This study focused on the preparation of poly(ε-caprolactone)/carbon nanotubes (PCL/CNTs) composite membranes via electrospinning technology and investigated their performance in oil–water separation. The effects of varying CNTs contents and spinning parameters on the structure and properties of the membrane materials were systematically studied. A highly uniform diameter distribution of the PCL fiber was achieved by using the dichloromethane/dimethylformamide (DCM/DMF) composite solvent with volume ratio of 7:3, as well as a PCL concentration of ca. 17 wt.%. The optimal electrospinning parameters were identified as an applied voltage of 18 kV and a syringe pump flow rate of 1 mL·h⁻¹, which collectively ensured uniform fiber morphology under the specified processing conditions. The critical threshold concentration of CNTs in the composite system was determined to be 1 wt.%, above which the composite fibers exhibit a significant increase in diameter heterogeneity. Both pristine PCL fibrous membranes and PCL/CNTs composite membranes demonstrated excellent and stable oil–water separation performance, with separation efficiencies consistently around 90%. Notably, no significant attenuation in separation efficiency was observed after ten consecutive separation cycles. Furthermore, when incorporating 0.5 wt.% CNTs, the PCL/CNT composite membranes exhibited a 20% increase in separation flux for heavy oils compared to pristine PCL membranes. Additionally, CNTs, as a prototypical class of nanofillers for polymer matrix reinforcement, can potentially enhance the mechanical properties of composite films, thus effectively prolonging their service life.

Nanofibers, as nucleating agents, can significantly alter the nucleation and growth dynamics of polymer crystallization, thereby modulating the morphology and structure of crystals to enhance mechanical performance of the materials. In this study, the effects of nanofibrillar nucleating agent 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS) content, melting temperature, and injection speed on the crystallization behavior and mechanical performance of isotactic polypropylene (iPP) were systematically investigated. The incorporation of DMDBS significantly increased the number of iPP nuclei, reduced crystal size and raised the onset crystallization temperature by approximately 11 °C. Concurrently, the tensile strength and elastic modulus of injection-molded iPP samples improved by 15% and 55%, respectively. However, a rise in the melting temperature led to a decrease in the crystallinity, tensile strength, elastic modulus, and impact strength of both neat iPP and iPP/DMDBS samples. With the increase in injection speed, the tensile strength and elastic modulus of iPP/DMDBS samples increased. During the crystallization process, DMDBS crystallizes prior to the iPP melt, forming the nanofibrillar network that effectively reduced the energy barrier for iPP crystal nucleation. Furthermore, under the influence of shear forces during processing, the presence of these nanofibrillar networks promoted the formation of oriented crystalline structures, which in turn contributed to the enhanced tensile strength and elastic modulus observed in iPP samples.

Shape memory polymers (SMPs) and their multifunctional composites have become important material systems for 4D printing because they can be processed into structures with programmed deformation and stimulus-responsive actuation. After being fixed in a temporary configuration, SMPs are able to recover their permanent shape when exposed to heat, electric or magnetic fields, and so on. This reversible shape change gives printed SMP structures functions beyond those of conventional static components, making them useful for biomedical devices, flexible electronics, and soft robotics. The performance of 4D-printed SMPs is determined not only by material chemistry but also by the design of the printed architecture and the manner in which external stimuli are applied. This review begins by covering the basic mechanisms that govern shape memory behavior in SMPs, including molecular switching, thermomechanical programming, and stimulus-controlled recovery. On this basis, representative printing methods for SMPs are compared, including stereolithography (SLA), fused deposition modeling (FDM), direct-write printing, and polymer inkjet printing. Recent applications are then considered in areas where programmed shape change has practical value, such as biomedical devices, soft robotics, and flexible electronics. The discussion also identifies unresolved problems in printing resolution, response speed, cyclic stability, structural design, and multifunctional coupling, which remain central barriers to wider use of 4D-printed SMP systems.

Large-diameter longitudinal submerged arc welded (LSAW) pipes represent a critical component of long-distance oil and gas transmission pipelines. To enhance the forming efficiency of the JCO (J-shape to C-shape to O-shape) forming process for LSAW pipes, and to reduce residual straight segment in order to minimize the ovality of the formed pipes, an asymmetric four-point air bending (AFB) process was proposed. In this process, one end of the sheet contacts the dies with a straight segment, while the other end contacts a circular arc segment. The distribution of bending moments and mechanical model under different bending stages were analyzed, and analytical formulas for the main forming indexes before and after springback were derived. Experimental and finite element simulation verification were conducted for the AFB process. The results indicated that the error between the experimental and simulation results and the theoretical results was small, and the variation trends were consistent. Furthermore, the ellipticity of the pipes formed by the AFB process was less than 0.66%, which is obviously lower than that of the pipe formed by the symmetric four-point air bending (SFB) process. The forming quality and production efficiency of the pipe is improved, thereby proving the feasibility and reliability of the AFB process and promoting the development of LSAW pipe JCO forming processes.

The current progressive forming process for large-scale longitudinally submerged arc-welded (LSAW) pipes is continuously losing competitiveness in terms of manufacturing quality and production efficiency. Based on the asymmetric four-point bending (AFB) mechanical model and classical elastic–plastic bending theory, in this paper, we investigate sheet bending behavior during the four-point bending stage. Analytical expressions are derived for the main influencing factors during the forming and springback process. Finite element simulation and experimental research into the mechanical model are conducted to analyze the effects of various process parameters on the forming results. On this basis, an AFB progressive forming process parameter formulation strategy is established and programmed. Experiments and simulations were conducted using the process parameters formulated by this strategy. The results showed that pipes could complete the progressive forming process in fewer passes, thereby improving production efficiency. The ovality of most experimental pipes was less than 1.5% and consistently below 0.7% in simulations—significantly lower than the engineering requirement of 2%. These results demonstrate the feasibility and reliability of the strategy, highlight the significant improvement in pipe quality achieved through the AFB process, and lay a solid foundation for the development and intelligentization of future progressive forming processes for LSAW pipes.

Flexible strain sensors are crucial for wearable electronics and human–machine interaction, yet simultaneously achieving high sensitivity and a broad working range remains challenging. Here, a high-performance strain sensor is developed by integrating carbon nanotubes (CNTs)/reduced graphene oxide (rGO) hybrid conductive networks with electrospun thermoplastic polyurethane (TPU) nanofibers, followed by pre-stretching to engineer a dual-microcrack architecture. The synergistic interplay between 1D CNTs and 2D rGO stabilizes conductive pathways, while strain-regulated microcrack evolution amplifies resistance variation. The sensor delivers a wide strain range of up to 100%, with gauge factors of 75.2, 1600.5, and 7484.5 across 0–32%, 32–60%, and 60–100% strain, respectively. It further exhibits a rapid response/recovery time of 30/40 ms, a low detection limit of 0.01%, and excellent durability over 1000 cycles. Benefiting from these comprehensive superior sensing performances, the sensor can reliably monitor both subtle human physiological signals and large-amplitude human motions, demonstrating great application potential in wearable health monitoring, intelligent motion perception and human–machine interaction fields.