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Colour Standards for Plastic – Plastic Colorants and Colour Concentrates

Author: Rahul Gupta
by Rahul Gupta
Posted: May 21, 2021

What are plastic Colorants?

We see plastic items, such as bottles, stationery, and food containers, every day around us. But these plastic items were not originally colored. Plastic (resin) is almost colorless (milky-white). Colorants, such as pigments, are used to create a wide range of colors in plastic items.

External coloring and internal coloring are the two main types of coloring. External coloring is a technique for coloring plastics' outer surfaces. Printing, coating, and plating are all examples of external coloring.

Internal coloring, on the other hand, is a process that involves kneading colorants into plastics. Since colourants are combined with plastics, products are coloured uniformly up to the inside, unlike external colouring where colours are present only on the outside.

Plastic Colorants are a common term for colourants used for internal colouring.

Colour Standards for Plastic

It is no secret, in particular in relation to plastics, that the standardisation of the colour process would increase production operations. The final product must be design-corresponding from batch to batch (or plant to plant). The only way to keep your plastics' colour quality under check is to test it accurately.

Since plastic colourants may affect the material's consistency, colour is an important feature of plastic standards. Colour charts are used by plastic manufacturers to compare their colours, and colour measurement instruments are the perfect way to do so. Manufacturers can create a match to a colour on the map using machines like spectrophotometers, which measure colour based on the light it absorbs and reflects.

Selecting the Correct Instrument

Manufacturing plants that make plastics use spectrophotometers to measure transmitted/reflected colour, yellowness, and haze. Spectrophotometers are colour measurement instruments that have numerical colour values.

Ensure consistent plastic colour across measurement points during R&D and production processes. To save the colour code of the product, use a spectrophotometer. When manufacturing changes change the colour in the future, the original colour may be reinstated.

Best practices Colour Measurement and Evaluation

When formulating your plastic product's colour, try the same colour recipe as the standard. If this cannot be done (often), then describe a formulation process of colour and produce a recipe that meets the quality of the original.

Set a standard colour. Use the application-specific colour measuring instrumentation. Measure the colour, and record the colour values you want the finished product to match.

  • Establish a colour palette. Use colour measurement equipment that is tailored to your application's requirements. Measure and record the colour values of the colour you want to fit for the finished product.

  • Colour values from the standard should be imported into your colour formulation software.

  • Calculate the recipe that most closely corresponds to the standard

  • Make a small batch of the colour recipe that the program has determined.

  • Prepare and condition the sample before using a spectrophotometer to test it.

  • Compare the sample's color values and reflectance curve to the standards.

  • To see if there are any obvious inconsistencies, use a light booth in a regulated environment.

What is Colour Concentrates?

Concentrates are usually mixed into the base resin (plastic) at a rate of 2 to 5 pounds per 100 pounds of natural material. As a result, if the concentrate is properly mixed, the carrier polymer will make up to 3% of the final compound.

As a result, it is the most significant component in the additive kit, and its selection necessitates some care. Chemical compatibility between the carrier resin and the base resin is important. The easiest way to ensure this is to make the pigment concentrate out of the same polymer as the base resin.

However, colorants have to meet increasing demands in plastic applications due to the growing number of polymers with specific properties. Crucial factors besides the plastic-type are the processing method and the required fastness level. Among the most important polymers for colouring with pigments and dyes are polyolefins, polyvinyl chloride, polyurethane, polyamide, polycarbonate, polyester, and elastomers.

Different processing methods are used for colouring of the individual plastics. The colouring processes need to be coordinated in accordance with the steps of the plastics processing leading to the final product.

Pigments for Plastic

Pigments are insoluble organic or inorganic particles that are mixed into the polymer base to give the plastic a clear colour. Organic pigments are difficult to disperse and appear to clump together in agglomerates (clumps of pigment particles). These clumps will result in spots and specks in the finished product.

Inorganic pigments, on the other hand, such as metal oxides and sulphides, carbon black, and so on, are more readily spread in the resin. Titanium dioxide, the most widely used inorganic pigment in the plastics industry, is the most widely used pigment among inorganic pigments.

Families of Pigments for Plastics

Pigment families are mainly categorized into:

  • Organic pigments

  • Inorganic Pigments

  • Carbon black

  • White pigments

  • Special effect pigments

  • Aluminum pigments

The following factors determine the major performance characteristics of pigments for plastics:

  1. Weathering

  2. Aging

  3. Light Fastness

  4. Warping

  5. Transparency

At Sigma, with our on-site standardization lab, we can precisely control the strength, shade, and physical properties of our colours to guarantee you get consistent, repeatable results every time.

Using our specially designed spectrophotometers, plastic manufacturers can measure colours for matching industry colour charts, build focus and easily adhere to ASTM requirements.

We conduct professional laboratory analysis and offer expert technical advice for selecting colours, auxiliaries, and application procedures to meet your specific needs. We offer fast, accurate custom shade matching using the latest colour management systems.

Explore our complete spectrophotometer inventory and contact our team to learn how we can help you operate!

About the Author

Contact Sigma Test and Research Centre. We are the Best Testing Laboratory in Delhi, India. Contact us at +91–9560222333 or Visit our Website https://www.sigmatest.org.

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Author: Rahul Gupta

Rahul Gupta

Member since: Jul 10, 2020
Published articles: 11

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