Cross-linked Network Structure Research Articles

Controlled Preparation of Cross-Linked SnO2 Hollow Nanotube Networks for Electrocatalytic CO2 Reduction

The electrochemical system based on water, CO2, and electricity is the key technology to realize the coexistence and combination of renewable energy and fossil energy, which can convert CO2 molecules into high-value-added products under mild and controlled conditions, thus achieving carbon neutrality. Designing efficient electrocatalysts to realize highly active, selective, and stable CO2RR has become one of the vital issues. Particularly, the nanostructure design and interface adjustment of electrocatalysts have been regarded as the key points for improving their catalytic performance. Herein, a tin dioxide hollow nanotube (SnO2 HNT) catalyst with a three-dimensional cross-linked network structure has been fabricated by electrospinning and rapid-heating calcination. The morphology and component structure of SnO2 HNTs were analyzed by a series of characterizations. The performance in electrocatalytic carbon dioxide reduction reaction (eCO2RR) was further tested. Owing to the hollow nanostructure, the catalyst possessed a large specific surface area and abundant active sites, which greatly accelerated mass transport and electron mobility. During eCO2RR, SnO2 HNTs achieved a peak faraday efficiency value of 87.4% for C1 products at −1.1 V vs RHE, which significantly suppressed the occurrence of hydrogen evolution side reactions. In addition, compared with the commercial SnO2 nanoparticles or partially reduced Sn/SnO2, the catalytic activity and selectivity of CO2-to-formate conversion significantly increased under the same potential, indicating that the optimization of electronic/geometric structure for high-yield metal oxides can effectively improve the comprehensive performance of eCO2RR.

Air oxidation and hyperbranched crosslinking approach for a boiling water-resistant sucrose-derived wood adhesive

At present, petroleum-based adhesives, which are widely used in the wood adhesive sector, are facing problems such as environmental pollution and harm to humans. It has therefore become crucial to replace traditional petroleum-based adhesives with new biomass-based adhesives. Sucrose, which is widely available in plants and has the advantages of being sustainable and inexpensive, provides the basis for the preparation of biomass adhesives. In this experiment, the preparation of sucrose based hyperbranched polyamine adhesive was achieved by air oxidation and hyperbranched cross-linking strategies. The structure of the sucrose based hyperbranched polyamine adhesive was investigated by FTIR, 13C NMR, XPS, LC-MS, DSC and GPC, and a tightly cross-linked network structure was formed by sucrose oxidation and internal graft copolymerisation of polyamino compounds. The best performing sucrose-based biomass binder was screened by the controlled variable method by varying the sucrose/hyperbranched polyamine molar ratio, reaction time, hydrolysis time and reaction temperature respectively. While the dry shear strength of the plywood reached 2.40 MPa, the wet shear strength in hot water and boiling water at 63 °C reached 1.16 MPa and 1.10 MPa respectively. The experimental procedure is simple, the material is inexpensive and the sucrose based hyperbranched polyamine adhesive produced has excellent properties. This hyperbranched crosslinking strategy provides a potential synthetic approach for the development of biomass-based wood adhesives.

Cross-linked Polyimide Nanofibrous Aerogels with Hierarchical Cellular Structure for Thermal Insulation

Due to their low bulk density, high porosity, and functional performance, aerogels are ideal candidates for a variety of applications. However, their potential application in a variety of fields is limited by their time-consuming and costly complex fabrication process. In this study, electrospun 3-aminopropyltriethoxysilane-grafted polyimide (PI@APTES) nanofibers were used to construct nanofibrous aerogels (NFAs) via freeze-drying a dispersion of cross-linked-PI short fibers and a binder (PI@APTES), resulting in improved properties and functionalities. A highly siloxane cross-linked network structure was formed by hydrolysis and condensation reactions to generate stable nanofibrous aerogels. The obtained polyimide nanofibrous aerogels (PiNFAs) had a hierarchically three-dimensional (3D) microporous structure, high porosity (over 98%), tunable densities (10.6 ± 0.7–13.6 ± 0.2 mg cm–3), solvent resistance, superhydrophobicity (water contact angle over 163°), low thermal conductivity (as low as 33.2 mW m–1 K–1), and mechanical stability. These PiNFAs are promising candidates for potential applications in thermal insulation, lightweight construction, filtration, and sensors.

