Biobased high-performance tri-furan functional bis-benzoxazine resin derived from renewable guaiacol, furfural and furfurylamine

Partially Bio-Based Benzoxazine Monomers Derived from Thymol: Photoluminescent Properties, Polymerization Characteristics, Hydrophobic Coating Investigations, and Anticorrosion Studies

In this work, four thymol-based benzoxazines were synthesized using four primary amines with different chain lengths, namely methylamine, ethylamine, 1-propylamine, and 1-butylamine, which are then named T-m, T-e, T-p, and T-b, respectively. The optical properties of the synthesized thymol-based benzoxazines were examined via the photoluminescent study of their solutions in acetone. The results show that all the prepared benzoxazines emitted blue light with the maximum wavelengths from 425 to 450 nm when irradiated by the excitation wavelengths from 275 to 315 nm. The maximum excitation wavelengths are found to be 275 nm. The polymerization of the thymol-based benzoxazines is triggered by heat treatments with different conditions (160, 180, and 200 °C for 1 h). According to the FTIR results, the heat-curing process introduces a presence of the OH peak, of which intensity increases as the curing temperature increases. Thermal decompositions of thymol-based benzoxazines regarding TGA analyses reveal the enhancement of thermal stability of the benzoxazines with respect to the N-substituent chain length, as significantly observed the change in the first thermal decomposition at temperature ranged from 253 to 260 °C. Synthesized benzoxazine derivatives are further employed to coat the substrate, e.g., the glass slides. The investigation of the water contact angle shows that the coating of the benzoxazines onto the surface improves the hydrophobicity of the substrate, resulting in the enlargement of the contact angle from 25.5° to 93.3°. Moreover, the anticorrosion performance of the polybenzoxazine coatings is examined using potentiodynamic polarization techniques. The results illustrate the anticorrosion efficiency of the thymol-based polybenzoxazine up to 99.99%. Both hydrophobic and electrochemical studies suggest the feasibility for employing benzoxazines in anticorrosion coating applications.

Bio-Based Thermosetting Resins: From Molecular Engineering to Intrinsically Multifunctional Customization

Recent years have witnessed a growing interest in bio-based thermosetting resins in terms of environmental concerns and the desire for sustainable industrial practices. Beyond sustainability, utilizing the structural diversity of renewable feedstock to craft bio-based thermosets with customized functionalities is very worthy of expectation. There exist many bio-based compounds with inherently unique chemical structures and functions, some of which are even difficult to synthesize artificially. Over the past decade, great efforts are devoted to discovering/designing functional properties of bio-based thermosets, and notable progress have been made in antibacterial, antifouling, flame retardancy, serving as carbon precursors, and stimuli responsiveness, among others, largely expanding their application potential and future prospects. In this review, recent advances in the field of functional bio-based thermosets are presented, with a particular focus on molecular structures and design strategies for discovering functional properties. Examples are highlighted wherein functionalities are facilitated by the inherent structures of bio-based feedstock. Perspectives on issues regarding further advances in this field are proposed at the end.

Recent advances in the development of green furan ring-containing polymeric materials based on renewable plant biomass

Fossil resources are rapidly depleting, forcing researchers in various fields of chemistry and materials science to switch to the use of renewable sources and the development of corresponding technologies. In this regard, the field of sustainable materials science is experiencing an extraordinary surge of interest in recent times due to the significant advances made in the development of new polymers with desired and controllable properties. This review summarizes important scientific reports in recent times dedicated to the synthesis, construction and computational studies of novel sustainable polymeric materials containing unchanged (pseudo)aromatic furan cores in their structure. Linear polymers for thermoplastics, branched polymers for thermosets and other crosslinked materials are emerging materials to highlight. Various polymer blends and composites based on sustainable polyfurans are also considered as pathways to achieve high-value-added products.

