Synthesis and properties of a novel high temperature pyridine-containing phthalonitrile polymer

Investigation on the Curing and Thermal Properties of Epoxy/Amine/Phthalonitrile Blend

The bisphenol A-type phthalonitrile (BAPH) was blended with the classic epoxy system E51/DDS to prepare the epoxy/phthalonitrile thermoset. The curing kinetics were investigated by differential scanning calorimetry (DSC) using the isoconversional principle, and the average activation energy (Eα) of the E51/DDS curing reaction was found to decrease from 87 kJ/mol to 68.6 kJ/mol. Combining the results of the rheological study, the promoting effect of phthalonitrile on the crosslink of epoxy/amine is confirmed. The curing reaction of the blended resin was characterized using FTIR, and the results showed that BAPH could react with DDS. The thermal behaviors of the thermosets were investigated via DMA and TGA. The glass transition temperature (Tg) is found to increase from 181 °C to 195 °C. The char yield increases from 16% to 59.6% at 800 °C in a N2 atmosphere, which is higher than the calculated value based on the proportional principle. The AFM phase images show that there is no phase separation in the cured thermoset. The results imply that the cured epoxy/amine/phthalonitrile blend is probably a kind of copolymer. The real-time TG-MS indicated that the pyrolysis of the thermoset can be divided into two relatively independent stages, which can be assigned to the cleavage of the E51/DDS network, and the phthalocyanine/triazine/isoindoline, respectively.

Preparation of phthalonitrile resins containing siloxane linkages with improved processability

To improve the processability of biphenyl phthalonitrile resin, a flexible siloxane structure was introduced into the phthalonitrile monomer through molecular design, which was then blended with a biphenyl monomer to prepare phthalonitrile alloy resins. When the ratio of phthalonitrile monomer containing flexible siloxane to biphenyl phthalonitrile monomer was 1:1, the processing window widened from 58 to 110°C, as compared to that of biphenyl phthalonitrile. Due to the introduction of the biphenyl structure into the phthalonitrile alloy resins, the initial decomposition temperature of the silicon-containing phthalonitrile resin increased from 385 to 516°C. More importantly, the phthalonitrile alloy resin exhibited a high bending strength (66 MPa) and bending modulus (3762 MPa), indicating that it could be potentially applied as high temperature structural composite matrices. Furthermore, it provides a new strategy for processing phthalonitrile resins with a high melting point and narrow processing window.

Self-catalytic phthalonitrile polymer with improved processing performance and long-term thermal stability

Phthalonitrile monomer with alkyl, pyrimidine, and amino is successfully prepared by nucleophilic substitution. The monomer is cured by autocatalysis of active hydrogen in the amino group, in order to obtain polymers through different temperature procedures. The low melting point (96°C) and curing kinetics of the monomer are analyzed by DSC, which manifest a processing window of 163°C. With lower energy barriers to overcome, the apparent activation energy ( E a) is 59.6 kJ mol−1 after fitting and calculating, signifying that the monomers are easier to process into polymers. This study focuses on the usefulness of the polymer, especially the long-term thermal stability by the comparison of numerous commonly used polymers. The consequence demonstrates that the polymer could be used for long periods at 300°C, keeping weight loss within 5 wt.% for 6 h. The advantage of long-term usage at high temperatures has not been proved in previous works on phthalonitrile polymer. Moreover, the thermal and thermal-mechanical stability are examined through TGA and DMA. The results indicate preferable thermal properties, that the glass transition temperature is up to 400°C.

