Novel Chain Extenders for Recycling Polyesters

­Executive Summary

Polyesters comprise a significant portion of plastics entering landfills. One issue that limits their recycling is natural degradation during melt processing which lowers their molecular weight and melt viscosity. Reactive chain extenders are often used to build back the molecular weight of the polyester, however, their use can lead to excessive crosslinking and gel formation. MSU researchers have developed novel chain extenders that prevent crosslinking reactions, but build melt strength back to their original levels. This allows efficient recycling of the materials and a more closed loop material system.


Description of Technology

This invention utilizes designed epoxies and capping agents that react with the acid end groups and block the resultant hydroxyl groups from further reacting. This prevents excessive crosslinking and gel formation while as the same time brings the molecular weight and melt viscosity back to the virgin levels.



  • Forms liner high molecular weight polyester. Low crosslinking.
  • Low gel content
  • Improved mechanical properties of polymers compared to competitive epoxy chain extenders
  • Can be used with a range of polyesters including PET, PBT, PLA



  • Recycling / upscaling of polyesters
  • Polyester bottles, containers, packaging


Patent Status

Published application 


Licensing Rights

Full licensing rights available



Dr. Muhammad Rabnawaz




Patent Information:

For Information, Contact:

Jon Debling
Technology Manager
Michigan State University
Muhammad Rabnawaz