There are several important characteristics to consider for plastic molded products, and color is a chief concern for many product types. Colored plastics undergo a wide range of uses every day in various applications and settings – how are these colors created and implemented in molded materials?

At EnviroTech Custom Injection Molders, we’re happy to detail any of the specific areas of your custom injection molding processes, including how we add resins and plastic colorants to any materials you require these additions for. In this two-part blog series, we’ll go over everything you need to know about colored resin in plastic injection molded products, including how they’re added, some differences in colorant, and how these factors impact plastic characteristics and the applications various materials are good for.

Plastic Resins and Coloring Basics

Within the plastic injection molding world, there are several plastic resin types utilized to create the final products you desire. Some of the most common of these products include polypropylene, acrylonitrile butadiene styrene (ABS), Acetyl, high-impact polystyrene (HIPS) and low-density polyethylene (LDPE).

These resins will be selected based on their qualities and how they fit the required application. When color needs to be added to these resins, one of several different coloring processes will be used, which we’ll detail in our next section.

Processes Utilized

Generally speaking, colorant will be added during the first step of the injection molding process. Here are the common processes used for coloring plastic resins during this process:

  • Compounding: The resins will be pre-mixed with a colored pigment, meaning they are already prepared to be molded.
  • Pigments are pre-mixed like with compounding, but are first extruded with uncolored plastic or rubber.
  • Solvent coloring: Pigment will be dissolved in a solvent, then sprayed onto uncolored pellets for molding.
  • Dry-pigment mixing: Plastic pellets are mixed in directly with powdered color for molding.

Colorant Differences

It’s important to note that not all plastic colorants are the same. Different qualities and quantities will produce varying results. Here a few colorant-related factors to be aware of:

  • Mix ratio: Generally, the ratio involved should be about 3 to 5 percent of colorant for every standard amount of base resin. So if you are using 100 pounds of base resin, 3 to 5 pounds of colorant should be used.
  • Carrier material: The material that holds the plastic together – which material is used may play a big role in the quality of the product.
  • Colorant material: This material must be compatible with the carrier material to ensure everything is held together properly.

For more on color within injection molded plastics, or to learn about any of our injection molding and product design services, speak to the staff at EnviroTech Custom Injection Molders today.