Polybenzoxazine Matrix Research Articles

Lignosulfonate/silica hybrid nanoparticles as a novel biobased filler in polybenzoxazine matrix

AbstractLignin is an abundant and sustainable resource that exhibits numerous attractive functional properties as a reinforcing agent for benzoxazine‐based composites, due to its stiffness, thermal stability, and high carbon content. However, the low quality of lignin particles dispersions associated with the weak particles‐matrix interactions reduces the reinforcement capability. In this work, hybrid lignin/silica (NaLS/SiO2) nanoparticles were obtained from sodium lignosulfonate (NaLS) and tetraethylorthosilicate (TEOS) under basic conditions. The particles were characterized by transmission electron microscopy (TEM) confirming their spherical morphology and narrow nanometric‐size distributions. The hybrid particles were incorporated into conventional benzoxazine (BA‐a) and a difuran biobased benzoxazine (SA‐dfda) to prepare nanocomposites with different mass compositions (3, 5, and 10 wt%). Morphological, mechanical, dynamo‐mechanical, and thermal properties of the obtained composites were assessed. All the materials exhibited a homogenous filler dispersion that contributed to improve the reinforcement properties. Hybrid nanoparticles proved to be an interesting alternative as a filler in the benzoxazine matrix to prepare high‐performance thermosetting composites.

Enhanced dielectric and hydrophobic behaviour of aurin based polybenzoxazine dye composites

Herein, three novel bi-functional benzoxazines were synthesized using aurin as the precursor phenol with three different aromatic amines (i.e.) aniline, fluoroaniline, and trifluoromethylaniline with paraformaldehyde through Mannich condensation. The structural confirmation was done using FTIR and proton NMR. The effects of substituents present in the amines on the curing behaviour and thermal stability were studied using DSC and TGA. The aurin based trifluoromethyl substituted benzoxazine shows better thermal stability than that of the other two benzoxazines and it was selected for the preparation of composites with varying weight percentages of graphitic carbon nitride derived from dicyandiamide (Dicy-GCN) to utilize them for high k applications. The dielectric behaviour and thermal properties of both neat polymer matrix and composites were studied and compared. The 15 wt% Dicy-GCN reinforced composite shows the highest dielectric constant value of 10.25, with a low dielectric loss value of 0.046 at 1 MHz frequency. The polybenzoxazine composites developed show better thermal stability and superhydrophobic behaviour than those of neat polybenzoxazine matrix. These properties ascertain that the aurin based bifunctional polybenzoxazines and its composites can be considered for high-performance high k applications.

Mechanical properties, thermal stability, and mechanism of main‐chain polybenzoxazine composites fabricated based on multi‐scale effects and surface functionalization of graphene oxide nanosheets

AbstractPolybenzoxazine (PBZ) has been recognized as a potential substitute for traditional phenolic resin. However, poor flexibility and low heat resistance limited obviously the application of PBZ. Herein, graphene oxide (GO) nanosheet and its amino‐rich derivatives (fGO‐g‐SiO2) with multi‐scale surfaces were designed, synthesized and incorporated into main‐chain PBZ through in‐situ polymerization to fabricate PBZ composites. The morphology, mechanical properties, and thermal stability of the composites were systematically investigated using x‐ray diffraction (XRD), contact angle tests, field emission scanning electron microscopy (FESEM), tensile and impact tests, and thermogravimetric analysis (TGA). FTIR and XRD analyses confirmed the multi‐scale surfaces of GO derivatives and ordered structures, respectively. The size of the in‐situ grown SiO2and the thickness of GO coated on PBZ were estimated as 6.5 and 19.07 nm, respectively. The contact angle test revealed thatfGO‐g‐SiO2and BZ had the closest solid surface energy of 32.002 and 43.519 mN/m, respectively, among the components of the composites. The impact and tensile evaluation revealed the highest impact, tensile strength and Young's modulus of 16.75 kJ/m2, 107.24 MPa and 3.17 GPa, respectively for 1.2%fGO‐g‐SiO2/PBZ composite. The modified Halpin‐Tsai equation was also utilized to develop a predictive function for the tensile strength. FESEM offGO‐g‐SiO2/PBZ composites indicated that the multi‐scale effect and amination effectively improved the restriction of GO derivatives on crack propagation in PBZ composites and played a more significant role in crack deflection and bridging. In addition, the highest thermal decomposition activation energy of 166.94 kJ/mol was achieved for 1.2%fGO‐g‐SiO2/PBZ composite.HighlightsGraphene oxide (GO) nanosheets were incorporated into main‐chain polybenzoxazine (PBZ) to improve its mechanical properties and heat resistance.GO with multi‐scale structure and amino‐rich interface were designed, synthesized to improve the interface interactions with PBZ matrix.The GO with multi‐scale structure and amino‐rich interface showed excellent similarity in the term of solid surface energy with benzoxazine oligomers.The morphology, mechanical and thermal stability of resulting PBZ composites was systematically investigated by using experimental and mathematical model to elucidate the relationships between the structure and properties.The composites exhibited excellent mechanical and thermal properties, and it is expected to be used as advanced engineering material in demanding environments.

