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.

Phthalide cardo chain extended imine skeletal linked maleimido end capped nanotitania reinforced novel polybenzoxazine (nTiO2/PBZ) hybrid nanocomposites

A new class of nanotitania reinforced polybenzoxazine (nTiO2/PBZ) hybrid nanocomposites was synthesized using newly designed phthalide cardo chain extended imine skeletal linked maleimido end capped polybenzoxazine (PHM-PBZ) and nTiO2 through in-situ sol-gel method. The formation of hybrid nanocomposites was confirmed by NMR and FT-IR spectra. The structurally stable nTiO2 present in the nTiO2/PBZ hybrids accounted their exceptional thermal stability and good char yield. The restricted motion of flexible polymeric chain resulted from the inclusion of nTiO2 in the PBZ system increased the glass transition temperature ( T g) to a higher percentage than that of neat PBZ system. With the successive enhancement in the incorporation of nTiO2, the synthesized nanocomposites exhibited better thermal stability, higher flame retardancy and lesser water absorption behaviour than the of neat PBZ. The sequential increments in the loading level of nTiO2 onto the PBZ matrices caused the lower value of dielectric constant than that of neat PBZ. The homogeneity and successful dispersion of the nTiO2 fillers in the PBZ matrix were ascertained from the strong fluorescent emissions observed in the wavelength range of 300–550 nm through optical studies. Scanning electron microscope and transmission electron microscopic micrographs evidenced the successful incorporation of nTiO2 as can be seen from the different morphology at the nanoscale level in the PBZ matrix. This kind of structurally designed nTiO2/PBZ nanocomposites may find multifaceted applications in the form of adhesives, encapsulants, matrices and sealants and in the fields of automobile and microelectronics applications for better performance and longevity.

Sesamol-based polybenzoxazines for ultra-low-k, high-k and hydrophobic coating applications

Sesamol-based polybenzoxazines, their dielectric behavior, and superhydrophobic properties for microelectronic insulation applications.

Mechanical and thermal properties of fully green composites from vanillin-based benzoxazine and silane surface modified chopped basalt fibers

By following the rules of green chemistry, a novel composite is developed from a renewable and ecofriendly resource, namely the vanillin. The latter was used as a phenolic precursor for the microwave synthesis of a bio-based benzoxazine resin (Va-BZ). Afterwards, high performance green composites were developed by reinforcing the Va-BZ with various amounts of chopped silane surface modified basalt fibers (BFs). The chemical structure of the Va-BZ monomers was confirmed by 1H NMR and FTIR spectroscopy. The grafting of the silane moiety on the BFs surface was assessed by FTIR and TGA analyses. The autocatalytic ring opening polymerization of the Va-BZ monomers was confirmed by DSC analysis. The mechanical performances of the developed green composites were studied by flexural and tensile investigations. The findings suggested that the maximum amount of 20 wt. BFs afforded the best results, with flexural and tensile strengths of 447 and 460 MPa, respectively. The SEM was used to study the fractured tensile surfaces and elucidated the toughening mechanism. Meanwhile, the TGA showed that the introduction of the BFs markedly improved the thermal stability of the benzoxazine matrix. Finally, the gamma rays shielding effectiveness was studied and revealed the highly benefic role of the BFs. For instance, a 1 cm thick Va-BZ polymer only showed a 6% gamma rays screening ratio, the latter was improved to 18.4% for the composite made of 20 wt.% of treated BFs. Overall, this study confirmed that greener approaches can also result in high performance composite satisfying the needs of exigent applications.

Vitrimers trigger covalent bonded bio-silica fused composite materials for recycling, reshaping, and self-healing applications

In this work, a recycling, reshaping, and self-healing strategy was followed for polybenzoxazine through S-S bond cleavage reformation in vitrimers, and the supramolecular interactions are described. The E-ap benzoxazine monomer was synthesized through the Mannich condensation reaction using a renewable eugenol, 3-amino-1-propanol and paraformaldehyde. Furthermore, the E-3ap monomer was reinforced with various weight percentages (5, 10, and 15 wt%) of the thiol-ene group. Various weight percentages of functionalized bio-silica (BS) were also copolymerized with E-3ap (10%-SH) to increase the thermal stability. The structure of the monomers was confirmed by NMR and FT-IR analysis and the thermal properties of the cured materials were analyzed by DSC and TGA. Tensile test was used to study the mechanical property of the poly(E-3ap-co-SH)/BS material. The film was characterized by SEM and optical microscopy to investigate the self-healing properties of the poly(E-3ap-co-thiol-ene)/BS. Moreover, photos and video clips show the self-healing ability of a test specimen. The vitrimer-based renewable polybenzoxazine material exhibits a good recycling, reshaping, and self-healing abilities, and thus is a prime candidate for several industrial and engineering applications.

