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In this article, thermosetting polyimide (TPI) composites based on two ideal ingredients (graphite/graphene‐like carbon nitride, g‐C3N4) were designed with different fibers and their tribological performance was comprehensively investigated at different high temperatures. It was found that the synergistic effect between solid lubricants graphite blended with g‐C3N4 and reinforced fibers on friction and wear performance. Extremely lower friction and wear behavior of TPI composite is attained with aramid pulps (APs) at high temperatures. More importantly, an obvious transition of wear rate and friction took place with aramid pulps under 200°C. When the cross‐sections of the transfer films were analyzed using focused ion beam transmission electron microscopy (FIB‐TEM) and X‐ray photoelectron spectroscopy (XPS), it was found that graphite and g‐C3N4 combined with APs led to simultaneous improvement in load‐carrying capability of TPI matrix and durability of tribofilms subjected to complex physical and chemical reaction. Our work discloses a route for developing the TPI composite exposed to high temperatures with extremely lower friction and wear rate. [ABSTRACT FROM AUTHOR]

ABSTRACT The polyimide (PI) composites reinforced with carbon fibers, glass fibers, and aramid fibers were fabricated by means of a hot-press molding technique and irradiated by electron or proton for a certain time. The friction and wear behavior after irradiation, sliding against GCr15 steel balls, were evaluated in a ground-based simulation facility using ball-on-disk tribosystem. The change of the chemical composition of the radiated surface was examined by X-ray photoelectron spectroscopy. The worn morphologies and radiated surfaces of the materials were observed by scanning electron microscope to reveal the wear mechanism. Experimental analysis indicated that the chemical composition of the materials changed and an irradiated layer was formed at the surface. This irradiation layer had an important effect on the friction and wear behavior of the PI composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40774. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effect of short carbon fiber (SCF), graphite (Gr) and nano-Si3N4 on the friction and wear behavior of polyimide (PI) composites were studied using a block-on-ring arrangement. Experimental results revealed that single incorporation of SCF and Gr can improve the friction-reducing and anti-wear abilities of the PI composites significantly. However, nano-Si3N4 deteriorated the wear resistance of the PI composite drastically as single filler. A synergistic effect was found for the combination of nano-Si3N4 and SCF and Gr, which lead to the best tribological properties. It also can be found that the filled PI composites exhibited better tribological properties under higher PV product (the product of load and sliding speed). Moreover, the filled PI composites showed better tribological properties under oil lubrication and worse tribological properties under water lubrication compared with that under dry sliding condition. [Copyright &y& Elsevier]

Abstract: To improve the friction and wear behavior of carbon fabric reinforced polymer composites (CFRP), nano-SiO2 was deposited on the fabric surface. The friction and wear behavior of the resulting composites were investigated on a model ring-on-block test rig. Experimental results revealed that fiber surface treatment contributed to largely improve the tribological properties of the CFRP composites. Scanning electron microscope (SEM) investigation showed that the worn surface of the surface modified CFRP composite was smoother under given load and sliding rate. Field emission scanning electron microscopy (FESEM), FTIR and X-ray photoelectron spectroscopy (XPS) studies of the carbon fiber surface showed that nanostructured Sio2 thin film can be obtained by SiO2 sols deposition, which improved the adhesion between the fiber and phenolic matrix and hence to improve the friction-reduction and anti-wear properties of the CFRP composite. [Copyright &y& Elsevier]

The tribological properties of materials exhibit a complex and non-linear correlation under varying operational conditions. Therefore, prioritizing a data-driven approach to predict service capability for accelerating material design and preparation is imperative in advancing tribology. The investigation was conducted to analyze the tribological performance and wear mechanism of PTFE composites. The machine learning (ML) approach was concurrently employed to predict tribological properties under diverse operational conditions. The gradient boosting regression (GBR) model demonstrated excellent predictive performance, with R2 of 82% and 91% for the friction coefficient and wear rate, respectively. Furthermore, Pearson correlation coefficient indicated that temperature and speed has a greater impact on friction coefficient and wear rate when compared to load. • The gradient boosting regression (GBR) model demonstrated outstanding predictive performance. • Pearson correlation coefficient indicated that temperature and speed had a greater impact. • With the increase in speed, the friction coefficient and wear rate exhibited a decreasing trend. [ABSTRACT FROM AUTHOR]