Synthesis of Pyridine Heterocyclic Low-Melting-Point Phthalonitrile Monomer and the Effects of Different Curing Agents on Resin Properties

A phthalonitrile monomer (DPTP) containing pyridine with sulfide bonds was prepared and cured into polymers using different curing agents under the same temperature-programmed process. We characterized and comprehensively evaluated the effects of different curing agents on the thermal and thermomechanical properties of phthalonitrile resin, showing that the DPTP monomer cured with naphthalene-containing curing agent exhibited the best performance among the three polymers. Differential scanning calorimetric (DSC) investigation manifested that the melting point of the DPTP monomer was 61 °C, with a processing window of about 170 °C, suggesting the presence of a wide processing range. Thermogravimetric analysis (TGA) demonstrated the outstanding heat resistance, T5%, of 460 °C in nitrogen, at the same time demonstrating superior long-term stability compared with other commonly used polymer materials, which proves the long-term usage under high temperatures of 300 °C. Dynamic mechanical analysis (DMA) revealed that the storage modulus at 50 °C was 3315 MPa, and the glass transition temperature (Tg) of the polymer was more than 350 °C. Therefore, DPTP resins have favorable thermal stability as well as prominent thermomechanical properties.

Synthesis and properties of a novel silicon-containing phthalonitrile resin and its quartz-fiber-reinforced composites

A novel silicon-containing phthalonitrile monomer named bis(4-(4′-(4′-phenoxy)phenyl)phenyl)dimethylsilane phthalonitrile (SiBPPN) was successfully designed and synthesized. The chemical structure was characterized by proton nuclear magnetic resonance and Fourier transform infrared (FTIR) analyses, and its molecular weight was determined by mass spectrometry. Its melting point is lower than that of 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPPN), which has no silicon atom, and its solubility is also much better than that of BPPN. The curing behavior of SiBPPN was studied by differential scanning calorimetry and FTIR analyses in detail. The thermal and thermomechanical properties of the polymer and laminate were studied by thermogravimetric analysis and dynamic mechanical analysis. The results show that the cured SiBPPN (c-SiBPPN) possesses excellent thermal and mechanical properties. Under nitrogen atmosphere, its residual weight ratio at 800°C is 81.5% and the 5% thermal degradation temperature is 546°C. In addition, quartz-fiber (QF)-reinforced c-SiBPPN composites exhibit mechanical properties superior to those of QF-reinforced cured BPPN composites. The interlaminar shear strength and bending strength of the composite are 30.44 and 389 MPa at room temperature, and the interlaminar shear strength and bending strength of the composite are 22.25 and 339 MPa at 300°C.

In situ preparation and properties of phthalonitrile resin/hexagonal boron nitride composites

Phthalonitrile resin/exfoliated hexagonal boron nitride ( h-BN) composites with high thermal conductivity were fabricated using a novel approach. The route included two steps, micro- h-BN was coated and dispersed by phthalonitrile monomers via the function of heterogeneous nucleation, and then micro- h-BN was exfoliated by heat release during the phthalonitrile curing process. The composites achieved a high thermal conductivity of 0.736W (m·K)−1 containing 20 wt% micro- h-BN, which is 3.17 times higher than that of pure phthalonitrile resin at 0.232W (m·K)−1. Compared to traditional routes, the novel preparation approach requires less BN fillers when improving the same thermal conductivity. Importantly, other thermosetting polymers can also encapsulate BN through this strategy, which paves a new way for preparing thermally conductive thermosetting polymer–matrix composites.

A high-performance functional phthalonitrile resin with a low melting point and a low dielectric constant

A monomer of fluorinated phthalonitrile, namely 4,4'-bis(p-perfluoro-phenol-(bis(p-phenol)propane-2,2-diyl)-p-oxy-diphthalonitrile) (PBDP), was synthesized by the nucleophilic substitution reaction of bisphenol A, decafluorobiphenyl and 4-nitrophthalonitrile. The structure of the monomer was characterized by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results indicated that the PBDP monomer was synthesized successfully. The monomer was cured in the presence of 4-(aminophenoxy)phthalonitrile (APPH) and the curing behaviour was investigated by differential scanning calorimetry (DSC), suggesting a low melting point of 96 °C and an excellent processing window (96-262 °C). Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the fluorinated phthalonitrile resin possessed outstanding thermal and thermo-oxidative stabilities as well as good mechanical properties. The glass transition temperature was >400 °C and the 5% thermal degradation temperature was 501 °C. When the frequency was 50 MHz, the dielectric constant and dielectric loss of the polymer were 2.84 and 0.007, respectively. The PBDP resin has ultra-low water absorption of 0.77% and 1.4%, when exposed to an aqueous environment for 50 days at 24 °C and for 24 h at 100 °C, respectively. The prepared PBDP resin with outstanding thermal stability and low dielectric constant is an ideal candidate for aerospace industries, and microelectronic and other electronic packaging materials.

