Many virgin plastic resins are natural, transparent, or in a milky-white state. Sometimes, a plastic parts’ aesthetics and final appearance play a significant role in its application and require coloring.

Painting plastics is expensive, may not last, or may not achieve the customer’s desired aesthetic. For those reasons, injection-molded plastic parts typically use colorants to give a wider range of aesthetic options.

Incorporating the colorant into the injection molding process can be done in four ways: Compounding, masterbatching, solvent coloring, and dry pigment mixing.

  • Compounding – In this process, the colored pigment is already in the plastic resin from the moment of its creation. This process uses mixing machines to blend specific portions into large or small batches through the mixers that can be delivered to the injection molding machine.
  • Masterbatching – A masterbatch is a collection of highly pigmented plastic pellets that can’t undergo injection molding as-is, so you must mix it well with uncolored resin. The colorant pellets combine with the base plastic pellets, creating the overall desired color.
  • Solvent coloring – In this process, colored pigment oil mixes with a solvent material, and the mixture is sprayed all over the uncolored or neutral plastic pellets. Because the solvent thins the pigment, you can color more plastic with less dye making it more economical on cost and materials.
  • Dry Pigment Mixing – Like solvent coloring, dry pigment mixing uses a base color pigment to coat the outside of uncolored plastic pellets. Instead of liquid, it uses powder which requires drying before the coating phases.

Indeed, color boosts a product’s attractiveness and saleability. Here are some helpful tips to consider when choosing plastic resin colorants.

Consider Appearance-related Issues

Hand-mixing colorant and base resin produce the same results as machine-mixing. While melting and injecting will handle much of the mixing of color and base, finding a provider with the knowledge to make the combination properly and know what it should contain is still crucial.

Be Process-oriented For Better Coloring Results

Injection molding starts with pellets of the solidified base resin. The base resin is placed into a hopper, heated, and fed into the mold. Plastic colorant should be introduced in a “salt and pepper” mixture of lighter base resin bits and darker color additives at the beginning of the process. This procedure helps to avoid swirling, uneven color or tone, or inaccurate color matching of the finished parts since this process enables the best mixing of colorant with the base resin.

Differentiate Colorants And Mixture Ratio

Similar to base resins, not all colorants are made equal. Various color concentrates, and additives can yield different outcomes when combined with different types of plastic resins, resulting in an unsatisfactory appearance. This is why it is essential to have the proper knowledge or to seek expert advice when differentiating colorants and ensuring the right mixture ratio.

There are specific combination ratios to consider when mixing the elements. Typically, 3 to 5 pounds of colorant per 100 pounds of the base resin is the primary ratio, but this may vary depending on the type of colorant used, the carrier that binds colors, and the base resin. Consulting with an experienced injection molding service provider is advisable to ensure proper colorant differentiation and mixture ratio.

Determine Resin Compatibility

Compatibility between resins, colorants, and carriers is essential. Resins are routinely molecularly modified for specific performance qualities. Adding a foreign element to a resin mix, which are the colorant and carrier in injection molding, might impair the performance, especially if the materials react negatively.

Incompatible colorants can affect a resin’s temperature tolerances and modify a resin’s flexibility, hardness, and moisture or humidity reaction. Incompatibility can make your final part flake or crack. It is essential to carefully prepare formulas and ensure that the colorant and resin are compatible in order to attain the desired results.

Review Certified Or Graded Use

As the components of a colorant-resin mixture can be a medical grade or food grade, it is essential to know what goes into the mix. Certifications for quality, safety, and “green” practices are also factors to consider.

In addition to the colorant, carriers can comprise between 1% and 3% of the final product. The attributes given by this quantity of material can determine whether or not a product receives safety certification. It is also essential to find a provider who can assist you in considering the medical- or food-grade qualities of the colorant mixture and conduct research to ensure that your product will continue to adhere to these standards.

Color Your Plastic Parts With D&M Plastics

With color-mixing and injection molding, creating exactly the look you want for your injection-molded parts has never been easier!

D&M Plastics has 50 years of experience in manufacturing high-precision injection-molded components. We match our client’s requirements for the desired tone, shade, and performance of their plastic products. We use high-quality injection molding colorants to produce aesthetic and quality colored plastics for any commercial, medical, or food-grade application.

Contact us to request a quote or inquire more about our capabilities and services.