Fabrication of anti-freezing and self-healing nanocomposite hydrogels based on zwitterionic proline and cellulose nanocrystals

Self-healing hydrogels with three-dimensional network cross-linked structure and adjustable properties have been considered as smart materials with promising multi-purpose applications. However, traditional self-healing hydrogels face the loss of mechanical properties at sub-zero temperatures, which may limit their application in various fields to some extent. In this manuscript, functional polydopamine (PDA) was successfully chemically modified on the surface of cellulose nanocrystals (CNCs) by self-oxidation polymerization in an alkaline environment. The nanocomposite hydrogels with self-healing and anti-freezing properties were successfully designed by introducing zwitterionic proline (ZP) and CNCs@PDA into the cross-linked network structure of gellan gum/polyacrylic acid (GG/PAA). When the ZP ratio increased, the anti-freezing performance of hydrogels was significantly enhanced. Even at −30 °C, the GG/PAA-CNCs@PDA-ZP-Ca2+ (GP/CP/ZP/Ca2+) nanocomposite hydrogels still maintain excellent stress (2.7 MPa) and high self-healing efficiency (82.9%). This work proposes an effective solution to prepare flexible hydrogels with anti-freezing capability, which will extend the temperature range of the flexible material and broaden the application area.

An initiator-free and solvent-free in-situ self-catalyzed crosslinked polymer electrolyte for all-solid-state lithium-metal batteries

Linear polymer (e.g. polyethylene oxide, PEO) based electrolytes have been widely studied due to their flexibility and relatively good contact against electrodes. However, the linear polymers are prone to crystallization at room temperature and melting at moderate temperature, restricting their application in lithium metal batteries. To address these problems, a self-catalyzed crosslinked polymer electrolyte (CPE) was designed and prepared by the reaction of poly (ethylene glycol diglycidyl ether) (PEGDGE) and polyoxypropylenediamine (PPO) with only the bistrifluoromethanesulfonimide lithium salt (LiTFSI) added and with no any initiators. LiTFSI catalyzed the reaction by reducing the activation energy to form a crosslinked network structure, which was identified by calculation, NMR and FTIR. The as-prepared CPE has high resilience and a low glass transition temperature (Tg = −60 °C). Meanwhile, the solvent-free in-situ polymerization technique has been adopted in the assembly of the CPE with electrodes to decrease the interfacial impedance greatly and improve the ionic conductivity to 2.05 × 10−5 S cm−1 and 2.55 × 10−4 S cm−1 at room temperature and 75 °C, respectively. As a result, the in-situ LiFeO4/CPE/Li battery exhibits outstanding thermal and electrochemical stability at 75 °C. Our work has proposed an initiator-free and solvent-free in-situ self-catalyzed strategy of preparing high performance crosslinked solid polymer electrolytes.

Tetrafunctional vinyl polysilsesquioxane and its covalently cross-linked vinyl liquid silicone rubber for resistance to high temperature oxidation combustion and ablative behavior

A novel lightweight tetrafunctional vinyl polysilsesquioxane (TV-DDSQ) was designed and synthesized as a crosslinking-modifier for vinyl liquid silicone rubber (SR) to form a denser cross-linked network structure and introduce a high-temperature resistant cage structure to obtained TV-DDSQ/SR resistance to high temperature oxidation combustion-ablation resistance composites (TV-DDSQ/SR). Compared to SR, 1 phr TV-DDSQ/SR exhibits good resistance to high temperature oxidation combustion (vertical combustion test to UL-94 V0) and excellent ablation properties (21.2 % reduction in linear ablation). The mechanism of ceramization transition of TV-DDSQ/SR under high temperature oxidation combustion and ablation resistance was investigated.

