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Carbon fiber reinforced thermoplastics (CFRTPs) demonstrate promising applications in engineering sectors, and the interfacial interaction between CFs and the matrix plays a significant role in determining the properties of CFRPs. This work attempted to study the influence of sizing agent on the properties of polyphenylene sulfide/CF (PPS/CF) composites with an aim to fabricate PPS/CF composites with enhanced mechanical properties. The results showed that the use of 2 wt% boron phenolic resin as the sizing agent favored the formation of a uniform interfacial layer on the surface of CFs. Contact angle tests revealed that corresponding sized CFs exhibited the smallest contact angle and the highest surface energy among the studied systems. As a result, the sizing agents acted as a protective layer for CFs during melt processing process, which mitigated the damage to the CFs. The average length of CFs was longer after melt extrusion process which was vital for achieving high mechanical performance of PPS/CF composites. Highlights: Coating sizing agent protected CFs from being fractured during melt processing.Applying 2 wt% BPR sizing agent yielded the best interfacial performance.The tensile strength and Yong's modulus of PPS/CFB2 reached as high as 155.9 and 7618.21 MPa.The tensile fracture mode between BPR‐treated CFs and PPS was cohesive damage. [ABSTRACT FROM AUTHOR]

Highlights Thermal Protection Systems (TPS) protect re‐entry space vehicles from the harsh heating they encounter when hypersonically flying through a planet or the earth's atmosphere. Carbon fiber‐reinforced phenolic resin composites were widely used for the thermal barrier structure of aerospace re‐entry vehicles. A Novel Aluminium Titanate (Al2TiO5/AT) micro powder‐modified Polyacrylonitrile (PAN) based Carbon Fiber Fabric‐Resorcinol Phenol Formaldehyde Resin (C‐PR) (AT‐C‐PR) composites are well prepared to meet the requirements of TPS. The AT may act as an insulating layer and anti‐ablative material due to its excellent thermal shock resistance in TPS. To understand the effectiveness of AT content on density, barcol hardness, interfacial interactions, thermal conductivity, and thermal stability, the C‐PR composites were produced with and without loading of AT with various weight percentages, namely 0 wt% (C‐PR), 1,3, and 5 wt% (AT‐C‐PR) by hot compression molding method. The microstructural and elemental change of the composites were analyzed by microscopic and spectroscopic studies. Results suggested that the Interlaminar Shear Strength (ILSS) of the composites was increased by about 14% at 1 wt% of AT loading. Mass, Linear Ablation Rates (MAR, LAR), and back‐face temperature of C‐PR and AT‐C‐PR composites were decreased to 0.15128 g/s, 0.01233 mm/s, and 405°C, respectively by loading of AT up to 1 wt%. The thermally ablated composites were also evaluated for their crystallographic phase changes. The work provided an effective way to improve the thermo‐mechanical and ablation performance characteristics of the AT‐C‐PR composites that can be potentially used in TPS of re‐entry vehicles. This investigation utilized innovative Al2TiO5/Aluminium Titanate (AT) ceramic powder as a filler in reinforcing Phenolic Resin (PR) with PAN‐based Carbon Fiber (C). It examined the impact of various loadings of AT in C‐PR composites (AT‐C‐PR) on their physical, mechanical, thermal, and anti‐ablation properties. The AT‐C‐PR composites exhibit reduced density, lower thermal conductivity, and enhanced ILSS (31 MPa) compared to the C‐PR composites. Optimal ablation resistance and thermal stability were achieved with a loading of 1 wt% AT (Mass Ablation Rate: 0.15128 g/s and Linear Ablation Rate: 0.01233 mm/s) compared to the C‐PR composites. Microstructural and elemental analysis of the composites were conducted using microscopy and energy‐dispersive spectroscopy, revealing the presence of oxides and carbides on the ablated surface. The phase transition and alterations in microstructure, coupled with the oxidation of AT, have enhanced the ablation resistance and reduced the back face temperature of different weight percentages of AT‐C‐PR composites, such as 1 wt% AT (413°C), compared to the C‐PR composites (704°C). [ABSTRACT FROM AUTHOR]

Thermal conductive polymer composites have broad application prospects in the field of thermal management. However, due to intrinsically low thermal conductivity of polymers, even if fillers with high mass fraction are filled, the thermal conductivity of polymer composites cannot be significantly improved. In this paper, bimodal diamond particles (70 wt.% 150 μm and 22 wt.% 25 μm) were incorporated into phenolic resin to construct continuous heat transfer pathways by close packing, thereby enhancing its thermal conductivity. The results indicated that diamond particles with smaller particle size can effectively bridge the gaps between larger ones, forming a continuous for heat conduction. As a result, a maximum thermal conductivity value of 12.45 W/(m·K) can be achieved, which is 65.5 times, 9.8 times and 8.4 times higher than pure phenolic resin, 25 μm diamond particles reinforced phenolic resin composite and 150 μm diamond particles reinforced phenolic resin composite, respectively. Furthermore, heat dissipation and water cooling experiments also confirm the superior heat dissipation performance of phenolic resin composites reinforced with bimodal diamond particles. When the heating voltage is 10 V and the water cooling rate is 30 mL/min, the upper surface temperature of bimodal diamond composites is 129.2°C lower than that of pure phenolic resin. This investigation provides a new type of polymer composite with high thermal conductivity, which has promising prospects for application in thermal management. It also provides new insights for preparing polymer composites with high thermal conductivity by close packing of bimodal particles. Highlights: Surface modification of the filler enhances its combination with resin.The interfacial bonding will be enhanced by D–OH bond on diamond surface.Bimodal diamond particles lead to the formation of a closely packed structure.This special structure can form a three‐dimensional heat conduction network.The highest TC of the DD/PR composite is 12.45 W/(m·K). [ABSTRACT FROM AUTHOR]

The effect of the off‐axis angle (note as θ) on compressive properties and failure mechanisms in needled carbon/quartz fiber reinforced phenolic resin (CF‐QF/PF) composite has been investigated. For this objective, a series of quasi‐static off‐axis compression tests were performed, and a more precise and general model for predicting the compressive modulus and strength has been proposed. Further, the acoustic emission (AE) technology, including parameter‐based analysis and the Hilbert Huang Transform (HHT) method, was also employed to scrutinize the intricate damage mechanisms. The results show that specimens with θ = 0° exhibit linear and brittle behavior and are the most dangerous scenarios because delamination (accounting for 58% of the total AE accumulative energy) dominates their failure. For specimens with small off‐axis angles (0° < θ ≤ 45°), the fiber‐matrix interface determines their compressive properties. While for specimens with large off‐axis angles(45° < θ ≤ 90°), the enhanced transverse load‐bearing capacity of fibers becomes the dominant factor, characterized by significant debonding (33% when θ = 60°) and fiber breakage (27% when θ = 90°). Finally, these results were verified by optical microscopy (OM) and scanning electron microscopy images (SEM). Highlights: Off‐axis compression behaviors of needled CF‐QF/PF composite are studied.A more precise and general model for predicting off‐axis compression properties is proposed.Acoustic emission technology is used to quantify different types of damage.Failure mechanisms are revealed by combining in‐situ and offline techniques. [ABSTRACT FROM AUTHOR]

