Microcapsules enable self-lubricating plastics
BECAUSE 23% of global energy consumption can be attributed to friction losses, components with reduced friction represent an important contribution to conserving resources and achieving climate protection targets. In the case of plastics, reduced friction can also reduce microplastics in the environment. With the development of microcapsules filled with liquid lubricants for plastics, the Potsdam Fraunhofer Institute for Applied Polymer Research IAP and the Plastics Centre SKZ in Würzburg are supporting these goals. Their self-lubricating plastics achieve up to 85% less wear.
Whether it’s sliding doors, laminate, plastic gears or other moving components – there is a variety of applications where materials are subject to friction. Plastics manufacturers often incorporate solid lubricants into plastics to reduce component wear. However, there are only a relatively small number of solid lubricants suitable for plastics processing. In contrast, there is a much wider range of liquid lubricants, some of which are more effective. In a cooperative effort, the two research institutes have succeeded in encapsulating liquid lubricants in such a way that they can be incorporated into polymers as functional substances and later develop all the advantages of a liquid lubricant in the component.
“We managed to incorporate Fraunhofer IAP‘s microcapsules filled with liquid lubricant into thermoplastics using a twin-screw extruder. The challenging task was to mix the microcapsules with thermoplastics under high temperatures without damaging the capsules. Only when friction occurs in the final component the capsules should break and release the lubricant. This allows the component to lubricate itself automatically”, explains Moritz Grünewald, researcher in the Materials Development Group at the SKZ Plastics Centre. “Our friction and wear tests showed a reduction in wear of up to 85% on plastic-steel pairings. Thus, components last significantly longer and generate less microplastic.”
Based on these results, the material system is being optimized further for potential applications. The development is now focusing on improved mechanical and thermal properties of the self-lubricating plastics.
Numerous inquiries from industry highlight the need for novel plastics with optimized friction and wear properties. Microencapsulation technology has major advantages for companies in this regard: the wide range of liquid and advanced lubricants can now be used as internal lubricants with on-demand release properties. The project is accompanied by a committee that includes companies from all sectors of the plastics industry, lubricant manufacturers and microencapsulators.