Valorization of agricultural waste to polybenzoxazine-carbon composites: Studies on microstructure, thermal and dielectric properties

Agricultural waste valorization has become a necessity to reduce global warming. In this context, absolute bio-waste derived cardanol, furfurylamine (ffa), and benzaldehyde were utilized for the synthesis of a novel card-bisphenol (BBC) and its benzoxazine (BBC-ffa) resin. Further, the reinforcement of carbon building blocks derived from three different sustainable resources, viz. Anacardium occidentale, Borassus flabellifer, and Tamarindus indica and named cashew apple carbon (CC), palmyra palm inflorescence (spadix) carbon (PC), and tamarind seed carbon (TC), respectively. The derived carbons were reinforced (1–20 wt%) separately with BBC-ffa polymer matrix [poly(BBC-ffa)] for the engineering of carbon integrated polybenzoxazine composites [poly(BBC-ffa)–CC/PC/TC] to achieve high-k dielectrics. Because the carbon with different functionalities intrinsically exhibit higher polarization and lower specific surface area. Dielectric constant (k) of the polybenzoxazine matrix (k = 4.62) has been increased to 8.58, 9.43, 10.60 for the reinforcement of 20 wt% of each CC, PC, and TC polybenzoxazine composites, respectively and the value of dielectric loss was also significantly decreased for the same. The dissemination of reinforced carbon particles in the polybenzoxazine matrix was ascertained through the surface analysis of the composites by FE-SEM. Based on the results of TGA, the carbon reinforced composites showed slightly lower thermal stability and about two-fold higher char yield than that of neat polybenzoxazine. Hydrophobicity of the composites enhanced with increasing the carbon content. The resulting sustainable polybenzoxazine-carbon composites could be effectively utilized as a gate dielectric in microelectronics.

High‐performance main‐chain polybenzoxazine composites by incorporating multi‐walled carbon nanotubes with different surfacial structure: Mechanical properties, thermal stability and mechanisms

AbstractHerein, multi‐walled carbon nanotubes (MWCNTs) with different surfacial structure were first designed and synthesized, and then incorporated into main‐chain polybenzoxazine (PBZ) to fabricate PBZ composites. Fourier transform infrared results showed that the ring‐opening crosslinking process of benzoxazine (BZ) oligomer was catalyzed due to the existence of COOH and NH2 groups on the surface of MWCNTs. The enhanced interface interactions between MWCNTs‐fBZ and PBZ contributed to the improvement of the mechanical properties. When the MWCNTs‐fBZ content was 1.5%, the MWCNTs‐fBZ/PBZ composites had excellent tensile strength of 102.64 MPa. The highest impact strength, which was 15.96 kJ/m2 and 64.15% higher than that of neat PBZ at 1.5% MWCNTs‐fBZ was achieved. Through the Halpin‐Tsai equation, combined with the experimental results, the correction factor was obtained to predict the mechanical properties. FESEM observations showed that the dispersion of MWCNTs in the PBZ matrix depended on the functional groups of MWCNTs. TGA tests and Horowitz‐Metzger calculation found that the thermal decomposition temperature of the composites reached 451.7°C and had the highest decomposition activation energy of 153.20 kJ/mol at 2% MWCNTs‐fBZ. In summary, the obtained MWCNTs‐fBZ/PBZ composite showed excellent comprehensive performance and can potentially be used as advanced engineering material in demanding environments.

