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This review mainly focuses on the latest development of high-strength and high-toughness polyurethanes based on supramolecular interactions, and provides a comprehensive analysis of the main types, synthetic strategies, and strengthening mechanisms.

A high-strength and high-toughness thermosetting polyurethane, which has shape memory effects as well as self-healing performance to extend its service life.

Traditional “top-down” methods for graphene preparation, like micromechanical cleavage and ultrasound methods, usually cannot preserve both efficiency and quality simultaneously. Herein, we provide an environmental-friendly graphene exfoliating method with high efficiency and high quality that combines the microfluidization process (liquid phase) and supercritical carbon dioxide process (gas phase), namely the dual-phase exfoliating (DPE) method. The combination of effective tangential force (shearing force) and normal force (push and pull), which are originally from microfluidization and supercritical carbon dioxide process, respectively, maximizes the exfoliating efficiency. The DPE method offers a high yield of up to 70.25% for graphene preparation (941.04 g per day theoretically), while the graphene sheets could remain single or a few layers (> 80%) and around micron size. By molecular dynamic simulations, it is theoretically proved that carbon dioxide can intercalate between graphite layers and expand the interlayer spacing under supercritical conditions. This DPE method, by combining the advantages of different phase processes, provides an ideal process design perspective for large-scale preparation of other 2D materials.

To address the challenge of realizing multifunctional polymers simultaneously exhibiting high strength and high toughness through molecular engineering, ultrastrong and supertough shape-memory poly(urea-urethane) (PUU) is fabricated by regulating: i) the reversible cross-links composed of rigid units and multiple hydrogen bonds, and ii) the molecular weight of soft segments. The optimal material exhibits an unparalleled strength of 84.2 MPa at a large elongation at a break of 925.6%, a superior toughness of 322.8 MJ m

Wave-absorbing materials are developing in the direction of “light weight, wide frequency band, thin layer and high strength”, and it is difficult to achieve the synergy between wave-absorbing performance and mechanical properties when graphene absorbent is compounded with a single resin matrix. In this paper, based on the preparation of a new composite absorbing wire with a graphene (GR)/spherical graphite (SG) double absorbent and polylactic acid (PLA)/thermoplastic polyurethane (TPU) double matrix, we proposed a new method to prepare samples for testing the electromagnetic parameters and tensile strength by fused deposition modeling (FDM). Furthermore, the effect of SG/GR ratio on the microwave absorbing properties and mechanical properties of PLA/TPU composites was specifically studied. It was found that when the ratio of SG/GR was small (0:5, 1:4), the dielectric loss (interfacial polarization loss, dipole polarization loss, conductivity loss) and attenuation ability of the composites were stronger, and the impedance matching was better. When the SG/GR ratio was large (5:0, 4:1), the composites had high strength and toughness. When the ratio of SG/GR was moderate (2:3, 3:2), it could retain the absorbing and mechanical properties of the absorbing materials. On the one hand, the SG and PLA/TPU matrix formed an “island structure”, which improves the dispersion of GR; on the other hand, the GR and PLA/TPU matrix formed a “core-shell structure”, which promotes polarization and multiple scattering.

Recycling is a major approach in developing sustainable polymers to cope with environmental pollution and resource waste, but it still remains a challenge to design high-performance closed-loop rec...

As an important industry to the national economy and people’s livelihood, the power industry has become a dataintensive industry after years of information construction. Among them, electricity data covers the whole industry and tens of thousands of households, so it is of great significance and value to conduct in-depth analysis and research on large power data. The existing power consumption data has the problem of low quality, which is mainly manifested in data missing and anomaly, which has a great impact on the accuracy of data analysis. Therefore, the cleaning of power consumption data is the first problem that industry personnel will face. However, there are many problems in the existing data cleaning methods, which have failed to achieve good results in the business scenario of power consumption data. Therefore, this paper presents a daily power data cleaning model based on FDA, which successfully finds and eliminates abnormal values of power data, and can repair the missing values. The experimental results show that the data cleaning method proposed in this paper has a good effect on the real electricity data scenario.

The study of materials with lightweight and high-performance microwave absorption in low frequency range is of great significance for many critical fields. Nevertheless, the prominent issues of traditional absorbing materials such as high dielectric constant and thick thickness seriously restrict their practical applications. Consequently, ultimate aims for the development of high-performance multicomponent microwave absorbing materials with lightweight and high reflection loss are urgently required in the low frequency range. A spherical-like nanohybrids of reduced graphene oxide/ZnFe2O4/Ni (RGO/ZnFe2O4/Ni) in paraffin with an outstanding microwave absorption property was synthesized by hydrothermal method. When increased content of RGO/ZnFe2O4/Ni nanohybrids to 40 wt%, the best reflection loss (RL) of − 22.57 dB occurred at 4.21 GHz with a thickness of only 2.5 mm and the absorption bandwidth (RL ≤ − 10 dB) covered from 3.6 to 10.22 GHz with thin thickness of 1.5–4.0 mm. A possible absorption mechanism of RGO/ZnFe2O4/Ni in Paraffin wax was discussed. This work demonstrates that RGO/ZnFe2O4/Ni nanohybrids as a powerful candidate microwave absorber in low frequency could provide a new strategy for designing carbon-based microwave absorbing materials with lightweight.