The Effect of Divinylbenzene on the Structure and Properties of Polyethylene Films with Related Radiation Chemical Grafted Polystyrene and Sulfocationite Membranes.

In the present work, the effect of divinylbenzene (DVB) on the kinetics of post-radiation chemical graft polymerization styrene (St) on polyethylene (PE) film and its structural and morphological features were investigated. It has been found that the dependence of the degree of polystyrene (PS) grafting on the DVB concentration in the solution is extreme. An increase in the rate of graft polymerization at low concentrations of DVB in the solution is associated with a decrease in the mobility of the growing chains of PS. A decrease in the rate of graft polymerization at high concentrations of DVB is associated with a decrease in the rate of diffusion of St and iron(II) ions in the cross-linked network structure of macromolecules of graft PS. A comparative analysis of the IR transmission and multiple attenuated total internal reflection spectra of the films with graft PS shows that graft polymerization of St in the presence of DVB leads to the enrichment of the film surface layers in PS. These results have been confirmed by the data on the distribution of sulfur in these films after sulfonation. The micrographs of the surface of the grafted films show the formation of cross-linked local microphases of PS with fixed interfaces.

Highly compressible and hydrophobic nanofibrillated cellulose aerogels for cyclic oil/water separation

Nanofibrillated cellulose (NFC)-based aerogels are ideal oil-sorbent materials, but the poor structural stability and hydrophilicity restrain their practical applications in the fields of oil/water separation. In the present work, we report a facile strategy for constructing a hydrophobic nanofibrillated cellulose aerogel for cyclic oil/water separation. Briefly, an aerogel matrix of C-g-PEI with multiple cross-linked network structures was constructed via the combined use of oxidized-NFC (ONC), polyethyleneimine (PEI), and ethylene glycol diglycidyl ether (EGDE), followed by rapid in situ deposition of poly(methyl trichlorosilane) (PMTS) through a low-temperature gas-solid reaction. The resulting ONC-based aerogel (C-g-PEI-PMTS) exhibits the advantages of ultralight (53.80 mg/cm3), high porosity (95.73 %), hydrophobicity (contact angle of 130.0°) and remarkable elasticity (95.86 %). Meanwhile, the composite aerogel of C-g-PEI-PMTS is extremely suitable for oil sorption-desorption by a simple mechanical squeezing method. After 10 cycles of sorption-desorption, the sorption capacity of the aerogel towards various oils reached almost the same level as in the first cycle. The filtration separation efficiency for the trichloromethane-water mixtures remained at 99 % after 50 cycles, demonstrating encouraging reusability. In summary, an efficient strategy to prepare NFC-based aerogel with highly compressible and hydrophobic properties is developed, which expands the applications of NFC in the fields of oil/water separation.

Silk fibroin/Ag nanowire-based multifunctional sensor for wearable self-powered wireless multi-sensing microsystems

Wearable sensing devices play an increasingly important role in advancing the rapid development of the Internet of Things (IoT) and artificial intelligence (AI), and a smart sensing network based on wide-distributed sensing nodes has become an appealing trend. However, monolithic integration of multiple sensing functions is still a critical issue for sensing nodes. Herein, we present a flexible multifunctional sensor based on a silk fibroin/silver nanowire (SF/AgNW) composite film. Mask spray coating technology is optimized to prepare the functional sensing layer with a cross-linked AgNW network structure inside. The association of the SF/AgNW composite film and the cross-linked AgNW network structure endows the developed sensor with pressure sensing characteristics and temperature sensing characteristics. Furthermore, by in-depth analysis of the coupling law between the input variables and the resistance changes, the sensor is successfully extended to realize the functions of finger proximity detection and human breathing monitoring. Additionally, the sensor is successfully confirmed to possess remarkable mechanical reliability and sensing characteristic stability by a systematic experiment. More importantly, to highlight the practical feasibility of the proposed sensor, an all-in-one self-powered wireless multi-sensing microsystem is constructed based on the developed sensor, a high-performance triboelectric-piezoelectric-electromagnetic hybrid generator (TPEHG), and system circuits. With the TPEHG as the only power source, the microsystem is successfully demonstrated to realize continuous self-powered work and sense environmental variables through the developed sensor. Meanwhile, the obtained sensing data are transmitted to a mobile phone in real time at 1 Hz. The multiple sensing characteristics of the sensor and the autonomous features of the microsystem give them outstanding potential and value in the smart IoT field, especially in constructing a distributed smart sensing network.

