Strong and sturdy bioplastic thanks to flexible building blocks

As part of the HIPLA project, the collaborating research partners have developed a new biobased plastic that has a higher impact resistance than traditional PLA. As a result, this PLA can be used for a broader range of applications, such as in high-quality plastic housings for laptops and tablets.

The aim of the study was to improve the biobased plastic polylactic acid, PLA for short, that was already commercially available. This bioplastic consists of linked lactic acid molecules, polymers, which are based on sugar. To make PLA tougher, the project team was able to draw on the experience they had gained from working on other materials. Incorporating a natural, flexible building block into the brittle plastic turned out to be a success.

Flexible building blocks

In an earlier study, Croda Nederland BV in Gouda was able to considerably strengthen a hard but brittle epoxy coating by adding fatty acid particles. The new coating was just as hard but its increased flexibility meant it did not break as easily. ‘The main question was whether this principle would also work for PLA,’ says Angela Smits of Croda Nederland. ‘One of the biggest challenges was incorporating this flexible building block into the PLA polymer. After all, it is a very different material than an epoxy coating.’

Ultra-tough bioplastic

By specifically experimenting with heat and friction in the polymerisation process, the researchers finally succeeded in building the biobased fatty acid molecule into the PLA polymer chain. ‘Since these fatty particles cluster together in the PLA polymer matrix, they look like spheres under the microscope,’ Smits explains. ‘In the hard PLA matrix, these built-in spheres now ensure the material is impact-resistant.’ And the result is impressive: an ultra-tough bioplastic that can be used for a wide range of applications.

Film coatings

This new basic material was used by AFP, a film manufacturer in Apeldoorn, to produce a film on a pilot scale. Smits thinks this new material could be used as packaging material that does not crack, as well as for film coatings for car dashboards and films that can be used in greenhouses. HSV Technical Moulded Parts in Ede successfully tested the material as a raw material for plastic components by injecting or pouring the melted mixture into larger moulds. HSV also successfully tested the material in an application as printer panel. ‘We are making good progress, but still need to make technical improvements and optimise costs before it can be used in mass production,’ says Smits. ‘The patent is being processed and in follow-up research we would like to apply these principles to other biobased plastics.’