In this study, the montmorillonite (MMT) clay was modified with NH4Cl, and then the structures were exfoliated or intercalated in a polylactic acid (PLA) matrix by a torque rheometer in the ratio of 0.5, 3.0, 5.0 and 8.0 wt%. X-ray diffraction (XRD) revealed that the organic modified-MMT(OMMT) was distributed successfully in the PLA matrix. After thermal pressing, the thermal stability of the mixed composites was measured by a TGA. The mixed composites were also blended with OMMT by a co-rotating twin screw extruder palletizing system, and then injected for the ASTM-D638 standard specimen by an injection machine for measuring the material strength by MTS. The experimental results showed that the mixture of organophilic clay and PLA would enhance the thermal stability. In the PLA mixed with 3 wt% OMMT nanocomposite, the TGA maximum decomposition temperature (Tmax) rose from 336.84 °C to 339.08 °C. In the PLA mixed with 5 wt% OMMT nanocomposite, the loss of temperature rose from 325.14 °C to 326.48 °C. In addition, the elongation rate increased from 4.46% to 10.19% with the maximum loading of 58 MPa. After the vibrating hydrolysis process, the PLA/OMMT nanocomposite was degraded through the measurement of differential scanning calorimetry (DSC) and its Tg, Tc, and Tm1 declined.
8 December 2010 in Journal of Applied Polymer Science
In this study, electroactive poly (amic acid) (EPAA) and corresponding polyimide (EPI) without or with a sulfonated group (i.e., S-EPAA, and S-EPI) were prepared and applied in electrochemical sensing of ascorbic acid (AA). The electroactive polymers (EAPs) containing EPAA/EPI and S-EPAA/S-EPI were synthesized by using an amine-capped aniline trimer (ACAT) and sulfonated amine-capped aniline trimer (S-ACAT) as an electroactive segment that controlled the redox capability and influenced the degree of sensitivity of the EAPs towards AA. Characterization of the as-prepared EAPs was identified by FTIR spectra. The redox capability of the EAPs was investigated by electrochemical cyclic voltammetric studies. It should be noted that the redox capability of the EAPs was found to show the following trend: S-EPAA > S-EPI > EPAA > EPI. For the electrochemical sensing studies, a sensor constructed from an S-EPAA-modified carbon paste electrode (CPE) demonstrated 2-fold, 1.27-fold, and 1.35-fold higher electro-catalytic activity towards the oxidation of AA, compared to those constructed using a bare CPE, S-EPI-, and EPI/EPAA-modified CPE, respectively. The higher redox capability of S-EPAA-modified CPE exhibited a good electrochemical response towards AA at a low oxidative potential, with good stability and selectivity. Moreover, an electrochemical sensor constructed from S-EPAA-modified CPE was found to reveal better selectivity for a tertiary mixture of AA/DA/UA, as compared to that of EPI-modified, EPAA-modified and S-EPI-modified CPE, based on a series of differential pulse voltammograms.
In this study, tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) were used as precursors for silica, combined with the ionic liquid [BMIM-ClO4]. Lithium perchlorate was added as the lithium-ion source, and formic acid was employed as a catalyst to synthesize silica ionogel electrolytes via the sol–gel method. FT-IR and NMR identified the self-prepared ionic liquid [BMIM-ClO4], and its electrochemical window was determined using linear sweep voltammetry (LSV). The properties of the prepared silica ionogel electrolytes were further investigated through FT-IR, DSC, and 29Si MAS NMR measurements, followed by electrochemical property measurements, including conductivity, electrochemical impedance spectroscopy (EIS), LSV, and charge–discharge tests. The experimental results showed that adding methyltriethoxysilane (MTES) enhanced the mechanical strength of the silica ionogel electrolyte, simplifying its preparation process. The prepared silica ionogel electrolyte exhibited a high ionic conductivity of 1.65 × 10−3 S/cm. In the LSV test, the silica ionogel electrolyte demonstrated high electrochemical stability, withstanding over 5 V without oxidative decomposition. Finally, during the discharge–charge test, the second-cycle capacity reached 108.7 mAh/g at a discharge–charge rate of 0.2 C and a temperature of 55 °C.