Electrical and electromagnetic shielding properties of thermally-stable polybenzoxazine/expanded graphite nanocomposites

The thermal, the electrical conductivity, and electromagnetic shielding properties of low cost high-performance expanded graphite (EG)-filled polybenzoxazine matrix nanocomposites produced by a solution blending and compression molding technique were investigated. At 2.26 vol.% EG, a percolation threshold was detected, at which the electrical conductivity increased by nine orders of magnitude in comparison to the unfilled matrix. The electrical conductivity values increased from 1.35 S.cm−1 to 28.3 S.cm−1 by increasing the EG ratios in the nanocomposites from 7 wt.% and 15 wt.%. In addition, the morphological analysis results revealed good nanofiller dispersion and the formation of 3D-conductive pathways of EG into the polybenzoxazine matrix, which are responsible for the electrical conductivity improvement. Moreover, the electromagnetic interference (EMI) shielding efficiencies, in the X-band, of these nanocomposites have been significantly improved, reaching 57.2 dB at a 15 wt.% EG ratio. Furthermore, the inclusion of EG nanofiller significantly improved the thermal properties of the nanocomposites in terms of first degradation temperatures, char yields, and thermal conductivities. Because of these exceptional properties, these nanocomposites are ideal for high thermal EMI shielding applications.

Strengthening and toughening of polybenzoxazine by incorporation of polyrotaxane molecules

A mechanically interlocked supramolecule polyrotaxane (PR) was utilized as a functional additive to modify the hydrogen bonding (H-bonding) and cross-linking network of polybenzoxazine (PBa). Epoxide and hydroxyl groups at the terminal end of polycaprolactone grafted on CDs were chosen to investigate how these functional groups influence H-bonding, morphology, and mechanical properties of PBa matrix. Fourier transform infrared spectroscopy and differential scanning calorimetry results show evidence of successful manipulation of H-bonding and curing kinetics of PBa in the presence of the functionalized PR. After curing, epoxide functionalized PR (EPR) shows a strong interaction with PBa, leading to molecular level dispersion in PBa compared to PR with the hydroxyl functional group. By introducing only 4 wt% of EPR in PBa, the ductility and fracture toughness of PBa are greatly improved without a noticeable drop in Young's Modulus, which is attractive for aerospace and microelectronic applications.

High Performance Composites Based on Highly Filled Glass Fiber-Reinforced Polybenzoxazine for Post Application

Glass fiber post based on the new polymeric material, polybenzoxazine, is prepared and the effects of glass fiber contents on mechanical and thermal properties are evaluated. The mechanical response to externally applied loads of tooth restored with glass fiber-reinforced polybenzoxazine composite posts is also simulated by finite element analysis of a tridimensional model and compared with the response to that of a natural tooth. The reinforcing of glass fiber can help improve the mechanical and thermal properties of the polybenzoxazine influenced by the interfacial adhesion between the glass fiber and polybenzoxazine matrix, except for the relatively high mechanical property of the glass fiber. The mechanical data, i.e., elastic modulus under flexure load or flexural modulus by three-point bending test of the glass fiber-reinforced polybenzoxazine composites are agreed with the elastic modulus of dentin and then used in the finite element model. The restoration using the glass fiber-reinforced polybenzoxazine composite post provided the maximum von Mises equivalent stress at the cervical third area of the endodontically treated tooth model as similarly observed in the natural tooth. In addition, the maximum von Mises equivalent stress of the tooth restored with the glass fiber-reinforced polybenzoxazine composite post is also quietly like that of the natural tooth. The finding of this work provided the essential properties of the glass fiber-reinforced polybenzoxazine composite for dental restorations and appliances.

Artificial neural network prediction of thermal and mechanical properties forBi2O3‐polybenzoxazinenanocomposites

AbstractPolybenzoxazine (BA‐a) based nanocomposites with varying amounts of Bi2O3particles reinforcement (10, 20, and 30 wt%) were produced. The structures of the Bi2O3before and after surface silane treatment, as well as the structures of the BA‐a matrix and its nanocomposites, were all evaluated using Fourier transform infrared spectroscopy (FTIR). The thermal stability of the samples was evaluated by thermogravimetric analysis (TGA) and the resistance to bending was studied using the three‐point bending test. Then, an artificial neural network approach was used to estimate the thermal degradation and flexural strengths of the polybenzoxazine matrix and its nanocomposites. The results of the TGA analysis showed that when Bi2O3content increased, the char yield (Yc) of the nanocomposites also increased from 27.98% to 43.53% for the experimental data and from 27.95% to 43 0.57% for the prediction, with allSDs less than 0.02. Moreover, both the experimental and predicted values of the flexural strengths for the unfilled BA‐a displayed 100.40 and 102.96 MPa, respectively and these values increased to 119.65 and 114.95 MPa when 10 wt% of fillers were incorporated into the matrix. However, for higher filler contents, 20 and 30 wt%, these values decreased to 112.94 and 108.01 MPa for the experiments, and 106.35 and 103.20 MPa for the prediction, respectively. The very small deviations (<0.05) between the experimental and predicted values demonstrated that the prediction approach using the artificial neural network is reliable and accurate.

