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Self-polymerization epoxy/phthalonitrile (APPEN) pre-polymers were studied systematically, and then, gelation time and differential scanning calorimetry (DSC) were employed to investigate their curing behaviors. Taking advantage of orthogonal test analysis, the key factors that affected the co-polymerization of APPEN were defined and the appropriate pre-polymerization conditions were analyzed. A possible curing mechanism of APPEN was proposed. Then, the thermomechanical and mechanical properties of glass-fiber-reinforced APPEN laminates (APPEN/GF) prepared at 180 °C were analyzed to understand the cross-linked and aggregation structures. Fracture surface of the composite laminates was also investigated to reveal the copolymerization degree and the interfacial binding. The results indicated that APPEN/GF composites exhibit outstanding mechanical and thermomechanical properties (flexural strength, 712 MPa, flexural modulus, 38 GPa, and Tg > 185 °C). The thermal stability (T5% > 334 °C and IPDT reached 1482 °C) of APPEN/GF composites was also investigated to further reveal the copolymerization between epoxy resin and aminophthalonitrile, which may be beneficial to the application of epoxy-matrix-based composites in the field of high-performance polymer composites. [ABSTRACT FROM AUTHOR]

Secondary dispersion of the nano barium titanate (BaTiO 3 ) was performed to obtain the fiber-reinforced polyarylene ether nitrile-based (PEN) composite laminates with improved mechanical properties. BaTiO 3 /PEN composite films were prepared via casting with ultrasonic dispersion, and then the glass fiber-reinforced (GF) composite laminates were obtained by the hot-melting method, which were favored to realize the secondary dispersion of the BaTiO 3 nanoparticles. The fracture surface of the BaTiO 3 /PEN films and BaTiO 3 /PEN/GF composite laminates investigated by SEM showed that the BaTiO 3 dispersed homogenously both in the PEN matrix and the gaps between the fibers. The mechanical and thermo-mechanical properties of the laminates were characterized and results indicated that the nano-BaTiO 3 particles and fibers show enhanced synergistic effects. That is, with increasing the BaTiO 3 content, the flexural strength and modulus of the composite laminates increased correspondingly, as well as the glass transition temperatures. Additionally, with the introduction of nano-BaTiO 3 particles, the dielectric constants (>5.5 at 1 kHz) of the composite laminates were improved obviously and the low dielectric loss (˂0.02 at 1 kHz) was maintained. The temperatures at weight loss 5% ( T 5% ) of all the composite laminates with various content of BaTiO 3 were over 490 °C both in N 2 and air atomosphere. Good dielectric properties and outstanding thermo-mechanical properties would enable the PEN-based fiber-reinforced composite laminates as the candidates in the material fields of structure-functional integrations. [ABSTRACT FROM AUTHOR]

Phthalonitrile resin is a kind of high-performance thermosetting resins. Decreasing the curing temperature and accelerating the curing reaction rate have become the focus of research on phthalonitrile modification. Based on the reactivity, thermal and mechanical properties of diamine-type benzoxazine, a monocyano-functionalized diamine-type benzoxazine (MD-cn) was synthesized and applied to modify bisphthalonitrile resin containing bisphenol-type benzoxazine/nitrile phenylenediamine (BA-ph/BAB). Curing reaction properties and curing mechanism of BA-ph/BAB/MD-cn were studied by gelation time, DSC, DRA and in-situ IR. Results showed that MD-cn could significantly boost the curing reaction rate and reduce its curing temperature of BA-ph/BAB. Meanwhile, glass fiber reinforced composites (BA-ph/BAB/MD-cn/GF) was prepared and their properties were studied. Results showed that MD-cn improved the crosslinking density and curing degree of BA-ph/BAB could make the BA-ph/BAB/MD-cn resin matrix possess higher stiffness. Therefore, BA-ph/BAB/MD-cn/GF composites exhibited higher flexural strength (494 MPa, increased 40%) and flexural modulus (26 GPa, increased 13%) as well as good dimensional stability. Compatibility between MD-cn and BA-ph/BAB was investigated by DMA and SEM. Moreover, with the increase of MD-cn content, the good thermal stabilities (T 5% >404.5 °C, Y c, 800 °C >66%) of cured BA-ph/BAB/MD-cn were obtained. Besides, interfacial adhesion properties of BA-ph/BAB/MD-cn/GF composite laminates were also studied. [Display omitted] • A novel highly active monocyano-functionalized diamine-type benzoxazine (MD-cn) is prepared by molecular design. • A new method of modifying the bisphthalonitrile resin containing bisphenol-type benzoxazine (BA-ph) with MD-cn is proposed. • MD-cn reduces the initial reaction temperature of BA-ph/BAB and significantly improves the curing reaction rate. • MD-cn improves crosslinking density and curing degree of BA-ph/BAB, also perfects interfacial compatibility of composites. • MD-cn makes BA-ph/BAB/MD-cn/GF composites exhibit good thermal stability and its flexural strength increased by 40%. [ABSTRACT FROM AUTHOR]

