Microtechnology Bonds Chrome to Plastic

A European Union-funded research project using nanotechnology to help attach chrome finishes to plastic materials to make auto parts look classy, while reducing vehicle weight, is being hailed as a success.

The European Commission has released a report on the benefits of the Ecosam project, which is being followed up with studies into other ways of fixing metallic finishes to plastics.

The project’s title, Ecosam, stands for “The development of a novel hexavalent chrome-free, environmentally sustainable pretreatment for plastic surfaces using molecular self-assembly    nanotechnology.”

This technology could be of increasing importance to the auto industry as it looks for ways to cut vehicle weight without compromising design quality.

Chrome always has been a key tool of auto makers seeking this goal. However, its application to plastics in the past has involved the use of hexavalent chromium in the pretreatment of the underlying polypropylene.

The chemical is classified as carcinogenic by the International Agency for Research on Cancer and the World Health Organization, and its use is restricted around the world; the EU, for instance, largely bans its use in electrical equipment.

Traditional plating also has used palladium catalysts in the process, which are expensive. The Ecosam project has tried to overcome these difficulties by using nanotechnology to avoid the use of these substances.

Because nanoparticles are so numerous on a given area, they have more surface area than standard-sized particles, making them stickier when coated onto a material.

Ecosam researchers have exploited this quality to develop a new chrome-fixing technique. They prepare the plastics with a mild oxidation using less-harmful chemicals, then deposit a layer of microscopic nanoparticles, making them ready to receive the layer of chrome.

The result eliminates the need for hexavalent chromium; lowers temperatures in the plating process; and reduces the number of manufacturing stages from five to three, cutting energy use and waste.

Indeed, the cost savings are 50% compared with traditional methods, the Commission says in its final assessment of the €1 million ($1.3 million) project.

“Commercialization of the process promises major benefits to people and the environment as well as significant cost reductions, further enhancing competitiveness of EU companies in the sector,” the report says.

“Chrome electroplating on plastics is widely used in the automotive and other industries to provide a high-quality, lustrous finish to plastic parts that may be preferable to metal ones due to their light weight, flexibility and ease of fabrication,” it says.

But conventional chrome electroplating typically involves pretreatment with hexavalent chromium, a cancer-causing substance facing a ban in the near future, “making the development of new technology more pressing than ever.”

Julio Gomez of Avanzare Innovacion Tecnologica, the Spanish company coordinating the research, tells WardsAuto his company is developing new nanotechnology applications for plating plastics with different metallic finishes. “These will also be useful for the automobile manufacturers,” he adds.

A technical briefing released by Avanzare explains that special oxidants are used to “functionalize the surface of the plastic, ensuring a good surface...without degradation.”

Applied nanoparticles produce a single layer of metallic particles over the surface of the polymer. The nanoparticles themselves are well-anchored to the plastic as a result of the pretreatment.

A technical report from the Ecosam consortium notes the process produces smaller hollows on the surface of the plastic “which act as anchorage points for the nanoparticles.” In contrast, the standard industrial process produces many “fused hollows, which are not good for adhesion of the nanoparticles.”

The report notes other benefits include improved stability and control over manufacturing and the fact that a wider range of plastics can be used for chrome-plating. “This project has used this technology to develop an effective, environmentally friendly and economically feasible solution,” it says.

Other companies involved in the research include the U.K.’s Smithers Rapra, the Netherlands’ Innoplate International and Ireland’s PR euroCHEM.