High ductility in poly(methyl methacrylate) induced by absorption and desorption of an acetonitrile aqueous solution
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Tension tests were conducted in air at room temperature on PMMA sheet specimens which had been previously soaked in a 40 vol % acetonitrile aqueous solution at 20 °C for 24 h and then dried in air at room temperature for 480 h. In contrast with an untreated specimen which fractured at a stress of 84 MPa and a strain of 9 %, shear yielding clearly took place at 42 MPa and the elongational fracture strain increased to about 148 %. No crazes were observed on the specimen surface and as a result the transparency of the PMMA was thoroughly maintained until fracture. Thus this soaking treatment may change PMMA to a completely ductile polymer without a crazing mechanism. The results of the dynamic viscoelastic measurements at 1 Hz show that the glass transition temperature was lowered to about 80 °C (as compared to about 110 °C), and the β relaxation became much sharper with a higher peak value of 20 °C (as compared to a broad curve with a peak at 50 °C). This clear β relaxation at room temperature may contribute to shear yielding and large plastic elongation of the treated PMMA.
KeywordsDuctility PMMA Methacrylate Glass Transition Temperature Methyl Methacrylate
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