Toward the realization of an energy-efficient society, weight reduction of automobiles and large transport vehicles is one of the key challenges. Polymer materials, composed primarily of carbon, are among the lightest classes of materials. However, their strength is insufficient for use in automotive components, where the strength exceeding 100 MPa - comparable to those of metals - are required. Until now, reinforcement of semi-crystalline polymers has mainly relied on increasing the degree of crystallinity. That is, high strength has only been achieved in limited cases where the crystallinity was greatly enhanced through some special processing techniques, inducing crystallization under flow.
Now, a joint research team led by Professor Eiji Abe’s research group at the Graduate School of Engineering, the University of Tokyo, Lecturer Katsumi Hagita at the School of Applied Sciences, National Defense Academy and Professor Hiromu Saito at the Institute of Engineering, Tokyo University of Agriculture and Technology discovered that applying a heat-elongation process to semi-crystalline polyethylene leads to a crystalline size refinement, and when the size reaches approximately 10 nanometers (1 nanometer = 10-9 meter), it exhibits remarkably high strength approaching that of metallic materials. Crystalline grain refinement is a well-known empirical rule for metallic materials, and the present study demonstrates for the first time that a similar strengthening principle can be applied to polymer materials. Also, the major advantage is that this nano-crystallization can be controlled through a relatively simple heat-elongation process. Polymer materials strengthened to the level of metals can be utilized in automotive and large transport components, enabling significant weight reduction and expected to contribute for the realization of an energy-saving society.
Figure: Discovery of the strengthening of polymer materials through nano-crystallization and elucidation of the strengthening mechanism
Papers
Journal: NPG Asia Materials
Title: Nano-structuring for strengthening semi-crystalline polymers
Authors: Katsumi Hagita*, Mamoru Endo, Daisuke Egusa, Hiromu Saito, Takashi Yamamoto, Eiji Abe*
Second-Generation Crystalline Sponge: Realizing Simple and Versatile Structural Analysis for Medium-Sized Pharmaceutical Compounds
Mild Catalytic Degradation of Crystalline Polyethylene Units in a Solid State Assisted by Carboxylic Acid Groups
