The effect of introduction of polyamide nonwoven materials on the thermal and mechanical properties of polymer composite materials based on phthalonitriles and a carbon fabric is studied. It is shown that the addition of 3 wt % of polyamide nonwoven material causes a 44% increase in the specific work of delamination. At room temperature elastic mechanical characteristics, such as compressive strength and compressive modulus, for the composite modified with the nonwoven material increase by 12 and 100%, respectively. According to dynamic mechanical analysis, upon reaching 169°C the melting of polyamide occurs; however, there remains the possibility to use the composites above this temperature, as confirmed by mechanical tests performed at 200°C.

The process of thermal oxidation decomposition of phthalonitrile resins which had been post-cured at various temperatures (603 K, 623 K and 648 K) was studied using dynamic and isothermal measurement modes. It was shown that the degradation process is a complex branched four-stage process. We have concluded that the first stage is an nth order reaction with autocatalysis. The second stage is described with the expanded Prout-Tompkins equation which corresponds to an autocatalytic solid-state reaction caused by the formation of im-perfections at the reaction surface. The third and fourth stages are also reactions of the nth order. The phtha-lonitrile resin post-cured at 603 K exhibited better thermal stability than the resins post-cured at 623 K and 648 K based on the activation energies of the 1st stage - 132 kJ/mol, 104 kJ/mol, and 106 kJ/mol respectively. These data were confirmed by comparable experimental activation energy values (111 kJ/mol, 87 kJ/mol, 86 kJ/mol respectively) and changes in mass loss and flexural strength values determined during long-term thermal aging in the temperature range of 553-623 K. It was shown that the phthalonitrile resin post-cured at 603 K with the initial flexural strength of 107 MPa is suitable for long-term application at temperatures up to 573 K.

The effect of modifying additives of polyphenylene sulfone or a nonwoven polyamide material on the thermal and mechanical properties of carbon fabric/epoxy resin polymer composite materials prepared by vacuum forming and vacuum infusion was studied. The addition of 10 wt % polyphenylene sulfone leads to slight improvement of the mechanical properties of the composite material, whereas introduction of the nonwoven material leads to a 15% decrease in the compression strength and to a 6% decrease in the interlayer shear strength. The specific peel work increases by 15 and 270% for the composites modified with polyphenylene sulfone and nonwoven cloth, respectively. Introduction of 4 wt % nonwoven material enhances the fracture toughness of the polymer composite material by a factor of 3.7.

Easy-pmcessable phthalonitrile resins were prepared from tris-phthalonitrile phosphate monomer TPP (tris(3-(3,4-dicyanophenoxy)phenyl)phosphate), bis-phthalonitrile RP (bis (3,4-dicyanophenoxy)benzene) and novel viscosity reducing comonomer CPN (4-(4-cyanophenoxy)benzene-1,2-dicarbonitrile). It was shown that TPP is more resistant to hydrolysis than reported phosphate based phthalonitriles (k =8.2.10(-4) s(-1) at 65 degrees C and pH 10). Two different type of curing agents: aromatic diamine DDS and 4-(4-aminophenoxy) phthalonitrile APN were used to study their effect on properties of the obtained resins and composites. Carbon fabric composites with APN-cured matrix fabricated by vacuum infusion demonstrated compression strength up to 633 MPa and 100% retention of ILSS after oxidative aging for 200 h at 300 degrees C. Post-curing of the matrix at 375 degrees C resulted in growth of Tg but at the same time micmcracking occurrence in the composite leading to decrease in mechanical properties and thermal aging sustainability.

Novel dual-functional phthalonitrile monomers containing a maleimide group were synthesized and characterized. Ortho, meta, and para isomers were obtained and only the meta-isomer can be considered as a low melting phthalonitrile monomer with a melting point of 107.4 degrees C. Analysis of the dual-curing behavior of monomers showed radical homopolymerization of maleimides followed by phthalonitrile polymerization with the formation of isoindoline, triazine, and phthalocyanine ring structures. Two alternative copolymerization processes of maleimide groups via ene reaction and ring-opening amidation were investigated. The approach of dual-curing maleimide and phthalonitrile fragments in a single molecule allowed combining the excellent inherent mechanical properties of bismaleimide resins and the outstanding thermo-oxidative stability of phthalonitriles. After curing of both functional groups impact strength was as high as 11.81 kJ m(-2), flexural strength was 108 MPa, Young's modulus was 4.38 GPa. On the contrary, T-g of this polymeric system was above 370 degrees C and T-5% was higher than 450 degrees C in air.