A Phosphorous-Containing Bio-Based Furfurylamine Type Benzoxazine and Its Application in Bisphenol-A Type Benzoxazine Resins: Preparation, Thermal Properties and Flammability.

Polybenzoxazine (PBa) composites based on phosphorous-containing bio-based furfurylamine type benzoxazines (D-fu) and bisphenol-A type benzoxazines (Ba) were developed for flame retardation. The structure of D-fu was analyzed by Fourier transform infrared (FTIR) spectroscopy and 1H-NMR spectroscopy. The curing temperature of Ba/D-fu mixtures was systematically studied by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) demonstrated the excellent char formation ability of the PBa composites with the addition of phosphorous-containing D-fu. The flame retardancy of the PBa composite materials was tested by the limited oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CONE). The LOI and UL-94 level of PBa/PD-fu-5% reached 34 and V0 rate, respectively. Notably, the incorporation of 5% D-fu into PBa led to a decrease of 21.9% at the peak of the heat-release rate and a mass-loss reduction of 8.0%. Moreover, the fire performance index increased, which demonstrated that the introduction of D-fu can diminish fire occurrence. The role of D-fu in the condensed and gas phases for the fire-resistant mechanism of the PBa matrix was supported by SEM-EDS and TGA/infrared spectrometry (TG-FTIR), respectively. Dynamic mechanical analysis (DMA) revealed that the Tg of PBa flame-retardant composites was around 230 °C. Therefore, PBa composites are promising fire-retardant polymers that can be applied as high-performance functional materials.

Enhanced thermal conductivity for polybenzoxazine matrix composites by constructing a hybrid conductive network and modification of fillers

Polyhedral oligomeric silsesquioxanes (POSS) and γ-glycidoxy propyl trimethoxy silane (KH560) were applied to modify boron nitride (BN) and boron nitride whisker (BNw), and modified BN (m-BN) and modified BNw (m-BNw) were added as thermally conductive fillers to polybenzoxazine (PBz) matrix to synthesize m-BN/m-BNw/PBz composite by hot press. The research results indicate that the modification of BN and BNw and the synergistic effect between m-BN and m-BNw can significantly improve the thermal conductivity of PBz composite. The thermal conductivity of PBz composite with 25 wt % m-BN and 25 wt % m-BNw reached to 1.27 W/mK, which is 35% higher than PBz composite with 50 wt % m-BN (0.94 W/mK), 76% higher than PBz composite with 50 wt % BN (0.72 W/mK), and also display excellent electrical insulation performance. The corresponding dielectric constant (ε) and dielectric loss (tan δ) were 3.83 and 0.0078, respectively. Besides, the Theat-resistance index (THRI) of PBz composite with 25 wt % m-BN and 25 wt % m-BNw is 242.26 °C, and the thermal degradation temperature at 30% weight loss (T30) is 557.72 °C, are higher than PBz matrix (224.46 and 498.88 °C). And the tensile strength of PBz composites with 25 wt % m-BN and 25 wt % m-BNw is 47.71 MPa.

Structure and Performance of Benzoxazine Composites for Space Radiation Shielding.

Innovative multifunctional materials that combine structural functionality with other spacecraft subsystem functions have been identified as a key enabling technology for future deep space missions. In this work, we report the structure and performance of multifunctional polymer matrix composites developed for aerospace applications that require both structural functionality and space radiation shielding. Composites comprised of ultra-high molecular weight polyethylene (UHMWPE) fiber reinforcement and a hydrogen-rich polybenzoxazine matrix are prepared using a low-pressure vacuum bagging process. The polybenzoxazine matrix is derived from a novel benzoxazine resin that possesses a unique combination of attributes: high hydrogen concentration for shielding against galactic cosmic rays (GCR), low polymerization temperature to prevent damage to UHMWPE fibers during composite fabrication, long shelf-life, and low viscosity to improve flow during molding. Dynamic mechanical analysis (DMA) is used to study rheological and thermomechanical properties. Composite mechanical properties, obtained using several standardized tests, are reported. Improvement in composite stiffness, through the addition of carbon fiber skin layers, is investigated. Radiation shielding performance is evaluated using computer-based simulations. The composites demonstrate clear advantages over benchmark materials in terms of combined structural and radiation shielding performance.

