Self-lubricating liners based on high-temperature friction-resistant fabric/resin composites play an important role in advanced industry. Meanwhile, the curing behavior of resin is one of the critical factors on the macroscopic properties of the cured products and the corresponding composites. Herein, aromatics-enriched structure of bismaleimide (BMI) were developed and the curing kinetics of BMI as well as the high-temperature tribological properties of fabric/BMI composites were strategically investigated. Model fitting methods have demonstrated that BMI adopted an autocatalytic reaction, which was highly consistent with the DSC measured curve. Based on the kinetic behavior and temperature-heating rates (T-beta) extrapolation, stepped curing process parameters were established and two other processes were designed for comparation from aspects of thermal resistance, hardness, bonding strength and friction performance of the composites. When the curing process was 180 degrees C/2 h + 220 degrees C/2 h + 240 degrees C/2 h, hardness and bonding strength of the fiber enhanced composites reached 0.654 GPa and 1.173 MPa, and, accordingly, the composite-based liner exhibited the best friction performance at 240 degrees C. The maximum (average) friction coefficient was 0.25 (0.084), and the wear rate was 1.53 & times; 10-13 m3/(N & centerdot;m). Compared with the other two processes, the wear rate was significantly reduced by 36.5% and 28.2%, respectively. The research provides a mode of theory guiding experiment, which is applicable to other resin systems. And furthermore, the findings explore a type of high-temperature wear-resistant composite, which is a potential candidate under harsh conditions.

Purpose The purpose of this study is to investigate the effects of oxygen plasma treatment on the interfacial adhesion, tribological properties and wear resistance mechanism of polytetrafluoroethylene (PTFE)/Nomex fiber composite (PNFC) for application as the self-lubricating pad (PNFC-SLP) under various test conditions. Design/methodology/approach The effects of oxygen plasma treatment on the interfacial bonding strength between fibers/fabric and resin and tribological properties of PNFC-SLP were evaluated through single fiber pull-out, peel and reciprocating sliding tests. The wear resistance mechanism was characterized using scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Findings The friction coefficient and wear volume of modified PNFC-SLP were lower than those of neat PNFC-SLP under various test conditions, indicating that oxygen plasma treatment improved tribological performance. Furthermore, the enhanced wear resistance of the PNFC-SLP can be attributed to improved interfacial adhesion, resulting from the rougher surface and hydrophilic groups introduced onto the PTFE fiber surface by plasma modification. The improved interfacial adhesion between fabric and resin reduced abrasive wear and promoted the formation of a PTFE lubrication film. Originality/value Plasma modification positively affected PTFE fiber, but had little effect on Nomex fiber. The enhanced interfacial adhesion and tribological properties of plasma-modified PNFC-SLP depended on the PTFE fiber’s physical morphology and chemical groups. In addition, this work provides a promising strategy for preparing PNFC-SLP with enhanced bonding strength and tribological properties. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2025-0095/

Embedded silver nanoparticles (Ag NPs) within nanofibers represent a highly promising alternative to common antimicrobial materials, due to the combined effective biocidal properties of Ag NPs with the biocompatibility and environmental friendliness of biobased polymers. In this study, we presented a novel one-step route to fabricate biobased polyamide 56 (PA56) nanofibers embedded with uniform Ag NPs. The process involved mixing reactive silver ammonia with PA56 solutions and then using formic acid as a reducing agent. Continuous electrospinning resulted in solvent evaporation, yielding Ag NPs highly dispersed within PA56 nanonet fibrous structures (PA56/Ag). Characterization assays confirmed the successful impregnation of Ag NPs in PA56 nanofibers, with an average size of about 32.4 nm. PA56/Ag nanofibers also displayed suitable morphology, mechanical properties, and good biocompatibility in vitro. Moreover, their antimicrobial effectiveness was evaluated against Staphylococcus aureus and Escherichia coli. Collectively, the proposed PA56/Ag nanofibers possess desirable characteristics suitable for antimicrobial applications.

The increasing use of glass-fiber reinforced polypropylene (GFPP) composites in a wide range of applications requiring long-term service in challenging environments underscores the importance of its long-term durability. This study aimed to investigate the effect of thermal aging on the long-term dynamic durability and stress relaxation of GFPP composites. The time-temperature equivalence principle (TTSP) was used to assess the dynamic modulus at various temperatures and frequencies, as well as the relaxation modulus at different temperatures and relaxation times. To better understand long-term durability behavior, the study also examined the impact of molecular structure on the durability of GFPP. Changes in chemical composition, crystallinity, melting point, and melt flow index of GFPP due to thermal aging were measured and analyzed using Fourier transform infrared spectroscopy, and differential scanning calorimetry, respectively. The results revealed that oxidation led to a decrease in the crystallinity and molecular weight of GFPP. The destruction of GFPP's molecular structure due to oxidation resulted in reduced long-term durability. While TTSP can predict the long-term durability of GFPP for decades or even centuries, its application in predicting the long-term durability of GFPP is more suitable for nonaging conditions.Highlights Thermal aging reduces glass-fiber reinforced polypropylene (GFPP's) long-term durability. Time-temperature equivalence principle predicts GFPP durability under aging. GFPP's activation energy drops with thermal aging. Long-term GFPP behavior aligns with Williams-Landel-Ferry model. Predictive models refine understanding of GFPP longevity. Thermal durability of GFPP. image

