Organo-layered double hydroxide/polypropylene (LDH/PP) nanocomposites were successfully synthesized via a solution blending method. As an attempt to improve the compatibility with hydrophobic PP, the LDH surface was modified by the incorporation of various anionic surfactants via electrostatic interaction with LDH cationic layers. Surfactants were selected by considering the aliphatic carbon chain length (laurate, palmitate, stearate and dodecyl sulfate) and anionic functional groups (-COO À , -OPO 3 2À , and -OSO 3 À ) with the purpose of optimizing the homogeneous dispersion in the PP matrix. In PP nanocomposites containing LDH modified with alkyl carboxylate, the (00l) X-ray diffraction (XRD) peaks originating from organo-LDH were not observed, indicating that organo-LDH layers were fully exfoliated and homogeneously dispersed within the PP matrix, which were also confirmed by cross-sectional TEM analysis. However, PP nanocomposites containing LDH modified with dodecyl sulfate and lauryl phosphate showed broad (00l) XRD peaks, indicating that organo-LDH was partially exfoliated.According to the thermogravimetric analysis, the thermal stability (T 0.5 ) of organo-LDH/PP nanocomposites was significantly improved by 37-60 K, depending on the type and loading content of organo-LDH compared to that of pristine PP. PP nanocomposites containing well-dispersed organo-LDH showed substantial enhancement of the elastic modulus with little decrease of tensile strength.These results are due to the increased interface volume fraction provided by the exfoliated LDH nanosheets.
New technology is constantly required for updating new generation flexible devices, such as stretchable sensors, flexible electronics, and actuators. In the present study, a stretchable strain sensor, and actuator were developed based on room‐temperature‐vulcanized (RTV) silicone rubber reinforced with carbon nanotubes (CNTs), nanographite (GR), and CNT‐GR hybrids. A CNT‐based strain sensor developed for RTV silicone rubber showed improved stiffness and brittleness. For example, at 5 phr of filler loading, the compressive and tensile modulus for the CNT‐reinforced RTV silicone matrix improved by 287% and 240%, respectively. Similarly, the improvements in the compressive and tensile modulus were moderate for the CNT‐GR hybrid (210% and 235%) and low for GR (135% and 125%). The improved brittleness resulted in a higher fracture strain of 170% and 155% for the CNT‐GR hybrid and GR, respectively. The improved mechanical properties were tested in real‐life applications of actuation. The actuation displacement at a filler loading of 2 phr increased to 1.65 mm (CNT), 1.25 mm (CNT‐GR), and 0.08 mm (GR). From 2 to 8 kV, the actuation displacement increased by 825% (CNT), 830% (CNT‐GR), and 32% (GR). The strain sensor showed a stretchability of >100% (CNT) and >100% (CNT‐GR). In addition, the gauge factor was higher for the CNT‐GR hybrid composites. The durability measurements showed that the change in resistance was negligible for up to 5000 cycles in both the CNT and CNT‐GR rubber composites. A series of experiments confirmed that compared to the composite based on RTV silicone rubber and CNT, the CNT‐GR hybrid showed a robust flexibility and stretchability as a piezo‐resistive strain sensor and actuator.
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