PF Composites Research Articles

Wear-resistant phenolic composites reinforced with attapulgite and short carbon fibers for applications subjected to both dry and oil-lubricated sliding

Attapulgite (AT) nanofibers were integrated into phenol-formaldehyde resin (PF) and PF composites reinforced with short carbon fibers (CF). Inclusion of AT significantly enhances the wear resistance of PF under both dry and oil-lubrication conditions. The hybrid nanocomposites, reinforced with both AT and CF, exhibit a high mechanical strength. Interestingly, AT and CF lower synergistically the friction coefficient of PF subjected to harsh dry sliding conditions. The hybrid nanocomposites exhibit excellent tribological performance under both dry and oil-lubrication conditions. Tribofilms’ nanostructures were comprehensively analyzed for disclosing dominant tribological mechanisms. Outcome of this work provides new ideas for developing tribo-materials of a high adaptability to various dry/oil-lubrication conditions.

Geometry effect of different PTFE fillers on self-lubricating PF composites: Mechanical and tribological properties

In order to further improve the performance of polytetrafluoroethylene (PTFE) as lubricant additives, PTFE fiber bundles (PTFE-F) were prepared by wet spinning to enhance phenolic resin (PF), and PTFE powders (PTFE-P) were used as a contrast phase. PF-based composites were prepared by hot pressing sintering, and their tribological properties were tested by ball-on-disc friction tests. The results showed that the shore hardness and compressive strength of PF-15 wt% PTFE-F were severally 5.8 % and 58.6 % higher than that of PF-15 wt% PTFE-P. The COF of PF-15 wt% PTFE-F and PF-15 wt% PTFE-P were 0.102 and 0.088, while the wear rates were 2.53 × 10−7mm3/Nm and 1.59 × 10−4 mm3/Nm respectively, with a difference of 628 times. It has been demonstrated that the transfer film formed on the friction pair ball is multi-layer structure, which formed by the physical adhesion of PTFE and the tribochemical reaction between the PTFE and the steel ball. Therefore, the geometry effect idea can be used to fabricate a new kind of self-lubricating materials applied widely in the fields of navigation, aviation, and aerospace.

Interfacial performance of phenolic‐sized continuous carbon fiber‐reinforced phenolic resin composites with different impregnation nozzle diameters via 3D printing

AbstractThe interfacial bonding strength of the 3D‐printed composites was poor due to the inadequate impregnation. To improve the interfacial performance and mechanical properties of the 3D‐printed composites, carbon fiber (Original‐CF) was modified by oxidation combined with sizing, to obtain Sized‐CF, and continuous carbon fiber‐reinforced phenolic resin (Original‐CF/PF and Sized‐CF/PF) composites were fabricated via in situ‐curing 3D printing. The impregnation nozzle diameter influences the resin content and the impregnation effect of the resin into the fiber bundles. Mechanical properties with different impregnation nozzle diameters of Sized‐CF/PF composites all increased compared to that of Original‐CF/PF composites. The flexural strength of Sized‐CF/PF composites increased by 15.3% and interlaminar shear strength increased by 28.6%, compared to that of Original‐CF/PF composites, when the impregnation nozzle diameter was 0.40 mm. The fiber‐resin interface and the effect of interfacial performance on fracture mode of the composites were investigated systematically. The interfacial performance was improved, owing to the decrease of void defect volume and the increase of impregnation uniformity between the fiber and resin interface; the fracture mode was transferred from longer fiber pulling‐out for Original‐CF/PF composites to shorter fiber pulling‐out for Sized‐CF/PF composites, owing to the improvement of interfacial performance.Highlights Carbon fiber was modified to improve interfacial and mechanical properties. Nozzle diameter of 0.4 mm obtains adequate resin content and extrusion force. Defect volume reduced and impregnation uniformity improved after modification. Flexural strength of the composite increased by 15.3% after CF modification.