Interfacial issues have always been the top priority of tribology which directly affect tribological performance of friction materials and output characteristics of Ultrasonic Motors (USMs). Therefore, from the perspective of bionics, a series of surface textures with different parameters were designed to regulate friction interface. The tribological properties of textured friction materials were systematically analyzed. The results found that tribological performance was affected by positive and negative aspects. Consequently, there is an optimal parameter in the case of the best tribological behavior. The optimal parameter was obtained by virtue of orthogonal experimental design and matrix analysis based on mathematical statistics. Additionally, the energy conversion efficiency of USMs with textured friction materials compared to untextured samples increased by 29%.

Integrating good strength and toughness, high thermostability, and easy processability into one shape memory polymers is highly desirable yet challenging. Herein, we demonstrate an approach to fabr...

Currently, the application of polyimide (PI) based materials often demands mutual additional properties, such as high thermal conductivity, good flexibility, high thermal stability and low dielectric constant and loss, etc.. Herein, a well-aligned hierarchical “brick and plank” architecture by rational assembly of dopamine modified hexagonal boron nitride flakes and nanoparticles (PDA-BNF@BNNPs) which can effectively improve the thermal conductivity, thermal stability, electrical conductivity, dielectric properties and shape memory performance of pure PI. The alternating stacking of vertically arranged h-BNNPs and horizontally laid h-BNFs yield a quasi-isotropic thermal conductivity of PI films with a high through-plane thermal conductivity of 6.43 W/(mK) and an in-plane thermal conductivity of 11.85 W/(mK) because of the simultaneously vertical and horizontal phonon scattering enabled by the vertically arranged h-BNNPs and horizontally laid h-BNFs. Besides, this special structure also endues PI films high thermal stability of over 560 oC, prominent electrical resistance of over 1.40 × 10-13 Ω•cm, and low dielectric loss of less than 0.02 in the high frequency. Moreover, the PDA-BNF@BNNP/PI films exhibit excellent flexibility and shape memory performance with faster recovery response time reduced over 50 % comparing with that of pure PI film. These outstanding properties combining with the facile and scalable fabrication process make PDA-BNF@BNNP/PI films are very promising in diverse electronic device applications, especially in flexible electronic devices or circuits requiring additionally high thermal conductivity and low dielectric loss.

The two-dimensional (2D) material of graphitic carbon nitride (g-C3N4) has shown great promise for tribo-materials due to special molecular structure. In this work, we report an effective approach to enhance anti-wear of thermosetting polyimide (TPI) by filling with g-C3N4 under high temperature. TPI composite (TPT-1) and g-C3N4 were firstly prepared. Then, friction and wear behavior of TPT-1 was studied and comparatively evaluated with neat resin from room temperature to 350 °C. As a result, the wear resistance of TPI was able to significantly improve and an much lower wear rate (7.29 × 10−7 mm3/N m) was achieved at 350 °C. Moreover, mechanism of friction and wear was demonstrated that transfer film formed by introducing g-C3N4 with high E-modulus and hardness could effectively share the load with TPI and prevent from further abrasion of resin in contact surfaces. This work could help researchers to design a new TPI tribo-material used at high temperature.

A series of asymmetric polyimide (PI) films were prepared via polycondensation of 2,3,3′,4′-biphenyl-tetracarboxylic acid dianhydride (a-BPDA) with a pair of isomer 4,4′-oxydianiline (4,4′-ODA) and 3,4′-oxydianiline (3,4′-ODA). The effects of isomerism on the thermal stability, mechanical and tribological properties were systematically investigated. When molar fraction of 4,4′-ODA was increased in PI macromolecular chain, it had little significant effect on the nano-indentation hardness number and thermal stability. Furthermore, more of 4,4′-ODA monomer in PI increased the elongation at break but reduced the tensile strength, as well as it resulted in a lower coefficient of frictions(COFs). This evolution was related to macromolecular chain conformation caused by different monomer configurations. PI with a linear monomer (4,4′-ODA) resulted in a lower COFs and better wear-resistance.

