Colour contamination at injection moulding and how to eliminate that

What it is:

Colour contamination, particularly when changing from dark to clear colour, occurs when previous colour is processed alongside the next processed polymer. It is especially critical to address this problem for change-overs to unpigmented (virgin transparent) polymers.

Causes:

In a thermoplastic processing environment, it can take a considerable amount of time to complete a colour change or return material to virgin transparent polymer status. The rapidity of a colour change can be influenced by pigment type, machine and process used, and polymer viscosity. Pigments impregnate the machine when processed for a long production run, and when injection moulding machines are fitted with a hot-runner or a stack mould, colour change could become extremely challenging due to the complexity of the tool itself. Any area where there is a lack of polymer flow can increase colour contamination issues.

Solutions:

The use of a purging compound that is compatible with your polymer and viscosity will help you save time and energy when performing the colour changing process.

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