What is "coinjection"

n. injection of multiple substances together

Coinjection is a polymer injection technology in which different polymers are injected into the same mold.

Reasons for using coinjection are:

1. reducing cost by using a cheaper fill material as the non-visible core of a product
2. combining desired properties of polymers, such as colour (the differently colored parts in car tail lights), feel (soft-touch toothbrush) or mechanical properties.
3. alter the density and elasticity of the final project making it either float in water or shock absorbent.

Despite these advantages, coinjection requires machinery that is more expensive and difficult to maintain than standard single injection machines. The coinjection process also has difficulty with complex geometric shapes.