Recent Progress of Low Dielectric and High-Performance Polybenzoxazine-Based Composites.

With the rapid advancement of intelligent electronics, big data platforms, and other cutting-edge technologies, traditional low dielectric polymer matrix composites are no longer sufficient to satisfy the application requirements of high-end electronic information materials, particularly in the realm of high integration and high-frequency, high-speed electronic communication device manufacturing. Consequently, resin-based composites with exceptional low dielectric properties have garnered unprecedented attention. In recent years, benzoxazine-based composites have piqued the interest of scholars in the fields of high-temperature-resistant, low dielectric electronic materials due to their remarkable attributes such as high strength, high modulus, high heat resistance, low curing shrinkage, low thermal expansion coefficient, and excellent flame retardancy. This article focuses on the design and development of modification of polybenzoxazine based on low dielectric polybenzoxazine modification methods. Studies on manufacturing polybenzoxazine co-polymers and benzoxazine-based nanocomposites have also been reviewed.

Study of the Self-Polymerization of Epoxy/Phthalonitrile Copolymers and Their High-Performance Fiber-Reinforced Laminates.

Self-polymerization epoxy/phthalonitrile (APPEN) pre-polymers were studied systematically, and then, gelation time and differential scanning calorimetry (DSC) were employed to investigate their curing behaviors. Taking advantage of orthogonal test analysis, the key factors that affected the co-polymerization of APPEN were defined and the appropriate pre-polymerization conditions were analyzed. A possible curing mechanism of APPEN was proposed. Then, the thermomechanical and mechanical properties of glass-fiber-reinforced APPEN laminates (APPEN/GF) prepared at 180 °C were analyzed to understand the cross-linked and aggregation structures. Fracture surface of the composite laminates was also investigated to reveal the copolymerization degree and the interfacial binding. The results indicated that APPEN/GF composites exhibit outstanding mechanical and thermomechanical properties (flexural strength, 712 MPa, flexural modulus, 38 GPa, and Tg > 185 °C). The thermal stability (T5% > 334 °C and IPDT reached 1482 °C) of APPEN/GF composites was also investigated to further reveal the copolymerization between epoxy resin and aminophthalonitrile, which may be beneficial to the application of epoxy-matrix-based composites in the field of high-performance polymer composites.

Benzoxazine Containing Fluorinated Aromatic Ether Nitrile Linkage: Preparation, Curing Kinetics and Dielectric Properties.

Benzoxazine containing fluorinated aromatic ether nitrile linkage (FAEN-Bz) had been synthesized from 2,6-dichlorobenzonitrile, 4,4'-(hexafluoroisopropylidene)diphenol (bisphenol AF), 3-Aminophenol, formaldehyde, phenol by condensation polymerization and Mannich ring-forming reaction. Structures of the monomer were verified by Proton NMR spectrum (1H-NMR) and Fourier transform infrared spectroscopy (FTIR). Curing behaviors and curing kinetics of designed monomers were investigated and discussed. The activation energy was calculated and possible polymerization mechanisms were also proposed. Then, properties of cured polymers including crosslinking degrees, thermal decomposition, surface wettability and energy, and dielectric properties were studied and discussed. Additionally, programmed integral decomposition temperature (IPDT) was also used to evaluate the thermal stability of final polymers. Results indicated that the incorporation of benzoxazine and nitrile resulted in increased thermal stability and char yields. Moreover, the surface wettability and dielectric properties of poly(FAEN-Bz) can be easily controlled by tuning the curing temperatures and time.

Synergistic Effects of Functional CNTs and h-BN on Enhanced Thermal Conductivity of Epoxy/Cyanate Matrix Composites.

Epoxy/cyanate resin matrix composites (AG80/CE) with improved thermal conductivity and mechanical properties were obtained with synergetic enhancement with functional carbon nanotubes (f-CNTs) and hexagonal boron nitride (h-BN). AG80/CE performed as polymeric matrix and h-BN as conductivity filler which formed the main thermal conductivity channels. Small amounts of f-CNTs were introduced to repair defects in conductivity channels and networks. To confirm the synergetic enhancements, the thermal conductivity was investigated and analyzed with Agari's model. Results indicated that with introduction of 0.5 wt% f-CNTs, the thermal conductivity coefficient (ƛ) increased to 0.745 W/mk, which is 1.38 times that of composites with just h-BN. Furthermore, the flexural strength and modulus of composites with 0.5 wt% f-CNTs were 85 MPa and 3.5 GPa. The glass transition temperature (Tg) of composites with 0.4 wt% was 285 °C and the initial decomposition temperature (T5%) was 385 °C, indicating outstanding thermal stability. The obtained h-BN/f-CNTs reinforced AG80/CE composites present great potential for packaging continuous integration and miniaturization of microelectronic devices.