Objectives . Determination of target products and byproducts is necessary for the quality control of phthalonitrile monomer synthesis as well as production scaling and performing related kinetic studies. High-performance liquid chromatography (HPLC) is a simple and affordable method for quantitative chemical analysis, which also verifies the quality of raw materials. The objective of this study was to develop an HPLC technique for determining the composition of the reaction mixture in the synthesis of 1,3-bis(3,4-dicyanophenoxy)benzene (DPB). Methods . Reversed-phase HPLC was used to quantitatively analyze the reaction mixture. Results . A simple and rapid method for the quantitative HPLC analysis of phthalonitrile monomers and their mixtures with reagents was developed. Reaction times and the accumulation of byproducts were also studied. Conclusions . The successful performance of the developed technique allows us to recommend it for practical applications. The results obtained for reactors of different sizes have good convergence, and DPB synthesis was successfully scaled up to intermediate scale equipment.

The microporous polyvinylidene fluoride (PVDF) membranes were prepared by the solvent evaporation method using 50 wt.% of different pore-forming additives: poly(1-ethyl-3-vinylimidazolium tetrafluoroborate) (PIL-BF4), polyethylene glycol 3000 (PEG-3K) and 40000 (PEG-40K), dibutyl phthalate (DBP). The influence of used additive on morphology, porosity, degree of crystallinity, tensile properties, electrolyte uptake and ionic conductivity of the membranes were investigated. The maximum electrolyte uptake of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) was 184 wt.% for the membrane prepared with PEG-40K, however, the membrane was fragile and unsuitable for practical use. The remaining membranes showed approximately the same porosity (45‒48%) and electrolyte uptakes (169‒175%). At the same time, the membranes significantly differed in mechanical properties and ionic conductivity. The membrane prepared with PIL-BF4, unlike others, has a sponge-like structure and demonstrated high mechanical properties, namely tensile strength is 17.7 MPa and fracture strain is 132.5%. Bucky gel actuators were fabricated using membranes prepared with different additives. The blocking force of the actuators based on membranes with different additives decreased in the sequence of PIL-BF4, DBP and PEG. The actuator based on the membrane prepared with PIL-BF4 demonstrates a blocking force of 5.7 mN and a deformation of 1.35 % at 3 V DC.

Composites consisting of propargyl- and allyl/propargyl- modified novolac resins and carbon fabric were obtained by the vacuum infusion molding process. It was established that the presence of potassium cations remaining after the synthesis increase the resin melt viscosity, and acid washing is needed to obtain resins suitable for cost-effective injection techniques of composite fabrication. The mechanical properties of all composites such as compressive strength, tensile strength, in plane shear strength, and interlaminar shear strength were determined at 25, 200 and 230 °С. The carbon fiber reinforced plastics (CFRPs) retained their mechanical properties at temperatures up to 200 °C. It was shown that the use of the obtained allyl-containing polymer matrices improved mechanical properties and increased the thermal stability of the CFRPs in comparison with the propargylated novolac matrices. The composite material with novolac matrices modified by 18% propargyl and 23% allyl groups retains only up to 70% of the initial interlaminar shear strength values at 230 °C which corresponds to the data of the dynamic mechanical analysis of neat cured resins.

A new monomer containing thermosetting groups of two types, namely, propargyl ether and phthalonitrile, in the structure of the molecule was synthesized and studied. It was found that thermal polymerization was accompanied by the degradation of the monomer with propargyl ether decomposition. This problem can be solved using catalysts based on Cu(i) favoring the polymerization at both the propargyl group and phthalonitrile fragments. The cured monomer has a non-porous structure and high thermal properties (Vicat softening temperature 395 °C, T5% 451 °C). The low viscosity of the melt (<200 mPa s at 120 °C) and low glass-transition temperature (9 °C) of the monomer make it possible to use it for the formation of composite materials by vacuum infusion or injection into a mold.

New phthalonitrile resins that provide processing properties at the level of epoxy resins and composites obtained from them are discussed. The processing parameters of the resins are improved due to the discovery of reactive diluents based on bisbenzonitriles. By introducing these comonomers into the resin composition the melt viscosity is reduced to less than 100 MPa s at a temperature of 120°C, which allows one to obtain carbon fibers by modern injection techniques. The curing programs of the composite are selected in order to attain the maximum compressive strength (852 MPa). Carbon fiber reinforced plastics postcured at 375°C retain up to 90% of their mechanical properties at 400°C (τ12 = 60–80 MPa). It is first shown that prepregs can be produced from phthalonitrile resins using the melt technology and composites from them can be obtained by hot pressing. Carbon fibers possess high limiting oxygen index values (LOI > 80%). Thus, phthalonitrile resins and prepregs are developed for non-autoclave processing of carbon and glass composites suitable for operation at elevated temperatures.

