What is the effect of colorant on plastic packaging?

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What should you take into account when choosing the colour of your packaging? There is more to this than maybe you think. Specialists from the A. Schulman Colour laboratory give tips and advice.

“When choosing packaging colours, appearance often plays an important role”, said Diana Lambrichs, Colour Laboratory Manager for the Benelux region. “Often a product is almost ready and colours are chosen on the basis of a company house style, for instance. But there is more that meets the eye to “just adding a colour”. There are so many possibilities and varieties. For blue alone you can already create 50 formulations. The most suitable choice will depend on a variety of factors.”

Starting with basics

“When we receive a colour request, often this is based on a PMS or RAL colour. Sometimes there are also special requirements, such as a company house colour based on a colour sample. This is where the selection process starts. Before you decide which formulations are suitable, you have to determine the carrier and the production process.  In case of plastic, it is either injection moulding or blow moulding.”

How and for what purpose are you going to use the packaging?

“Before we go on to formulating the colours, it is good to know how the packaging is going to be used”, said Ann Delmotte, R&D Technology Manager at Masterbatch. “Is the packaging intended for multiple use? Will it be used indoors or outdoors? In what part of the world will it be used? The application also has an influence. For instance, if you are packing foodstuffs or food ingredients, then odour will probably play a role. Certain pigments emit a strong odour and some products do not tolerate this.  We can consider this if we know it upfront.”

Should the packaging offer protection against UV light?

If packaging is exposed to UV light, the content can be affected.  Diana: “Packaging that does not have UV stabilisation and which is exposed to UV light for a longer period can perfectly well retain its colour, but it can also become brittle. There are also known cases where the packaging has almost no colour left, but it is still solid.”

There is more that meets the eye to just adding a colour

Ann: “Black and white have the strongest base coverage. In case of specific colours, the coverage power is variable.  Sometimes we add a sun filter. This is similar to the SPF of a suntan lotion and absorbs or blocks UV radiation. If the packaging is destined for outdoor use or for storage, then weather resistance becomes important. A colour must be able to resist light, UV radiation, ozone and acid rain. It is often thought that light resistance is the same as weather resistance, but that is not the case.”

How long should packaging remain colour and light fast?

Colour and light fastness (the ability to withstand colour changes on exposure to light), is determined using a so-called blue wool scale. “This scale ranges from 0 to 8, with 0 being very poor and 8 being very good. The required colour and light fastness is specifically determined by the required lifespan of the packaging”, says Diana.

Do the dimensions of the packaging change?

Diana: “HDPE is highly susceptible to shrinkage. Certain pigments can also influence the dimensions of a packaging. When you want to produce packaging that fits perfectly and is easy to stack, you have to take into account the shrinkage caused by the pigment.”

What is the chemical composition of your product?

“The chemical composition of a product can affect colours. Some colours can migrate under the influence of water or grease. This is also an aspect that should be taken into account in advance.”

When choosing a colour it is good to look beyond the rules and legislation and the desired appearance. Ann: “Get a colour specialist involved at an early stage of your product development. A colour is made up of various pigments. Each of these pigments must comply with certain requirements and taken together, cannot detract from the results that you require.”

A good understanding of your packaging process saves you time and money. It also provides you with the certainty that you have a safe and good-quality packaging. Would you like advice about the best choice of colours for your packaging? CurTec works together with recognised colour specialists and will be pleased to help you.

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