Affiliation:
1. School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
2. Singapore‐HUJ Alliance for Research and Enterprise (SHARE), Smart Grippers for Soft Robotics (SGSR) Campus for Research Excellence and Technological Enterprise (CREATE) Singapore 138602 Singapore
3. Department of Materials Science and Engineering Stanford University Stanford CA 94305 USA
Abstract
AbstractEnhancing fracture toughness and self‐healing within soft elastomers is crucial to prolonging the operational lifetimes of soft devices. Herein, it is revealed that tuning the polymer chain mobilities of carboxylated‐functionalized polyurethane through incorporating plasticizers or thermal treatment can enhance these properties. Self‐healing is promoted as polymer chains gain greater mobility toward the broken interface to reassociate their bonds. Raising the temperature from 80 to 120 °C, the recovered work of fracture is increased from 2.86 to 123.7 MJ m−3. Improved fracture toughness is realized through two effects. First, strong carboxyl hydrogen bonds dissipate large energies when broken. Second, chain mobilities enable the redistribution of localized stress concentrations to allow crack blunting, enlarging the size of dissipation zones. At optimal conditions of plasticizers (3 wt.%) or temperature (40 °C) to promote chain mobilities, fracture toughness improves from 16.3 to 19.9 and 25.6 kJ m−2, respectively. Insights of fracture properties at healed soft interfaces are revealed through double cantilever beam tests. These measurements indicate that fracture mechanics play a critical role in delaying complete failure at partial self‐healing. By imparting optimal polymer chain mobilities within tough and self‐healing elastomers, effective prevention against damage and better recovery are realized.
Funder
National Research Foundation Singapore