Plastic materials are presented in different colors: from transparent, such as some plastic bags and water bottles, to red, blue, and yellow, like toys and other everyday objects. However, what is pigment for plastics, and how to use it?
If you have this question, this content is for you! Read on to better understand the pigment for coloring plastics. Take the opportunity to find out how Polyexcel contributes to this matter.
Understanding the pigment for plastics
Simply, pigment for plastics is an element that gives color to the product. Yet, the theme goes a little deeper than this explanation: pigments are chemical compounds divided into particles of microscopic size and that have their own color, which can dye a certain object.
It also influences thermal resistance, tinting power, and migration. As pigments do not only act on the tonality of the plastic in question, it is necessary to analyze a series of factors, such as:
- origin of the pigment;
- shade of the pigment;
- compatibility of the material to be colored with the pigment;
- food purpose of the plastic, or not, for example.
As we have seen, it is important to know the origin of the pigment to know if it is the most appropriate choice for your goal. So what are the origins of the pigment for plastics and the differentials of each?
Origin of the pigment for plastics
The pigment for plastics can come from three main sources: organic, inorganic, and synthetic. The first is created from animals or vegetables; the second is obtained from minerals, such as rocks and stones; and the latter is manufactured (or refined) and, generally, intended for industry.
Inorganic pigments require some attention because it needs to be treated before being used, so as not to cause any harm to health. An example of this is the white pigment, commonly found in soil.
Titanium dioxide (TiO2) is the main component of it, but there are also some heavy metals and constituents that, even in small amounts, are harmful to health. Two examples are lead and cadmium.
It is also important to treat the white pigment before use to neutralize the constituent bases, in case of lack of interaction between them, which are polycarbonate and aluminum (or potassium) hydroxide.
What are the main types of pigments?
Now that you know what is the pigment for plastic, it is also important to know the pigment types and their main differentials.
The masterbatch is a resin, commonly solid, used to give color to plastics. It is one of the options used in machines that can not mix, evenly, powder pigments and resins.
In addition to being a pigment for plastics, masterbatch contains some additives, which make it:
- flame retardant;
- UV protector;
- optical brightener;
- biodegrader of polymers made from petroleum;
- carrier of mechanical attributes (reinforced with fiberglass);
- carrier of the conductive properties of plastic;
- carrier of antistatic qualities.
The concentration of the masterbatch varies between 1% and 5% of the molecular weight of the processed piece. Therefore, to increase the productivity of the material, it is necessary that this resin has a high pigment content. Thus, the concentrate of the vehicle will have a minimal presence in the final product.
It is important that the masterbatch is as compatible as possible with the plastic to be colored. For example, if the material to be dyed is polypropylene, the pigment for this plastic must be of the same matter. However, if the masterbatch is made of polypropylene, it can be used to pigment both polyethylene and polypropylene resin.
The liquid master is a type of pigment for plastics that has a greater use, as it allows for more homogenization. Because of this, it is ideal for translucent colors. In addition, it has advantages such as:
- low content of applications;
- thermal stability;
- less storage space;
- greater versatility in formulations.
How to choose the best pigment for plastics?
Besides knowing what are some types of pigments for plastics, it is important to know the main factors that should be considered when choosing the product that will give color to the material.
It is necessary to take into account the tinctorial strength of the chosen pigment because the ability to dye the plastic will directly influence the appearance and maintenance of the properties of the resin.
It is necessary to know the thermal stability of the pigment since it can not change due to the temperatures to which the material will be subjected. Therefore, more than knowing if they are chemically compatible, make sure that the pigment will remain unaltered during the coloring process.
Negative reactions tend to occur more quickly at high temperatures, with large (mechanical) energy inputs, as in extrusion. Therefore, it is necessary to verify that there is no chemical incompatibility between the polymer and the colorant system.
The size of the pigment particles influences the polymer behavior when some colors are added to it. For example, opaque colorants do not affect materials that have a higher molecular weight.
Check out our publications!
Did you like to know more about pigments for plastics? So be sure to check out our other publications! On our blog, you will find much more information about the universe of polymeric compounds and related products.
If you are looking for a high-quality masterbatch, contact us and request a quotation. Count on Polyexcel quality!