Thermal stability of natural fiber reinforced biodegradable composites

Polymer composites reinforced with natural fibers are being increasingly developed by researcher and scientist in the recent field of material science due to their various applications in aerospace, marine and industries. The hydrophilic natural fibers are incompatible with the hydrophobic polymer matrices this leads to less interfacial bonding between fibers and matrix. In this paper, fibers were collected from desert plant prosopis juliflora and NaOH treatment was done to increase interfacial bonding of fiber-Matrix. Prosopis Juliflora fiber reinforced phenol formaldehyde composites were prepared with different fiber loading up to 20wt% and then characterized by thermo gravimetric analysis. This paper describes thermal properties composites materials by Thermo gravimetric analysis TGA and Differential scanning calorimetric DSC analysis of composite materials with different heating rates and hence establishes a connection between temperature and physical properties of substances. This study highlights the potential of alkali treatment in improving the thermal stability of the composites. This paper concludes that by, increasing the fiber weight percentage (fiber loading) in PF resin does increase the thermal stability of the resulting composite. The mass residue of untreated fiber reinforced PF composites with fiber loading 15% wt. UTFRPFC 15was 35%, while treated fiber reinforced PF composites with fiber loading 15% wt. ATFRPFC 15 had a mass residue of 75% at a temperature of 400°C. This clearly shows that alkali treatment significantly enhances the thermal stability of the composites. Alkali pre-treatment activates the fibers’ surface and helps increase the fiber’s mechanical strength.

Improved flame retardancy and smoke suppression properties of phenolic resin by incorporating MoO3 particles

Phenolic resin (PF) is widely used in aerospace, composite materials, and other fields. However, large amount of heat and smoke are produced during its combustion process, which is an important factor limiting its usage. To solve this problem, additive flame retardant MoO3 has been incorporated into PF for improving its flame retardancy and smoke suppression properties. Thermogravimetric analyses results show that the T5% of PF composites was gradually decreased from 264°C to 184°C and the char yield of PF-10% MoO3 is 57 wt.%, higher than that of neat PF (50 wt.%). The PF composites with 10 wt.% MoO3 passed UL-94 V-0 rating with a limiting oxygen index value of 29.8%. Meanwhile, the total heat release and total smoke production of PF-10% MoO3 are 37.60 MJ/m2 and 5.79 m2 respectively, which are reduced by 30.5% and 24.8% compared with neat PF. Only 10 wt.% MoO3 provide a 56.5% reduction (from 255 to 111) in maximal smoke density, meaning the good smoke suppression properties of MoO3. The pyrolysis products components are determined by thermogravimetric analysis combined with Fourier transform infrared spectroscopy. Furthermore, the micromorphology and chemical structure of char residue are also investigated by scanning electron microscopy, x-ray diffraction and Raman spectroscopy techniques. The promoting carbonization effect of MoO3 significantly reduces the heat release and toxic smoke production of PF composites.

Halloysite/phenol-formaldehyde nanocomposites with enhanced mechanical properties and lowered fire hazard

Development of highly filled nanocomposites with simultaneous enhanced properties in mechanical properties, anti-ablation and inflaming retarding is still a challenge. In this study, halloysite/ phenol-formaldehyde (Hal/PF) composites with different filling rate (10, 20, 30, 40 and 50%, g/g, Hal/PF) were prepared. Hal can achieve good dispersibility even at highest filling rate, in which the tensile strength increases by 39%. The ablation performance tests indicate that the linear ablation rate decreases by 23% as compared to PF resins without the addition of Hal. Moreover, the formation of ceramic-like particles has been confirmed based on the characterizations of XRD, SEM, TEM mapping and Raman spectrometer. Cone calorimetry and vertical combustion tests show that the Hal/PF composites exhibit reduced combustion, retarded fire spread, reduced harmful gas production, lowered fire risk and reduced combustion degree. The as-prepared Hal/PF composites with simultaneous enhanced properties in stretching, impact, anti-ablation and inflaming retarding may provide more room to enrich the family of PF composites and extend their potential application in heat protection field.

A Combination of Calcination and the Spark Plasma Sintering Method in Multiferroic Ceramic Composite Technology: Effects of Process Temperature and Dwell Time.

This study reports a combined technological process that includes synthesis by the calcination powder route and sintering by the Spark Plasma Sintering (SPS) method for multiferroic ceramic composites in order to find the optimal sintering conditions. The effects of temperature on the SPS process and dwell time on the microstructure and dielectric properties of the PF composites were discussed. Research has shown that using the SPS method in the technological process of the multiferroic composites favors the correct densification of powders and allows for obtaining a fine-grained microstructure with good properties and electrophysical parameters in the composite material. The optimal set of parameters and properties is demonstrated by the sample obtained at the temperature of 900 °C for 3 min, i.e., resistivity (6.4 × 108 Ωm), values of the dielectric loss factor (0.016), permittivity at room temperature (753) and permittivity at the phase transition temperature (3290). Moreover, due to the high homogeneity of the microstructure, the strength of the material against electric breakdown increases (when examining the ferroelectric hysteresis loop, the application of a high electric field (3—3.5 kV/mm) is also possible at higher temperatures). In the case of the composite material tested, both the lower and higher temperatures as well as the shorter and longer dwell times (compared to the optimal SPS process conditions) did not contribute to the improvement of the microstructure or the set of usable parameters of the composite materials. The strength of the ceramic samples against electric breakdown has also diminished, while the phenomenon of leakage current increased.

