Creating and controlling colour in plastic products can be challenging

Manufacturers of goods made of “Plastics”, using the generic term, while understanding that different materials require different criteria, have always found colour to be a tricky issue.

It could take up to four months to create a reproducible recipe to create a desired colour in a say a polyester fibre. Noting that these fibres are often blended with natural fibres such as wool or cotton.

Adding colourants to molten material in an extruder is not a simple task, as many practical problems have to be resolved.

Manufacturers solve many production problems by moving to a “masterbatch” process, where colourant was blended into a polymer (PET, HDPE, PP etc.) in concentrated form. Masterbatch pellets are mixed according to a recipe with raw polymer material (PET, HDPE, PP, etc.) which is either oqaque or transparent, to produce a consistent colour.

Using masterbatch proved to be a quicker and more affordable method of production, with less waste and trials. Challenges are then found when mixing virgin polymer with recycled polymer, as each have there own optical properties.

Consumers of today are turning to sustainable, eco-friendly alternatives and solutions to plastic products. Manufacturers have to evolve and improve recycling and assess the impact they have on the environment. Even with the move towards sustainable solutions, consumers have increased there expectations and demand the same quality in terms of colour and apperance of their products.

‘Fashion Colours’  have inspired consumers to demand quick colour matching to meet the latest colour trends. Modern consumers seek appliances, cookware, decor and consumer items that are fasionable and conform to their desired colour scheme, while remaining budget and eco-friendly.

Quick, affordable colour matching is now almost a requirement at most plastic manufacturers.

What common challenges are faced in producing perfect plastic colour?

As many plastic manufacturing professionals will know, colour consistency in the manufacturing process is full of challenges. We note the top challenges that are faced as:

1. Laboratory to Production extrusion.
   In many cases, a laboratory size extruder does not necessarily offer a compatible result with bulk machines, so manufacturers rather work directly on a production unit, despite extra waste risk.
2. Colourants.
   Colourants have to be of the highest standards and compatibility with the materials used.
   Temperature stability, as well as temperature control is key in this case. Changes in colourant or polymer may cause colour inconsistencies in production.
3. Quality material.
   Quality material is required, and the pressure to recycle create a conflict where post consumer waste (PCW) may not recycle well when polymers are mixed or adulterated.
4. Masterbatch.
   Time Poverty requires that producers have to buy coloured masterbatch and these colours have to be accurate as well as the same colour from batch to batch. This means stable production environment within the extruder, and from one extruder to another.
5. Opacity.
   Plastic goods are not always fully opaque, so measuring their colour adds extra considerations of conditions under which the measurement takes place.
6. Edge Loss.
   Even a solid colour can give unreliable measurements due to a phenomenon known as “Edge Loss” or a percentage of transmitted light escapes from the object via a 90° diversion of light from the surface to the edge. This “Bending” effect is also colour specific, so blended colours may bend on colour more than another.
7. Metamerism.
   Metamerism is a further visual hazard, created by different colourant chemistry from one material to another. Typically, cheaper options will not match more costly materials as the actual colourant “chromophore” differs in chemical composition.
8. Colour specification and standardisation.
   Colour specification and standardisation can be difficult across different sites and between suppliers and customers. Instruments with poor Inter-Instrument Agreement does not allow for the clear communication of colours.
9. Quick Colour Matching.
   Visual matching takes time and resources and often leads to more trial and error than actual formulations. Customers also demand quick colour matching to meet market needs.

These challenges can be resolved with the following tips:

• Continuous Colour Monitoring.
  Continuously monitor colour during production and in the laboratory with in-line colour measurement solutions. In-line systems that provide real time data that can be actioned in the plant immediately. Ensure every gram of product produced conforms to customer and internal standards.
• Colour Measurement Instruments.
  Colour measurement instruments with high levels of accuracy, performance and inter-instrument agreement. Reproducible conditions of accuracy and performance across different instruments from hand-held to bench-top with seamless efficiency. Communicate and standardise colour between sites, customers and suppliers.
• Colour Data Management Software.
  Advanced quality control software allows ‘poor’ measurements to be deleted but not edited. ISO standard quality control software that transforms the way you understand and interpret your colour data. Colour data can provide insights into quality control.
• Colour Specification and Formulation.
  Colour specification and formulation software designed for the plastic industry.
  Colibri – Computer Colour Matching software is the most advanced in the market and allows you to perfectly reproduce and create new colours seamlessly.

• All-in-one Colour and Appearance measurement.
  Measure and control important properties associated with plastic, such as colour, gloss and opacity with a single handheld spectrophotometer. Not only a leader in versatility but also performance and usability. See the Solution.
• Support, Implementation and The Narich Academy.
  Guidance and training on instrument usage and best practice. Discussions and suggestions relating to technical aspects such as metamerism and edge-loss to improve consistent colours in production.
• Instrument Certification and Service.
  Maintaining and Certificating optical instruments like spectrophotometers is highly recommended to ensure performance and inter-instrument agreement.

Producing consistent colour in plastic can be challenging especially when taking into account sustainability, recyclability and forever changing consumer demands. Through the latest technology, software and measurement procedure guidelines, these challenges can be reduced if not eliminated completely.

At Narich we specialise in finding complete colour measurement solutions to assist companies in improving quality control, optimising process and reducing waste. From in-line continuous monitoring to high level spectrophotometers and gloss meters to colour creation, formulation and communication, “We Only Do Colour, and We Do It All”

Tell us about some of the challenges and examples where you have struggled with colour management?
Or give us example of the last time you had issues controlling colour or gloss in your plastic products and wondered if there was a solution?

For sharing your story with us, you will immediately receive a complete colour management guide, Precise Colour Communication Book. You will also receive a complimentary assessment and report on how your company manages colour following a visit a meeting at your site.