Well-defined, linear, wholly aromatic polymers with controlled content and position of pyridine moieties in macromolecules from one-pot, room temperature, metal-free step-polymerizations

Synthesis of processable, aromatic pyridine-containing polymers has always been a great challenge.

Synthesis and properties of pyrazine-based oligomeric phthalonitrile resins

The pyrazine-based oligomeric phthalonitrile (PN) monomer, 2,6-bis[3-(3,4-dicyanophenoxy)phenoxy]pyrazine (BCPP), was synthesized from the reaction of an excess amount of resorcinol with 2,6-dichloropyrazine in the presence of potassium carbonate, followed by end-capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. 4-(Aminophenoxy)phthalonitrile was applied to promote the curing reaction. The curing behavior was investigated by differential scanning calorimetry and rheological behavior, showing a wide processing window of 94°C, a complex viscosity of less than 1.5 Pa·s and a lower reaction activation energy of 32.57 kJ mol−1. The structure of the BCPP monomer was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The unit cell was determined to be tetragonal system by wide-angle X-ray diffraction. The monomer was cured to yield cross-linked polymers, which exhibited a high initial storage modulus, excellent glass transition temperature, outstanding thermal stability, and low water uptake.

Synthesis and properties of a novel high-temperature vinylpyridine-based phthalonitrile polymer

A novel vinylpyridine-based phthalonitrile monomer, 2,6-bis[3-(3,4-dicyanophenoxy)styryl]pyridine (BDSP), was resoundingly produced by a nucleophilic substitution reaction of 2,6-bis(3-hydroxystyryl)pyridine with 4-nitrophthalonitrile in the presence of potassium carbonate. The chemical structure of the synthesized BDSP was confirmed by proton (1H) and carbon (12C) nuclear magnetic resonance (NMR) as well as Fourier transform infrared (FTIR) analysis. The curing behavior of BDSP was investigated by FTIR and differential scanning calorimetry (DSC) analyses. The resin showed a low complex viscosity in the wide processing window between the monomer melting temperature and the curing temperature of the polymer, as discovered by rheological analysis. In addition, the properties of the polymer were studied by thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Based on the test results, the BDSP polymer demonstrated superior processing performance, excellent thermal stability, outstanding mechanical properties, and low water uptake, and these advanced performance characteristics are critical to many fields.

A novel high temperature vinylpyridine-based phthalonitrile polymer with a low melting point and good mechanical properties

This article is the first report on a phthalonitrile monomer containing vinyls in the main chain.

Synthesis and properties of a novel naphthyl-containing self-promoted phthalonitrile polymer

A novel naphthyl-based self-promoted phthalonitrile monomer, 4-(8-amino-2-naphthyloxy)phthalonitrile (8-ANP), was successfully synthesized via nucleophilic substitution reaction through a one-pot reaction, and it exhibited desirable processing feature with a wide process window (temperature between the melting point and the cure temperature) and low complex viscosity. The activation energy ( Ea) value of the self-promoted curing reaction was ascertained using integral isoconversional Starink method. Even without post cure at high temperature for a long time, the properties of 8-ANP polymers were still outstanding, which exhibited high glass transition temperatures, high storage modulus, low average coefficient of thermal expansion, and excellent thermal and thermo-oxidative stabilities.