Polymers最新文献

Advances in modern industry largely depend on the development of high-performance materials. In this study, the influence of hexagonal boron nitride (h-BN) filler on the performance of glass fiber/epoxy laminates was systematically investigated. Composites containing h-BN with different particle sizes (65-75 nm and 790 nm) and contents (0.2 and 0.4 wt.%) were fabricated, and their mechanical (tensile, in-plane shear, hardness, impact), thermal (Differential Scanning Calorimetry, DSC), electrical (volume resistivity), and spectroscopic (Fourier Transform Infrared Spectroscopy, FTIR) properties were examined. The results demonstrated that specimens with 65-75 nm h-BN at 0.2 wt.% exhibited the highest tensile and shear strengths, whereas those with 790 nm h-BN at 0.4 wt.% showed superior impact resistance and hardness. DSC analyses revealed that h-BN addition increased the glass transition temperature (Tg), while FTIR confirmed interfacial interactions between h-BN and the epoxy matrix. Electrical measurements indicated that h-BN preserved the insulating nature of the composites, with only limited reductions in resistivity observed at higher contents of larger particles due to morphological effects. Overall, these findings highlight that h-BN filler enhances load transfer efficiency, thermal stability, and mechanical reliability, offering significant potential for applications requiring multifunctional performance, such as aerospace, marine, and electrical and electronic insulation systems.

Powder melt extrusion (PME) represents an alternative approach for personalized oral dosage forms. Furthermore, the utilization of agricultural waste has gained increasing attention because it helps reduce pollution from waste. This study investigated cellulose powders and short fibers from agricultural waste as supporting materials for the PME-based production of shape-changing levodopa printlets. Formulations containing cellulose powder (CP), cassava short fiber (CSF), and pineapple short fiber (PSF) demonstrated successful printing. The selected formulations were characterized for morphology, thermal transitions, crystallinity, shape-changing behavior, and drug release. CSF demonstrated superior printability, enhanced shape recovery, and the greatest reduction in crystallinity, supporting amorphous solid dispersion formation. Levodopa-loaded printlets showed uniform and high drug content. The formulation containing 5% CSF and levodopa exhibited the fastest initial release, attributed to its low crystallinity and Super Case II transport mechanism. Overall, this study highlights the feasibility of using natural cellulose as an additive in PME to develop sustainable, shape-changing drug delivery systems and advances PME knowledge by integrating agricultural waste derived cellulose fibers with levodopa processing that provide new insight into the material-process-performance relationship in PME systems.

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Magnetorheological elastomers (MREs) have attracted considerable attention in high-precision sensing and intelligent control due to their responsive sensitivity. The magnetostrictive properties of MREs excited by magneto-mechanical coupling at the mesoscopic scale show broad application potential but have not yet been fully elucidated. In this study, the magnetostrictive properties were investigated at the mesoscopic scale through theoretical modeling, numerical simulation and experimental research. A correction factor was introduced to address the limitations of conventional magnetic dipole theory under near-field conditions, thereby providing a rational theoretical explanation of magnetostrictive behavior. Visualization analysis was performed using the finite element method (FEM). Subsequently, MREs were prepared under various solidified magnetic fields, and their performance was validated through scanning electron microscopy (SEM) and a laser displacement sensor. The results demonstrated that magnetostriction is determined by the relative angle between the particle chain and the magnetic field direction. The linearity of the particle chain was found to be positively correlated with magnetostriction. The maximum theoretical and experimental magnetostrictive elongations reached 0.9% and 0.565%, respectively, while the maximum theoretical and experimental magnetostrictive compression reached 2.77% and 1.81%, respectively. This work provides significant scientific insights into the magneto-mechanical energy conversion mechanism and contributes to the development of magnetostrictive instruments.