In this study, aramid fiber (AF)/phenolic resin prepreg was fabricated by impregnating low content carbon nanotube (CNT)‐reinforced phenolic resin with aramid fabric through a two‐roll pressing process. Both non‐functionalized and carboxylic‐functionalized CNTs (CNTs and CNTs‐COOH) were used for comparison study. For each of the formulations, composite laminate was made by a hot‐pressing process with a number of the prepregs stacked together. Mechanical properties and ballistic performance of the laminates and material failure mechanisms were evaluated and analyzed. Both non‐functionalized and CNTs‐COOH can effectively improve the mechanical and ballistic performance of the laminates. With CNTs‐COOH reinforcement, better results were achieved. As compared with the laminate without CNT reinforcement, 1.0 wt% CNTs‐COOH‐reinforced laminate showed 19.41%, 22.29%, and 45.83% improvement in tensile, flexural, and adhesion shear strength, respectively. The ballistic test results showed that the V50 and the specific energy absorption (SEA) were increased by 5.77% and 13.44%, respectively. The correlation between mechanical and ballistic performance of the composites was analyzed and conducted. [ABSTRACT FROM AUTHOR]

Epoxy film adhesives are typically used in different industries. However, these adhesives suffer from brittleness, low flexibility, and thermal stability problems. In this research, phenolic resin (Novolac) and poly (butyl acrylate‐block‐styrene) were used in the formulation of epoxy film adhesive (Diglycidyl ether bisphenol A) to increase thermal stability and adhesion strength and as the toughening agent, respectively. Alumina nanoparticles were also employed to enhance the mechanical properties. The influence of block copolymer and alumina nano particles was also assessed on the mechanical and thermal properties of epoxy‐based film adhesives. The investigation of the mechanical properties of dumbbell‐shaped samples and adhesion strength of the Al‐Al bonded joints were evaluated by tensile, lap shear, and T‐peel tests. The thermal stability of the optimal samples was assessed by thermogravimetry analysis (TGA). SEM analysis was also utilized to study the toughening mechanism. Tensile test of the dumbbell‐shaped samples indicated that the incorporation of 2.5 phr block copolymer and 2 phr alumina nanoparticles enhanced the toughness to 250%. The shear and peel strengths of this sample also exhibited 51% and 76% increase, respectively, showing a remarkable synergistic effect. On the other hand, TGA results revealed that the incorporation of block copolymer improved the thermal stability of the adhesive matrix. The copresence of these two materials also showed a considerable synergistic effect on the thermal stability. The SEM results were also in line with the results of mechanical tests as the crack deviation, crack pinning, and debonding were the most important mechanisms of toughening. Highlights: A new platform was developed for designing epoxy films adhesives with high mechanical, adhesion, and thermal properties.The hybrid of butyl acrylate block styrene copolymer, phenolic resin, and alumina nanoparticles showed synergistic effects on the lap shear and T‐peel strength.The greatest improvement in toughness was related to the epoxy adhesive containing 2.5 phr block copolymer and 2 phr alumina nanoparticles.Analysis of the fracture surface showed that by using hybrid of nanoparticles and block copolymers in the epoxy film adhesive formulation, the cohesive failure occurred.The use of hybrid additives in film adhesive formulations enlightened manufacture of adhesives for future studies on adhesive formulations. [ABSTRACT FROM AUTHOR]

Phenolic resins (PRs) find extensive use in adhesives and constructions, but they suffer from low curing rate and high brittleness. Herein, we drew inspiration from the lobster sclerotization process and proposed a simple approach to fabricate PRs by integrating pyrogallol‐functionalized graphene nanoplatelets (PG@GnPs), amine‐terminated hyperbranched phosphonitrilic chloride trimer (HPNC), and phenol formaldehyde (PF) resin. The resulting PRs exhibited significant improvements in comprehensive performance. The onset curing temperature decreased from 115.6 to 101.7°C, while the adhesion work increased by 126.5% and the toughness increased by 494%. Additionally, the wet bonding strength increased by 68.7% and the flexural strength increased by 208%. The accelerated curing rate was attributable to the oxidative crosslinking between catechol moieties in pyrogallol and amino groups in HPNC under alkaline conditions, as well as the high reactivity between pyrogallol or amino groups and PF chains. The outstanding mechanical properties were resulted from the synergistic enhancement effects of PG@GnPs and HPNC, which effectively transferred and absorbed energy upon loading. Overall, this work presented an attractive design strategy for developing high‐performance and multifunctional polymer composites. Highlights: A bioinspired strategy was proposed for preparing advanced phenolic resins.PG@GnPs were produced via a green and low‐cost ball milling method.Adhesion work and toughness increased by 126.5% and 494%, respectively.Bonding and flexural strength have improved by 68.7% and 208%, respectively.Significantly accelerated curing rate was achieved. [ABSTRACT FROM AUTHOR]

In this research, the effect of adding aluminum oxide nanoparticles on the flexural strength of glass/phenolic composites that were exposed to water environment was experimentally investigated. To make glass/phenolic composites, IL‐800 phenolic resin, H002 hardener, T400 bidirectional glass fibers and Al2O3 nanoparticles were used. Four‐layer composite plates were made by hand layup method. Beam‐shaped samples were extracted from the plates with the help of laser cutting method. Rectangular composite beams made of glass/phenolic and Al2O3/glass/phenolic were subjected to three‐point flexural test. The moisture absorption test was continued until the amount of water absorption reached a constant level. Bending test was performed on the samples before and after immersion in water. Based on the results, the average flexural strength of the samples after water absorption shows a decrease of about 15%. This parameter is equal to 118.96 MPa for glass/phenolic composite samples immersed in water, and by adding 0.25 wt% of Al2O3 nanoparticles into the matrix material of glass/phenolic composite samples, the flexural strength reaches 142.54 MPa, which shows an increase of 19.82% compared to samples without nanoparticles. Furthermore, the amount of flexural modulus decreases after water absorption, and the addition of nanoparticles in the base material can compensate this reduction. Scanning electron microscopy images illustrate that the addition of Al2O3 nanoparticles into the phenolic resin can enhance the strength of matrix material and improve the adhesion of glass fibers to the resin. Highlights: Addition of nano Al2O3 reduces water absorption of glass/phenolic composites.Nano Al2O3 improves composite flexural strength after water absorption.Addition of nano Al2O3 increases the adhesion between the layers of the specimens. [ABSTRACT FROM AUTHOR]