Preparation and Properties of a Lightweight, High-Strength, and Heat-Resistant Rigid Cross-Linked PVC Foam.

A rigid poly(vinyl chloride) foam with a cross-linked network structure was prepared by adding 3-glycidoxypropyltriethoxysilane (KH-561) into the universal formulation. The resulting foam had excellent heat resistance because of the increasing degree of cross-linking and number of Si-O bonds with a high heat resistance. The as-prepared foam was verified using Fourier-transform infrared spectroscopy (FTIR), energy-dispersive spectrometry (EDS) and foam residue (gel) analysis, which demonstrated that KH-561 was successfully grafted and cross-linked on the PVC chains. Finally, the effects of different KH-561 and NaHSO3 additions on the mechanical properties and heat resistance of the foams were studied. The results showed that the mechanical properties of the rigid cross-linked PVC foam were raised after adding a certain amount of KH-561 and NaHSO3. The residue (gel), decomposition temperature, and chemical stability of the foam significantly improved compared to the universal rigid cross-linked PVC foam (Tg = 72.2 °C). The Tg of the foam could reach 78.1 °C without any mechanical degradation. The results have important engineering application value regarding the preparation of lightweight, high-strength, heat-resistant, and rigid cross-linked PVC foam materials.

Skin substitutes based on gellan gum with mechanical and penetration compatibility to native human skin.

The study reports on a simple system to fabricate skin substitutes consisting of a naturally occurring bacterial polysaccharide gellan gum. Gelation was driven by the addition of a culture medium whose cations induced gellan gum crosslinking at physiological temperature, resulting in hydrogels. Human dermal fibroblasts were incorporated in these hydrogels and their mechanical, morphological, and penetration characteristics were studied. The mechanical properties were determined by means of oscillatory shear rheology, and a short linear viscoelastic regime was noted up to less than 1% of strain amplitude. The storage modulus increased with an increasing polymer concentration. The moduli were in the range noted for native human skin. After 2 weeks of fibroblast cultivation, the storage moduli showed signs of deterioration, so that a culture time of 2 weeks was proposed for further studies. Microscopic and fluorescent staining observations were documented. These depicted a crosslinked network structure in the hydrogels with a homogeneous distribution of cells and an assured cell viability of 2 weeks. H&E staining was also performed, which showed some traces of ECM formation in a few sections. Finally, caffeine penetration experiments were carried out with Franz diffusion cells. The hydrogels with a higher concentration of polymer containing cells showed an improved barrier function against caffeine compared to previously studied multicomponent hydrogels as well as commercially available 3D skin models. Therefore, these hydrogels displayed both mechanical and penetration compatibility with the ex vivo native human skin.

Performance of Thermal-Oxidative Aging on the Structure and Properties of Ethylene Propylene Diene Monomer (EPDM) Vulcanizates.

