Product category:
Joining and bonding
News Release from: Smithers Rapra | Subject: Conference on plastics joining and bonding
Edited by the Manufacturingtalk Editorial
Team on 01 May 2006
Wasting time and money trying to bond
plastics?
How do you select the best method for bonding plastics - at a recent conference, delegates had a frequent complaint that joining is not considered until the product design is complete.
Bonding experts had a frequent complaint that joining is not considered until the product design is complete and materials have already been specified Sometimes clients do not know which plastics they are working with as components are purchased ready-made
This article was originally published on Manufacturingtalk on 25 Apr 2002 at 8.00am (UK)
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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 also 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.
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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.adhesivestoolkit.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.
Joint testing is a key area for research as currently most effective methods are destructive.
Joining of composite materials was also discussed at the conference, particularly the growing area of thermoplastic composites.
Dr Turvey (Lancaster University) covered the strength of bolted plates and Dr Yousefpour (NRC Canada) discussed induction welding in aerospace applications.
Dr Kellar (TWI) described a new technique for composite to metal bonding.
Joining Plastics 2006 provided an expert forum on the latest technologies and methods to help manufacturers to choose the optimal way forwards in bonding polymers.
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