Fast, Easy, Effective: Utilizing Spectrophotometers to Measure Colour Pigment Content in Plastics

Plastic products come in a variety of colours. However, final product colour is determined long before these final stages of production. Image Source: Flickr user oatsy40

Plastics come in a wide array of colours and must undergo various steps of processing to achieve desired results. Measuring colour pigment throughout each processing phase is important for maintaining consistency and avoiding product rejection due to colour discrepancy. Spectrophotometers allow for the continual monitoring and analysis of colour pigments to ensure consistency throughout the supply chain, reducing errors and wasted materials.

Adding Colour to Raw Materials

There are various methods for adding colour to plastic products, all involved in the early stages of production. These techniques (described below) rely on different methods of colour pigment analysis which utilize spectral technology to achieve desired results.

1. “Masterbatch” Method: chemically altered, high pigment content pellets are mixed together with naturally colored pellets to achieve desired results.
2. Pigment Additives: naturally-colored pellets are mixed together with raw pigments to create colored pellets, which are then used to product colour specific plastic products.
3. Pigment/Solvent Method: pigments are first dissolved in a solvent and then sprayed on naturally colored pellets to alter final product colour.
4. Real-time Colour Additives: pigments and natural pellets are molded together simultaneously to develop final colour specifications.

Colored pigment is often added to naturally colored plastic pellets to alter final colour results. Image Source: Flickr user tiffany terry \

Whichever method is used to alter the colour of the plastic product, each one will undergo various changes throughout processing. Continual monitoring of colour pigment, dissolved pigment, natural raw plastic materials, and final product colour is needed to provide valuable data that can alert production changes and guarantee desired results.

Colour Pigment Analysis

Plastic pellet colour is most often analyzed before the pellets are extruded or molded into final products. Colour pigment measurement is an important step towards ensuring that these raw materials will produce the desired colour results. Spectrophotometers offer a quick and simple method of colour pigment analysis that can be quantified and repeated to help maintain consistency and quality.

These materials often exhibit differences in shape, texture, and transparency. Therefore, colour measurement instrumentation must be designed to measure a variety of sample attributes. From powdered colour pigment to dissolved liquid samples to plastic pellet materials that vary in transparency, spectrophotometers rely on advanced geometric principles to accurately quantify colour and develop the data need to reproduce these colour effectively. Advanced spectrophotometers allow for rapid, in-line colour process monitoring to continually monitor colour changes and provide valuable feedback for processing adjustments and changes.

Plastic pellets range in colour, shape, and texture which requires advanced measurement instrumentation to effective quantify colour and change. Image Source: Flickr user NOAA Marine Debris Program

Monitoring Inconsistencies

Spectral data and feedback is highly utilized for its ability to monitor inconsistencies both during production as well as in final product appearance. Spectrophotometers can be used to set colour standards at various checkpoints throughout production by assigning numerical values and establishing colour tolerances. These quality standards1 ensure that products pass final inspections, increase final batch quantities and company profits. Integrating colour pigment monitoring with advanced colour evaluation instrumentation, creates a system of precise colour comparisons that match human eye perception. Using these methods to compare products to manufacturer standards throughout processing will eliminate inconsistencies early on and positively affect final product colour.

Need to Measure Colour Pigment? Trust Advanced Spectral Technologies

Spectrophotometers are designed to view colour in the same way as it is seen by the human eye.2 Advanced instrumentation utilizes non-contact and height sensing technology so that colour data is not distorted by interference from outside sources. This assures that final products will meet consumer expectations for quality and consistency every time.

At HunterLab, we specialize in advanced spectrophotometric instrumentation and offer a variety of tools designed to meet the various needs of colour pigment analysis in the plastic industry. For more information on the use of spectral technology in plastic colour and pigment evaluation, please contact HunterLab today.