Bio-based polybenzoxazines as an efficient coatings to protect mild steel surfaces from corrosion

New types of mono and bi-functional benzoxazine monomers were synthesized using cardanol (C) and 4-aminobenzonitrile (abn), p-phenylediamine ( ppda) along with paraformaldehyde. The synthesized benzoxazine monomers structure was elucidated by 1H, 13C-NMR and FTIR spectroscopic techniques. The polymerization temperature (Tp) of C-abn and C- ppda are noticed at 280oC and 237oC, respectively. It was also noticed that bi-functional benzoxazine (C- ppda) possesses lower curing temperature than mono-functional benzoxazine (C-abn). The ring opening polymerization of benzoxazine was confirmed by FTIR spectroscopy. Thermal analyses indicate that, benzoxazine [poly(C- ppda)] possesses higher thermal stability than poly(C-abn). The surface roughness of the benzoxazine coated MS specimen was analysed by atomic force microscope. The values of water contact angles obtained for poly(C-abn) and poly(C- ppda) are 145o and 148o, respectively. It was noticed that the mild steel specimen coated with bio-based benzoxazine C-abn exhibit excellent resistance to corrosion.

Solvent-free synthesis of a formaldehyde-free benzoxazine monomer: study of its curing acceleration effect for commercial benzoxazine

A new 2-substituted benzoxazine bearing a phenol was blended with commercial benzoxazine for improving curing and thermomechanical properties.

Performance Study of Nano/SiO2 Films and the Antimicrobial Application on Cantaloupe Fruit Shelf-Life

In the current study, novel films with chitosan/nano/SiO2/nisin films and their antimicrobial application on cantaloupe fruit shelf-life have been studied. Novel films were prepared by the addition of 1% chitosan, 1% nano silicon dioxide, and 1% nisin and freeze-dried for the performance study. Physicochemical properties such as tensile strength, optical, and thermal properties with the performance characteristics of the novel films were measured. Coated and uncoated cantaloupes with various coating solutions were stored and chilled at 4 °C in a relative humidity of 70% for up to nine days. The microbial population measurements have been detected every three days. Results show that the fourier transform infrared intensity (FTIR) of nano/SiO2 and with the addition of nisin (nano/SiO2/n) were higher than chitosan (CH) film except in the wavenumber (3150–3750 cm−1) films peaks. Novel nanofilms enhanced tensile strength as well as optical and thermal properties. XRD analysis reported two distinct peak values of 32.08 and 45.99 to correspond to nano/SiO2/n film orientation (7095) and (3316), respectively. Zeta potential values and turbidity were increased, while nano/SiO2 films decreased the hydrophobicity of the film surface by 80.07°. The coating treatments with nano/SiO2 and nano/SiO2/n both reduced the yeast and mold counts 2.49 and 1.92 log CFU/g, respectively, on day nine. In summary, chitosan/nano/SiO2/n novel film improved the functional properties of coating films, and those bio-nanocomposites are effective in food packaging.

Eco-Friendly Sustainable Poly(benzoxazine-co-urethane) with Room-Temperature-Assisted Self-Healing Based on Supramolecular Interactions

This work is an attempt to develop bio-based eco-friendly poly(benzoxazine-co-urethane) [poly(U-co-CDL-aee)] materials using cardanol-based benzoxazines (CDL) and hexamethylene diisocyanate (HMDI) to check their self-healing ability and thermal properties. CDL monomers were synthesized using cardanol, amino ethoxyethanol (aee) or 3-aminopropanol (3-ap), and paraformaldehyde through the Mannich reaction. Later, CDL-aee or CDL-3-ap monomers were copolymerized with a urethane precursor (HMDI), followed by ring-opening polymerization through thermal curing. The thermal properties of poly(U-co-CDL) were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The self-healing behavior of the bio-based poly(U-co-CDL) was checked by applying a mild external pressure. The results revealed that the developed poly(U-co-CDL) showed repeatable self-healing ability due to supramolecular hydrogen-bonding interactions. Further, the self-healing ability of poly(U-co-CDL) was studied using density functional theory (DFT). From the above results, the developed material with superior self-healing ability can be used in the form of self-healing coatings and composites for various applications with extended shelf-life and reliability.

