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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]

In this work, Phthalonitrile containing benzoxazine (BA‐ph) and Bisphenol A based cyanate ester (CE) were chosen as the matrix resin. Various amount of nano‐SiO2 was incorporated into BA‐ph/CE and their glass fiber‐reinforced composite laminates were fabricated. Curing reaction and processability of BA‐ph/CE/SiO2 blends were studied by differential scanning calorimetry and dynamic rheological analysis. Results showed that BA‐ph and CE exhibited good processability and curing reaction of BA‐ph/CE was not obviously affected by SiO2. Scanning electron microscope images of the composites showed that SiO2 particles were well dispersed in BA‐ph/CE matrix. Moreover, SiO2 could act as physical crosslinking points and diluent in matrix as well as between the glass fibers to improve the mechanical properties of composite laminates. As the results of dynamic mechanical analysis and thermogravimetry analysis, composite laminates possessed satisfactory Tg and good thermal stability. With incorporation SiO2 particles into matrix resin, dielectric constant and dielectric loss of BA‐ph/CE/SiO2/GF composites were increased and showed frequency dependence. [ABSTRACT FROM AUTHOR]

The curing behavior and dielectric properties of cyanate ester/epoxy (EP) with a latent initiator imidazole was investigated as a function of blend composition. Differential scanning calorimetry (DSC) was used to investigate the dynamic cure behavior of the blends. Multiheating rate DSC, peak fitting, and iso-conversion method were applied to analyze the curing kinetic parameters. Two distinct peaks were fitted from the dynamic DSC curve and the activation energies of each reaction varied with the increase of curing degrees. Fourier transform infrared spectra revealed that several reactions coexisted during the curing processes of cyanate and EP, resulting in the coexistence of the polymers and copolymers in the final composites. The dielectric properties of the composites were studied and the phenomenon that the dielectric constants for all of the composites are independent of frequency was observed. The thermal decomposition characteristics of the blends were investigated using thermogravimetric analysis. By increasing the content of EP, the thermal properties of the cured blends were improved to a small extent, while the char yield markedly decreased. [ABSTRACT FROM AUTHOR]

Phthalonitrile-based resins play important roles in advanced materials due to their outstanding properties, which would be determined by the curing process and curing mechanisms. Thus, in this work the curing behaviors of phthalonitrile-based resin containing benzoxazine were investigated and the kinetic parameters were determined by non-isothermal differential scanning calorimetry (DSC) at various heating rates. Sequential double exothermic thermograms were separated by PeakFit v4.12 and analyzed as independent reaction processes. The kinetics model of each reaction was evaluated by multi-heating-rate DSC methods assisted with the iso-conversion method, and an autocatalytic model for the curing reaction of BA-ph resin was confirmed. The curing kinetics parameters including activation energyE α , pre-exponential factor A, reaction orders m and n were evaluated and calculated. The activation energies for reactions of benzoxazine and nitrile groups were 102.2 and 90.6 kJ/mol with reaction orders approximately 1.8 and 2, respectively. Additional, the predicated mathematical models for curing reactions of benzoxazine and nitrile groups were obtained and fitted well with the experimental data derived from the non-isothermal DSC thermograms. [ABSTRACT FROM AUTHOR]

Phthalonitrile containing benzoxazine resin (BA-ph) was a new type of high-performance resin which could be used at high temperature by autocatalytic molding at low temperature. However, its brittleness after polymerization and weak interaction with fibers when it as the matrix of fiber reinforced composites (FRC) were obstacles to its wide application. In this study, Poly (arylene ether nitrile) containing phenolphthalein (PP-PEN) was introduced by solution blending to toughen BA-ph and its glass fiber (GF) FRC. The effects of PP-PEN on the crosslinking behavior and processability of BA-ph were studied by differential scanning calorimetry (DSC) and dynamic rheology analysis (DRA). The effect of PP-PEN on the structural strength and thermal stability of BA-ph/GF was further studied by other characterization methods. The non-notchable impact strength of BA-ph/PP-PEN/GF FRC formed at lower temperature (200 °C) could reach 148 kJ/m2, which was 91.4% higher than that of BA-ph/GF FRC. Furthermore, the fracture morphology showed that PP-PEN significantly enhanced the interfacial strength between BA-ph and GF. It has potential applications in aerospace, rail transportation and the fields requiring high-performance polymer matrix FRC. [Display omitted] • A simple and effective toughening strategy was proposed. • The self-assembled thermoplastic particles were conducive to toughen BA-ph. • This work adopted a simple and effective processing and molding strategy. • A kind of BA-ph matrix composite with lower thermal expansion coefficient was prepared. [ABSTRACT FROM AUTHOR]

Allyl-functional phthalonitrile monomer (DBPA-Ph) was blended with the phthalonitrile containing benzoxazine (BPNBZ) to achieve good processing property with low curing viscosity. The processing behavior of BPNBZ/DBPA-Ph system was studied by differential scanning calorimetric analysis (DSC) and dynamic rheological analysis. The result indicated that the BPNBZ/DBPA-Ph system exhibited relatively low viscosity, good reactivity and processing property. The similar thermal and thermo- stabilities of DBPA-Ph and BPNBZ polymer endued the BPNBZ/DBPA-Ph system stable thermal ( T ≥ 437 °C) and thermo- stabilities ( T ≥ 449 °C) with the change of BPNBZ content. Compared with the poor mechanical property of pure DBPA-Ph/GF composites, the introduction of BPNBZ enhanced the mechanical property of BPNBZ/DBPA-Ph/GF composites distinctly, especially at low curing temperature. Therefore, the low viscosity, good polymerization property, stable thermal and thermo- stabilities and improved mechanical property indicated wider application for DBPA-Ph polymer. [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]

Self-promoted copolymerization behavior and processability of phthalonitrile oligomer/phthalonitrile containing benzoxazine (Po/BA-ph) system were investigated by differential scanning calorimetry and dynamic rheological analysis. The results revealed that Po/BA-ph systems exhibited double-stage curing behaviors which corresponded to the ring-opening polymerization of benzoxazine rings and ring-formation polymerization of nitrile groups. Compared with Po, processability of Po/BA-ph blends was improved and could be tuned by varying BA-ph contents, processing temperature, and time. The structures of the copolymers were also characterized and discussed to further confirm the copolymerizing behaviors. Then Po/BA-ph copolymers were employed to prepare Po/BA-ph/glass fiber (GF) composite laminates, and their mechanical and thermal properties were investigated. Compared with those of Po/GF composites, the flexural strength and modulus of Po/BA-ph/GF composites were increased by 6.5 and 25 %, respectively. All of the Po/BA-ph/GF composite laminates were stable up to 430 °C in air. The systematic study of Po/BA-ph system could enrich the thermosetting resin/thermosetting resin systems in industrial applications. Meanwhile, the outstanding mechanical properties and thermal stabilities enable the Po/BA-ph/GF composite laminates to be further applied in the areas which require excellent mechanical properties and high temperature resistance. [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]