Poly (arylene ether nitrile)/fullerene (PEN/fullerene) nanocomposites were prepared by a facile solution-cast method and the rheological, dielectric, mechanical, and morphological properties of the resulted nanocomposites were systematically studied and compared. Rheological studies showed PEN/fullerene nanocomposites percolation network formed at fullerene containing of 1.50 wt %, when the shear frequency was fixed at 0.1 Hz, the fitted rheological percolation threshold was about 1.55 wt %, very close to the experimental observations. The dielectric transaction occurs when the fullerene loading reached 1.50 wt %, that is very close to its rheological percolation threshold. At this point, PEN/fullerene nanocomposites also showed the optimal mechanical properties with a tensile strength of 93.6 MPa and modulus of 1951.5 MPa, which is increased by 27% and 15% compared with the pure PEN. SEM and TEM images have manifested the separate fullerene aggregated to fullerene bundles in PEN/fullerene nanocomposites, and the dispersion of fullerene bundles begin to go bad when the containing above 1.50 wt %. The PEN/fullerene nanocomposites can be widely used due to its excellent dielectric and mechanical performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40100. [ABSTRACT FROM AUTHOR]

The nitrile groups of 2,2-bis [4-(3,4)-dicyanophenoxy phenyl] propane (bisphthalonitrile; BAPh) can be cured by the nucleophilic phenol groups. Bisphenol A (BPA) can react with 4-nitrophathalonitrile to synthesize BAPh. Therefore, BPA was used as a novel curing agent to react with BAPh. The BAPh/BPA prepolymers and polymers were prepared by heat polymerization. The curing behaviors were characterized using differential scanning calorimetry, dynamic rheological analysis, and thermogravimetric analysis. The results indicate that BPA can decrease the melting temperature of BAPh, shorten the curing time of BAPh with lower curing temperature at 243°C, and widen the processing windows of BAPh to 95–120°C. Meanwhile, BAPh/BPA polymers could withstand temperatures up to 443°C under nitrogen atmosphere and 420°C in air when cured at 240°C for 10 h. The mechanical properties of BAPh/BPA polymers were investigated, and it exhibits a flexural strength of 75 to 122 MPa. Dynamic mechanical analysis was used to evaluate the dynamic mechanical properties of BAPh/BPA polymers. The polymers show glass transition temperature ranging from 244 to 299°C heating and cured to 240°C. Herein, the BAPh/BPA polymers can be a good candidate resin for high-performance polymeric materials. [ABSTRACT FROM AUTHOR]