A polytetramethylene ether glycol system polyurethane elastomer that meets the TBM main drive sealing requirements was prepared. Based on the working condition of the TBM main drive seal lacking oil lubrication, the wear morphology, wear chemical changes and failure mechanism of the elastomer under different dry friction conditions are mainly explained. The results show that the hydrogen bond content and molecular structure of soft and hard segments of polyurethane elastomer will change when the friction temperature increases, leading to a decrease in mechanical properties and wear failure. With the increase of rotation speed and load, there are different temperature rise trends, wear morphologies and mechanisms, and there is an obvious sudden temperature rise before wear failure, which can be used as an important criterion for seal failure monitoring. • The three stages of change that the polyurethane elastomer material undergoes during the friction and heating process are proposed. • Revealed the influence between friction heat and working conditions parameters during the dry friction process of polyurethane elastomer. • An important criterion for the wear and failure of polyurethane elastomer materials was discovered. • The wear morphology and wear pattern of polyurethane elastomer under different dry friction conditions were explored. [ABSTRACT FROM AUTHOR]

The friction coefficients of composites prepared by traditional fillers and structure design are usually uncontrollable, which gradually cannot meet the requirements of intelligent response behavior in the modern manufacturing industry. Hence, an epoxy, graphene oxide, and paraffin wax composite (GPEP@ PW) with a network-like sandwich structure was prepared by a four-step method (template method-vacuum impregnation-de-template-vacuum impregnation). Due to sensitive photothermal conversion of GO and excellent ability to control heat (absorption and release) of paraffin wax, GPEP@ PW can respond to near-infrared light to realize the real-time conversion of friction coefficient (0.052 and 0.062), while the wear rate was reduced by two orders of magnitude rate (10−4 to 10−6 mm3/N·m). The light response behavior of tribology under different near-infrared intensities was studied. This strategy is simple and versatile, providing a new idea for the design and preparation of light stimulus-responsive materials to achieve smart tribological properties. [Display omitted] • Ternary hybrid composite with 3D sandwich structure was prepared by a four-step method. • Real-time controllable friction was achieving by structural functionalized photothermal conversion of GO. • The COF changed between 0.052 and 0.062 with NIR switching on and off. • Extremely low wear rate (3.33 × 10−6 mm3/N.m) was got by synergy in GO and paraffin wax. [ABSTRACT FROM AUTHOR]

The poor interfacial compatibility between functional fillers and matrix greatly restricts development of polymer composites. Therefore, in the present paper, carbon fibers (CFs) were modified by biomimetic polydopamine (PDA) and amino silane (KH550) to improve interfacial bonding strength with epoxy (EP) substrate. The grafting of PDA and KH550 was divided into "PDA", "PDA-KH550" and "(PDA + KH550)" methods for regulating interfacial compatibility and exploring the reaction mechanism. Improved interfacial strength was beneficial to transfer stress from the matrix to fillers. Consequently, mechanical properties of modified CF/EP were obviously superior to those of unmodified EP/CF. Besides, wear resistance of EP/CF-(PDA + KH550) had an increase of 76%, 67%, 60% and 49% compared to that of EP, CF/EP, CF-PDA/EP and EP/CF-PDA-KH550. Image 1 • PDA and KH550 were used to regulate interfacial compatibility of CF and EP. • The different reaction mechanisms of PDA and KH550 were explored. • The tribological mechanism of modified CF/EP were systematically analyzed. • "CF-(PDA + KH550)" method significantly improved simultaneously the mechanical properties and wear resistance. [ABSTRACT FROM AUTHOR]