New zinc complexes derived from "self-adaptable" acyclic diiminodipyrromethanes as potent catalysts for the reduction of curing temperature of bisphenol-A/F benzoxazines

The simple modification of the Schiff-base ligands often brings significant changes in the coordination properties of the metal-complexes, providing newer prospects for their unexplored applications. In this context, the present work utilized the “self-adaptable” acyclic diiminodipyrromethane Schiff's bases (2a and 2b) for the synthesis of their Zn-based complexes and explored their potential in the ring-opening polymerization of benzoxazines. The two zinc complexes of composition [Zn{(Ph)(CH₃)C(2,6-ⁱPr₂C₆H₃–N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH–C₄H₂N)(2,6-ⁱPr₂C₆H₃–NCH–C₄H₂NH)}₂] (3) and [ZnCl₂{(Ph)(CH₃)C(Ph₃C–NHCH–C₄H₂N)₂}] (4) were synthesized in good yields, and the structures were confirmed by single crystal X-ray diffraction (XRD). Later, zinc complexes (3 & 4) were used as catalysts to reduce the curing (ring-opening polymerization) temperature of benzoxazine monomers such as Bisphenol-A (BA-a) and Bisphenol-F (BF-a) benzoxazines. Dynamic scanning calorimetry (DSC) studies revealed that the on-set curing (T_p) temperatures were reasonably decreased upto 20% for the benzoxazines. Furthermore, the thermal stabilities of the polybenzoxazines (PBzs) derived in the presence of zinc catalysts (3 and 4) were compared with PBz obtained in the absence of catalyst under similar conditions. The thermal studies reveled that there is no significant changes in the initial degradation of polymers. However, the thermal stability in terms of char yields at 800 °C improved upto 10–21% for the bisphenol-A/F benzoxazines.

The present work utilized the “self-adaptable” acyclic diiminodipyrromethane Schiff's bases (2a and 2b) for the synthesis of their Zn-based complexes and explored their potential in the ring-opening polymerization of BA-a and BF-a benzoxazines.

Evaluation of thermo-mechanical, dielectric and corrosion resistant properties of cardanol benzoxazine-epoxy based hybrid composites: A very low temperature curing pre-polymer for high performance paint related applications

In the present work, the hybrid siloxane-based cardanol-benzoxazine-epoxy (1:1 ratio) matrix (SBCBz-EP) capable of curing at substantially low temperature when compared with that of conventional benzoxazines was prepared and characterized. The matrix SBCBz-EP was reinforced with varying weight percentages (1, 3 and 5 wt%) of hydroxyl-terminated cyclotriphosphazene (HTCP) and the resulting hybrid composites were characterized by modern analytical methods, which can be used for paint-related applications due to their low-temperature curing behaviour. Data obtained from differential scanning calorimeter analysis infer that the glass transition temperature of the hybrid matrix (SBCBz-EP) and HTCP reinforced with 1, 3 and 5 wt% composites was 73°C, 75°C, 82°C, and 88°C, respectively. The polymerization temperature obtained for SBCBz-EP matrix and HTCP-reinforced hybrid composites was considerably lower than that of conventional benzoxazines. The present hybridization approach of benzoxazine and epoxy paves an avenue to alleviate the deficient characteristics of both industrially valuable resins namely high curing temperature and brittle behaviour of benzoxazines and also to improve thermal stability, mechanical strength and flame-retardant behaviour of epoxy resins. Data obtained from mechanical, dielectric, thermal stability and corrosion-resistant studies indicate that the properties of hybrid composites (HTCP/SBCBZ-EP) were enhanced to an appreciable extent according to the wt% of HTCP and it can be suggested that these hybrid composite materials can be used in the form of adhesives, sealants, encapsulants and water-resistant coatings for high performance industrial applications.