Development of an Atomic-Oxygen-Erosion-Resistant, Alumina-Fiber-Reinforced, Fluorinated Polybenzoxazine Composite for Low-Earth Orbital Applications

An atomic-oxygen-erosion-resistant fluorinated benzoxazine resin and composite were developed. The benzoxazine resin, abbreviated as “BAF-oda-fu,” consists of four benzoxazine rings, and was synthesized from bisphenol AF (BAF), 4,4′-oxydianiline (oda), furfurylamine (fu), and paraformaldehyde. The resin was characterized by infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). An analysis of the solvent-washed product showed a technical grade purity (>95%) and a yield of approximately 85%. Subsequent polymerization of the resin was successfully performed by heating step-wise and opening the benzoxazine rings to form a crosslinked network. Thermal analyses showed a melting temperature of 115 °C and polymerization temperature of 238 °C, both being characteristic values of benzoxazine monomers. The benzoxazine resin was also blended with polyoctahedral sisesquoxane (POSS) and reinforced with alumina fibers. The Tg of the resin, as determined by DMA of the composite, could reach as high as 308 °C when post-curing and the POSS additive were utilized. The low-Earth orbit atomic-oxygen erosion rate was simulated by an RF plasma asher/etcher. The atomic-oxygen resistance of poly(BAF-oda-fu) fell along an established trend line based on its fluorine content.

Metal Complexes of the Porphyrin-Functionalized Polybenzoxazine

New porphyrin-functionalized benzoxazine (Por-BZ) in high purity and yield was synthesized in this study based on ¹H and ¹³C NMR and FTIR spectroscopic analyses through the reduction of Schiff base formed from tetrakis(4-aminophenyl)porphyrin (TAPP) and salicylaldehyde and the subsequent reaction with CH₂O. Thermal properties of the product formed through ring-opening polymerization (ROP) of Por-BZ were measured using DSC, TGA and FTIR spectroscopy. Because of the rigid structure of the porphyrin moiety appended to the benzoxazine unit, the temperature required for ROP (314 °C) was higher than the typical Pa-type benzoxazine monomer (ca. 260 °C); furthermore, poly(Por-BZ) possessed a high thermal decomposition temperature (T_d10 = 478 °C) and char yield (66 wt%) after thermal polymerization at 240 °C. An investigation of the thermal and luminescence properties of metal–porphyrin complexes revealed that the insertion of Ni and Zn ions decreased the thermal ROP temperatures of the Por-BZ/Ni and Por-BZ/Zn complexes significantly, to 241 and 231 °C, respectively. The metal ions acted as the effective promoter and catalyst for the thermal polymerization of the Por-BZ monomer, and also improved the thermal stabilities after thermal polymerization.

Bio-Based Bisbenzoxazines with Flame Retardant Linker

This work explores the strategy of incorporating a highly substituted reactive flame retardant into a benzoxazine moiety. For this purpose, a DOPO-based flame retardant received a chain extension via reaction with ethylene carbonate. It was then reacted with phloretic acid to obtain a diphenol end-capped molecule, and further reacted with furfurylamine and paraformaldehyde to obtain a benzoxazine monomer via a Mannich-like ring closure reaction. This four-step synthesis yielded a partly bio-based halogen-free flame retardant benzoxazine monomer (DOPO-PA-fa). The successful synthesis was proven via NMR, IR and MS analysis. The polymerization behavior was monitored by DSC and rheological analysis both showing the polymerization starts at 200 °C to yield pDOPO-PA-fa. pDOPO-PA-fa has a significant thermal stability with a residual mass of 30% at 800 °C under ambient atmosphere. Furthermore, it reached a V-0 rating against small flames and an OI of 35%. Blended with other benzoxazines, it significantly improves their thermal stability and fire resistance. It emphasizes its potential as flame retardant agent.

Sustainable and Ecofriendly Chemical Design of High Performance Bio-Based Thermosets for Advanced Applications

High performance thermosetting resins are targeted in many exigent applications, such as aerospace and marine fields, for the development of lightweight structural composites. Till now, these industries only rely on petroleum-based materials for their supposedly better performances. However, the latest developments in the field suggest otherwise. In fact, many reports confirmed that sustainable and ecofriendly thermosetting polymers can display similar or even better performances. Additionally, exploring alternative renewable feedstock's to meet the ever increasing demands of these industries is an essential step towards sustainable development. Aiming to unravel the potential of these materials, the present review summarizes the most relevant chemical routes allowing the preparation of fully or partially bio-based thermosetting resins. Meanwhile, the overall performances of these exceptional materials are also compared with their petroleum-based counterparts.

A guide towards safe, functional and renewable BPA alternatives by rational molecular design: structure–property and structure–toxicity relationships

Putting the pieces together: a guide for rational molecular design of safe, functional and renewable BPA alternatives.

Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites

A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR ¹H-¹H COSY, ¹H-¹³C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm^-1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46-77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.