If you’re looking to achieve a splash of colour, texture or even anti-bacterial into your plastic components, chances are your moulder is using masterbatch in the mix. With the global masterbatch market set to increase in value to USD 15 billion by 2026[i], Thomas Catinat, Operations Manager at Broanmain Plastics explains why masterbatch is so popular and how as a moulder they go about achieving the perfect blend to ensure consistency batch-to-batch.Masterbatch is commonly divided into five segments – black, white, colour, additive and fillers. Each formulation offers different functions that when distributed evenly through the polymer mix give it its unique plastic fingerprint.
Colour masterbatch is a highly concentrated pigment. Supplied in pellet form rather than powder or liquid, it is blended into plastics to create a range of end-use applications, for example food and beverage packaging, appliances, automotive and pharmaceutical packaging.
Additive masterbatch offers improved performance of plastic products, for instance illumination, UV resistance, anti-oxidants, antimicrobials or anti-static. Filler masterbatch is used to create better properties such as stiffness or a lighter weight polymer. Chalk, for example, is used to bulk out the plastic. Specific fillers can also be added to make a component fire retardant.
Black and white masterbatch are typically used in building and construction, automotive, consumer goods and domestic appliances.
Achieving a special effect, such as chrome, wood grain, stone, marbling and even sparkle is also possible. These types of compounds are often used to boost consumer appeal and mimic heavier materials.
Ready mixed or create on demand?
Compounded mixes might be purchased in bulk when creating larger quantities of components. But for many end customers, masterbatch is often the most cost effective way for moulders to create the perfect recipe time and again.
Blended in-house, moulders use volumetric dosing units to automatically mix the material ready for processing. Using granular masterbatch can be a lot less messy than powders or liquid, with fewer health and safety risks from dust or spillages.
The ability to maintain a low stock holding and call up a specific blend when required from an external supplier can be more economical, helping to keep production costs down on short runs.
Universal masterbatch offers convenience, are more readily available from suppliers and work with most polymers. The downside is not all universal masterbatches are compatible with all base materials. Conversely, polymer specific masterbatches are formulated using the same base polymer that it will be blended with. These tend to be bespoke and customised to suit a specific customer’s requirement for pigment colour, as well as special properties like heat stability.
Jet blacks and bright whites
For a number of components, such as electronics, producing the deepest blacks and the purest whites can be more challenging that some think. It requires a high pigmentation concentration, especially to make contemporary products such as mobile phones really stand out. Achieving uniform colour is critical. And although there’s usually a standard range of around 40+, there can be over 1000 different masterbatch formulations.
Typically, a white masterbatch is used to add opaqueness or whiteness into plastic products. Different grades of titanium dioxide (TiO2) are applied to reflect or scatter light. As well as outdoor applications, some whites are suitable for food contact plastics. One of the key advantages of the white masterbatch is it has a high rate of dispersion, so can easily incorporate other colourants.
Black masterbatch is good for electro-static conductibility, durability and exposure to extreme weather. That’s why black is used in a lot of functional outdoor plastic applications, such as construction pipes, as it is stronger and lighter than coloured equivalents.
Performance enhancing additives are often added to both black and white masterbatch
Colour matching
Picking the perfect colour is one thing. Ensuring consistency batch-to-batch is quite a science. Everyone sees colour differently. While Newton divided the spectrum into seven named base colours – red, orange, yellow, green, blue, indigo and violet, according to psychophysicists we see tens of millions of different hues and shades. Given this, the human eye cannot be relied upon to match samples accurately.
Once a specific masterbatch has been created, specific formulation details, including colour pigments, raw material ratios, notes and directions are held on a recipe card. A moulder can call up these instructions at any time to ensure production consistency.
Should a recipe card be unavailable, physical samples can also be matched using a light box or spectrophotometer.
Homogenisation of a blend, including the dispersion of the masterbatch during dosing, plays a big role in minimising colour and product performance variations. Most recipes detail the percentage by weight of masterbatch to be applied. Yet, discrepancies can occur. Changing the host polymer or switching suppliers is typically when this might happen. For this reason, moulders tend to stick with the same supplier.
As with all plastic processing, stability is essential. Thermal resistance and durability need to be factored in. It’s precisely for this reason why most processors avoid using a high percentage of recycled plastic mixes for the base polymer. The more plastic is reprocessed, the greater the molecular structure changes. This loss of chemical properties affects the composition and therefore is likely to affect the compatibility of all the ingredients within a blend.
Aesthetics aside, understanding the environment in which the end component will be used is critical. For example, components exposed to direct sunlight will need to use a specific masterbatch to prevent discolouration. The chemistry of some colour pigments may be incompatible with the chemistry of some base polymers. Additionally, other agents, such as fillers, could impact the fusion.
One thing is certain, masterbatch has become integral to modern day plastic processing. Out of all the product types, colour masterbatch is experiencing heavy global demand. This robust growth can be attributed to brand differentiation trends in packaging, FMCG, furniture, construction, agriculture and aerospace. Likewise, black and white mastermatch is being extensively utilised by automotive manufacturers for lighweighting and to improve fuel efficiency.
Just like a paint swatch, new innovations emerge on the market all the time. To trial a different pigment or plastic effect, contact us for advice on what’s new and how a new formulation might impact processing stability.