An easy and efficient approach by using carboxyl functionalized CNTs (CNT-COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA-ph) grafted with CNTs (CNT- g-BA-ph), obtained from the in situ reaction of BA-ph and CNT-COOH, was used as polymer matrix and processed into glass fiber (GF)-reinforced laminates through hot-pressed technology. FTIR study confirmed that CNT-COOH was bonded to BA-ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA-ph laminate to 650 MPa and 28.4 GPa in CNT- g-BA-ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT-COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin-rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal-oxidative stabilities with the onset degradation temperature up to 624°C in N2 and 522°C in air. This study demonstrated that CNT-COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A series of bisphenol A (BPA)-based 2,2-bis-[4-(3,4-dicyanophenoxy)phenyl]propane (BAPh) prepolymers and polymers were prepared using BPA as a novel curing agent. Ultraviolet-visible and Fourier transform infrared spectroscopy spectrum were used to study the polymerization reaction mechanism of the BAPh/BPA polymers. The curing behaviors were studied by differential scanning calorimetry and dynamic rheological analysis, the results indicated that the BAPh/BPA prepolymers exhibit large processing windows (109.5-148.5°C) and low complex viscosity (0.1-1 Pa·s) at moderate temperature, respectively. Additionally, the BAPh/BPA/glass fiber (GF) composite laminates were manufactured and investigated. The flexural strength and modulus of the composite laminates are 548.7-632.8 MPa and 25.7-33.2 GPa, respectively. The thermal stabilities of BAPh/BPA/GF composite laminates were studied by thermogravimetry analysis. The temperatures at 5% weight loss ( T5%) of the composite laminates are 508.5-528.7°C in nitrogen and 508.1-543.2°C in air. In conclusion, the BAPh/BPA systems can be used as superior matrix materials for numerous advanced composite applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Copolymerizing behavior and processability of epoxy/benzoxazine containing cyano groups (EP/BA-ph) systems were investigated by differential scanning calorimetry and dynamic rheological analysis. The results showed that EP/BA-ph systems exhibited two characteristic peaks corresponding to ring-opening of benzoxazine and ring-formation of cyano groups, respectively. Compared with BA-ph, EP/BA-ph copolymer processability was improved and can be controlled by varying EP contents, processing temperature, and time. Then EP/BA-ph copolymers were employed to prepare EP/BA-ph/glass fiber (GF) composite laminates and their mechanical, morphological, and thermal properties were investigated. Compared with those of BA-ph/GF composites, the flexural strength, and modulus of EP/BA-ph/GF composites with 50 wt % EP content were increased by 13.5 and 20%, respectively. The enhancements in mechanical properties are mainly due to the strong interfacial adhesions between GF and matrices, which was confirmed by SEM observations. All EP/BA-ph/GF composite laminates are stable up to 510°C in air. EP/BA-ph/GF laminates will have potential applications in the areas where require of excellent mechanical properties and high temperature resistance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Abstract High performance composites are not only pursued with the high modulus, high strength and high service temperature, but also most of their mechanical performances should be maintained after the high-temperature thermal aging. To improve thermal oxidative mechanical properties of phthalonitrile (PPN) composites, microsilica (MS) as complementary reinforcement was introduced into PPN to form particle-filled GFRP (MS/PPN/GF) composite. DSC and DRA studies showed that the introduction of MS could lower the curing temperature and increase melt complex viscosity of MS/PPN prepolymers. Thermal oxidative stabilities of the MS/PPN composites with 16 wt% MS content were improved by 25.4 °C in T 5% , 41.3 °C in T 10% and 14.7% in char residue at 800 °C compared those of PPN matrix, respectively. Mechanical performances of MS/PPN/GF composites were significantly improved with the increasing MS content. More importantly, most of their mechanical performances could be maintained after being aged at 400 °C for various durations. After 400 °C/12 h thermal aging, all MS/PPN/GF composites showed a retention ratio of flexural modulus and strength higher than 90% and 70%, respectively. These improvements can be mainly attributed the complementary reinforcement of MS and better thermo-oxidative stabilities of the MS/PPN composites. Fracture surface images of MS/PPN/GF-8 composite reveal an obvious interfacial structure transformation as the thermal oxidative process goes. This study demonstrate that the introduction of particles like MS into polymer-based GFRP composite as complementary reinforcement can be an easy and effective way to improve the thermal oxidative mechanical properties. Highlights • Microsilica (MS) was introduced into phthalonitrile (PPN) as complementary reinforcement to form MS/PPN/GF composites. • MS/PPN/GF composites showed significant improvements in thermal oxidative mechanical properties. • Interface layers on the GF surface and between adjacent fibers were mainly responsible for mechanical increments. [ABSTRACT FROM AUTHOR]