Comparative Study on the Structure, Mechanical, Thermal, and Tribological Properties of PF Composites Reinforced by Different Kinds of Mesoporous Silicas

In the presence of three kinds of mesoporous silica, mesoporous silica/phenolic resin hybrid materials (MS/PF) were prepared by in-situ polymerization with phenol and formaldehyde, then MS/PF composites were manufactured by molding with curing agent and other auxiliaries. The structure characteristics of the mesoporous materials with different structures and the thermal property of MS/PF hybrid materials were characterized, the influence of the reinforcement of mesoporous materials with different structures on the mechanical, thermal and friction properties of MS/PF composites were explored. The results revealed that three synthesized mesoporous silicas accorded with the typical structure characteristics of SBA-15, SBA-16 and KIT-6. After the in-situ reinforcement of three mesoporous silicas, the glass transition temperature and thermal stability of the MS/PF hybrid material were improved to a certain extent in contrast to pure phenolic resin. Besides, the reinforcement of three mesoporous silicas didn’t have an apparent influence on the mechanical properties of the MS/PF composites but significantly enhance the high temperature storage modulus of the composite materials. The friction coefficient and wear rate of the MS/PF composites were more stable and much lower under high temperature, respectively. Moreover, the MS/PF composites reinforced by KIT-6 showed the most stable friction coefficient and the least wear rate. It showed that the reinforcement of mesoporous silicas was expected to intensify the friction properties of MS/PF composites, which could be a modifier for materials with high friction properties.

5564 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B1690078219/2019©BEIESP DOI: 10.35940/ijeat.B1690.129219 Journal Website: www.ijrte.org Theoretical and Experimental Analysis of Tensile Characters of Prosopis Juliflora Fiber-Reinforced Phenol Formaldehyde Composites

The experimentally perceived tensile characters (tensile strength and tensile modulus) of Prosopis juliflora fiber reinforced phenol formaldehyde composites with different fiber aspect ratios (FAR) and fiber loadings (FL) have been fabricated and compared with the prevailing reinforcement theories. This analysis illustrates that the most favorable fiber aspect ratio and fiber loading of Prosopis Juliflora Fiber reinforced PF composites. FAR136 and 20 weight% of fiber loading were found as good combination to attain better bonding with superior mechanical characteristics in the Phenol Formaldehyde polymer matrix. In this study, an evaluation is made between theoretical models and experimental data. Theoretical models like parallel and series, Halpin-Tsai and modified Halpin-Tsai have been trying to fit the experimental data.

Influence of the Addition of Nano-porous Graphite/Parafffin Additive on the Wear Properties of Phenol-Formaldehyde Resin Composites

Phenol-formaldehyde resin (PF) composites with a nano-porous graphite additive (NPGA) in various contents were fabricated and the wear behaviors under low and high sliding speeds were studied. The addition of NPGA significantly improved the wear resistance of the PF. The specific wear rates of PF composites under low sliding speed first decreased with increasing NPGA and then slightly increased when the NPGA content surpassed 15 wt%; the specific wear rate of the composite with 15 wt% NPGA was reduced by 77% compared with the neat PF. Under high sliding speed the specific wear rates of the composite material decreased continuously with increasing NPGA content and the maximum wear resistance of the composite with 20 wt% NPGA was more than 12 times that of the neat phenolic resin. The results are attributed to the combined effects of load-capacity and the lubrication role of the included NPGA. The surface morphology of the worn surface was characterized, and the wear mechanism for the composites is discussed.

Bionic boron/silicon‐modified phenolic resin system with multifunctional groups: synthesis, thermal properties and ablation mechanism

A kind of silicon-and-boron-modified phenolic–formaldehyde resin (SBPF) with excellent thermal stability was fabricated via a simple two-step method and used for the matrix of ablation materials. The structure and thermal stability of the modified phenolic–formaldehyde resins (PFs) were characterised. The results showed that boron and silicon elements have been incorporated into SBPF in the form of a chemical bond. Meanwhile, the cured products showed an increase in graphite structure and a decrease in disordered structure due to the incorporation of boron and silicon. Compared with the ordinary phenolic resin, the initial thermal degradation temperature and charring yield at 800°C of SBPF increased by 73°C and 15 wt%, respectively. Further, the modified PFs, nano-Al2O3 powders, glass powders and vitreous silica fibres were used to obtain a novel ceramizable phenolic moulding composite. The morphology, chemical composition and ablative characteristics of the composites were explored. The results showed that a compact and homogeneous SiO2–Al2O3 layer formed on the ablated surface and protected the carbonised matrix and fibres from further oxidation. Compared with the ordinary PF composites, the SBPF composites showed a highly decreased linear/mass ablation rates, indicating the synergistic effect of boron and silicon modification on the enhanced ablation property.

