New biobased recyclable polyesters exhibiting excellent tensile properties beyond polyethylene and polypropylene

The research group of Professor Kotohiro Nomura, Tokyo Metropolitan University, in cooperation with the research group of Director Hiroshi Hirano, Osaka Research Institute of Industrial Science and Technology, has developed biobased polyesters from inedible plant resources, which can be easily chemical recyclable and exhibit promising mechanical properties in film than commodity plastics.

The development of high-performance sustainable, recyclable plastics is an important subject to realize circular economy. Biobased polyesters made from plant resources are expected to become promising alternative materials to polymers such as polyethylene and polypropylene produced from petroleum. However, there have been few examples of the development of high-performance materials that exceed required mechanical properties such as tensile strength and elongation at break.

Synthesis methods for high molecular weight (long chain) polymers had been a pending issue in conventional polycondensation methods. To solve this issue, the research group has developed an olefin metathesis polymerization method* using a high-performance molybdenum catalyst, focusing on polyesters derived from inedible plant resources, glucose and so forth. In general, there is an antinomic relationship between tensile strength and elongation at break in polymer film, as well as increase in molecular weight and elongation at break. However, the present polymer film demonstrates that the tensile properties (strength and elongation at break) of the polymer film increased with the molecular weight, exhibiting superior properties beyond conventional plastics.

The present result is the first success in developing the biobased polyester materials that can be decomposed/recycled and has excellent tensile strength and elongation at break than commodity plastics. The film properties can be further improved by combination with naturally derived fibers such as cellulose nanofibers. Therefore, the material is expected to be a large breakthrough in the research and development of plastic materials aiming at the circular economy.

* Olefin metathesis polymerization method: "olefin" is a general term for hydrocarbons with one carbon-carbon double bond. The word “metathesis” means “substitution”. Therefore, the recombination reaction of substituents on the double bond of an olefin is called the olefin metathesis reaction. For example, there is a reaction where a carbon-carbon double bond in an olefin is replaced with a catalytic metal-carbon double bond (catalytically active species) through the reaction using a catalytic metal such as ruthenium or molybdenum. The polymer synthesis method using such reaction is called the olefin metathesis polymerization method. The present method is a polycondensation synthesizing polymer through producing ethylene as by-product (acyclic diene metathesis polymerization).

The research was conducted under the JST CREST program, Research Area “Precise Material Science for Degradation and Stability, ” Research Theme “Development of Bio-Based Advanced Polymers and their Depolymerization, Chemical Recycle.”