Abstract: We report an easy and efficient approach to the development of advanced thermoplastic composites based on multi-scale carbon fiber (CF) and graphene nanoplatelet (GN) reinforcement. Poly (arylene ether nitrile) (PEN)/CF/GN composites, prepared by the twin-screw extrusion, exhibited excellent mechanical properties. For example, the flexural modulus of PEN/CF/GN composites was 18.6GPa, which is 1.7, 4.5 and 6.4 times larger than those of PEN/CF composites, PEN/GN composites and PEN host, respectively. Based on the SEM image observation, such mechanical enhancements can be attributed to the synergetic effect of micro-scale CF and nano-scale GN in the PEN matrix (decreased matrix-rich and free-volume regions and enhanced interfacial interactions). For 5wt.% GN-filled PEN/CF/GN composites, the Td 30% of PEN/CF/GN composites was 145°C and 62.8°C compared with those of PEN host and PEN/CF composites, respectively. This study has demonstrated that multi-scale CF and GN have an obvious synergetic reinforcing effect on the mechanical properties and thermal stabilities of thermoplastic composites, which provides an easy and effective way to design and improve the properties of composite materials. [Copyright &y& Elsevier]

Abstract Benzoxazine and phthalonitrile-based resins play an important role in fields of advanced materials because of their excellent properties. In this work, a kind of matrix resin with various ratios of phthalonitrile and benzoxazine were designed and prepared via co-reaction between aniline and 3-aminophenoxy phthalonitrile in the presence of biphenol and formaldehyde. Curing behaviors and dynamic rheology of matrix resins were investigated with DSC and DRA. Results indicated that obvious double curing stages can be assigned to ring-opening polymerization of oxazine rings and ring-forming polymerization of nitrile groups. Possible polymerization mechanisms were discussed in this work. Thermal stability of cured resins was evaluated by TGA testing and an integral decomposition temperature (IPDT). Then, fiber-reinforced composite laminates were prepared and their mechanical properties were investigated and confirmed with SEM images of fracture surfaces. Results demonstrated that this work proposed an improved matrix resin system with outstanding thermal stability and mechanical properties that broadened the foundation and ideas for subsequent researches. Graphical abstract Image 1 Highlights • A novel benzoxazine composites were prepared with copolymerization of oxazine and nitrile groups. • Improved thermal stability and mechanical properties were obtained due to the enchantment of nitrile groups. • The thermal stability of the fiber-reinforced laminates were discussed with IPDT. • The possible copolymerization processes between oxazine and nitrile groups were proposed. • The enhanced mechanical properties of the composites were backed up with the interfacial adhesion effects. [ABSTRACT FROM AUTHOR]

The interfacial compatibility plays an important role in the performance of fiber-reinforced composite laminates. Aramid fiber is an important class of high performances fibers. However, the inertia of fiber surface is not conducive to the improvement of composite properties. In this work, polyarylene ether nitrile terminated with phthalonitrile (PEN-t-Ph) was supplied to modify the aramid fiber (m-AF). By heat treatment and riveting PEN-t-Ph to the fiber surface, a rough fiber surface can be obtained, and then the composite material with improved performance can be obtained through the entangling compatibility. Through SEM images, it could be seen that the fiber surface had the best rivet surface morphology when the fiber surface coated with 5 wt% PEN-t-Ph (m(5 wt%)-AF). At the same time, the interfacial adhesion between m(5 wt%)-AF and the resin matrix showed the best peel strength of 1.594 kN/m. Based on these results, modified fiber resin composite laminates (m(5 wt%)-AF/PEN-t-Ph) were fabricated. The results indicated that the laminates had good interfacial compatibility and the interlaminar shear strength (ILSS) of modified aramid fiber laminates was 112.58 MPa, which is increased by 21.4% than that of original fiber composite laminates. In addition, the flexural strength of m-AF/PEN-t-Ph laminates was 324 MPa, increased by 10% compared to AF/PEN-t-Ph. The results of DMA showed that the energy storage modulus of the m-AF/PEN-t-Ph laminate was greatly improved compared with that of AF/PEN-t-Ph laminate, which was increased by 60% under the initial condition of 100 °C. To sum up, through surface treatment, the mechanical properties of fiber-reinforced composite laminates had been greatly improved, making them have great application prospects in bulletproof and other fields. [ABSTRACT FROM AUTHOR]