Morphologies and compression performance of graphene oxide/SiO2 modified phenolic foam

In this study, the graphene oxide/SiO2 hybrid materials with different sizes (GO/SiO2-80, GO/SiO2-170, GO/SiO2-250) were prepared via in situ preparation. Different sizes and weight fraction of GO/SiO2 were added into phenolic resin to prepare phenolic foam composites. The cell properties, morphologies, and mechanism of GO/SiO2 reinforced PF composites were studied. The results showed that the GO/SiO2-80 can improve the cell structure and compressive property obviously than other size nanoparticles. The PF modified with 1 wt% GO/SiO2-80 exhibited most uniform cell structure, and it showed a mean cell size of 117 µm and narrow cell size distribution from 50 µm to 225 µm. The obtained PF/(1 wt% GO/SiO2-80) also showed an excellent compressive strength and modulus of 0.18 and 3.22 MPa, which has increased by 80% and 61%, respectively, compared to the pure PF. This method may make it possible for using GO/SiO2 hybrid materials to enhance the cell structure and compression performance of the phenolic foam composites with broader applications.

Thermosetting composites prepared using husk of pine nuts from Araucaria angustifolia

The high consumption of pine nuts as food leads to high amounts of husk dispensed as waste. The incorporation of the husk from pine nut into composites appears as a strategic route to explore the commercialization of the Araucaria angustifolia. The present study aims to prepare and characterize thermosetting composites of urea and phenol formaldehyde and husk of pine nuts. For this, husk particles, paraffin emulsion, ammonium sulfate, and resins, were mixed with a high‐shear mixer and then cured by flat‐pressing at 4 MPa, 120°C, for 5 min. SEM and optical images revealed good homogenization between resin and husk. DTG and DSC results showed chemical affinity between filler and matrix—tracked by shifts in the DTG peaks of the husk. The UF composites showed higher wettability and water absorption; therefore higher thickness swelling. The UF and PF composites with 30% of resin provided the greatest repellency to water, and the highest mechanical properties. It was possible to prepare composites of UF and PF resins loaded with 70% and 80% of husk from pine nuts. POLYM. COMPOS., 39:476–483, 2018. © 2016 Society of Plastics Engineers

Utilisation of finished leather wastes for the production of blended fabrics

Ignorance regarding finished and used leather wastes leads to environmental pollution. Conversion of these solid wastes into energy and resource efficient products proves to be challenging. Nevertheless, leather fibres (LFs) were extracted from these solid wastes and they are mixed with various proportions of natural (cotton, CF) and synthetic (polyester, PF) fibres to prepare LF:CF and LF:PF composites. These composites were further processed into leather blended yarns (LBYs) and leather blended fabrics (LBFs). The fibres, LBYs, LBFs were characterized for their physicochemical and mechanical properties. Scanning electron microscopic images revealed the structure and compactness of the yarn. Mechanical properties of LBYs and LBFs were promising, which enables their use in leather and textiles industry applications. Blended fabrics made from LF:CF and LF:PF were of good quality with smooth finish. Hence, the study has unravelled a novel concept of fabric manufacture which is energy efficient, eco-friendly and cost effective.

Wear behavior of filled polymers for ultrasonic motor in vacuum environments

Friction materials with favorable mechanical and tribological characteristics are critical to the drivability and reliability of ultrasonic motors. Preliminary screening at atmospheric conditions suggests that filled polymer composites such as poly-tetrafluoroethylene (PTFE), phenol formaldehyde resins (PF), and poly-p-hydroxybenzoic acid (Ekonol®) are potential candidates for use as friction materials ultrasonic motors. The wear behavior of these polymers in contact with duralumin (2A12) stators was examined and compared under various environmental conditions: room temperature (RT) and atmospheric pressure, RT and low vacuum (5Pa), RT and high vacuum (5×10−3Pa), and both low temperature and low vacuum. The wear loss of these various polymers was characterized by tracking changes in their surface roughness parameters (Ra and Rv). Wear tracks on the surfaces of different frictional materials were inspected using scanning electron microscopy. Results show that the wear resistance of Ekonol and PF composites is poorer in vacuum than in ambient conditions, whereas that of PTFE composite is not readily susceptible to ambient conditions. Lastly, wear modes and mechanisms at the various conditions are discussed.