This article characterized the mechanical performance and failure mode of single‐lap joints (SLJs) of carbon fiber reinforced boron‐modified phenolic resin plastic (CF/BPR) and TC4 titanium alloy by quasi‐static tensile tests at four temperatures (25, 100, 175, and 250°C). The experimental results indicated that the shear strength of SLJs is 10.8 MPa at 25°C, which experiences monotonic drop to 80%, 42.6%, and 18.5% with temperature increase from 100 to 175°C, and to 250°C, respectively. Additionally, there was a transformation in the failure mode from composite material failure to cohesive failure in the adhesive along with the temperature increase. The intralaminar elasticities of CF/BPR were predicted using representative volume element (RVE), and the mechanical properties of three types of bondlines (i.e., the interlamination, interface of CF/BPR and the epoxy adhesive layer) were determined by both experiment and predictive methods. A finite element model taking into account the intralaminar damage of CF/BPR and the cohesive behavior of three bondlines was established. The simulated results showed good consistency with the experimental data for failure prediction, and the mechanical performance and damage propagation of SLJs at different temperatures were discussed. This research provides reference for the design and manufacture of high‐temperature bonded structures. Highlights: RVE and degradation factor methods evaluate the elasticity of composite material.Four types of damage behaviors are considered in the established FE model.The SLJs exhibit single or multiple failure modes at different temperatures.The mechanical properties of SLJs severely degraded with increasing temperature. [ABSTRACT FROM AUTHOR]

Nanoporous composites have been extensively applied in aerospace applications for their outstanding thermal insulation and ablation resistance. A ceramizable polysilazane (PSZ)‐modified phenolic resin (PSZ‐PR)/carbon fiber fabric (PSZ‐PR/CF) aerogel composite was synthesized through ambient pressure drying (APD). The homogeneous nanopore structure and improved thermal stability of the PSZ‐PR aerogel matrix provided the composites with good performance (thermal conductivity as low as 0.126 W/(m·K)). The PSZ‐PR/CF composites achieved high compressive strength (up to 43.75 MPa), tensile strength (59.22–124.75 MPa), and bending strength (23.35–97.94 MPa). Furthermore, the generation of ceramization products during the oxyacetylene flame ablation process, specifically SiC and Si3N4, enhanced the ablation resistance of PSZ‐PR/CF composites: the linear ablation rates are as low as 0.112 and 0.018 mm/s at 4.18 MW/m2 (20 s) and 1.20 MW/m2 (120 s) of oxyacetylene heat flow, respectively. The corresponding maximum back temperatures are only 51.0°C and 60.3°C. Notably, the carbon/ceramic network is still present in the ablation layer to protect the carbon fibers from oxidation. This ceramizable PSZ‐PR/CF composite has good potential for application in the field of thermal protection. Highlights: PSZ improves thermal stability and ablation properties of PSZ‐PR/CF.The PSZ‐PR/CF composites exhibit excellent mechanical and ablation properties.The ceramic products improve the scouring resistance of aerogel matrixes.The ceramizable PSZ‐PR/CF was prepared by low‐cost ambient pressure drying. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

The present study was an attempt to improve the toughness, mechanical and adhesion properties, and thermal stability of a two‐phase epoxy DGEBA/Resole phenolic resin through the use of carboxyl‐modified multi‐walled carbon nanotubes (c‐MWCNTs) and ground rubber tire (GRT) powder. The effect of a hybrid reinforcement containing GRT and c‐MWCNT blend on the mechanical properties, thermal stability, and microstructure of the epoxy‐phenolic adhesive were evaluated by tensile test, TGA, and FESEM, respectively. The formulated adhesive was utilized in a lap joint metal to a composite in order to peruse the adhesion features, where the composite was an epoxy resin reinforced with carbon fibers and the metal was stainless steel 316 L. According to the tensile test, there were 32% rise in tensile strength, 27% rise in modulus, and a 64% rise in toughness with adding 0.5% wt c‐MWCNTs and 15 phr waste GRT powder to the epoxy‐phenolic matrix. Furthermore, adding 1% wt c‐MWCNTs of nanoparticles and GRT powder has resulted in a 15% increase in lap shear strength. It also can be seen that thermal stability for the formulated samples has experienced an upward trend compared to the neat epoxy composite. Highlights: Epoxy adhesives based on GRT Powder, c‐MWCNTs particles and phenolic resin have been successfully prepared.The hybrid uses of GRT Powder and c‐MWCNTs particles can synergistically increase the tensile and lap shear strengthThe addition of c‐MWCNT nano particles and GRT Powder in an epoxy adhesive can have a dramatic rise in the toughness system compared to the neat epoxy adhesive.Maximum degradation temperature of the produced newly adhesive has increased considerably in contrast with the neat epoxy adhesive. [ABSTRACT FROM AUTHOR]

Ramie fiber‐reinforced polymer (RFRP) composites are widely used in various fields owing to their environmental friendliness and cost efficiency. To understand the influence of different resin matrices on the mechanical properties and durability of RFRP composites under the same conditions and obtain better performance, ramie fiber‐reinforced phenolic resin (RFRPR) composites and ramie fiber‐reinforced unsaturated polyester (RFRUP) composites produced through compression molding were studied under hydrothermal conditions of 60°C with 50%, 85%, and 98% relative humidity for 3 months. The water absorption, tensile, flexural, and short‐beam shear properties were studied. The RFRPR composite had better flexural strength and short‐beam strength than the RFRUP composite. The saturated water absorption, water molecule diffusion coefficient, and retention rate of the RFRUP composite were higher than those of the RFRPR composite owing to the difference in the interfacial adhesion properties. The erosion of water molecules led to serious deterioration in the interfacial bonding performance of the RFRPR composite. It was found that the greater the humidity, the greater was the degree of interfacial degradation. This study lays the foundation for the further promotion and application of RFRP composites. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of blending cashew nutshell oil modified phenolic resin and nitrile rubber (NBR) on the thermal, mechanical, and tribological performance of brake friction materials. The friction materials, which have a total binder of 25 wt% and different ratios of cashew nutshell oil modified phenolic resin and NBR, were prepared by hot press molding process. The experimental results show that NBR is beneficial to improve the hardness and compression modulus of the brake friction materials. The coefficient of friction (COF) is proportional to the wear rate, when the ratio of cashew nutshell oil modified phenolic resin and NBR is 13:12, the friction material has good heat resistance and exhibits excellent friction stability in the braking process, and the COF is steady between 0.420 and 0.448 at different braking speeds, while the wear resistance of material is optimal. The worn surfaces of the friction materials were examined by scanning electron microscope, and it was determined that the friction film is predominantly secondary plateaus, which can stabilize the COF and reduce the wear rate. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced plastic (GFRP) has become one of the most commonly used materials in the structure of aero engines in the last decades. In this study, GFRP was fabricated by molding with phenolic resin as the matrix. Specimens were prepared along horizontal and vertical directions. Fiber distribution, tensile properties, long‐term creep performance, and damage mechanism were systematically investigated. Experimental results shows that horizontal specimens have better tensile properties, lower viscoelasticity, and excellent creep resistance. The fibers inside the cylindrical material exhibit a 3D core‐shell morphology with transverse isotropy in the core region. Load is carried by the fibers and the damage is in the form of fiber fracture and pull‐out in horizontal specimens. Random distribution and interweaving leads to double fracture sections of fibers. Load is carried by the interface and resin, and the damage is in the form of fiber pull‐out laterally and interfacial debonding in vertical specimens. High viscoelasticity of the resin and the weak interfacial bonding ability lead to large creep deformation of vertical specimens. In addition, the creep strain under different loads can be accurately predicted by Modified Time Hardening model. [ABSTRACT FROM AUTHOR]