在聚合物基体中构建由高导热填料相互连接而成的导热通路是提高复合材料导热性能的有效策略.本文采用共还原法,在Al2O3 微球表面沉积低熔点纳米锡铋合金颗粒(Sn57Bi43),制备杂化材料(Al2O3-Sn57Bi43),用于环氧树脂的导热绝缘填料.当环氧树脂受热固化时,Al2O3-Sn57Bi43 表面Sn57Bi43 纳米颗粒熔融,将填料相互连接而形成有效的导热通路,提高复合体系导热性能.当填料体积含量为 60vol%时,Al2O3-Sn57Bi43/环氧树脂复合材料的导热系数为 2.95 W·(m·K)-1,比 Al2O3/环氧树脂复合材料的导热系数(1.82 W·(m·K)-1)提高了 62.1%.Fogyel及Agari模型分析表明,Al2O3 表面沉积Sn57Bi43 有利于降低填料间接触热阻,形成导热通路.与Al2O3/环氧树脂复合材料相比,Al2O3-Sn57Bi43/环氧树脂复合材料的介质损耗增加,介电强度及体积电阻率降低,但仍具有电绝缘性能.由于填料-基体间界面性能改善及Al2O3-Sn57Bi43 形成的网链结构能起到传递应力,阻止裂纹扩张的作用,Al2O3-Sn57Bi43/环氧树脂复合材料的拉伸断裂强度提高.

In this study, the mechanical properties and damage modes of pultruded glass fiber/unsaturated polyester composite square pipe for automotive parts were investigated. The pipe structure, fiber mass content, dynamic mechanical analysis, tensile, and bending properties and acoustic emission detection damage mechanism of pultruded glass fiber composite pipe were studied. The structure of the cross-section of the pultrusion pipe is like a sandwich composed of mat layers on both surfaces and a unidirectional fiber layer in middle. Based on the failure analysis of pipe by acoustic emission signal technology, it is found that the tensile damage process was considered into four stages, initial damage, mat layer fracture, intermediate damage, and fiber fracture; while the bending damage process can be divided into two stages as initial and overall damages.

Background Iodophors are known to be a treatment for biofilm-related periprosthetic joint infection. However, the efficacy and mechanism of eradicating biofilms from different artificial joint materials after iodophor treatment are unknown. This study was conducted to understand the effect and mechanism of iodophors with respect to the adhesion and virulence of Staphylococcus aureus biofilms attached to artificial joint materials. Methods Biofilms of Staphylococcus aureus strains were grown on titanium alloy, cobalt chromium molybdenum and polyethylene coupons, which are commonly used materials for artificial joints, for 24 h. Afterward, all coupons were divided into experimental and control groups: (1) exposed to a 0.5 ± 0.05% iodophor for 5 min and (2) exposed to phosphate-buffered saline for 5 min. To gauge the level of biofilm, colony forming units (CFU), live/dead staining confocal microscopy and crystal violet staining were used. Meanwhile, the expression of icaACDR and clfA, which are related to virulence and adhesion, was examined in both the experimental and control groups. Results A roughly three-log decrease in CFU/cm 2 was seen in the viable plate count compared to the control group. Confocal imaging and crystal violet staining verified the CFU data. Moreover, the expression of icaACDR was reduced on three different orthopaedic implant materials, and the expression of clfA was also inhibited on titanium alloy coupons exposed to the iodophor. Conclusions Our results indicated that exposure to an iodophor for 5 min could significantly eliminate biofilms. When Staphylococcus aureus that had adhered to these three materials, which were used for artificial joints, was treated with an iodophor for 5 min, the expression of icaACDR was significantly reduced. This provides strong evidence for clinically clearing periprosthetic joint infections without removing the artificial joints.

Three-dimensional braided composite materials have the advantages of high specific strength and good specific rigidity, they are widely used in various fields. With the help of the full-scale macrostructure model finite element analysis method to pre-test the mechanical properties of the axial compression, the simulation can observe the failure process, stress distribution and propagation form of the pipe, and study its failure mechanism. Then verify the correctness of the simulation through experiments. The conclusion is that the compressive performance of the material changes with the change in the braid angle. A smaller braiding angle can bear a larger load, but its material failure process is relatively rapid, and the load drop increases as the braiding angle decreases.