The paper continues the authors' efforts to characterize and control the shape memory effect (SME) occurring in 3D printed specimens of recycled polyethylene terephthalate (rPET) and polyethylene terephthalate glycol (rPETG). Lamellar and "dog-bone" configuration specimens were 3D printed in the form of stratified composites with five different rPET/rPETG ratios, 100:0, 60:40, 50:50, 40:60, and 0:100, and two different angles between the specimen's axis and the deposition direction, 0° and 45°. The lamellar specimens were used for: (i) free-recovery SME-investigating experiments, which monitored the variation of the displacement, of the free end of specimens which were bent at room temperature (RT), vs. temperature, during heating, (ii) differential scanning calorimetry (DSC), which emphasized heat flow variation vs. temperature, during glass transition and (iii) dynamic mechanical analysis (DMA), which recorded storage modulus vs. temperature in the glass transition interval. Dog-bone specimens were subjected to tensile failure and loading-unloading tests, performed at RT. The broken gauges were metallized with an Au layer and analyzed by scanning electron microscopy (SEM). The results showed that the specimens printed with 0° raster developed larger free-recovery SME strokes, the largest one corresponding to the specimen with rPET/rPETG = 40:60, which experienced the highest storage modulus increase, 872 MPa, and maximum value, 1818 MPa, during heating. The straight lamellar composite specimens experienced a supplementary shape recovery when bent at RT and heated, in such a way that their upper surface became concave, at the end of heating. Most of the specimens 3D printed at 0° raster developed stress failure plateaus, which were associated with the formation of delamination areas on SEM fractographs, while the specimens printed with 45° raster angle experienced necking failures, associated with the formation of crazing areas. The results suggested that 3D printed stratified rPET-rPETG composites, with dedicated spatial configurations, have the potential to serve as executive elements of light actuators for low-temperature operation.

Self-powered perovskite photodiodes provide an attractive platform for low-power and high-sensitivity photodetection; however, their performance capabilities are often constrained by inefficient interfacial charge extraction and noise suppression. Here, we report a polymer-mediated interfacial engineering strategy for methylammonium lead iodide (MAPbI₃) photodiodes by integrating thermally optimized nickel oxide (NiO_x) hole-transport layers (HTLs) with a nonionic polymeric surfactant, poly(oxyethylene)(10) tridecyl ether (PTE). NiO_x films annealed at 300 °C establish a favorable energetic baseline for hole extraction, while the ppm-level incorporation of PTE into the MAPbI₃ precursor enables the molecular-scale modulation of the NiO_x/MAPbI₃ interface without forming an additional interlayer. The external quantum efficiency at 640 nm increases from 78.7% for pristine MAPbI₃ to 84.1% and 84.6% for devices incorporating 30 and 60 ppm PTE, corresponding to enhanced responsivities of 406, 434, and 437 mA/W. These improvements translate into reduced noise-equivalent power and an increase in the noise-limited detectivity from 2.50 × 10¹² to 2.76 × 10¹² Jones under zero-bias operation. Importantly, enhanced sensitivity is achieved without compromising the dynamic performance, as all devices retain fast temporal responses and kilohertz-level bandwidths. These results establish polymeric-surfactant-assisted interfacial engineering as a scalable and effective platform for low-noise, high-sensitivity self-powered perovskite photodiodes for renewable-energy-integrated systems.

Shape memory polymer (SMP) has broad applications in various industries, including automotive, aerospace, and medical, as it can maintain a given shape and return to its original form upon exposure to external stimuli such as heat, magnetic fields, or light. However, the intrinsic limitation of epoxy results in the low thermal conductivity of SMP, which reduces the difference in temperature (ΔT) between the glass transition temperature (T_g) and the actuation temperature, thereby negatively affecting the performance of shape recovery. In this study, the thermal stability and curing characteristics of SMP fabricated by blending Bisphenol-A epoxy with two types of amine curing agents were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to establish optimal fabrication conditions. Subsequently, carbon-based fillers, graphite and 60 μm long carbon fibers, were added to fabricate shape memory polymer composites (SMPCs). The curing and mechanical properties of the SMPCs were subsequently evaluated, and the shape recovery characteristics were found to be optimal at a filler content of 3 wt%. The recovery time for the SMPC with graphite was 25 s, representing a 68.75% improvement in shape recovery time from the SMP. Furthermore, the addition of carbon fibers, with improved dispersion, led to the highest increases in tensile strength and impact strength of 24.71% and 59.36%, respectively.