Carbon‐phenolic ablators are very efficient heat shields for atmospheric reentry vehicles: they are able to protect a capsule from hyper thermal environments characterized by intense heat fluxes (>1 MW/m2) and very high temperature (also exceeding 300°C). Ablative materials can be modified by the addition of nano‐fillers in order to improve their performance: small amounts of nano‐fillers (in the order of 2–5 wt%) are able to enhance the matrix material properties, guarantying a weight saving too. In this work, three different kinds of ceramic nano‐particles (ZrO2, SiC, and MgO) were tested as fillers for a phenolic resin and for a carbon‐phenolic ablator: the variation in the mechanical properties and ablative performances were verified through mechanical tests and oxyacetylene flame exposure. The influence of the nano‐particles in the composite materials properties and the phenomena connected to their presence in the ablative material were deeply investigated with scanning electron microscope, EDS, XRD, and FTIR analysis. [ABSTRACT FROM AUTHOR]

Slag waste‐filled phenolic resin‐based automotive brake friction composites were formulated, fabricated, followed by mechanical, physical characterization, and tribo‐evaluation. According to economic commission for Europe regulation, the tribological performance of the composites was evaluated on a Krauss friction‐testing machine. The increase in slag waste content led to increased physical properties such as density, porosity, ash contents, and compressibility, whereas hardness, acetone extraction, and shear strength increased with increased phenolic resin content. The fade and friction performance has been observed to be highly dependent on the slag waste content, that is, both followed a consistent decrease with the increase in the phenolic resin content, whereas the frictional fluctuations have been observed to decrease with the increase in slag waste content. In particular, the composites containing 65 wt% slag waste and 5 wt% phenolic resin showed the highest friction coefficient (0.406), lowest fade (20.44%) and frictional fluctuation (0.209), but the wear (10.80 g) and disc temperature rise (618°C) remains highest. Composite with the lowest slag waste content of 50 wt% combined with the highest phenolic resin of 20 wt% showed higher recovery performance (120.63%), lowest wear (4.45 g) and disc temperature rise (536°C), but exhibits lowest friction coefficient (0.315) and friction stability (0.79) along with highest friction variability (0.60) and fluctuations (0.238). Friction and wear data analysis revealed the predominance of the fade factor for friction performance while the fade factor and disc temperature‐induced results significantly influence the wear performance. The worn surface micrograph showed higher phenolic resin‐filled composites form smooth contact plateaus that successfully reduced wear. [ABSTRACT FROM AUTHOR]

Silica phenolic ablative composites are used in many high‐temperature applications like rocket/missile solid motor nozzles, space re‐entry vehicles, and so forth. As ablative composite with lower thermal conductivity and density can save considerable cost, a hybrid silica phenolic ablative composite was developed by establishing a novel processing methodology using chopped silica fiber, phenolic resin, and hollow glass microsphere. The thermophysical properties of the developed hybrid composite are analyzed and established the scientific know‐how. The developed composites, with 36% lower density, displayed 50% lower thermal conductivity and 50% lower thermal diffusivity than standard silica phenolic composite. Since a proper thermal conductivity model for a three‐component composite with matrix, fiber, and hollow glass microsphere is not available, the most suitable model for the developed composite is established. [ABSTRACT FROM AUTHOR]

In this study, an effective microscale method based on the parametric modeling scheme of the finite volume method is improved to evaluate the effective thermal conductivity and localized thermal fields of the fiber‐reinforced composites. By comparing with the finite element method and experimental data, it is indicated that the proposed microscale method exhibits a high accuracy in solving their effective properties. On this basis, the mesh sensitivity and fiber volume fraction influence on the thermal conductivity are both investigated. The number of 36 × 36 sub‐cells is employed as the RVE model to balance the computational efficiency and simulating accuracy. In addition, affected by the thermal conductivity and microstructure of constituent materials, the heat flux distribution near the interface between phenolic resin matrix and glass fiber is relatively uniform. The study on the influencing factors of the volume fraction shows that the equivalent thermal conductivity increases slowly at the low volume fraction, while the growth rate of the equivalent thermal conductivity increases significantly at the high‐volume fraction. [ABSTRACT FROM AUTHOR]

This research article has developed a novel composite material using natural fiber and PAN fiber. The study aims to remove harmful materials from the composites on the market these days. Asbestos and aramid fiber has good properties and is used in those composites where good mechanical properties are needed. However, using these materials causes many environmental issues and harms humans and other animals. There are very rare studies of PAN and natural fiber based hybrid composites. So Grewia optiva, which has good mechanical properties, and PAN fiber, which has good tribological properties, has been used to develop composites. The percentages of both materials were taken (4–16 wt%) with other ingredients such as phenolic resin, G. optiva fiber, PAN fiber/Kevlar, and lapinus ceramic, potassium barium, titan, mica, and ceramic. The developed composites have shown physical, mechanical, and tribological properties. [ABSTRACT FROM AUTHOR]

