To remove the pigments of polymers, you need to use a suitable solvent or extraction technique that can dissolve or separate the pigments from the polymer matrix. Depending on the type and color of the pigments, and the type and properties of the polymers, different methods may be more or less effective. Some different ways to remove pigments from HDPE and LDPE of waste plastic polymers that have been reported in the literature are:

• Reactive removal techniques, such as peroxide oxidation, that can break down the pigments and additives in the polymer. However, this method may also damage the polymer chains and leave residues in the polymer matrix1.
• Solution processing techniques, such as using o-dichlorobenzene, that can dissolve the polymer and precipitate it out after removing the pigments. However, this method may be costly and energy-intensive, and require closed-loop solvent systems1.
• Supercritical fluid techniques, such as using carbon dioxide, that can extract the pigments and other compounds from the polymer under high pressure and temperature. However, this method may require special equipment and conditions2.
• Solvent extraction techniques, such as using hexane, that can combine pressing and chemical solvents to remove the pigments from the polymer. However, this method may have environmental and safety issues due to the use of hexane3.

Some references for more information on how to remove the pigments of polymers are:

• Report: Colour Removal from Recycled Plastics, a research report that discusses various techniques and their advantages and disadvantages for decolorizing recycled polyolefins.
• Lipid Extraction Methods from Microalgae: A Comprehensive Review, a review article that covers the principles and methods of lipid extraction from microalgae, which can also be applied to pigment extraction from polymers.
• Algae Biodiesel Engineering: Extracting Oil from Algae, a web page that explains some common methods of oil extraction from algae, which can also be applied to pigment extraction from polymers.

Learn more:

1. arvifinalreport.fi2. polymer-additives.specialchem.com3. dober.com4. arvifinalreport.fi5. polymer-additives.specialchem.com6. dober.com

Good luck

Thanks dear E.A. Gawad

I will study references that you introduced

you are welcome