Micro/Mesoporous Fe3O4/Fe-Phthalocyanine Microspheres and Effects of Their Surface Morphology on the Crystallization and Properties of Poly(Arylene Ether Nitrile) Composites.

The surface morphology of nanoparticles significantly affects the final properties and interfacial characteristics of their composites. Thus, investigations on the surface morphology of the nanoparticles is essential to fabricate improved nanoparticle-reinforced composites. Fe3O4/Fe-phthalocyanine (FePc) hybrid microspheres with micro/mesoporous structures were prepared via a solvothermal process and solvent etching method. The surface morphology and compositional distribution were respectively investigated using a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to rule out that FePc monomers have been blended with Fe3O4 to form Fe3O4/FePc hybrid microspheres without serious agglomeration. The surface roughness of Fe3O4/FePc microspheres was investigated by the scanning probe microscope (SPM), and confirmed by the adsorption and desorption isotherms of N2. The effects of the various surface morphologies on the crystallization behavior of crystallizable poly(arylene ether nitrile) (c-PEN) were first employed to confirm the surface characteristics of the resulted microspheres. Results indicated that the etched Fe3O4/FePc microspheres would improve the crystallization degree of c-PEN, due to their much more micro/mesoporous structures than that of original Fe3O4/FePc. Then, Fe3O4/FePc hybrid microspheres reinforced PEN composite films were prepared and their interfacial compatibility was monitored using an SEM. Excellent thermal stability and improved mechanical properties were obtained by combining the etched Fe3O4/FePc and PEN matrix. The excellent surface properties and micro/mesoporous structures make the novel Fe3O4/FePc an excellent candidate of organic/inorganic hybrid fillers and micro/mesoporous materials.

Thermal Stability of Allyl-Functional Phthalonitriles-Containing Benzoxazine/Bismaleimide Copolymers and Their Improved Mechanical Properties.

Copolymerization is the typical method to obtain the high-performance resin composites, due to its universality and regulation performance. It can be employed among various resin matrices with active groups to obtain the desired structures, and subsequently, the outstanding properties. In this work, the copolymerization between the allyl-functional phthalonitrile-containing benzoxazine resin (DABA-Ph) and 4,4'-bis(Maleimidodiphenyl)methane (BMI) were monitored. The interactions among the active groups including allyl moieties, maleimide, benzoxazine rings and nitrile groups were investigated. Differential scanning calorimetry (DSC) and dynamic rheological analysis (DRA) were used to study the curing behaviors and the processing properties. The possible curing processes were proposed and confirmed by Fourier transform infrared spectroscopy (FTIR). Then, glass fiber-reinforced DABA-Ph/BMI composites were designed, and their thermal-mechanical properties were studied. Results indicated that all the composites exhibited outstanding flexural strength, flexural modulus, and high glass-transition temperatures (Tg > 450 °C). The thermal stability of the composites was studied by thermogravimetry (TGA) and evaluated by the integral program decomposition temperature (IPDT). it is believed that the excellent thermal mechanical properties and outstanding Tg as well as good thermal stability would enable the reinforced copolymer-based laminates to be applied in wider fields.

Designing and Preparation of Fiber-Reinforced Composites with Enhanced Interface Adhesion.

The interfacial properties between fibers and resin matrices show great influence on the properties of fiber-reinforced composites. In this work, phthalonitrile containing benzoxazine (BA-ph) was chosen as the resin matrix, which combined with the glass fiber (GF) to prepare reinforced composite laminates at low temperature (200 °C). The poly(arylene ether nitrile) (PEN) was used to modify the GF and BA-ph matrix. Curing behaviors of the BA-ph/PEN were investigated with Differential scanning calorimetric (DSC) and Dynamic rheological analysis (DRA), and results indicated that the polymerization would be hindered by PEN due to the dilution effects. Moreover, the formation of triazine rings which assigning to the ring-forming polymerization of nitrile groups in BA-ph and PEN could improve the compatibility of BA-ph and PEN in the matrix. The SEM images of the fracture surface of the composites revealed that the brittleness of BA-ph matrix and interfacial adhesion between GFs and matrix was improved. The enhanced interfacial adhesion was detailedly discussed from the perspective of physical entanglement and the copolymerization between PEN chains on the surface of GFs and BA-ph/PEN matrix. The results of DMA also explained the toughness of BA-ph/PEN matrix, the semi-interpenetrating polymer networks and the interfacial adhesion. In sum, a feasible strategy that modifies the surface of GFs and the brittleness of the thermosetting matrix by high-performance thermoplastic polymers, which can be employed to prepare the composite laminates with improved properties.