High Performance Polymers

Poly (aryl ether ketones), known as PAEK, encompass a range of thermoplastics including poly (ether ketone) (PEK), poly (ether ether ketone) (PEEK), poly (ether ketone ether ketone ketone) (PEKEKK) and poly (ether ketone ketone) (PEKK) among many more. PAEK possess aryl, ether, and ketone building blocks; there are over 340 reported variations of PAEKs to date. This review explores detailed research on high-performance poly (aryl ether ketone) nano-composites, incorporating metal oxide, clay, boron hydride, and polyoctahedral silsesquioxanes (POSS) nanoparticles, and provides in-depth analyses of thermal degradation mechanism, heat release rate, combustion heat, and fire-retardant properties of PAEK polymers.

Bio-based phthalonitrile resins were synthesized using a two-step process. Initially, vanillin underwent a nucleophilic reaction with nitro and potassium carbonate to form intermediates, which were then dissolved in N, N-dimethylformamide. The intermediate was divided into two portions, with 4,4’-oxydianiline and 4,4’-methylenedianiline added to each portion, respectively, to produce two different vanillin-based phthalonitrile monomers: OVA monomer and DVA monomer. The successful synthesis of these two bio-based phthalonitrile monomers was confirmed using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Differential scanning calorimetry was employed to study the processability of the monomers, revealing that OVA monomer and DVA monomer had a wide processing window of 110°C and 69°C, respectively, which were advantageous for resin processing. Dynamic mechanical analysis showed that the storage modulus of the OVA and DVA resins reached 4818 MPa and 3526 MPa, respectively, with a 24-h water absorption rate of only 1.03% and 0.90%. This study presents a viable method for synthesizing bio-based phthalonitrile resins, which can be widely utilized as functional and structural materials in daily life due to their renewability, degradability, and minimal environmental impact.

High heat-resistant polymer materials are required urgently as the fast development of the aerospace field. The cross-linking characteristic of polymers with the acetylene group provides us with an effective strategy. Here, a series of acetylene-functional benzoxazine monomers with different phenolic compounds, TERT-apa, BA-apa and THPE-apa, were synthesized, and their chemical structures were confirmed by Fourier transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectra. Their curing behaviors and polymerization reactions were analyzed by differential scanning calorimetry (DSC) and FTIR technology, and possible cross-linking structures were proposed. Meanwhile, their gelation reaction activation energies were obtained by the gelation time test. After curing at 200°C, the thermal properties of these cured polybenzoxazines were studied by Dynamic mechanical analysis (DMA) and Thermogravimetric analysis (TGA). Among them, the glass transition temperature (T_g) of p(BA-apa) can reach as high as 428°C, while p(THPE-apa) had a weight loss temperature over 400°C and a char yield of 60% at 800°C under N₂. Therefore, this study shows that the introduction of the acetylene groups is a effective strategy for the preparation of high-performance polymers, which provides some promising high heat resistant materials for the aerospace field.

Poly (aryl ether ketone) (PAEK) plays a critical role in the production and application of special engineering plastics. However, the traditional PAEK has some limitations in processing, such as high melt viscosity and high energy consumption. This study successfully synthesized a series of PAEK copolymers with bisphenol A and phenolphthalein side groups through nucleophilic polycondensation, aiming to reduce the high energy consumption associated with material processing. By adjusting the ratio of bisphenol A to phenolphthalein side groups, this research explores their influence on the properties of the copolymers. Comprehensive characterization using various testing methods revealed that increasing the bisphenol A content led to a decrease in heat deflection temperature and glass transition temperature. Although mechanical performance showed a slight decline, it remained comparable to other advanced engineering materials. Notably, tuning the ratio of bisphenol A to phenolphthalein significantly improved the melt rheological properties of the copolymers, reducing melt viscosity, enhancing polymer chain flexibility, decreasing crosslinking tendencies, broadening the processing window, and lowering energy consumption. This study provides a novel strategy for tailoring the performance of PAEK copolymers, offering substantial potential for further research and application. These copolymers are good candidates for next-generation high-performance engineering plastics.

A flame-retardant functionalized boron nitride (BN@DT) was prepared through the modification of boron nitride (BN) by a reaction product (DT) among 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 4-aminobenzoic acid, and p-phthalaldehyde, and the effect of BN@DT on flame retardancy, thermal conductivity and mechanical properties of epoxy resin (EP) was investigated. The EP composite with 15 wt% BN@DT (EP/15BN@DT) achieves the UL-94 V-0 rating and a limiting oxygen index of 40%. The peak heat release rate, total heat release and total smoke production of EP/15BN@DT are reduced by 36.3%, 31.9% and 38.9%, respectively compared with the ones of pure EP. The thermal conductivity of EP/15BN@DT increases by 148% in comparison with that of pure EP. Moreover, the tensile and impact strengths of EP/15BN@DT are higher than the ones of the EP composite containing 15 wt% unmodified BN. This work provides a promising method for the preparation of the thermally conductive EP composites with excellent flame retardancy.