Camellia oleifera shell is rich in lignin and tea saponin and other natural active substances, and it is used to directly prepare fuel and biochar, which are low‐value applications. Inspired by the tea oil fruit shell, a new type of wood‐based composite was designed, which was bonded between inner layers and coated on the surface with Camellia oleifera shell‐based phenolic resin through a one‐step manufacturing process. The acid catalyst type, reaction time, and substitution ratios (Camellia oleifera shell/phenol) were used to optimize the formulation and process of Camellia oleifera shell phenolic resin. The chemical structure, wet bonding strength, harsh‐weather resistance, thermal properties, and flame resistance of the composites (Camellia oleifera shell phenolic resin surface coated plywood [CSPCPs]) were evaluated. The results indicated that the CSPCPs showed better‐wet bonding strength and thermal properties and harsh‐weather resistance compared with the common uncoated plywood. CSPCP‐3 presented the maximum wet bonding strength of 1.63 MPa. The limiting oxygen indexes of the CSPCPs were all higher than that of common plywood. All CSPCPs displayed excellent acid rain corrosion resistance, with little mass loss under simulated acid rain conditions. Grayscale was used to compare the samples' color to assess their self‐mildew resistance. As the amount of shell increased, the mold resistance of CSPCPs increased. CSPCP‐3 showed excellent comprehensive performance and can be a multifunctional wood composite suitable for outdoor applications. [ABSTRACT FROM AUTHOR]

Paper‐based friction materials with phenolic resin as the matrix are prone to thermal damage under harsh working conditions easily leading to materials failure. To satisfy the requirements of high speed and heavy load service situations, paper‐based friction materials with different polyimide resin content were prepared by wet forming technology to reveal the effect of polyimide resin on the properties of composites. And a paper‐based composite with phenolic resin was used for comparison. Results show that compared with the phenolic composite, tensile strength, and shear strength of the polyimide composite were increased by 50.5% and 36.4%, respectively. Due to the strong hydrogen bond in the imide ring of polyimide, the temperature of the polyimide composite at 2% weight loss was 292.7°C, which was 106.3°C higher than that of the phenolic composite. Moreover, the wear rate was reduced by 30.3% because the friction transfer film was produced during friction. To sum up, polyimide resin has the potential to replace phenolic resin under the condition of high speed and heavy load. Besides, the composite with polyimide resin content of 40.0 wt% demonstrated the best wear resistance and considerable strength attributed to the best interface combination. This research lays a theoretical foundation for the application of polyimide resin to paper‐based friction materials. [ABSTRACT FROM AUTHOR]

In this study, the alkali‐treated and untreated hybrid fibers incorporated with bio phenolic matrix to enhance the chemical interactions, mechanical and thermal properties have been investigated. The oil palm fiber (OPF) and pineapple fiber (PALF) were utilized as reinforcements into bio phenolic resin. The improvements in chemical interactions were monitored by the Fourier transform infrared spectrometer. The modifications of the surface for hybrid natural fibers (OPF/PALF) were enhanced in comparison to pure fiber composites. The composites' dynamic mechanical behavior such as storage modulus, loss modulus, and damping properties were also investigated by dynamic mechanical analysis. Thermogravimetric analysis analyzed the performance of untreated (OPF and PALF) and treated (OPF/OPF) composites at elevated temperature and observed adequate interfacial bonding as a result of the improvements in thermal stability. The results presented that alkali) NaOH(incorporation in hybrid composites (OPF/PALF) results in increased the tensile strength and modulus among all composites. Furthermore, the tensile strength and modulus improved to the maximum value for treated 50% PALF composite compared to other composites. The hybridisation of treated alkali (5% NaOH/50% PALF) fiber shows best performance on tensile strength and modulus with 33.3 and 7535.2 MPa, respectively compared to other composites. The alkali‐treated hybrid composites (NaOH/1OPF.1PALF) exhibited the greatest flexural strength (99.8 MPa) and modulus (8813.1 MPa). The enhancement of the interfacial adhesion between pure and hybrid fiber composites and bio phenolic matrix through the mercerisation of OPF and PALF fibers reinforced composite played an essential role in improving the mechanical properties of composites via alkali treatment with NaOH solution. Natural fiber reinforced composites are commercially attractive for high‐volume applications; while their properties can be improved by adding alkali solution as stabilizers. It can be recommended from the findings of this study that the alkali treatment (5% NaOH) can be used to enhance the efficiency of agriculture waste biomass. Additionally, the hybridization of bio‐fiber composites has potential to develop novel type of biodegradable and sustainable composites suitable for various industrial and engineering applications. [ABSTRACT FROM AUTHOR]

In this research, phenolic resin and poly (butyl‐acrylate‐block‐styrene) copolymer were used in the formulation of epoxy adhesive to improve its thermal stability and toughness. Also, in order to improve the mechanical properties such as the modulus and tensile strength, aluminum oxide nanoparticles (NPs) were added to the epoxy based resin. Effects of different factors such as percent contents of phenolic resin, toughening agent, and aluminum oxide NPs on the microstructure, mechanical properties, and thermal stability of the epoxy‐based adhesives were investigated. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and field‐emission scanning electron microscopy were used to investigate the thermal, mechanical, and morphological properties of the prepared epoxy adhesive samples. In addition, the curing kinetics of the optimal specimens was studied based on differential scanning calorimetry (DSC). The experimental results indicated that the phenolic decreased strength of dog‐bone samples, while increased the adhesion strength in metal‐to‐metal single‐lap strength. On the other hand, addition of block‐copolymers as toughening agent led to a consistent decrease in the modulus as well as increasing the tensile strength. Also, results of single‐lap strength tests showed that, in the optimal quad system, the four components exhibit synergetic effects and show a single‐lap strength that is 152% higher than that of pure epoxy. The DSC analysis indicated that the presence of alumina NPs and block‐copolymers tend to reduce the initial curing temperature while increasing the curing reaction heat. [ABSTRACT FROM AUTHOR]

Phenolic resin‐carbon fiber composites are used in various industries due to their high flame resistance, high strength to weight ratio, and high thermal stability as an insulator. In this study, to expand the applications of this composite in marine structures, phenolic resin‐carbon fiber‐nanosilica composites were fabricated with eight layers of twill carbon fibers and 0, 1, 2, and 3 wt% of nanosilica then flexural and flame resistance was investigated. To evaluate the stability of the composites in seawater, the samples were placed in seawater for 30, 60, and 90 days then the flexural test was performed and the percentage of strength reduction was calculated. Thermogravimetric analyzer test was performed on a sample that had the highest strength after 90‐day immersion. Finally, it was found that nanosilica particles had a significant effect on increasing the flexural strength and flame resistance of samples so that the sample with 3 wt% silica had flexural strength and burning rate of 690 MPa, 0.098 g/s, respectively. [ABSTRACT FROM AUTHOR]