Viscoelastic behaviour of untreated and chemically treated banana Fiber/PF composites

The dynamic mechanical properties such as storage modulus, loss modulus, and tan δ of banana fiber reinforced PF composites fabricated by RTM and CM techniques were investigated as a function of fiber content, fiber treatment, temperature and frequency. Storage modulus (E′) increases with increase in fiber content and records maximum for the composites having a fiber loading of 40 wt % at all temperature ranges. The loss modulus and damping increases to great extent by the addition of filler, a maximum was observed for filler with 10–20 wt % fiber content followed by a slight decrease in loss modulus and damping with increasing filler content. Alkali treatment of the fiber shows a great enhancement in E′ and T g of the composites. Comparison is made between the composites fabricated by RTM and CM. RTM composites exhibited higher storage modulus and lower damping compared to CM composites.

In situ chemical reduction and functionalization of graphene oxide for electrically conductive phenol formaldehyde composites

We report an efficient one-step approach to reduce and functionalize graphene oxide (GO) during the in situ polymerization of phenol and formaldehyde. The hydrophilic and electrically insulating GO is converted to hydrophobic and electrically conductive graphene with phenol as the main reducing agent. Simultaneously, functionalization of GO is realized by the nucleophilic substitution reaction of the epoxide groups of GO with the hydroxyl groups of phenol in an alkali condition. Different from the insulating GO and phenol formaldehyde resin (PF) components, PF composites are electrically conductive due to the incidental reduction of GO during the in situ polymerization. The electrical conductivity of PF composite with 0.85vol.% of GO is 0.20S/m, nearly nine orders of magnitude higher than that of neat PF. Moreover, the efficient reduction and functionalization of GO endows the PF composites with high thermal stability and flexural properties. A striking increase in decomposition temperature is achieved with 2.3vol.% of GO. The flexural strength and modulus of the PF composite with 1.7vol.% GO are increased by 316.8% and 56.7%, respectively.

Environmental ageing studies of chemically modified micro and nanofibril phenol formaldehyde composites

Cellulose micro and nano fibrils were extracted from banana macro fibres and chemically modified using sodium hydroxide, formic acid, 3-methacryloxy propyltrimethoxy silane. These untreated and chemically treated fibrils were incorporated into PF resin and the specimens were prepared. The composites were subjected to long-term water ageing, thermal ageing soil burial and outdoor weathering. The mechanical properties are reduced under all ageing conditions. The present study investigates the effects of different types of ageing on macro fibre, microfibril and nanofibril reinforced PF composites. The effect of chemical modifications of fibres on the degradability of the composites at different environments also has been analysed.

Fabrication of electrically conductive polymer composites for bipolar plate by two‐step compression molding technique

ABSTRACTElectrically conductive polymer composites for bipolar plate were fabricated by two‐step compression molding technique. Raw materials consisted of natural graphite flakes (G), expanded graphite (EG), carbon black (CB), and phenol resin (PF). The G/EG/CB/PF composites were first compressed at a temperature lower than curing point (100°C) and then cured at a high temperature above curing point (150°C) and high pressure (10 MPa). Results showed that G and EG are oriented in the direction parallel to the composite plate surface. CB is dispersed not only in the phenol resin matrix but also in the packing and porous space of G and EG. The addition of EG and CB significantly increases number of the electrical channels and thus enhances the electrical conductivity of the composite. Under optimal conditions, electrical conductivity and flexural strength of the composite were 2.80 × 104 S/m and 55 MPa, respectively, suggesting that the dipolar plates prepared by two‐step compression molding technique are adequate to meet the requirement of proton exchange membrane fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2296–2302, 2013

Research of Nanometer TiO<sub>2</sub>/PF Composites and the Properties of Semi-Metallic Friction Material

A type of phenolic resin (PF) was prepared by using TiO2 nanoparticles modified with KH-550 as composite filler and modifier, and then the composite modified PF were used as adhesive to prepare semi-metallic friction materials samples. TG analysis of the prepared nano-TiO2 /PF composites was conducted on SETARAM-TG2DSC92216 thermal analyzer that was made in France, and the friction and wear property comparison tests of the samples were carried out on XD-MSM fixed speed friction-wear machine. The results show that the heat resistance of phenolic resin after being compositely modified by TiO2 nanoparticles can be improved, carbon residue rate increases10% at 600°C；the friction coefficient of the corresponding sample slightly increases；the wear rate clearly decreases at high temperature, and wear rate decreases 10% at 350°C.