A thermal-oxidative aging test at 120 °C was conducted on ethylene propylene diene monomer (EPDM) vulcanizates of the semi-efficient vulcanization system. The effect of thermal-oxidative aging on EPDM vulcanizates was systematically studied by curing kinetics, aging coefficient, crosslinking density, macroscopic physical properties, contact angle, Fourier Transform Infrared Spectrometer (FTIR), Thermogravimetric analysis (TGA) and thermal decomposition kinetics. The results show that the content of hydroxyl and carbonyl groups as well as the carbonyl index increased with increasing aging time, indicating that EPDM vulcanizates were gradually oxidized and degraded. As a result, the EPDM vulcanized rubber chains were crosslinked with limited conformational transformation and weakened flexibility. The thermogravimetric analysis demonstrates that the thermal degradation of EPDM vulcanizates had competitive reactions of crosslinking and degradation, and the thermal decomposition curve can be divided into three stages; meanwhile, the thermal stability of EPDM vulcanizates gradually decreased with increasing aging time. The introduction of antioxidants in the system can promote the crosslinking speed and reduce the crosslinking density of EPDM vulcanizates while inhibiting the surface thermal and oxygen aging reaction. This was attributed to the fact that the antioxidant can reduce the thermal degradation reaction level, but it is not conducive to the formation of a perfect crosslinking network structure and reduces the activation energy of thermal degradation of the main chain.

Tailoring the microstructure and solid electrolyte interface of hard carbon to realize high-initial-coulombic-efficiency and high-rate sodium storage

As the most promising anode material for sodium-ion batteries (SIBs), hard carbon still suffers the drawbacks of low initial Coulombic efficiency (ICE) and poor rate performance, which restrict its practical application. How to tailor-design its microstructure and solid electrolyte interface (SEI) is crucial to address these challenges. Herein, a novel hard carbon material was fabricated by pyrolyzing the intermediate carbon precursor with crosslinked network structure generated through the interaction between phenolic resin and lignin. Its microstructure, consisting of the defect sites and interlayer distance, has been tailored and optimized through adjusting the carbonizing conditions. By employing ether electrolytes, the generated thinner SEI film endows the hard carbon electrode with lower interface impedance and faster Na+ transport kinetics. Benefiting from the tailored microstructure and SEI film, the obtained hard carbon material shows a higher ICE of 87%, a remarkable reversible capacity of 338 mA h g−1 after 500 cycles and superior rate performance of 268 mA h g−1 at 1C over 200 cycles (205 mA h g−1 at 6 C), much higher than the recently reported work. This work provides an effective strategy to develop the hard carbon anode with high ICE and high-rate sodium storage for practical SIBs.

Preparation and Characterization of Soybean Protein Adhesives Modified with an Environmental-Friendly Tannin-Based Resin.

Soybean protein-based adhesives are limited in their application due to their poor wet bonding strength and poor water resistance. Herein, we prepared a novel, environmentally friendly soybean protein-based adhesive by adding tannin-based resin (TR) to improve the performance of water resistance and wet bonding strength. The active sites of TR reacted with the soybean protein and its functional groups and formed strong cross-linked network structures, which improved the cross-link density of the adhesives and then improved the water resistance. The residual rate increased to 81.06% when 20 wt%TR was added, and the water resistance bonding strength reached 1.07 MPa, which fully met the Chinese national requirements for plywood (Class II, ≥0.7 MPa). SEM observations were performed on the fracture surfaces of all modified SPI adhesives after curing. The modified adhesive has a denser and smooth cross-section. Based on the TG and DTG plots, the thermal stability performance of the TR-modified SPI adhesive was improved when TR was added. The total weight loss of the adhesive decreased from 65.13% to 58.87%. This study provides a method for preparing low-cost and high-performance, environmentally friendly adhesives.

