Nanoscale Metal Coatings for Plastic Components
Together with the two Canadian companies Morph Technologies Inc. and Integran Technologies Inc. as well as PowerMetal Technologies, USA, DuPont Engineering Polymers has developed a new nanoscale metal/plastic hybrid technology. Using the MetaFuse process, a high-strength metal skin is deposited onto injection molded plastic parts. The average grain size of the nanocrystalline metals is about 20nm and is thus approximately 1000 times smaller than that of conventional metals. This permits production of high-strength plastic/metal hybrids with very thin coatings with a typical thickness of 25 to 200µm. In many practical applications, selective deposition of the nanoscale metal coating suffices to achieve the desired properties and coating of the entire part is not necessary.
Under bending and torsional loads, the greatest tensile and compressive stresses occur within the skin of the component. It is for this reason that the exceptional mechanical characteristics of the nanoscale metal coatings are most effective. This was confirmed by means of tests performed on tensile bars injection molded from PA66 with 25 wt.-% glass fiber reinforcement and coated with a 100-µm-thick nanocrystalline nickel-iron alloy. The flexural modulus and impact strength were two to four times higher than that of the uncoated plastic.
The nanometal/plastic hybrids also retain their very good mechanical properties at temperatures where the performance capabilities of purely plastic parts already start to decline significantly. For instance, the stiffness of test specimens with the nanometal coatings was still 70 to 80% of the initial room temperature value even after exceeding the glass-transition temperature. This means that MetaFuse will permit the use of plastics in high-load applications at elevated temperatures and raise the continuous service temperature of plastics by 50 to 75°C.
In addition the strength and stiffness, nanometal/plastic hybrids offer further benefits such as wear resistance, creep resistance, electrical conductivity, chemical resistance, electromagnetic screening, reduced permeability for gases and liquids as well as UV and hydrolysis resistance. This will open up a wide range of applications in automotive, consumer electronics, sporting goods and other areas.
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