Thermal and mechanical characterization of a healable polymer

Abstract

A cross-linked polymer capable of reforming broken bonds is considered a healable polymer. One such polymer, 2MEP4FS, has previously been shown to regain full toughness under ideal fracture and healing conditions. Here, a more purified 2MEP4FS polymer is characterized using thermal and mechanical techniques and compared with the previous 2MEP4FS polymer. Differential scanning calorimetry (DSC) confirms the presence of the thermally reversible Diels-Alder bonds necessary for healing. Dynamic mechanical analysis (DMA) establishes mechanical properties and the glass transition temperature. Fracture tests are conducted using the double cleavage drilled compression (DCDC) geometry. Compression drives symmetric cracks up and down a rectangular column of material with a central through-thickness hole. Correlating the applied stresses and crack lengths with a finite element model, critical stress intensity factors are estimated. The cracks are healed with a thermal treatment and light pressure, and the sample is retested. Over the course of multiple fracture and healing cycles, changes in the critical stress intensity factor are used to establish healing efficiency. ©2010 Society for Experimental Mechanics Inc.