Plastic fade under the sunlight (UV light) is a common issue in appliances exposed to the elements. It’s been battled for years and chemical additives have been developed to aid this issue. Image to the left represents two injection moulding plastic samples. Bottom blue part was stored away from sunlight, top sample is the same material but was subject to the sunlight for 36 months. Sample contained maximum amount of UV stabiliser.

After some experimenting, is was found that two reliable colours can be used for injection moulded parts that exposed to prolonged UV light: Black and Silver. One would think, that black colour will absorb maximum amount of sun radiation but despite this fact black is the colour that allow maximum percentage of the UV stabilizer added to the mix during injection moulding. This is due to stabilizers original colour been black as well. That allows a maximum UV protection of the plastic part, and a minimum fade over prolonged exposure to UV.

Silver on the other hand is unique. It reflects a lot of sunlight, it is immune to UV radiation to very high degree. In plastic injection moulding silver colour is achieved by adding silver powder to the mix. This generates homogeneous mix with silver additive concentration been the same throughout depth of the part. This have a nice side effect of protecting the plastic components from UV radiation even if it’s been scratched. The draw back of this solution are the flow marks on the plastic component surface. Caused by the flow of the melted plastic, flow marks are visible to an observer and have negative impact on the appearance on the component.

An easy solution to flow marks in injection moulded part is to apply layer of the matching colour paint. Often painting plastic components viewed as non desirable due to low scratch resistance of the paint. But with colour matching, even if paint is scratched observer do not see the mark due to underlying substructure blending in with top layer colour.

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