The moisture absorption behavior of a composite comprising phenolic resin and activated carbon fibers was characterized. The resin starts with a water content from curing and the active fibers both adsorb water on their surface and absorb water in sub‐surface pores, acting as a sink or source of water. Measured data showed that the dependence of this water uptake on the surrounding relative humidity was highly nonlinear, and that the effective diffusion rate through the composite was very dependent on the starting and end conditions. A physically based model has been successfully developed to simulate this behavior. Diffusion was assumed to be Fickian and entirely through the resin, with a linear dependence of resin water content on external humidity. Water movement between resin and fibers was determined so as to maintain equilibrium, based on measured steady‐state water uptake curves across a range of relative humidities. This meant that in mid‐range humidities, most water movement was between fibers and resin rather than through the resin, giving low effective diffusion rates. This model and a simple Arrhenius expression for the diffusion coefficient through the resin enabled measured composite diffusion behavior to be accurately predicted over a range of temperatures and humidity changes. [ABSTRACT FROM AUTHOR]

High‐performance composites reinforced with natural fibers are next‐generation structural materials due to their recyclability and light weight. Manufacturing composites with high strength has been a challenge. Here, we describe the manufacture of novel composites reinforced with wood fibers using densification by hot‐pressing and fixing by curing reaction with phenolic resin. This composite with 1.4 g/cm3 had high mechanical properties, high water stability, and aging‐resistance, and exhibited a flexural strength and internal bonding strength of 102.4 and 7.5 MPa, respectively. The strength and modulus are 1.5–6.0 and 1.3–28.1 times higher than those of most of the wood fibers reinforced composites. After immersing in water for 24 h, the water absorption and thickness swelling are only 1.3% and 0.8%, respectively. Scanning electron microscope characterization indicates that the cell wall is totally collapsed and became complete densification. And the collapsed cells are fixed by phenolic resin. This production strategy for the composites was shown to be universally effective for various species of natural fibers. These novel wood fiber‐reinforced composites were suitable for commercial manufacture in the current production line, making them a low cost and high‐performance alternative to automotive and aerospace industries. [ABSTRACT FROM AUTHOR]

The hybridization of composites has recently seen an exponential growth in acceptance due to its ability to improve the property such as toughness of composites. Hybridization of fibers is known to give a better balance of properties and increases the opportunity to use natural fibers, thereby reducing the impact on the environment without compromising utility. This study deals with hybridization of ultrahigh‐molecular‐weight polyethylene (UHMWPE) with natural fibers such as flax and jute using phenol formaldehyde as the resin. Composite panels of 4 mm thickness, comprising of eight layers were fabricated in six different fiber stack sequences using hand lay‐up and compression molding techniques. The effect of stack sequence on the composites' flexural, interlaminar shear, and impact properties were investigated using scanning electron microscopy and cone beam computed tomography techniques. Composites with outer UHMWPE fibers and having flax fibers as inner core were found to have superior flexural and interlaminar shear properties of 44.45 and 5.52 MPa, respectively. Also composites with surface layers of flax fibers displayed maximum impact strength of 91.08 kJ/m2. The results indicate that the stack sequence has a significant influence on the properties of the composite under flexural and impact loading. [ABSTRACT FROM AUTHOR]

Phenolic resin is an important binder for refractory ceramics. Herein, aluminum and organic rectorite were employed to improve the antioxidant activity of phenolic resin. X‐ray diffraction revealed that the silicate layers of phenolic resin exfoliated rectorite were uniformly dispersed in the modified phenolic resin (MPF) matrix. Moreover, TEM revealed that the peeled silicate nanoparticles from rectorite were well distributed without clustering. The structure of the MPF resin was also analyzed by infrared spectroscopy and nuclear magnetic resonance. The results showed that the strength of the ether bridge of MPF resin with aluminum and rectorite considerably decreased than that of pure phenolic resin. The MPF resin was anhydrous and had AlO bonds to link the benzene rings. Pyrolytic carbon experiments revealed that the decomposition temperature of the MPF resin was 759.2°C, which indicated that it had a better oxidation resistance and bonding strength than those of pure phenolic resin. The incorporation of aluminum and rectorite improved thermal performance of the phenolic resin, and enhanced mechanical performance of the MgOC refractory. [ABSTRACT FROM AUTHOR]

Surface modification of carbon fabrics (CFs) by nitric acid and multiwall carbon nanotube (MWCNT) incorporation into the resin matrix were simultaneously applied for CFs/resin composites to improve their tribological properties. The results show that surface roughness (Ra) of CFs increases from 8.20 to 15.10 nm after nitric acid treatment due to the remove of sizing agent on CFs surface. Surface hardness of the composites with 0.1 wt% MWCNT (CFR‐H‐0.1%T) is enhanced from 0.745 to 1.216 GPa compared with that of untreated CFs/phenolic resin composites (CFR), which is attributed to the toughening effect of MWCNT in resin matrix. The friction coefficient increases from 0.10 for CFR to 0.16 for CFR‐H‐0.1%T, while the wear rate significantly decreases from 5.75 × 10−14 m3 (N m)−1 to 2.05 × 10−14 m3 (N m)−1. The improvement of friction and wear properties is ascribed to the synergistic effect of the oxidation etching of nitric acid and the strengthening and toughening of MWCNT. [ABSTRACT FROM AUTHOR]

Phenolic resin (PR) grafted graphene (G‐PR), synthesized from the versatile graphene modification platform 2‐(3, 4‐dihydroxyphenyl) pyrrolidine grafted pristine graphene (G‐OH), is used to develop high‐performance phenolic composites. Benefiting from good properties of G‐PR, uniform dispersion of G‐PR and strong PR/G‐PR interfacial interaction, G‐PR shows obvious advantages as a filler in improving mechanical, electrical, and thermal properties of PR over pristine graphene (pG) and graphene oxide (GO) derivatives. For PR/G‐PR composites, the maximum tensile strength attains 51.4 MPa at 0.5 wt% graphene content. Electrical and thermal conductivities reach to 10−3 S·cm−1 and 0.374 W·m−1·k−1 at 5 wt% graphene content, respectively. The decomposition temperature and residue at 800°C separately increase by 61°C and 3.5 wt% at 1 wt% graphene content. In a word, this contribution provides an alternative avenue for preparing high‐performance and multifunctional PR/graphene composites, avoiding the high risk and serious pollution of graphene oxide (GO) avenue. [ABSTRACT FROM AUTHOR]

