes
- Non-destructive and destructive testing for plastics welds, including a specialised whole-pipe tensile rupture test rig
- Facilities for testing polymers in extreme environments
- Process review and optimisation
- Failure investigation
- Personnel who combine many years' experience with cross-industry-sector knowledge and contacts
- Plastics welder training via our industry training and certification programme
- Plastics industry updates
Applications that involve welding plastics range from assembly for mass-produced domestic appliances to fabrication welding of pipelines and from high-speed welding of films and fabrics to precision welding of medical devices. Methods are also diverse, extending from well-established processes such as ultrasonic or hot gas welding to novel techniques employing laser or infrared energy.
Technology challenges
Current technology challenges being focused on by TWI include:
- Welding of dissimilar materials – dissimilar plastics and plastics to other material
- Three-dimensional welds
- Welding high-temperature polymers
- Lifetime prediction of welds
- Soft seams for fabrics
- Managing weld morphology
Recent projects
Recent projects undertaken include:
- Altex (PDF)– Textile joining by laser welding, for waterproof garment and bed manufacture
- Leapfrog – Automated laser welding of natural to synthetic textiles
- Vascutek (PDF) – Replacement of blood vessels with textile vessels
- PolyTank– Development of phased array ultrasonic non-destructive examination (NDE) for joints in polyethylene sheet
- Powerweave– Development of textiles for electrical energy generation and storage – from making fibre forms of photovoltaic energy generation and energy storage through to the fabrication and evaluation of lengths of textile that can be used as a standalone power supply
- PolyTest – Development of phased array ultrasonic NDE for joints in plastic pipes
- Improving the quality and reliability of landfill storage by the training and certification of on-site welding personnel
- A review of welding procedures and design guidelines for moulded plastic components to guard against failure in service, resulting in the development of a three-day training course and the establishment of a new specialist BSI sub-committee
- Forced cooling of butt fusion welds in polyethylene
- Friction stir welding of plastics
The diversity of these projects highlights the range of equipment and adaptability of the personnel within the polymer group.
Standards activities
TWI is represented on the following committees:
- BSI PRI/80 (Welding Thermoplastics)
- CEN TC249/WG16 (Thermoplastics Welding)
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- Standards published:
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- EN 12814-5:2000 (Macroscopic examination)
- EN 13067:2012 (Qualification testing of welders)
- EN 14728:2005 (Classification of imperfections)
- EN 16296:2012 (Quality levels for imperfections)
- Standards under development:
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- Plastics welding supervisor – tasks, responsibilities, knowledge, skills and competencies
- Specification of welding procedures for thermoplastic materials
- AWS G1A (Hot Gas and Extrusion Welding)
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- Standards published:
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- AWS G1.6:2006 (Qualification of plastics welding inspectors)
- AWS G1.10:2001 (Evaluation of hot gas, extrusion and heated tool butt welds)
- AWS B2F (Plastics Welding Qualification)
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- Standard published:
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- AWS B2.4:2012 (Procedure and performance qualification for thermoplastics)
- ASTM F17 (Plastic Piping Systems)
- EWF WG A2.4 (Certification of Plastics Welders)
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- Standard published:
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- EWF 581-01 (Requirements for the education, examination and certification of plastics welders)
- ASME
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- Codes published:
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- BPV III WG HDPE Materials
- BPV IX SG Plastic Fusing
- SWG HDPE Stakeholders
- Code under development:
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- Rules for construction of Class 3 buried polyethylene piping