Longhai Zhuo

The effect of bis allyl benzoxazine on the thermal, mechanical and dielectric properties of bismaleimide–cyanate blend polymers

Thermosetting terpolymers composed of bis allyl benzoxazine (Bz-allyl), cyanate ester (BADCy) and 4,4′-bismaleimidodiphenyl methane (BMI) were prepared via co-curing reactions. The curing kinetics of Bz-allyl/BMI/BADCy were investigated via non-isothermal DSC at different heating rates using the Flynn–Wall–Ozawa method. The dielectric, thermal and mechanical properties of Bz-allyl/BMI/BADCy terpolymers were systemically investigated in detail through mechanical measurement, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The results show that a suitable addition of Bz-allyl can enhance the impact strength and flexural strength as well as reduce the dielectric constant and the dielectric loss of BMI/BADCy. The dynamic mechanical analysis reveals that the cross-link density of the blend is higher than BMI/BADCy. The higher crosslinking density of the terpolymer led to good thermal stability of the terpolymer. Scanning electron microscopy analysis shows the distinct characteristics of ductile fracture of the blends. All of these changes in properties are closely correlated to the copolymerization between Bz-allyl and BMI/BADCy, which could form an interpenetrating polymer network in the system.

Synthesis and characterization of pyrimidine-containing hyperbranched polyimides

We reported the design, synthesis, and properties of two series of polyimides based on pyrimidine nuclei with adjusted monomers’ molar ratios, using 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomer, 2,4,6-triaminopyrimidine (TAP), and 4,4′-diaminodiphenyl ether (ODA) as amine monomers. Nuclear magnetic resonance spectroscopy (1H NMR) was used for chemical structural characterization, and the results indicated the various forms of TAP and branched structure units in the obtained polyimides. The morphology and structures of the polyimides were evaluated by X-ray diffraction patterns. The results suggested that all the polyimides, except co-HBPI-3, were hardly crystallized. Most of the resulting polyimides possessed excellent solubility in polar aprotic solvents. The thermogravimetric analysis results showed that the polyimides obtained by copolymerizing with ODA exhibited better thermal stability; and incorporating moderate amount of ODA was helpful for imidization.

Preparation and properties of Nano-SiO2/TDE-85/BMI/BADCy composites

A new type of the nanometer particles and epoxy/bismaleimide-triazine nanocomposites were prepared using a nanometer silica (nano-SiO2), a 4,5-epoxycyclohexane 1,2-dicarboxylic acid dilycidyl (TDE-85) epoxy resin, a 4,4′-bismaleimidodiphenymethane (BMI) and a bisphenol a dicyanate (BADCy). The properties of nano-SiO2/TDE-85/BMI/BADCy composites, such as mechanical and thermal properties, were systemically investigated in detail by mechanical measurement, scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The experimental results showed that the addition of the appropriate amount of nano-SiO2 could improve the impact strength and the flexural strength of the nano-SiO2/TDE-85/BMI/BADCy composites. Simultaneously, the thermal stability of the blends was found to be higher than that of the TDE-85/BMI/BADCy copolymers.

Thermal, mechanical and dielectric properties of BMI modified by the Bis allyl benzoxazine

In this paper, Bis allyl benzoxazine (Bz-allyl) was blended with 4, 4′-Bismaleimidodiphenyl methane (BMI) to improve the properties of BMI. The properties of Bz-allyl/BMI copolymers, such as mechanical properties, thermal properties and dielectric properties were systemically investigated in detail by mechanical measurement, scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The results show that a suitable addition of Bz-allyl can enhance the impact strength and flexural strength as well as reduce the dielectric constant and the dielectric loss of BMI. The dynamic mechanical analysis reveals that the cross-link density of the blend is higher than neat BMI. Scanning electron microscopy analysis shows distinct characteristics of ductile fracture of the blends. In addition, the dielectric constant and the dielectric loss of modified system decreases, compared with the cured BMI. BMI containing suitable Bz-allyl still remains a good thermal resistance. All these changes in properties are closely correlated to the copolymerization between Bz-allyl and BMI, which could form an interpenetrating polymer network in the system.

Study of thermal decomposition kinetics for polyimides based on 2,6-bis(4-aminophenyl)-4-(4-(4-aminophenoxy) phenyl) pyridine

This study reports on the preparation and thermal decomposition kinetics of a polyimide (PI) with phthalimide pendant (PI-1) and an analogous hyperbranched PI (PI-2). PI-1 was synthesized from 2,6-bis(4-aminophenyl)-4-(4-(4-aminophenoxy) phenyl) pyridine (BAAP) and 4,4′-(hexa-fluoroisopropylidene) diphthalic anhydride using a simple method with BAAP terminated by phthalic anhydride. The morphology of the PI structures was examined using X-ray diffraction. The thermal decomposition processes of the PIs were then studied according to a two-stage method using thermogravimetric analysis. The results indicated that both PIs exhibited excellent thermal stability, with a decomposition pattern of 5% mass loss beyond 508°C and 10% beyond 529°C. The two PIs exhibited similar levels of thermal stability in the first decomposition stage, but PI-1 exhibited higher stability in the second stage. The results indicate that PIs into which phthalimide pendants have been introduced retain their thermal stability in the first stage of decomposition and demonstrate enhanced thermal stability in the second stage.

Influence of terminating triamine by phthalic anhydride on polyimides’ properties

In this study, hyperbranched polyimides were prepared from 2,6-bis(4-aminophenyl)-4-(4-(4-aminophenoxy)phenyl)pyridine (BAAP) and commercial dianhydrides by strictly controlling the reaction conditions. Polyimides with phthalimide pendants were also prepared to study the influence mechanisms of terminating BAAP by phthalic anhydride (PA) on polyimides’ properties. Fourier transform infrared and proton nuclear magnetic resonance spectroscopies were utilized to observe the chemical structures of the hyperbranched polyimides. The influence of terminating BAAP by PA on polyimides’ properties was studied by comparing the two series of polyimides. All the polyimide samples held completely amorphous structures and possessed excellent solubility and thermal stability. Terminating BAAP by PA decreased the d-spacing values of the obtained polyimides and slightly weakened their solubility and thermal stability.