Natural fibers are very versatile materials; their properties vary with chemical composition to physical structure. The present study deals with the incorporation of different ratios pineapple leaf fiber and kenaf fiber into a phenolic resin to develop hybrid composites. Incorporation of pineapple fibers in kenaf composites are supposed to improve the thermal properties due to higher cellulosic content of pineapple fibers and thermal characterization are studied by thermo‐gravimetric analysis, dynamic mechanical analysis and thermo‐mechanical analysis. Thermo‐gravimetric of 7P3K displayed lowest percentage of weight decomposition and highest residue indicated thermal stability among all the composites. The storage modulus showed decreasing trend with increasing temperature for all the hybrid composites due to constituents of natural fibers. Among all hybrid composites 3P7K hybrid composite showed highest storage modulus and loss modulus at 55.13°C and 101.68°C, respectively. The recorded peak heights of tan δ were minimum for 1P1K (128°C) and maximum for 7P3K hybrid composites (137°C). The Cole–Cole graph determines the heterogeneity of the hybrid composites. Thermo‐mechanical analysis was used to investigate the coefficient of thermal expansion and the mechanical stability of the composites against increasing temperature. Overall results showed that the hybridization of pineapple fibers and kenaf revealed various thermal properties on various fiber ratios. However, 7P3K improves the thermal stability of the obtained material, whereas the 3P7K hybrid composite showed the highest dynamic mechanical properties among all the hybrid composites. 7P3K improved the thermal properties due to presence of cellulosic content whereas 3P7K improved the dynamic mechanical analysis due to better interfacial bonding. POLYM. COMPOS., 40:3814–3822, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this research, the use of date palm tree trunk fiber as a reinforcement of phenolic resin has been studied. Laminated composite sheets were prepared by compression molding of the pre‐impregnated fibers with phenolic resin (novolac‐type). The prepared samples were tested for mechanical properties, water absorption, flammability, and thermal gravimetric analysis. The results showed that the flexural strength and modulus of the composite samples were 73.25 MPa and 5.9 GPa, respectively. Also the tensile strength and modulus were obtained 30.25 MPa and 3 GPa, respectively. The effect of surface treatment of the fiber with NaOH solution (6%, w/w) on the mechanical properties of the composites was investigated, too. An increase of 19%, 14%, and 140% in flexural, tensile and impact strengths and 6% and 16% in flexural and tensile modulus was observed, respectively. Scanning electron microscopy (SEM) images of the fractured surface confirm the improvement of the surface wettability of the treated fibers. Surface treatment had no significant effect on the physical and thermal properties of the composites, while water uptake of the samples was increased. POLYM. COMPOS., 40:3657–3665, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The contact area between the filler and the polymer is a critical region that influences to a great extent the filler–matrix adhesion and therefore the mechanical properties of the composite. Controlling the type of interactions at this interface has a significant effect on the properties of the composite materials. In this context, we prepared composites by covalent reaction of diazonium‐functionalized zeolite with phenol‐formaldehyde resin. Introducing the hydroxymethyl groups onto the surface of the filler via diazonium chemistry allows for covalent bonds between the resin and the modified filler. Such a modification resulted in higher flexural strength of the composites, better ability to dissipate mechanical energy during load and also better damping properties (which are strongly linked to the final product durability) compared with the composites bearing pristine zeolite filler. Moreover, application of modified filler accelerates the crosslinking of novolac resin used as a binder in abrasive tools. One key feature of the work was brought by thermogravimetric analysis–mass spectrometry results which indicate no release of toxic urotropine degradation products for composites containing modified fillers. This work demonstrates conclusively that diazonium‐functionalized zeolite filler particles improve remarkably the thermal and mechanical properties of novolac‐based composites. Such robust composites have high potential in the production of novel abrasive tools. POLYM. COMPOS., 40:3209–3219, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Precious wood has high performances, but has limited availability, increasingly rising cost, and requires a long growth cycle. Imitation precious wood was prepared from low‐cost and fast‐growing poplar wood using the method of wood polymer composites (WPCs). Poplar wood was impregnated with phenol formaldehyde (PF) resins in the presence of surfactants as osmotic agents to achieve efficient PF permeability. The effects of formaldehyde/phenol (F/P) molar ratio, surfactant type, and surfactant amount on the performances of PF resins and the modified woods were investigated in detail. The wetting process of PF resins on wood surface and its molecular weight distribution were observed by contact angle measurement and matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry (MALDI‐TOF‐MS), respectively. The physical and mechanical properties of the resultant WPCs were also evaluated. The poplar wood treated with PF‐DTAB‐0.8% resin (F/P = 1.6) exhibited lower viscosity (23.9 mPa s), lower molecular distribution and better permeability. The weight percent gains (WPG) of the treated material reached 104.82%, and its hardness reached 66.86 shore D. overall, this approach has the potential to make a wood product that can partially substitute for precious wood. POLYM. COMPOS., 39:2431–2440, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Demand has been growing for natural fibers that are eco‐friendly, renewable, and show sustainable development during their service lifetime. In this study, a series of novel phenolic foam‐based composites, modified by polyaryl polymethylene isocyanate (PAPI), were synthesized and then reinforced with flax fiber mats. The structure and reactive behavior of PAPI and phenolic resin were investigated using Fourier transform infrared spectroscopy. The effect of formulation of PAPI:Resol‐type phenolic resin (PR) on the mechanical properties of the composites were studied. The results suggested that the impregnation of PAPI and PR into mats showed good mechanical properties, furthermore, PAPI:PR in a 3:1 ratio led to the best reinforced material with inner bonding, flexural, and impact strengths of 3.39, 25.91 MPa, and 3.88 kJ/m2, respectively. In addition, the morphology of the composites was observed using scanning electron microscopy. Thermal stability and flame retardancy were examined using thermogravimetric analysis and limiting oxygen index (LOI) tests. It was found that the composites exhibited good thermal stability and high char yields. The LOI value of the modified phenolic foam‐based composites decreased with increasing PAPI content, but it still remained at about 24%. POLYM. COMPOS., 39:1809–1817, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Mesoporous silica SBA-15/phenolic resin hybrid materials (SBA-15/PF) were fabricated through in situ polymerization of phenol and formaldehyde in the presence of SBA-15 and subsequent SBA-15/PF nanocomposites were prepared by compression moldings. The results revealed that the glass transition temperatures and thermal stability of SBA-15/PF hybrid materials were obviously enhanced compared to pure PF. In addition, the dynamic mechanical and friction properties of SBA-15/PF nanocomposites were improved remarkably. For SBA-15/PF nanocomposites containing 5.0 wt% of SBA-15, the glass transition temperature of the nanocomposite increased by 13.0°C. Moreover, the nanocomposite showed stable friction coefficient and decreased wear rate. The wear mechanism was a combination of adhesive wear and abrasive wear for PF/SBA-15 nanocomposites, while for pure PF friction material was a combination of adhesive wear and fatigue wear. POLYM. COMPOS., 38:E351-E358, 2017. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this work, novolac bisphenol-F-based vanadium-phenolic resin/modified zirconia (Bis-VPF/m-ZrO) composites were obtained successfully. In the preparation process, ammonium vanadate reacted with Bis-PF resin to form Bis-VPF resin with the VO chemical bonds. Simultaneously, zirconia (ZrO2) was modified with N-(2-aminoethyl-3-aminopropyl)trimethoxysilane (AEAPTMS). Then, this modified zirconia (m-ZrO) was fully mixed with Bis-VPF to form Bis-VPF/m-ZrO composites. The thermal properties and mechanical strength of Bis-VPF are higher than those of Bis-PF. When the m-ZrO was additionally incorporated into Bis-VPF, the well-dispersed and well-adhered m-ZrO can further promote all the above-mentioned properties of the composites. Furthermore, Bis-VPF/m-ZrO was compared with Bis-PF in the performance as a binder for cBN grinding wheels. The results of grinding experiments indicated that Bis-VPF/m-ZrO is a better binding resin than Bis-PF, and so the grinding wheels made from the Bis-VPF/m-ZrO composites have better grinding effect and quality. POLYM. COMPOS., 37:3354-3364, 2016. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Cross-linked polymers, such as phenolic resin and its composites are widely used in industrial practice, but the absence of clear understanding on their thermal expansion behaviors in glassy state limits their applications, especially in the occasions where dimensional accuracy are addressed. The coefficients of thermal expansion (CTEs) of cured phenolic resin and inorganic particles filled phenolic resin at glassy state at different temperatures are analyzed in this article. The results show that the CTEs of glassy cross-linked polymers change with temperature, and exhibit a strong dependence on the temperature. By modifying the state equation of linear amorphous polymer, the equation that can be used to quantitatively describe the temperature dependence of CTEs of cross-linked polymers is established. By analyzing the temperature dependence of CTE, an equation is proposed to predict the CTEs of filled phenolic resins with different filler loadings at a specific temperature. The results of this study have contributed to a better understanding of the thermal expansion behaviors of glassy crosslinked polymers, and are of great significance in industrial practice. [ABSTRACT FROM AUTHOR]