Characterization of novel composites from polybenzoxazine and granite powder

The potential of using granite dust as reinforcement into polybenzoxazine matrix was investigated. In this article, novel granite powder waste-reinforced bisphenol-A aniline-based benzoxazine composites were prepared using solution blending technique by varying the content of granite powder from 10 to 40 wt%. The effect of the granite powder content on the thermal, structural, dimensional, and morphological properties of granite powder/polybenzoxazine composites have been investigated. Thermogravimetric analysis (TGA) was performed on the composite samples. Char yield of the composites increased from 44.55 to 67.70% for increasing filler content from 10 to 40wt%, whereas 22% for pure polybenzoxazine. The maximum weight loss temperatures of the composites were analyzed from derivative of thermogravimetric analysis (DTG). Limiting oxygen index (LOI) values also increased as granite powder content increased. Structural properties of benzoxazine, polybenzoxazine, and composites were observed with Fourier-transform infrared spectroscopy (FTIR). Dimensional stability of the composites was investigated through the water absorption test up to 30 days. The composites exhibited zero percent water absorption. Micro-hardness of the composites increased from 17.45 to 78.66% for increasing filler content from 10–40 wt% when compared with pristine polybenzoxazine. The morphological analysis using scanning electron microscopy (SEM) showed the distribution of filler, aggregate formation, compatibility between polybenzoxazine and granite powder. Overall, the importance of using granite powder waste as reinforcement in polybenzoxazine composites revealed from results of the structural, dimensional, and morphological analysis along with the improvement in thermal properties and micro-hardness.

Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites.

A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR 1H-1H COSY, 1H-13C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm−1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46–77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.

A tetraphenylethylene-functionalized benzoxazine and copper(II) acetylacetonate form a high-performance polybenzoxazine

In this study, we synthesized TPE-BZ, a new tetraphenylethylene (TPE)-functionalized benzoxazine (BZ) monomer (1,1,2,2-tetrakis(3-phenyl-3,4-dihydro-2H-benzo[e] [1,3]oxazin-6-yl)ethane), through reduction of the Schiff base formed from TPE-4OH–CHO (1,1,2,2-tetra(3-formyl-4-hydroxyphenyl)ethylene) and aniline and subsequent reaction with paraformaldehyde. Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry confirmed the structure of the TPE-BZ monomer. We used differential scanning calorimetry (DSC), FTIR spectroscopy, and thermogravimetric analysis (TGA) to investigate the thermal ring opening polymerization (ROP) and thermal stability of the TPE-BZ monomer after thermal treatment at various temperatures (from room temperature to 250 °C). The TGA profiles revealed that thermal treatment at 250 °C under a N2 atmosphere gave a poly(TPE-BZ) that possessed excellent thermal stability and a high char yield (435 °C, 64.3 wt%). Furthermore, water contact angle measurements of the poly(TPE-BZ) obtained at 210 °C for 2 h indicated a relatively low surface free energy (18.6 mJ m−2), presumably because of strong intramolecular hydrogen bonding between the phenolic OH groups and the N-Mannich bridge in the polybenzoxazine matrix. We also employed DSC, FTIR spectroscopy, and TGA to examine the specific interactions in TPE-BZ/Cu(acac)2 complexes. DSC analysis revealed that blending the TPE-BZ monomer with various weight ratios of Cu(acac)2 lowered the thermal curing temperature of TPE-BZ from 250 to 239 °C, accompanied by a lower curing temperature at 189 °C. Using the Kissinger method, the activation energy of the TPE-BZ/Cu(acac)2 complex (127 kJ mol−1) was lower than that of the TPE-BZ monomer (141 kJ mol−1), suggesting that Cu(acac)2 functioned as a catalyst that initiated ROP of the oxazine units, while providing a product that retained high thermal stability.

Comparative studies on thermal and toughness properties of polybenzoxazine composites with two functionalized graphene oxides

Graphene oxide (GO) was functionalized by polyether amine (PEA) via two methods which were one-pot modification in acetone (GON) and two steps with the intermediate product of GOCO-Cl generated (GONS). There were more PEA successfully grafted onto GO for GONS than GON. The onset polymerization temperatures of the benzoxazine (Bz) composites decreased by the inclusion of 1 wt% of GO, GON or GONS. Thermal stability of the polybenzoxazine (PBz) composites was significantly improved indicated from the increase of weight loss temperature. T10, T20 and T50 values of the composites with GONS were higher than that of the others. Toughness of PBzs may be enhanced by the incorporation of nanofillers, and GONS had stronger interfacial interaction with PBz matrix than GON.