Reinforcing mechanically reclaimed polyurethane foam wastes‐based elastomer with modified recycled polyester fibers

AbstractPolyurethane foams are widely used in daily life due to their superior performance. However, it is very challenging to recycle and reuse waste polyurethane foams since the three‐dimensional crosslinking network structure makes them non‐melting and insoluble. In this work, a low‐cost, green, room‐temperature solid‐state shear milling method is proposed to break the cross‐linking bonds of waste polyurethane foam (crosslinking density decreases from 0.768 to 0.489 mol dm−3). The recycled polyurethane (RPU) powders regain their thermoplastic processability. Recycled waste polyester (PET) fibers are modified through plasma treatment and used as reinforcing fillers for the reprocessed RPU elastomer. Compared to original PET fibers, modified polyester (m‐PET) fibers construct strong interfacial interactions and physical interlocks with RPU matrix, leading to significantly enhanced mechanical properties. Molecular dynamics studies demonstrate that RPU/m‐PET composites have higher cohesive energy density and lower free volume, and significantly improved compatibility, which greatly promotes stress dissipation upon stretching. This study provides a feasible strategy for the high‐value recycling of waste polymer materials.

Preparation and Properties of a Novel Cross-Linked Network Waterborne Polyurethane for Wood Lacquer.

Waterborne polyurethane (WPU) is a waterborne coating with excellent physicochemical properties. Its deficiencies of water resistance, chemical resistance, staining, and hardness have limited the wide application of polyurethane in the wood lacquer market. In this study, polycarbonate diols (PCDL) were used as soft segments and WPCU was modified by cross-linking using Trimethylolpropane (TMP) to prepare polycarbonate type WPU (WPCU) with cross-linked network structure. The new wood lacquer was prepared by adding various additives and tested by applying it on wood board. The successful synthesis of WPCU was determined by FTIR testing, and the cross-linking degree of WPCU was probed by low-field NMR. The viscosity of the cross-linked WPCU emulsion showed a decreasing trend compared to the uncross-linked WPCU emulsion, and WPCU-2 had the smallest particle size. Compared with the uncrosslinked WPCU film, the crosslinked WPCU film had lower water absorption (2.2%), higher water contact angle (72.7°), excellent tensile strength (44.02 MPa), higher thermomechanical, and better water and alcohol resistance. The effect of crosslinker content on the microphase separation of WPCU chain segments on the surface roughness of the film was investigated by SEM. The wood paint prepared by WPCU emulsion has good dry heat resistance, chemical resistance, and adhesion, and the hardness of the wood paint when the TMP content is 3% reaches H. It also has good resistance to sticky stains, which can be used to develop new wood lacquer.

Reprocessable, Photothermal Phase Change Material-Based Hybrid Polymeric Networks for Solar-to-Thermal Energy Storage

Polymeric photothermal phase change material composite (PPCMC) networks with excellent reprocessability, high latent heat, and intrinsic network stability have the great advantages of solar energy storage and conservation and environmental protection resulting from the covalent crosslinking network structure and long-life inorganic photothermal agents. Herein, the reprocessable PPCMCs were successfully prepared by introducing the reactive diisocyanate-terminated poly(ethylene glycol) (PEG) and multiple amino-functionalized carbon black (CB)that serve as the phase change component and the photothermal curing agent, respectively. The phase change properties, mechanical strength, and photothermal efficiency of PPCMCs can be tuned by the chain length of PEG and the loading content of CB and the catalyst. PPCMCs possess the largest latent heat of 126.7 J/g, the highest photothermal conversion efficiency of 89.0%, superior shape stability even at 140 °C, high thermal stability beyond 300 °C, and reprocessing ability by introducing the catalyst of the transcarbamoylation reaction. Also, the PPCMCs exhibit high thermal reliability after accelerated thermal cycling and reprocessing, featuring nearly consistent chemical and crystalline structures, latent heat, phase change temperature, and photothermal properties. This synthetic strategy provides an alternative to obtain multi-functional PPCMCs due to the enhanced interfacial interaction between inorganic particles and the polymer matrix via covalent linkages.

Rheological and Aging Properties of Vegetable Oil-Based Polyurethane (V-PU) Modified Asphalt.