环氧树脂(EP)具有优良的综合性能,在电子封装等领域应用广泛,但其自身热导率较低,如何提升环氧树脂的热导率成为了近年来的研究热点.根据制备工艺,目前主要有本征型和填充型两种制备方法.文章综述了填充型导热环氧树脂复合材料研究进展,从填料类别、填料处理方法以及导热机理与路径进行介绍,最后总结了该领域研究的不足,并对其发展趋势进行了展望.

It is of great significance to achieve excellent thermal conduction for polymer composites in electrical insulation application. However, traditional polymer composites exhibit limited thermal conduction due to the absence of efficient heat transfer pathways. Herein, Al2O3 microspheres absorbed with silver acetate (AgAc) and 2-ethyl-4-methylimidazole (2E4MI) complex were prepared as fillers for constructing heat transfer paths in epoxy composites. At a suitable temperature, 2E4MI was released from Ag(2E4MI)(2)Ac complex and initiated the curing reaction of epoxy. Simultaneously, nano silver ions were reduced, sintered in situ and then bridged separate Al2O3 microspheres to 3D filler network, which acted as thermal transport pathways in matrix. The thermal conductivity increased from 1.38 W/mK for Al2O3/epoxy composites to 2.62 W/mK for Al2O3@Ag(2E4MI)(2)Ac/epoxy composites at 60 vol% Al2O3 loading. Thanks to the 3D filler network, the tensile strength of Al2O3@Ag(2E4MI)(2)Ac/epoxy composites was obviously improved. Both the electrical resistivity and dielectric strength of the composites were basically preserved. Al2O3@Ag(2E4MI)(2)Ac/epoxy composites exhibit promising application in thermal management materials for advanced electric machinery and electronic devices.

Thermal management plays an important role in electrical and electronic systems. Owing to both excellent thermal conduction and electrical insulation, boron nitride nanosheets (BNNSs) are particularly attractive as fillers in polymer composites. While the thermal properties rely on the connection of BNNSs in polymer matrices significantly. Herein, BNNSs absorbed with silver acetate and 2-ethyl-4-methylimidazole (Ag (2E4MI)(2)Ac) complex were prepared as thermal conductive fillers for epoxy resin. During the cure of matrix, nano silver ions were in-situ reduced, sintered and bridged individual BNNSs together. Therefore, thermal contact resistance between BNNSs decreased and thermal conducting networks were effectively constructed. The thermal conductivity increased from 1.26 W/mK for the composites only with BNNSs to 2.35 W/mK for the composites with BNNS/[Ag (2E4MI)(2)Ac] hybrids at 20 vol% BNNSs content. Fitting the measured thermal conductivity results indicated that the thermal contact resistance between fillers decreased with the connections by sintered silver. In addition, the electrically insulating properties of the composites were well preserved and the tensile strength of the composites containing sintered silver interconnects was obviously improved.

采用液相还原法,制备了BN表面沉积纳米Sn粒子(BN-Sn NPs)杂化材料,用于环氧树脂(EP)的导热绝缘填料.BN-Sn NPs表面纳米Sn的粒径和熔点分别为10～30 nm和166.5～195.3℃.BN表面沉积纳米Sn后,粉体Zeta电位及压片的导热系数增加,EP滴在压片表面的接触角降低.在BN-Sn NPs/EP复合材料固化过程中,BN-Sn NPs表面纳米Sn熔融烧结,有利于填料相互桥联在一起,降低接触热阻,并改善界面性能,从而提高BN-Sn NPs/EP复合材料的导热系数.当填料体积含量为30vol％时,BN-Sn NPs/EP复合材料的导热系数达1.61 W(m·K)-1,比未改性BN/EP复合材料的导热系数(1.08 W(m.K)-1)提高了近50％.MonteCarlo法模拟表明,BN和BN-Sn NPs在EP基体中的接触热阻(Rc)分别为6.1×106 K.W-1和3.7×106 K·W-1.与未改性BN/EP复合材料相比,BN-Sn NPs/EP复合材料的介质损耗增加,介电强度及体积电阻率降低,但仍具有良好电绝缘性能.

Octadecyltrimethyl ammonium bromide (OTAB) was used as a cationic surfactant to modify micron BN platelets with an organic surface.The effects of BN surface modification on the thermal conductivity of BN/epoxy composites were studied.The adsorption of OTAB on BN surface is close to saturation at OTAB concentration of 0.6 g· L-1.BN surface modification improves the wettability of epoxy resin on BN surface and decreases the thermal conductivity of BN.SEM and viscosity characterization show that the interfacial and compatible properties of BN/epoxy composites are improved by the surface modification of BN.Due to the decrease in interfacial thermal resistance,the thermal conductivity of the modified BN/epoxy composites is higher than original BN/epoxy composites.When the filler loading is 30％ (mass ratio of filler to matrix resin),the thermal conductivity of the modified BN/epoxy composite is 1.03 W(m · K)-1,2.15 times of the thermal conductivity (0.48 W(m · K)-1) of original BN/epoxy composites.