Investigating the effects of amine-functionalized carbon balls in a polybenzoxazine matrix

This study contains arithmetical and experimental examinations of the effects of adding carbon nanoballs (CBs) on the curing behavior and material properties of a benzoxazine system.

Preparation, characterization and evaluation of polybenzoxazine thermoset/clay nanocomposites for metal coating

A series of polybenzoxazine-clay nanocomposites with various organoclay contents (3, 5, 10, and 20 wt%) were prepared by the one-shot procedure. from organo-montmorillonite (OMMT) and bifunctional benzoxazine, namely, bis-(3-dodecyel-3,4-dihydro-2H-1,3-benzoxazine) isopropane (B-dod). OMMTs were prepared by modification of Na-MMT with different ammonium salts of amines such as tyramine (Tyr), amino lauric acid (ALA) and N,N-dimethyl stearyl amine (DMS). Transmission electron microscope (TEM), X-ray diffraction (XRD) and infrared measurements (FTIR) were used to examine the structure and modification of OMMTs. The morphology of polybenzoxazine nanocomposites (B-dod/Tyr-MMT, B-dod/ALA-MMT, B-dod/DMS-MMT) was investigated by X-ray and TEM analyses. The X-ray analysis and TEM photos indicated that organoclay was exfoliated into polybenzoxazine matrix even at the highest organoclay loading (20%). Mechanical properties (viz, adhesion on metallic substrate, scratch hardness, tensile modulus, and elongation at break) of the prepared nanocomposites were measured. The tensile properties of prepared samples were examined; as the content of modified clay was increased, the tensile modulus increased; however, the elongation at break decreased. In addition, the optimum adhesion and scratch hardness values of the prepared nanocomposites were increased more than the neat resin, also, thermogravimetric analysis has the same manner. Therefore, the prepared nanocomposite materials could be successfully used for metal coatings.

Developing Polybenzoxazine Composites Based on Various Carbon Structures

AbstractThe synthesis of composite materials based on various carbon structures and polybenzoxazines (PBZs) gives products with noticeable thermal, electrical, and mechanical properties. The role of different carbon materials is emphasized in terms of the main advantages in both structure and properties. On the other hand, the PBZ features are significant considering the high glass transition temperatures, low flammability, high char yields, and good thermal stability. This review article describes the synthesis, structure, and properties of polybenzoxazine composites based on carbon fibers, carbon nanotubes, graphene, graphene oxide, and other carbonaceous materials. Particular attention is given to the interactions possible to occur between the polybenzoxazine matrix and carbon component.

Multifunctional Hybrid Composites with Enhanced Mechanical and Thermal Properties Based on Polybenzoxazine and Chopped Kevlar/Carbon Hybrid Fibers.

This work studied the structural, morphological, mechanical, and thermal properties of newly designed polymeric materials using high-performance hybrid fibers to reinforce the polybenzoxazine resins. To achieve this goal, hybrid fibers consisting of chopped Kevlar and carbon fibers were subjected to a silane surface treatment, incorporated into the resin matrix in various combinations, and then isothermally cured using the compression molding technique. The mechanical performances of the prepared composites were scrutinized in terms of bending and tensile tests. By way of illustration, the composites holding 20 wt % Kevlar fibers and 20 wt % carbon fibers accomplished a bending strength and modulus of 237.35 MPa and 7.80 GPa, respectively. Additionally, the same composites recorded a tensile stress and toughness of 77 MPa and 0.27 MPa, respectively, indicating an increase of about 234% and 32.8% when compared to the pristine resin’s properties. The thermogravimetric analysis denoted an excellent thermal resistance of the reinforced hybrid composites. Fourier transform infrared spectroscopy proved that the functional groups of the as-used coupling agent were effectively grafted on the external surfaces of the reinforcing systems, and further confirmed that the chemical reaction took place between the treated fibers and the polybenzoxazine matrix, although the scanning electron microscope showed a uniform dispersion and interfacial adhesion of the fibers within the resin matrix. In fact, the incorporation of treated fibers along with their good dispersion/adhesion could explain the progressive enhancement in terms of thermal and mechanical properties that were observed in the hybrid composites.