Coloured PET foam
A foamed PET blow-moulding process that creates lightweight bottles in white or silvery-colours, without using additives, has been developed, according to polymer researchers in the USA. They say the technique creates recyclable decorative and textured PET bottles.
Plastic Technologies Inc (PTI) has unveiled the oPTI bottle process, which is based on microcellular foam injection technology from MuCell in Woburn, USA. Bottles are created by injecting nitrogen into the PET melt using a modified preform moulding machine. As the cavity-fill pressure in the chamber drops below the nucleation pressure, foam cells are produced and expand as gas diffuses into them. The resulting preform can be blow-moulded using conventional technology.
The presence of foam reduces the weight of the bottle by up to five per cent, according to the company, while offering a reduction of up to 95% in transmitted light. The white or silvery colours are achieved by the scattering of light, says Frank Semersky, Vice President of PTI. ‘The microcellular structure creates many refractive surfaces,’ he explains. This returns to a transparent state when the bottle is remelted.
The technique also gives a textured feel to products, enabling a surface with more traction. ‘This could be a benefit for products like shampoo which are used in the shower,’ says Semersky.
The process can also incorporate coloured additives used in other PET bottles, such as green or blue.
Semersky adds that the system is not time-consuming, ‘We have blown oPTI bottles at full speed on commercial equipment’. He believes it could also be used with other resins suitable for reheat stretch blow-moulding, such as PLA and PEN.
Bottles produced so far have been able to hold liquids with temperatures of up to 85ºC, without excessively shrinking, opening up new applications in hot-filling.
The company is working on other beverage uses for the technology.
Further information: PTI