The flake graphite, polytetrafluoroethylene, and molybdenum disulfide (MoS2) filled phenolic resin-based composites were prepared by hot press molding. The thermal, mechanical, and tribological properties of composites were studied systematically. The morphologies of the worn surfaces and the change of chemical compositions during the sliding process of the composites were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. It was found that the heat-resisting performance and the hardness of the composites are less affected by solid lubricants, while the solid lubricants did harm to the flexural strength of the composites. The friction and wear behaviors of composites highly depended on the volume fractions of solid lubricants and the sliding conditions. The wear resistance increases and the coefficient of friction decreases when the filler load increases. In addition, the appropriate content of solid lubricants is beneficial to reducing the sensitivities of the composites to load and sliding speed. [ABSTRACT FROM AUTHOR]

Thermoplastic vulcanizates (TPVs) are a special group of thermoplastic elastomer with the characteristic that consists of rubber elasticity and the processability of thermoplastic polymers. TPVs based on high density polyethylene (HDPE)/ground tire rubber (GTR) with phenolic resin (HY-2045) and dicumyl peroxide (DCP) as vulcanizing agents are prepared through dynamic vulcanization in this article. The blends consisting of 40/60 HDPE/GTR are melt-mixed in an internal mixer and then pressed with a compression molding machine. The aim of this experiment is to study the influence of a compound curing agent system on the mechanical properties of the HDPE/GTR composites. The results indicate that the mechanical properties of the HDPE/GTR blends are improved significantly by adding 4 phr HY-2045 and 0.3 phr DCP than those of TPVs without any vulcanizing agents after dynamic vulcanization. The X-ray photoelectron spectroscopy study and the FTIR-ATR analysis confirmed that the crosslinking phenomenon occurred in the preparation of TPVs; and the gel fraction analysis indicates that the GTR components and the HDPE components of the HDPE/GTR blends are all moderately crosslinked. In addition, the morphology of the HDPE/GTR blends has been investigated by scanning electron microscopy. POLYM. COMPOS., 36:1907-1916, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Six types of phenolic foaming resins were synthesized at room temperature with different formaldehyde/phenol (F/P) ratios in this study. The effects of F/P ratios on physicochemical characteristics and foaming properties of the resulting resins were analyzed based on viscosity, solids content, hydroxymethyl index, residual monomer content, molecular structure of the foaming resin, flame retardancy, and foam compression strength measurements. The results of the present study indicated that viscosity and solids content of the foaming resins increased with an increase in F/P; the hydroxymethyl index of the resin first increased and then decreased with an increase in F/P, reaching its maximum at F/P = 1.6; the trimer, tetramer, and pentamer contents of the resins increased with an increase in F/P. Nuclear magnetic resonance (13C NMR) spectral analysis indicated that the presence of para/ para-methylene, para-hydroxymethyl, and ortho-hydroxymethyl groups in the resin gradually increased with an increase in F/P; the proportions of ortho/ortho- and ortho/ para-methylene bonds of the resin increased as F/P was increased. The increase in F/P was demonstrated to be conducive to improving the compression strength, thermal stability, and flame retardancy of the phenolic foam and reducing its peak heat release rate and total smoke release. The morphology of phenolic foams show that the closed cell content in the PF foam increases with the F/P ratio until it reaches a ratio of 1.6. Furthermore, the cell size becomes more uniform. POLYM. COMPOS., 36:1531-1540, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The effect of nano cupric oxide (CuO) in combination with surfactants on the curing characteristics of phenol formaldehyde (PF) resin analyzed using solid 13C CP/MAS NMR, including the bonding strength of plywood prepared by modified resin, was investigated in this study. The results showed that nano CuO alone improved the cure of PF resin. The intensity of the functional groups of the PF mixture was maintained during the curing process as sodium lignosulfonate was simultaneously introduced. Furthermore, nano CuO and alkane surfactant together modified the PF resin conformation. The shear strength of the plywood showed that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosulfonate (0.55%) to the PF resin mixture was effective. And this approach met the important criteria for its application in the manufacture of plywood. POLYM. COMPOS., 35:113-117, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this article, samples of phenolic resin reinforced with graphene oxide were prepared. Mechanical properties of the composite were tested. Dynamic mechanical analysis, Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermogravimetric analysis were employed to study the mechanical properties in varied temperatures to infer the influence of graphene oxide on thermal performance of phenolic resin. The results show that the addition of graphene oxide resulted in a significant improvement in the elastic modulus of phenolic resin; Young's modulus, and tensile strength increase along with the graphene oxide content. Esterification reaction happened between alcohol OH groups on resole and carbonyl (sbond]COOH) groups on graphene oxide. Addition of graphene oxide improved residue rate of phenolic resin by 5.8%, whereas the temperature distribution of phenolic pyrolysis stay unchanged. The glass transition temperature of phenolic resin has been improved by 30°C. POLYM. COMPOS. 34:1245-1249, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]