A major challenge for halogen-free flame retardants is their tendency to migrate under high-temperature and high-humidity environments. For instance, the combination of aluminum diethylphosphinate (ADP) and melamine polyphosphate (MPP) used in polyamide 66 (PA66) easily migrated to the surface, leading to a white and frost-like appearance. To address this issue, a core-shell elastic flame retardant (SiR@FR) was prepared via a solution deposition method, wherein a polymethylsiloxane (SiR) layer was encapsulated on the surface of ADP and MPP. This shell not only improved the hydrophobicity of the FR but also the toughness of PA66. Experimental results demonstrated that PA66 with 9-SiR@FR (PA66-5) exhibited excellent migration resistance, with no visible surface whitening after 480 h of aging at 85 °C and 85% relative humidity. Meanwhile, PA66-5 displayed outstanding flame retardancy, achieving a UL-94 V-0 rating with an approximate 65% decrease in peak heat release rate compared with control PA66. Furthermore, SiR@FR enhanced the toughness of PA66 by alleviating stress concentration, resulting in a 21% increase in impact strength. This study presents a simple but reliable encapsulation strategy for fabricating flame-retardant PA66 composites that combine superior migration resistance and satisfactory mechanical properties, showing promising potential for demanding applications requiring long-term usability and stability.

Ultra-high-molecular-weight polyethylene (UHMWPE) thin films are considered promising shielding materials against hypervelocity microparticle impacts in space environments. In this study, a finite element-smoothed particle hydrodynamics (FEM-SPH) adaptive coupling simulation method was developed to reveal the damage mechanisms of UHMWPE films impacted by alumina (Al₂O₃) particles with a diameter of 10 μm. A 100 μm thick single-layer UHMWPE film was subjected to normal impacts at velocities ranging from 1 to 30 km/s. The morphology and characteristics of craters formed on the film surface were analyzed, revealing the velocity-dependent transition from plastic deformation to complete perforation. At 10 km/s, additional oblique impact simulations at 30°, 45°, 60° and 75° were performed to assess the effect of impact angle on damage morphology. Furthermore, the damage evolution in double-layer UHMWPE films was examined under impact velocities of 5, 10, 15, 20 and 25 km/s, showing enhanced protective performance compared to single-layer films. Finally, the critical influence parameters for UHMWPE failure were discussed, providing criteria for evaluating the shielding limits. This work offers computational methods and predictive tools for assessing hypervelocity microparticle impact and contributes to the structural protection design of spacecraft operating in the harsh space environment.

To optimize the aerodynamic performance of the aircraft across its entire cross-section, wing shape control must be maintained based on flight operating conditions. A high-temperature flexible textile composite, which is the key to achieving the deformation of an aircraft wing, is urgently required in the deformable structure of high-speed aircraft. In this work, a novel type of flexible textile composite with enhanced temperature resistance was fabricated by plain-woven carbon fibers coated with silicone rubber. The material testing was carried out in a wind tunnel to simulate both the harsh temperature field distribution and the mechanical loads caused by aerodynamic forces under the flight profile. For the first time, temperatures exceeding 1000 °C were attained on the windward side of an aircraft wing with a peak recorded temperature of 1600 °C. The failure mechanisms of the flexible composites are revealed, and the thermal stability of the composites is evaluated. The results show that the significant tensile anisotropy in the flexible composites is along different off-axis angles, and the failure modes also change with the off-axis angle. The material does not show significant high-temperature oxidation ablation under thermo-mechanical coupling. This work reveals that under the triple action of such high temperatures, stress caused by wing surface tensioning, and the mechanical load caused by aerodynamic forces, the failure mechanism of the flexible textile composite is dominated by the mechanical load at high temperatures rather than by thermal instability, as is conventionally claimed.