End-functionalized thermoplastic-toughened phthalonitrile composites: influence on cure reaction and mechanical and thermal properties

Abstract: The development of phthalonitrile resins is of particular interest for aerospace applications because of their excellent heat resistance. Here, heteroaromatic phenyl-s-triazine moieties have been introduced into the architecture of the phthalonitrile resin as thermally stable segments via a two-step, one-pot reaction. Bis(4-[4-aminophenoxy]phenyl)sulfone was selected to promote the curing reaction, and the gelation time could be readily controlled by the diamine concentration and the curing temperature as evidenced by rheometric measurements. The curing procedure was optimized to give high cross-linking density networks. The resulting networks exhibit high glass transition temperatures at around 400 °C, outstanding thermo-oxidative stability with weight retention of 95% ranging from 539 °C to 552 °C, suggesting an improvement of the thermal properties imposed by phenyl-s-triazine units. Additionally, the CF laminate of the resin possesses high flexural strength of 1722 MPa and interlaminar shear strength of 71 MPa at ambient temperature, and these values retain 255 MPa and 36 MPa at 450 °C, respectively.

Abstract: Novolac polymers bearing varying proportions of propargyl and phthalonitrile groups on the same backbone and capable of self and co-curing to a thermally stable matrix have been synthesized. Spectral and thermal studies gave evidence for both homopolymerization of propargyl groups and its co-reaction with nitrile groups during thermal curing. Propargyl groups promoted curing of phthalonitrile groups through the hydroxyl and chromene intermediates formed from the thermal cyclization reactions of this group. Resins rich in propargyl groups showed higher crosslink density and higher modulus values. Among the copolymers, phthalonitrile rich systems exhibited relatively higher thermal stability with initial decomposition temperature at around 435 °C. All the cured compositions showed anaerobic char yields of 73–76% at 900 °C.

Abstract: A new type of nanocomposites based on a high performance bisphenol-A phthalonitrile resin and surface-modified alumina nanoparticles was prepared by a hot compression molding technique. The effect of adding different amounts of the reinforcing phase on the thermal and mechanical properties of the resulting nanocomposites was investigated. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 15 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced, reaching 346°C and 3.4 GPa, respectively. The tensile strength and modulus as well as the microhardness values increased with the increasing amount of the nanoparticles. The tensile modulus calculations were investigated using Series, Halpin-Tsai, and Kerner models. Haplin-Tsai model was found to reproduce the experimental data with the best accuracy. Estimation of the nanofillers shape factors for both Haplin-Tsai and Kerner models significantly improved the precision of the cited predictive models. The fractured surface of the nanocomposites analyzed by SEM exhibited homogeneous and rougher surfaces compared to that of the pristine resin. Finally, this new kind of nanocomposites is a highly attractive candidate for use in advanced technological applications such as the aerospace and military fields.POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Abstract: The thermosetting 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPh) was modified with the hydroxy-terminated poly(aryl ether nitrile) (PEN-OH). Two different crosslinking reactions including the polymerization of the nitrile groups and the formation of triazines were coexisted in the BPh/PEN-OH system, which depended on the different curing temperature. Moreover, along with the processing of crosslinking, the microstructure changed to plastic fracture first and then became brittle fracture (T > 320 °C), which was observed from SEM. The copolymer system showed good mechanical properties, outstanding thermal stability (over 520 °C) and high char yield (86.1% at 600 °C). Furthermore, they exhibited excellent dielectric properties. Both the dielectric constant and dielectric loss were found to be relatively stable over a wide range of frequencies ranging from 100 Hz to 200 kHz. Moreover, the dielectric stability was also found with respect to temperature.

Abstract: Copolymerization is the typical method to obtain the high-performance resin composites, due to its universality and regulation performance. It can be employed among various resin matrices with active groups to obtain the desired structures, and subsequently, the outstanding properties. In this work, the copolymerization between the allyl-functional phthalonitrile-containing benzoxazine resin (DABA-Ph) and 4,4′-bis(Maleimidodiphenyl)methane (BMI) were monitored. The interactions among the active groups including allyl moieties, maleimide, benzoxazine rings and nitrile groups were investigated. Differential scanning calorimetry (DSC) and dynamic rheological analysis (DRA) were used to study the curing behaviors and the processing properties. The possible curing processes were proposed and confirmed by Fourier transform infrared spectroscopy (FTIR). Then, glass fiber-reinforced DABA-Ph/BMI composites were designed, and their thermal-mechanical properties were studied. Results indicated that all the composites exhibited outstanding flexural strength, flexural modulus, and high glass-transition temperatures (Tg > 450 °C). The thermal stability of the composites was studied by thermogravimetry (TGA) and evaluated by the integral program decomposition temperature (IPDT). it is believed that the excellent thermal mechanical properties and outstanding Tg as well as good thermal stability would enable the reinforced copolymer-based laminates to be applied in wider fields.