Poly (arylene ether nitrile) (PEN) is a kind of high-performance engineering plastic and their properties can be tuned by the copolymerization of various structural diphenols and dichloro (fluoro)-benzonitrile. In this work, a series of phenolphthalein and bisphenol AF based PEN (PP/BPAF-PEN) copolymers were designed and synthesized. Structures, molar weights, mechanical and thermal properties were studied. Results showed that PP/BPAF-PEN copolymers were successfully synthesized and exhibited good compatibility, outstanding thermal and mechanical properties. Besides, PP/BPAF-PEN exhibited excellent T g up to 260 °C (DSC), tensile strength of 120 MPa, high T d5% and char yields (>70%). With incorporation of –CF 3 into molecular chains, dielectric constant of PP-PEN (3.41 at 1 MHz) was decreased to 3.05 of PP/BPAF-PEN and dielectric loss was around 0.01. Hence, the obtained PP/BPAF-PEN copolymers possessing excellent properties could be applied as the candidates in flexible printed circuit (FPC) substrate. • PP/BPAF-PEN copolymers were synthesized and results showed that the copolymers exhibited well compatibility. • PP-PEN possessed excellent T g (260 °C) and mechanical properties (tensile strength > 120 MPa, tensile modulus > 3434.6 MPa). • PP/BPAF-PEN gained dielectric constant of 3.05 at 1 MHz and all of PP/BPAF-PENs exhibited T g > 200 °C (by DSC). • Thermal stability was enhanced with incorporation of BPAF into molecular chains. [ABSTRACT FROM AUTHOR]

For fiber reinforced composite laminates, properties of laminates can be significantly affected by interfacial properties. In this work, a kind of phthalonitrile containing aromatic ether nitrile linkage (PEN-BAPh) was applied to modify glass fibers (GFs). Cured PEN-BAPh on GFs surface were investigated by Fourier transform infrared spectroscopy (FT-IR) and Ultraviolet–visible spectroscopy (UV–Vis). Scanning electron microscope (SEM) and thermogravimetry (TGA) testing were also applied to confirm the modification. Then, modified fiber-reinforced phthalonitrile-based resin composite laminates were fabricated. As the results indicated that all of the composite laminates showed improved flexural strength, flexural modulus and glass transition temperature (T g = 296.8–299.6 °C). Improved interfacial adhesion was also studied via interlaminar shear strength (ILSS), impact strength test and monitoring the fracture surfaces. Stable dielectric constants, relative low dielectric loss and outstanding thermal stability (T 5% > 350 °C) were obtained for designed composite laminates. Image 1 • Phthalonitrile containing aromatic ether nitrile linkage (PEN-BAPh) was applied to modify glass fiber (GF) surface. • Copolymerization and molecular entanglement between PEN-BAPh and BA-ph/CE contributed to the interfacial adhesion. • Improved interfacial properties contributed to the increase of mechanical properties and T g (increased 16 °C). • Composites with improved interfacial properties were confirmed by flexural properties, DMA, SEM, ILSS and impact strength. • Decreasing of interfacial polarization and polar nitrile groups on GF surface leaded to improved dielectric properties. [ABSTRACT FROM AUTHOR]