Advanced phthalonitrile resin systems based on recently introduced low-melting phosphorus-containing monomers were developed. A new class of bis-benzonitirle reactive plastisizers allowed to obtain resin systems possessing improved processability (melt viscosity < 100 mPa·s at temperatures down to 120 °C) suitable for manufacturing composites by vacuum infusion molding process or RTM at the lowest reported processing temperature of 120 °C on carbon fabric (3K HTA40, twill). The curing cycle was adjusted to achieve the best mechanical properties of the composites reaching 852 MPa in compressive strength. The influence of post-curing conditions on the resulting composites properties was established. After post-curing at 375 °C the obtained composites demonstrated up to 90% mechanical properties retention at 400 °C ( τ 12 = 60-80 MPa). Solvent-free phthalonitrile prepregs were developed for the first time. Prepreg consolidation yielded high-quality composites. Flame retardant properties of investigated composites demonstrated extremely high LOI > 80%. Thus easy-processable phthalonitriles for out-of-autoclave manufacturing techniques with convenient curing conditions and excellent heat resistant and flame-retardant properties were developed.

A new tri-functional phthalonitrile monomer tris(3-(3,4-dicyanophenoxy)phenyl) phosphate (TPP) was first synthesized and characterized with the intent of increasing the cross-linking rate of phthalonitrile resins. By combining TTP and di-functional phthalonitrile with aromatic diamine easy-processable formulations (η < 200 mPa·s at 150 °C) were developed. Thermosets were derived from the formulations by curing at 330 and 375 °C. The polymers that were post-cured at 375 °C demonstrated Young's moduli up to 7.2 GPa — which is the highest value reported for phthalonitriles. Thermal stability of these materials was on the high level featured to phthalonitriles (Tg > 450 °C, T5% > 500 °C, TOS5% > 500 °C, Yc at 900 °C > 80%). TPP, the introduced monomer, can be used as a stiffness increasing additive with common di-functional phthalonitriles, and easy-processable formulations for cost-effective techniques of composites manufacturing.

Hydrolysis data for Bis(4-cyanophenyl) phenyl phosphate (CPP), introduced as a reactive diluent for phthalonitrile monomers, under pH 4, 7 and 10 are presented. Conversion/time plots collected by HPLC analysis, typical chromatograms and NMR spectra of the substrate and the reaction products are given. Pseudo-first order rate constants are determined for CPP at 25, 50 and 80 °C. Activation parameters were calculated from Arrhenius equation.

Bis(4-cyanophenyl) phenyl phosphate (CPP) is introduced for the first time as a viscosity reducing comonomer for phthalonitrile resins. In comparison to the common phthalonitrile resins, the blends of CPP with 4,4'-[benzene-1,3-diylbis(oxy)] diphthalonitrile demonstrated advanced processing properties suitable for cost-effective injection processing (eta as low as to 180 mPa.s at 100 degrees C). Thermal copolymerization was performed indicating complete inclusion of bis-benzonitrile CPP into the phthalonitrile network resulting in formation of thermosets with great thermal performance. Hydrolysis of CPP at pH 4, 7, and 10 was studied to confirm its suitability as a reactive diluent for phthalonitrile. Conversion vs. time plots were obtained via HPLC analysis, and pseudo-first order rate constants were determined in the range of 25-80 degrees C. The activation parameters were calculated from the Arrhenius equation.

The microporous poly(vinylidene fluoride) (PVDF) membranes were prepared by phase inversion process using poly(1-ethyl-3-vinylimidazolium tetrafluorborate) (PIL) as a pore-forming agent. The membranes were activated by soaking in room temperature ionic liquids (EMImBF4 and BMImBF4) as a liquid electrolyte. The influence of PIL content on morphology and structure, electrolyte uptake of porous membranes and ionic conductivity of the activated membranes were investigated. The properties of the PVDF microporous membranes, such as crystallinity and porosity were characterized. The membrane with the maximum porosity demonstrates the highest electrical properties. The electrolyte uptake of EMImBF4 is 210 wt.% and the ionic conductivity is 9.2 mS/cm. Actuators with carbon nanotube bucky gel electrodes based on obtained membranes were prepared. The influence of ionic liquid and actuator thickness on electromechanical properties was discussed. The actuators with BMImBF4 as a electrolyte demonstrated high blocking force up to 9.5 mN.

ABSTRACTNovel self‐curing monomer containing two thermosetting groups, namely propargyl ether and phthalonitrile (PN) in a molecular structure, is synthesized and investigated. The study of catalyzed and uncatalyzed curing is performed and high heat release during curing is observed. This disadvantage can be adjusted by catalysis of propargyl ether polymerization with Ni (II), Co (II), and Cu (II) salts. The cured monomer possesses high thermal properties featured to phthalonitrile matrices (Heat deflection temperature, HDT = 428 °C, T5% = 499 °C) and moderate mechanical properties (E = 4.9 ± 0.65 GPa, GIC = 106 ± 26 J/m2), it can be applied as a high temperature matrix for carbon fiber reinforced plastics (CFRP). Low melt viscosity (223 mPa s at 120 °C) of the monomer provides a possibility to consider its application for composite material formation by vacuum infusion or resin transfer molding (RTM) techniques, which are exceptionally rarely applied for matrices with HDT > 300 °C but allow to obtain composites of complex shape with minimal joining parts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44786.