Abstract
A novel electroactive shape memory polymer nanocomposite of epoxidized linseed oil plasticized polylactic acid and multi-walled carbon nanotubes (MWCNTs) was prepared by a combination of solution blending, solvent cast technique, and hydraulic hot press moulding. In this study, polylactic acid (PLA) was first plasticized by epoxidized linseed oil (ELO) in order to overcome the major limitations of PLA, such as high brittleness, low toughness, and low tensile elongation. Then, MWCNTs were incorporated into the ELO plasticized PLA matrix at three different loadings (2, 3 and 5 wt. %), with the aim of making the resulting nanocomposites electrically conductive. The addition of ELO decreased glass transition temperature, and increased the elongation and thermal degradability of PLA, as shown in the results of differential scanning calorimetry (DSC), tensile test, and thermo gravimetric analysis (TGA). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to observe surface morphology, topography, and the dispersion of MWCNTs in the nanocomposite. Finally, the electroactive-shape memory effect (electroactive-SME) in the resulting nanocomposite was investigated by a fold-deploy “U”-shape bending test. As per the results, the addition of both ELO and MWCNTs to PLA matrix seemed to enhance its overall properties with a great deal of potential in improved shape memory. The 3 wt. % MWCNTs-reinforced nanocomposite system, which showed 95% shape recovery within 45 s at 40 DC voltage, is expected to be used as a preferential polymeric nanocomposite material in various actuators, sensors and deployable devices.
Highlights
Polylactic acid (PLA) has been extensively studied to develop actuators for potential medical and industrial applications, due to its biodegradability, biocompatibility, renewability, and relatively low cost [1–5]
As Epoxidized linseed oil (ELO) was added into the PLA matrix, the morphology changed from brittle fracture surface to a smooth and uniform surface
A continuous and dense surface formation, in the nanocomposite with a 3 wt. % loading of multi-walled carbon nanotubes (MWCNTs), could be attributed to uniformly dispersed MWCNTs; which provided a greater matrix/MWCNTs interfacial area and an enhanced matrix–MWCNTs interface contact. It is well-known that uniformly dispersed MWCNTs in a matrix serve as decent bridging elements, help to construct a surface with adequate features, and serve as barriers that avoid the growth of micro-cracks and void formation in the nanocomposites
Summary
Polylactic acid (PLA) has been extensively studied to develop actuators for potential medical and industrial applications, due to its biodegradability, biocompatibility, renewability, and relatively low cost [1–5]. The relatively high cost of the above-mentioned polymers has provided motivation for the use of low cost polymeric materials, such as epoxidized vegetable oils (EVOs) This substitution presents an interesting alternative, because are EVOs lower cost, but they offer other advantages, such as being a natural product, harmless, biodegradable, etc. Epoxidized linseed oil (ELO), as an attractive alternative to ESO, shows a high compatibility with PLA matrix, due to the availability of more epoxide groups As we know, this epoxidation increases the polarity and the stability of vegetable oils by improving their compatibility with polymers, and provides a more energetic interaction to the matrix. Several studies have been conducted on using ELO as a plasticizer and stabilizer in polymers; for polyvinyl chloride (PVC), resulting in mechanical and thermal properties improvement. The obvious changes in mechanical, thermal, electrical, and morphological properties of the resulting nanocomposite with the addition of both ELO and MWCNTs were studied by typical analytical techniques, such as tensile testing, differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), and atomic force microscopy (AFM)
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