Preparation and characterization of a naphthalene-modified poly(aryl ether ketone) and its phase separation morphology with bismaleimide resin

The Preforming of an Interlaminar Toughened Carbon Fiber/Bismaleimide Resin Composite by a Benzoxazine-Based Tackifier

When thermoplastic resin-toughened carbon fiber (CF) composites are formed by liquid resin transfer molding (RTM), the conventional methods cannot be used to set the fabric preform, which affects the overall mechanical properties of the composites. To address this challenge, the benzoxazine-based tackifier BT5501A was designed, a preforming-toughening bifunctional CF fabric was fabricated by employing thermoplastic polyaryletherketone (PEK-C), and an aviation RTM-grade bismaleimide (BMI) resin was used as the matrix to study the effect of the benzoxazine-based tackifier on the thermal curing property and heat resistance of the resin matrix. Furthermore, the preforming and toughening effects on the bifunctional CF fabric reinforced the BMI resin composites. The tackifier BT5501A has good process operability. The application of this tackifier can advance the thermal curing temperature of the BMI resin matrix and decrease the glass transition temperature of the resin, compared to that of the pure BMI resin. Furthermore, when the tackifier was added into the CF/PEK-C/BMI composites, the obtained CF/BT5501A/PEK-C/BMI composites had comparable compression strength after impact, pit depth, and damage area, compared to the CF/PEK-C/BMI composites, while the tackifier endowed the fabric preform with an excellent preforming effect.

Characterization and properties of high-temperature resistant structure adhesive based on novel toughened bismaleimide resins

A series of high-temperature resistant structural adhesives were prepared based on the copolymerization of 4,4′-bismaleimidediphenylmethane (BDM) and 2,2′-diallylbisphenol A (DABPA) together with a novel maleimide-capped polyetherimide containing cardo side groups (mPEI-C) as toughening agent. The chemical structure of the adhesives and their cured networks was characterized by Fourier transform infrared (FTIR) spectrometer. Their curing behavior and kinetics were analyzed using differential scanning calorimetry (DSC). The thermal properties, mechanical properties, bonding strength and moisture absorption behavior of the cured products were investigated by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMA), etc. The modified resin system with mPEI-C exhibit similar curing behavior, and the apparent activation energy ( E a) and reaction order ( n) are equal to around 85.14 kJ/mol and 0.91, respectively. With increasing mPEI-C contends, the thermal stability is improved, the char yield is increased from 26.5% to 37.1%, and the glass transition temperatures have a slight decrease. The maximum flexural strength, impact strength and bonding strength are increased by 28.4%, 93.1% and 44.6%, respectively. The results of hygrothermal aging experiments exhibit the addition of mPEI-C has no obvious influence on the hygroscopicity of the modified resins.

Poly(ether ether ketone)s containing benzene pendant in the molecular chain: Synthesis, characterization and optical properties

A series of modified poly(ether ether ketone)s containing different content of benzene pendant group in the molecular chain have been successfully synthesized with 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bisphenol A and 4,4′-difluorobenzophenone by nucleophilic substitution. The inherent viscosities of obtained polymers were in the range of 0.261–0.889 dLg−1. They were found to have high glass transition temperatures (Tg) of 150–168°C and 148–169°C (examined by DSC and DMA, respectively), good thermal stability with 5% weight-loss temperature (T5%) of 439–469°C. The tensile strengths of the obtained polymers were 67.7–86.6 MPa, and the storage modulus was over 0.9 GPa at about 140°C. The modified poly(ether ether ketone)s showed the excellent solubility property, they could be processed by solution method. Additionally, the obtained polymers had good optical transmittance (>70%) at 400 nm, suggesting that they have potential to be applied to the heat-resistant optical films.

New poly(aryl ether ketone)s containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups

4-(4-Diphenylphosphino)phenyl-2,6-bis(4-hydroxyphenyl)pyridine, as a new bisphenol monomer, was prepared from 4-(diphenylphosphino)benzaldehyde and 4-hydroxyacetophenone and used in the preparation of several aromatic poly(ether ketone)s (PEKs) containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups via a nucleophilic aromatic substitution polycondensation with difluorinated aromatic ketones. The polycondensation proceeded quantitatively in tetramethylene sulfone in the presence of anhydrous potassium carbonate and afforded the polymers with high molecular weights. The resulting PEKs are amorphous and exhibit high glass transition temperatures of 209–255°C and 5% weight loss temperatures of 536–554°C with char yields of 57–62% at 800°C in nitrogen. Their high char yields and good limited oxygen index values ranging from 39 to 43 indicated these polymers exhibited good thermal stability and flame-retardant property. All new PEKs were soluble in common organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and chloroform and could form tough, flexible, and strong films with tensile strengths of 74.6–86.8 MPa, tensile moduli of 2.9–3.6 GPa, and elongations at break of 5–9%.