Investigation of the accelerated thermal aging behavior of polyetherimide and lifetime prediction at elevated temperature

Polyetherimide (PEI) nanocomposite with WS2 nanotubes

Nanocomposite materials, integrating nanoscale additives into a polymer matrix, hold immense promise for their exceptional property amalgamation. This study delves into the fabrication and characterization of polyetherimide (PEI) nanocomposite strings fortified with multiwall WS2 nanotubes. The manufacturing process capitalizes on the preferential alignment of WS2 nanotubes along the string axis, corroborated by scanning electron microscopy (SEM). Mechanical measurements unveil a remarkable acceleration of strain hardening in the nanocomposite strings, chiefly attributed to the WS2 nanotubes. Structural analyses via X-ray diffraction (XRD) and wide-angle X-ray scattering (WAXS) reveal intriguing structural alterations during tensile deformation. Notably a semi-crystalline framework ∼100 nm in diameter surrounding the WS2 nanotubes emerges, which is stabilized by the π-π interactions between the PEI chains. The amorphous majority phase (97% by volume) undergoes also major structural changes upon strain becoming more compact and closing-up of the distance beweeetn the PEI chains. Dynamic mechanical analysis (DMA) demonstrates improved thermal stability of the evolved semi-crystalline π-π oriented PEI molecules, characterized by delayed thermal "structural melting", underscoring the pivotal role of the WS2 nanotubes in reinforcing the nanocomposite. The insight gained in this study of WS2 nanotube-reinforced PEI nanocomposite strings, could offer diverse applications for such tailor-made polymeric materials.

3D MXene-Based Flexible Network for High-Performance Pressure Sensor with a Wide Temperature Range

With the increasing popularity of smart wearable devices, flexible pressure sensors are highly desired in various complex application scenarios. A great challenge for existing flexible pressure sensors is to maintain high sensitivity over a wide temperature range, which is critical for their applications in harsh environments. Herein, a flexible piezoresistive sensor made of polyetherimide (PEI) fibrous network evenly covered with MXene nanosheets is reported to construct conductive pathways, showing ultrahigh sensitivity over a wide temperature range from -5 °C (sensitivity of 80 kPa^-1 ) to 150 °C (20 kPa^-1 ), low detection limit of 9 Pa, fast response time of 163 ms, outstanding durability over 10 000 cycles at room temperature, 2000 cycles at 100 °C and 500 cycles at -5 °C. The pressure sensor can monitor various human activities in real-time, apply to human-machine interaction, and measure pressure distribution. It also can sensitively respond to external mechanical stimuli at 150 °C and extremely low temperature (in liquid nitrogen). Moreover, the fibrous network exhibits an excellent Joule heating performance, which can reach 78 °C at an applied voltage of 12 V. Thus, the piezoresistive sensor has considerable potential for wearable garments and personal heating applications in harsh temperature conditions.

Mixed-Matrix Membranes Based on Polyetherimide, Metal–Organic Framework and Ionic Liquid: Influence of the Composition and Morphology on Gas Transport Properties

In this work, membranes based on polyetherimide (PEI), a ZIF-8 metal–organic framework and 1-ethyl-methylimidazolium tetrafluoroborate ionic liquid (IL) were prepared. IL and ZIF-8 contents amounting to 7 wt% and 25 wt%, respectively, were investigated. CO₂, He and H₂ transport properties of PEI/IL/ZIF-8 membranes were compared to those obtained for the respective PEI/ZIF-8 and PEI/IL systems. Membranes’ gas permeability and selectivity are discussed as a function of the membrane composition and morphology, and they were assessed in relation to existing experimental and theoretical data from the literature. Promising gas transport properties were obtained using the appropriate combination of ZIF-8 and IL amounts in the PEI matrix. Indeed, an increase in the CO₂ permeability coefficient by a factor of around 7.5 and the He and H₂ permeability coefficients by a factor of around 4 was achieved by adding 7 wt% IL and 10 wt% ZIF-8 to the PEI matrix. Moreover, diffusion was evidenced as a governing factor in the studied membrane series.