To study the rheological and aging properties of vegetable oil-based polyurethane (V-PU) modified asphalt, V-PU terminated with an -NCO group was synthesized from renewable castor oil, and liquefied MDI-100LL and 10-40 wt% V-PU modified asphalts were prepared. Temperature classification, multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out. The results showed that the modulus, the creep recovery rate (R), and the yield stress and yield strain of the V-PU modified asphalts significantly increased in the order: 0 wt% < 10 wt% < 20 wt% < 40 wt% < 30 wt%, while the phase angle and the unrecoverable creep compliance (Jnr) changed in the opposite order, and the high temperature grade of 30 wt% V-PU modified asphalt was 4 grades higher than that of the base asphalt, which indicated that the addition of V-PU enhanced the fatigue, permanent deformation, and recovery deformation resistance. The 30 wt% sample exhibited phase inversion had the best performance. Comprehensive FTIR, GPC, and fluorescence microscopy analyses showed that the molecular weight significantly increased and the V-PU molecules agglomerated after aging. The excess -NCO groups of V-PU prepolymer react with water in the air and the active hydrogen in the asphalt system and finally form a cross-linked three-dimensional network structure with the asphalt to improve performance. The mechanism of intramolecular cementation reaction and the aging process of V-PU modified asphalt was creatively derived.

Facile preparation of epoxidized soybean oil-hexanediamine resin for fabrication of pressure-sensitive adhesives

Due to the massive consumption of petroleum-derived resources, it is imperative to develop biomass adhesives to replace traditional petroleum-derived materials. The current work deals with the possibility to undergo crosslinking of epoxidized soybean oil (ESO) using hexanediamine (HDA) via one-pot method to produce a pressure-sensitive adhesive, poly(epoxidized soybean oil)-hexanediamine (PESH). The chain growth reaction between ESO and HAD involved the ester group in ESO be destroyed via aminolysis, as evidenced by Fourier Transform Infrared Spectroscopy (FTIR) and 1H Nuclear Magnetic Resonance (1H NMR). The bonding properties of PESH pressure-sensitive adhesive were studied by rolling ball method, shear strength and 180° peeling. The results revealed that the initial viscosity, adhesion persistence and peeling were significantly improved when the molar ratio of ESO to HDA was 1:3. At the same time, the PESH adhesive exhibited good bonding performance under water, especially with PVC substrates, in which the underwater bonding strength can reach 1043 KPa. In addition, PESH adhesive with high crosslinking degree presented excellent resistivity at high voltage. It can be implied that the addition of HDA can acquire the PSA antifungal action. All the results support that at a molar ratio of ESO to HDA of 1:3, it is easier to produce robust crosslinked network structure with overall upgraded properties. Conclusively, the developed PESH adhesive can provide a good application prospect in packaging and insulating fields.

Study on formation mechanism and corrosion resistance of an environmentally protective insulating coating on non-oriented electrical steel

In the present work, we developed an environmentally protective insulating coating for non-oriented electrical steel, which was composed of phosphate film-forming agent, rare-earth passivating agent, silane coupling agent and polyurethane additive. The morphology, composition, electrochemical properties and corrosion resistance of the coating were characterized by scanning electron microscopy (SEM), confocal Raman microscopy (CRM), scanning vibrating electrode technique (SVET), and electrochemical measurements. The formation mechanism of the coating revealed that the synergistic effect of rare-earth passivating agent and silane coupling agent made the distribution of rare-earth oxides uniform and hindered the agglomeration of phosphate. Further addition of polyurethane formed cross-linked network structures with the original coating to enhance corrosion resistance. The electrochemical results indicated a relatively low corrosion current density (0.12 μA cm−2) and a relatively high polarization resistance (143 kΩ cm2). The SVET results illustrated a good passivation effect of the coating, contributing to a continuous protection to the substrate. In addition, the coating could withstand the annealing test for 2 h and resist the neutral salt spray test for 8 h. Consequently, the comprehensive properties of the coating were found to be higher than industrial standards, satisfying application requirements for non-oriented electrical steel.