Abstract: Localized Chemical bonding Delocalized Chemical Bonding Bonding Weaker than Covalent Stereochemistry Carbocations, Carbanions, Free Radicals, Carbenes and Nitrenes Mechanisms and Methods of Determining Them Photochemistry Acids and Bases Effects of Structure on Reactivity Aliphatic Nucleophilic Substitution Aromatic Electrophilic Substitution Aliphatic Electrophilic Substitution Free-Radical Substitution Addition to Carbon-Carbon Multiple Bonds Addition to Carbon- Hetero Multiple Bonds Eliminations Rearrangements Oxidations and Reductions The Literature of Organic Chemistry Classifications of Reactions by Type of Compound Synthesized.

Abstract: Series of sulfonated poly(ether ether ketone)s (SPEEKs) were prepared by sulfonation of commercial Victrex ® and Gatone ® PEEK for a comparative study of proton exchange membranes (PEM) intended for fuel cell applications. The degree of sulfonation (DS) of the sulfonated PEEK was determined from deuterated dimethyl sulfoxide (DMSO-d 6 ) solution of the purified polymers using 1 H NMR methods. The second method using a solvent suppression technique, in which DS results were obtained directly from 1 H NMR spectra of SPEEK dissolved in sulfuric acid (non-deuterated) reaction medium was evaluated. The variation between the two methods was determined. The room temperature sulfonation of PEEK, monitored directly by second 1 H NMR method, proceeded rapidly initially, reaching DS∼0.8 within 1 week, but progressed slowly thereafter. A maximum DS of 1.0 was determined after 1 month at ambient temperature (∼22 °C). The thermal properties of SPEEK were characterized by means of DSC and TGA. The mass averaged molecular weights M w of both Victrex ® and Gatone ® PEEK were estimated from intrinsic viscosities measured in sulfuric acid solutions. It was verified that higher temperature (55 °C) did not induce any apparent chain degradation of Victrex ® (or Gatone ® ) PEEK by M w tests. The water uptake and swelling properties of prepared films were studied and the proton conductivities at different temperatures were measured. The conductivities of the SPEEKs were found to increase with increasing DS and temperatures. The effect of film casting solvents on the conductivities is also discussed.

Abstract: Preparation a partir de bisphtalonitrile ponte avec de l'oxygene, du soufre ou du selenium. Insolubilite dans l'acide sulfurique indique une teneur elevee en phtalocyanine dans le polymere reticule ponte avec de l'oxygene. Les polymeres et composes modeles ont une resistivite electrique elevee et ne peuvent etre dopes par l'iode

Abstract: A multiple aromatic ether linked phthalonitrile was synthesized and characterized. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A with 4,4'-difluorobenzophenone in the presence of K 2 CO 3 as the base in an N,N-dimethylformamide/toluene solvent mixture, followed by end capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. The monomer properties were compared to those of the known resin 2,2-bis[4-(3,4-dicyanophenoxylphenyl]propane after being cured in the presence of bis[4-(4-aminophenoxy)-phenyllsulfone. Rheometric measurements and thermogravimetric analysis showed that the oligomeric phthalonitrile resin maintained good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long-term oxidative stability. The ether-linked phthalonitrile resin absorbed less than 2.5% water by weight after exposure to an aqueous environment for extended periods.

Abstract: Phthalonitrile monomers can be polymerized thermally in the presence of small amounts of curing agents into thermosetting polymers. The thermosets exhibit outstanding thermo-oxidative stability, display good mechanical properties, and offer promise as matrices for composite applications. The phthalonitrile cure reaction is typically accomplished with an aromatic diamine, 1,3-bis(3-aminophenoxy)benzene (m-APB), added in the range of 1.5–2% by weight of the monomer in the melt phase. This article addresses the cure reaction with a sulfone-containing diamine, bis[4-(4-aminophenoxy)phenyl] sulfone (p-BAPS), which shows lower volatility as determined from thermogravimetric studies (TGA) compared to m-APB at the processing temperatures typically employed for phthalonitrile cures. Rheometric studies conducted to monitor the viscosity increase during a cure reaction suggest that the cure reaction with m-APB is faster compared to the reaction with p-BAPS. Even though differences are seen in the initial cure rates, the final cured products are similar in terms of the glass transition temperatures and thermal and oxidative stabilities. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1885–1890, 1998