Welcome to the rebirth of a good idea: injection moulded plastic parts in colour to replace paint. This is a process in which colour masterbatch is added to natural (uncoloured) pellets, or a pre-coloured polymer formulation is used. The resulting parts offer a level of colour brilliance comparable to painted plastic parts, including metallic looks, and they can be manufactured at a significantly lower cost and without the volatile organic compounds (VOCs) emitted during painting.
With MIC, parts exit the mould ready for assembly. The process is more flexible than painting, enabling speedier colour changes. And scratches are less noticeable, because the “inside” colour and the “outside” colour are the same. With added UV resistance within masterbatches and pre-coloured materials, MIC plastic parts also retain brilliant colour through years of weather and sunlight.
Car manufacturers have been interested in replacing painted plastic parts with MIC parts for years. In fact, one of the first MIC front bumper fascias appeared on an early Saturn model vehicle using DuPont Surlyn material in the 1990s.
With MIC, the entire painting and curing line becomes unnecessary. Potential cost savings exceed 30%, and MIC ups the sustainability factor by reducing energy and water consumption.
So why are we seeing momentum only recently? Automotive suppliers and OEMs initially resisted the change and were not financially motivated to deactivate paint lines that were already in place. Also, incorporating a masterbatch requires a small investment in feeding equipment, and it demands employee training, which furthered the resistance.
Today, the industry has reached a point in which no OEM can look past the savings available with MIC. After over 100 years of developing only internal combustion engines, carmakers now must also invest in developing electric vehicles, autonomous travel, and even MaaS (Mobility as a Service) platforms. Implementing MIC may be their best shot at boosting available investment capital to cover these additional needs.
To gain the full benefits, there are a few challenges to overcome in implementing MIC, including:
• Matching the colour and effect of paint as closely as possible
• Maintaining the effect after multiple conversion processes
• Moulding parts without unacceptable appearance defects
• Providing UV stability
Developing a formulation filled with, for example, soft metallic flake, and maintaining its aesthetic and mechanical properties requires a degree of experience. Material suppliers must also understand how the orientation of special effect pigments can alter visible flow lines.
OEMs and suppliers who are successful at incorporating MIC plan for it early in the design cycle, before a mould has been made because another critical element for success in MIC is the correct design (gating, weld lines) of the part and mould. Too often in the past, refusal to invest in a new mould has spelt disaster.
These manufacturers are developing new technical requirements for MIC parts, recognising that they are different than painted parts. More work is being done to align an OEM’s purchasing, design and engineering departments on the benefits and challenges of MIC. These separate departments need to collaborate more closely with each other, and with their material suppliers, to fully realise the savings available with MIC.