Henniker invited to discuss future of plasma treatment for leading composites manufacturing magazine
Surface effects – Composites In Manufacturing Magazine
Composites in Manufacturing magazine recently contacted Henniker Plasma to discuss the growing role of plasma technology within UK composites manufacturing.
The full article and link to the original publication appear below.
plasma surface treatment in composites manufacturing
*courtesy of CIM Magazine
Traditional methods to clean and activate composite surfaces can be time-consuming and imprecise – hence automated techniques are coming to the fore.
Blasting a material surface with plasma may sound like something out of James Bond – requiring at least a particle accelerator – but nothing is further from the truth. “Plasma is not even hot – it’s only slightly above ambient temperature,” says Terry Whitmore, managing director of Henniker Plasma, which supplies a range of plasma treatment devices.
The technique is used to prepare many material surfaces – including composites – for processes such as bonding or painting. There are two variants: vacuum plasma, which encases components – normally large ones – in a chamber and treats their entire surface; and atmospheric plasma, which is used to treat smaller components – or portions of a large part.
“Plasma treatment does two things,” continues Whitmore. “It cleans the surface of organic contaminants, and it activates the surface – to make it more likely to bond.”
The charged ions in the plasma first break down organic compounds such as grease. The remnants are then removed in the gas phase, leaving the surface pristine. Next, it raises the surface energy, which ‘activates’ it, and promotes the adhesion process.
Adhesion has become a more important property for composites, as it allows them to be joined to metals to form ‘hybrid’ parts – which are well established in motorsports, and becoming increasingly common in the automotive industry.
Composite surfaces are traditionally prepared for adhesion by roughening them by hand – or ‘hand sanding’ – using a piece of Emery paper. “The difficulty is to do it consistently across the whole part,” states Whitmore.
He reports seeing instructions in an aerospace lab to “lightly sand the part” – in preparation for bonding cable harnesses to the fuselage. This is open to wide interpretation, he says – meaning that an automated technique like plasma treatment ensures a more consistent surface activation.
Henniker recently used the technique to improve the mechanical properties of a natural fibre composite – by applying the principle at a microscopic scale.
*Image courtesy of CIM Magazine
Once composites have been surface-treated, they can be bonded more effectively
It was a partner in UK-Biocomp – a project within the Composites Innovation Cluster – which has developed a family of reinforcement materials based on aligned natural flax fibres. They can be supplied as tapes in widths up to 170mm, or as full-width non-crimp fabrics.
“Ordinarily, composites based on natural fibres like jute or flax have lower mechanical properties than conventional materials,” comments Whitmore.
However, their low weight and low environmental impact made them a potentially attractive material for industries such as automotive.
“Plasma treatment helped to improve adhesion between the resin and the matrix,” he adds.
Whitmore is confident that this type of value-added application is the future for plasma treatment. He says the Henniker has already looked at applying polymer films onto material surfaces.
“If we use a polymer with liquid repellent properties, we can apply it to a surface at the microscale without affecting bulk properties,” he says.
Henniker is working with several companies to apply this kind of technology – with surfaces including hydrophilic and biocompatible.