New Study Reveals Polymers with Flawed Fillers Boost Heat Transfer in Plastics

In the quest to design the next generation of materials for modern devices – ones that are lightweight, flexible and excellent at dissipating heat– a team of researchers led by the University of Massachusetts Amherst made a discovery: imperfection has its upsides. 

This research, published in Science Advances, experimentally and theoretically found that polymers (commonly referred to as plastics) made with thermally #conductivefillers containing defects performed 160% better than those with perfect fillers. This counterintuitive finding challenges long-held assumptions that defects compromise material performance.

The study was led by #UMassAmherst with collaborators from #MassachusettsInstituteofTechnology, #NorthCarolinaStateUniversity, #StanfordUniversity, #OakRidgeNationalLaboratory, #ArgonneNationalLaboratoryandRiceUniversity.

Polymers have revolutionized modern devices with their unmatched lightness, electrical insulation, flexibility and ease of processing qualities metals & ceramics simply can’t rival. Polymers are embedded in every corner of our tech landscape, from high-speed microchips and LEDs to smartphones and soft robotics. However, common polymers are thermal insulators with low thermal conductivity, which can lead to overheating issues. Their inherent insulating properties trap heat, spawning dangerous hot spots that sap performance and accelerate wear, heightening the risk of catastrophic failures and even fires.

For years, scientists have attempted to enhance the thermal conductivity of polymers by incorporating highly thermally conductive fillers such as metals, ceramics or carbon-based materials. The logic is straightforward: blending in thermally conductive fillers should improve overall performance. 

However, in practice, it is not this simple. Consider a polymer blended with diamonds.

Given a diamond’s exceptional thermal conductivity of about 2,000 watts per meter per kelvin (W m-1 K-1), a polymer that is composed of 40% diamond filler might theoretically achieve conductivity of around 800 W m-1 K-1. Yet, practical results have fallen short due to challenges like filler clumping, defects, high contact resistance between polymers and fillers,& low thermal conductivity of polymer matrices, which undermine heat transfer. 

Understanding thermal transport mechanisms in polymeric materials has been a long-standing challenge, partly due to the complicated polymer structures, ubiquitous defects & disorders.

For their study, aimed at laying the foundation for understanding thermal transport in #polymericmaterials and controlling heat transfer across heterogeneous interfaces, the team created two polymer composites of polyvinyl alcohol (PVA)- one incorporating perfect graphite fillers and the other using defective graphite oxide fillers, each at a low 5% volume fraction.

source: University of Massachusetts Amherst