2-methylimidazole salt (2MZS) was used as a latent accelerator of epoxy resin/anhydride curing system to prolong the pot life of product.The latent accelerating effects of 2MZS in bisphenol A epoxy resin (E51)/methyl nadic anhydride (MNA) curing system was confirmed by storage stability experiment and gelation time test.The non-isothermal curing processes of E51/MNA/2MZ and E51/MNA/2MZS systems were investigated by DSC,and their curing kinetics were analyzed.Finally,the thermal stability and electrical properties of the curing products were tested.The results show that the apparent activation energy (Ea) of the E51/MNA/2MZS system obtained by the Kissinger and Ozawa models is 70.88 kJ/mol and 78.36 kJ/mol respectively,which are higher than those of the E51/MNA/MZ system (59.82 kJ/mol and 67.32 kJ/mol).The curing raction rate constant (k') of the E51/MNA/2MZS system is lower than that of the E51/MNA/2MZ system below certain critical temperature,and above this temperature the k'of E51/ MNA/2MZS system is higher than that of E51/MNA/2MZ system.These results indicate that 2MZS has latent accelerating effects on the curing of E51/MNA system,and the thermal stability and electrical properties at high temperature of the E51/MNA/2MZS curing products are better than that of the E51/MNA/ 2MZ system.

介绍经编机牵拉机构牵拉辊包覆绒布的种类,结合牵拉辊绒布要求,详细阐述正确包缠牵拉辊绒布的步骤及方法,包括放开间隙、清理干净、确定剪位、剪切布头、均匀刷胶、包缠绒布、切尾封头、敲打压实、候时使用等,并通过模拟还原法对剪切布头参数的确定进行分析.指出包覆绒布时需要注意的几点问题及胶水选择问题,并对牵拉辊的日常维护和调整提出建议,为正确包缠牵拉辊绒布,保证经编机牵拉机构的正常运行提供参考.

A novel method for the immobilization of sodium alginate sulfates (SAS) on polysulfone (PSu) ultrafiltration membranes to achieve selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylamide on the membrane and the Hofmann rearrangement reaction of grafted acrylamide followed by chemical binding of SAS with glutaraldehyde. The surface modification processes were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy characterization. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes. An enzyme-linked immunosorbent assay was used to measure the binding of LDL on plain and modified PSu membranes. It was found that the PSu membrane immobilized with sodium alginate sulfates (PSu-SAS) greatly enhanced the selective adsorption of LDL from protein solutions and the absorbed LDL could be easily eluted with sodium chloride solution, indicating a specific and reversible binding of LDL to SAS, mainly driven by electrostatic forces. Furthermore, the PSu-SAS membrane showed good blood compatibility as examined by platelet adhesion. The results suggest that the PSu-SAS membranes are promising for application in simultaneous hemodialysis and LDL apheresis therapy.

A novel method of constructing a glycosylated surface on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] membrane surface for the selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylic acid followed by the chemical binding of carboxyl groups with glucosamine in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. The chemical structures of the fabricated membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes, respectively. An enzyme linked immunosorbent assay was used to measure the LDL adsorption on the plain and modified membrane surfaces. It was found that the surface glycosylation of P(3HB-co-4HB) membrane greatly enhanced the affinity interactions with LDL and the absorbed LDL could be easily desorbed with eluents, indicating a specific and reversible binding of LDL to the surface. Furthermore, the hemocompatibility of glycosylated membrane was improved as examined by platelet adhesion. The results suggest that the glycosylated P(3HB-co-4HB) membrane is promising for application in LDL apheresis therapy.

Poly(N-vinylpyrrolidone) (PVP) groups were grafted onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. Based on these graft copolymers, electrospun fiber mats and commonly cast films were explored as drug delivery vehicles using tetracycline hydrochloride as a model drug. Toward that end, the fibers were electrospun and the films were cast from chloroform solutions containing a small amount of methanol to solubilize the drug. The Brookfield viscosities of the solution were determined to achieve the optimal electrospinning conditions. The vitro release of the tetracycline hydrochloride from these new drug delivery systems was followed by UVvis spectroscopy. To probe into the factors affected on the release behavior of these drug delivery systems, their water absorbing abilities in phosphate buffer solution were investigated, together with their surface hydrophilicity, porosity and crystallization properties were characterized by water contact angles, capillary flow porometer, DSC, and WAXD, respectively. The morphological changes of these drug delivery vehicles before and after release were also observed with SEM. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012