Conventional polyimide nanocomposites reinforced with graphene-based nanofillers usually possess excellent properties, such as high thermal decomposition temperature, enhanced tensile strength, tensile modulus, etc. However, the elongation at break of the nanocomposites is reduced. Here, we prepared N-doped graphene quantum dots/colorless polyimide nanocomposite (N-GQDs/CPI) films for the first time by in-situ polymerization, whose elongation at break is about 2 times that of the pure film. Meanwhile, the thermal properties and other mechanical properties of the films are improved. Through analyzing FT-IR, XPS, XRD, TAG SEM, etc. of N-GQDs and the films, we consider that the strengthening mechanism of matrix performance is attributed to N-GQDs' well dispersion, its small size effects and strong interface interaction with the matrix. Furthermore, at the indicative wavelength of 550 nm, the optical transmittance of the film with 1 wt% N-GQDs still maintains 79%, indicating the resulting films have excellent optical transmittance. The hydrophilic properties of the prepared films' surface is reduced, their water surface contact angle are increased from 63 ± 2.7° to 92 ± 1.7° with the content of N-GQDs increasing. This research shows that N-GQDs can enhance the various properties of polyimide and provides a high performance nanocomposite films for potential flexible substrates. Keywords: N-doped graphene quantum dots, Polyimide nanocomposite films, Thermal properties, Mechanical properties

With the development of energy-saving industries, the tribology and thermal management of composites were increasingly urgent. Here, we explored the dual-network graphene/epoxy composites with enhanced tribological and thermal management. The 3D graphene was prepared using calcium ions as the crosslinker and melamine foam as template. Subsequently, the reinforced concrete-like composites were obtained by dipping in silica-filled epoxy. The research results show that the thermal conductivity of the composites was enhanced by 1015.52% compared to the silica-filled epoxy. Simultaneously, the friction coefficient of the composites was reduced to 0.29 with the wear rate be reduced to 0.19 × 10−5 mm3/N∙m under the condition of 5 N and 2 cm/s. This dual-network model provides a new strategy for the development of solid lubricating materials with excellent thermal management.

The combination of shape memory with other new-fashioned functions will facilitate great potential in the development of shape memory materials. Demonstrated here is a multifunctional polymer based on hyperbranched polyimides (HBPIs) that integrates shape memory into a gas capture membrane. The new kind of shape memory gas capture HBPIs were prepared by branching conventional thermoplastic polyimides via a two-step method with 2,4,6-triaminopyrimidine (TAP) as the branched center. The optimized HBPIs exhibit good shape-memory properties with shape fixity above 98% and recovery values above 82%. Moreover, they show large Brunauer–Emmett–Teller (BET) surface areas (218–387 m2 g−1), mesoporous characteristics (3–5 nm) and narrow pore size distribution, which endow them with preferable CO2 capture (up to 36.93 cm3 g−1) and selectivity (up to 66.3). The comprehensive properties, especially the shape recovery ratio and CO2 uptake, of the HBPIs can be effectively controlled by adjusting the degree of branching (DB) or the content of the rigid heterocyclic diamine, 5-amino-2-(4-aminobenzene) benzoxazole (BOA). Our multifunctional shape memory polymer (SMP) may expand the application field of shape memory and accelerate the development of SMPs.

The seperation of control layer from data layer through SDN (software defined network) enables network administrators to plan the network programmatically without changing network devices, realizing flexible configuration of network devices and fast forwarding of data flows. The controller sends the flow table down to the switch, and the data flow is forwarded through matching flow table items. However, the current flow table resources of the SDN switch are very limited. Therefore, this paper studies the technology of the latest SDN Flow table optimization at home and abroad, proposes an efficient optimization scheme of Flow table item on the main road through the directional flood algorithm, and realizes related applications by setting up experimental topology. Experiments show that this scheme can greatly reduce the number of flow table items of switches, especially the more hosts there are in the topology, the more obvious the experimental effect is. This method can solve the problem of insufficient resources of Flow table items of Open Flow switch, and the experiment proves that the optimization success rate is over 90%.

The soft lithographic fabrication of high-aspect-ratio polydimethylsiloxane (PDMS) microstructures is quite challenging because of the strong interfacial adhesion between them and masters during demolding. This paper presents a simple method for fabricating high-aspect-ratio PDMS microstructures by reducing the interfacial adhesion through the cooling process. The effect of cooling process on the topography, elastic property, and adhesion property of Sylgard 184 PDMS is studied. It is found that wrinkles are formed on the surface of PDMS and that the Young’s modulus of PDMS is increased by the air cooling process. Consequently, the air-cooled PDMS has lower adhesion than the traditional oven-cooled PDMS. This result could be explained by the adhesion parameter theory: both the high amplitude of the wrinkles formed on the surface of PDMS and the high Young’s modulus of PDMS increase separation forces and reduce adhesive forces in the interface. Application of this method is demonstrated by fabricating PDMS microchannels from a silicon master which has microstructures with different aspect ratios. Compared with PDMS microchannels obtained by the oven cooling process, PDMS microchannels with a depth of 200 μm and an aspect ratio of 10 are successfully fabricated by the air cooling process.