How The Plastic Properties Are Affected By The Colorant

Date: Mar 11 2020 | By:LC Rapid
Tag:Plastic Injection Molding, Materials,

There are some synthetic polymers, they have their own unique properties. Lots of them are more resistant to impact than the other one, many are more resistant to UV rays, and some bend more than breaks. Anyone who starts a custom plastic injection project should have a preliminary discussion with the injection molder about material selection for purpose of selecting the material that best suits the functional properties of the part.

One aspect of polymer properties is not always given due consideration, and it is the addition of colorants. There's a whole set of scientific knowledge about how adding color to plastic effect affects its behavior. In this paper, the influence of colorants on plastics is studied in an advanced way, and it is surprising.



When developing some colorant packages for a lot of polymer, it is significant to think about the chemical properties of polymers and the chemical properties of colorants. Some compounds in the colorant break down the chemical composition of the polymer, weakening its original properties, such as impact resistance. The high heat used in injection molding also affects the degree of influence of the colorant on the polymer. The colorant itself must be able to withstand high processing temperatures. Moreover, the effect of one colorant on one polymer may be different from that of another based on temperature, despite its chemical compatibility. It’s worth noting that the interaction between polymers and colorants is affected by other additives. As an example, when a flame retardant is added to a PC, polycarbonate, otherwise unaffected by the colorant, may react differently to it.

Coloring dose

The properties of the polymer are also preserved as a function of the coloring dose in which it is added. The colorant is a contaminant, the more colorant you add, the greater the negative impact on plastic. Adding 2% of the colorant is usually harmless as long as the above compatibility issues do not work. As this level of colorants increases, the more likely it is that the plastic properties will change.

Different colors, different properties

"Molecular weight" and "crystallinity" are factors in the equation, but in layman's words, the bottom line is that different colors can affect polymers in different ways. AS an example, transparent colors can be made of dyes, which may have less impact on polymer structures than pigments used in opaque colors. Pigments are made of particles whose size affects the performance of the material. Forming the same part in different colors can actually lead to different part sizes, which is significant if very strict tolerances are important.


Colorant merge method

There’re some different plastics coloring methods, including masterbatches, composites, surface coatings, and dry blends. Each of them has its own unique properties and varies in color consistency, costs, and other factors. The coloring method used can affect the mechanical properties of the plastic. As an example, in the master material method, particles of natural color are mixed with "mother mass" particles with high pigment content. Since most polymers usually do not mix good with other polymers, must be taken carefully to make sure the material compatibility, otherwise the mixture may cause problems.

Totally, the effect of colorants on precision plastic injection molding is more complex than we think, and it is not usually a top priority when planning injection molding projects. But it’s significant and should be addressed at the material selection stage.

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