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The development of a novel hexavalent chrome free environmentally sustainable pre treatment for plastic surfaces using molecular self assembly nano technology

Final Report Summary - ECOSAM (The development of a novel hexavalent chrome free environmentally sustainable pre treatment for plastic surfaces using molecular self assembly nano technology)

The ECOSAM project has worked to develop a novel surface pre-treatment method for chrome plating on a broad range of plastics. The majority of industries worldwide currently use a hexavalent chrome based pre-treatment. The major disadvantage of this is that hexavalent chromium (Cr(VI)) is classified as a carcinogenic by the International Agency for Research on Cancer (IARC) and the World Health Organization (WHO). Disposal of waste effluent is also a major issue that companies need to address; cost effective alternatives would improve the environment and reduce the risks to the health of workers in the industry.

The ECOSAM process is based on a molecular self-assembly technology (SAM) which eliminates the need for chromium (VI) chemical etching and provides a stable and secure surface suitable for subsequent chrome plating operations. With a possible ban on the use of hexavalent chromium in the future, the need to find an alternative for the chrome based pre-treatment technology could not be greater. Unfortunately, the technology is not easy to replace, though the emergence of molecular self-assembly technology used in the development of sensors could be the answer. This project has used this technology to develop an effective, environmentally friendly and economically feasible solution.

The ECOSAM process was developed and adjusted to allow the successful coating of polyamides, poly(oxmethylene) (POM), poly(vinyl chloride) PVC and poly(ethyleneterephthalate) PVC-PET. However, it was not possible to find suitable conditions by which to plate poly(cyclohexyleneterephthalate)PCt.

Injection processing parameters were optimised in order to facilitate good adherence in the metallic layer, given that, by and large this depends on the processing conditions of the polymer as well as the nature of the base plastic material.

Moreover, residual stress was minimised to achieve a good surface appearance with adjustment to the parameters. Failure to control the residual stress in the plastic samples can lead to poor adherence on plating.

The developed ECOSAM process is capable of being used to successfully plate polypropylene that on average has a cost which is almost half that of the conventional ABS used today. That is the cost of PP is 50 % less than ABS.

The advantages of the SAM technology include the elimination of carcinogenic hexavalent chromium and expensive palladium catalysts from the process, improved control and stability of the process, reduction of waste chemicals and reduction of process steps leading to a cost reduction. In addition a wider range of plastics may potentially be plated or alternatively, a surface suitable for painting or printing can be prepared.