APP – Mixing materials

By mixing a small percentage of pigment (typically less than 2%wt) with a “virgin” polymer, you can obtain a fully colored filament.

Before adding a colorant, it is recommended to experiment with the virgin polymer first.

1. Types of colorants

Colorants are often found in either of these shapes :

  • powder, most likely pure pigment. It can be mixed with any polymer, preferably with a polymer in powder form.
  • pellets of “masterbatch”. Those pellets consist of pigment already dispersed and highly concentrated in a base polymer. The base polymer must be the same as the rest of the batch (ex : PLA masterbatches can be added to PLA only, not ABS)

It is easier to work with pellets of masterbatch, since powders can cause feeding issues in the hopper.

2. How do I know if my colorant is compatible with my polymer ?

Pure pigment is inert : it does not melt nor react, but is simply dispersed in the polymer matrix. On paper, all pigments are compatible with all thermoplastics. This does not mean that the process is easy. Because pigments are powders, it is often preferable to choose a polymer in powder form.

A masterbatch is a pigment already pre-mixed in pellets of a base polymer. The polymer inside those pellets needs to melt. In terms of behavior and processing window, it must be compatible with the plastic you are trying to process. The rule is simple : PLA masterbatches are compatible with most grades of PLA, ABS masterbatches with most grades of ABS….

3. How much colorant should I add ?

The supplier of the colorant should indicate how much colorant should be added to a batch, in order to achieve good dispersion. Typically, only 2% (weight) of masterbatch can be added to 98%wt of virgin thermoplastic ; even less than 2% when working with pure pigment.

It is always wise to start small :

  • 0% colorant : only pure polymer, until you achieve good results and understand its behavior
  • 0.5% : you might have to adjust the settings slightly
  • 1% : you might have to adjust the settings again
  • …. up to 2%, maybe a bit more

Of course, you have the freedom to add as much colorant as you want, or even mix different colorants together.

By choosing the percentage very finely, you can also play with the transparency of the filament.

4. How do I mix the colorant and the polymer ?

The simplest method is to weigh the quantities separately :

  • about 2% of masterbatch/pigment
  • about 98% of thermoplastic (preferably in pellet form for masterbatch, or powder form with pure pigment)

Then you can mix both components together in a jar, by shaking it in all directions for 30s.

The mixing does not have to be perfect at this point. Once you start feeding the blend in the hopper, the Filament Maker will take care of the rest.

Of course, you are free to use a special device specifically designed for mixing powders and/or pellets.