This paper reports the preparation, characterization, and performance of three low viscosity fully bio-based benzoxazine resins synthesized from bio-based furfurylamine, paraformaldehyde, and three new enzymatic originated diphenols obtained through a sustainable and highly selective lipase-catalyzed enzymatic process from p-coumaric acid, and three bio-based diols (propanediol, butanediol, and isosorbide, respectively). The enzymatic method is used for the first time, to the authors' knowledge, to design specific diphenolic structures dedicated to the preparation of benzoxazine thermosetting resins whose precursors exhibit easy handling within a wide processing window (from room temperature up to 200 degrees C). The resulting cross-linked materials present high glass transition temperature (T-g > 200 degrees C) and inherent charring ability upon pyrolysis (approximate to 50 wt% at 1000 degrees C). These results open a valuable and new pathway to develop enhanced benzoxazines and bring them new properties.

Phenol‐paraphenylenediamine (P‐pPDA) benzoxazines exhibit excellent barrier properties, adequate to protect aluminum alloys from corrosion, and constitute interesting candidates to replace chromate‐containing coatings in the aeronautical industry. For the successful application of P‐pPDA coatings, it is necessary to decrease the curing temperature to avoid the delamination of the coating while preserving the mechanical properties of the alloy, as well as the barrier properties of the coating. However, decreasing the curing temperature leads to less polymerized films, the extent of which requires a quantitative assessment.While the conversion rate of the polymerization reaction is commonly evaluated for bulk samples using differential scanning calorimetry (DSC), a tool for its evaluation in thin films is missing. Therefore, a new approach was developed for that matter using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The relation between the SIMS data integrated from inside thin films and the DSC results obtained on bulk samples with the same curing cycle allowed to calibrate the SIMS data. With this preliminary calibration of the technique, the polymerization of P‐pPDA coatings can be locally determined, at the surface and along the depth of the coating, using dual‐beam depth profiling with large argon cluster beam sputtering.

In this paper, laboratory synthesized Phenol-paraPhenyleneDiAmine (P-pPDA) benzoxazine containing different amounts of B-trimesityl-N-triphenylborazine was applied by spin coating on aluminum and thermally cured. The addition of the borazine derivative (borazine 1) does not appear to modify the curing characteristics of the P-pPDA matrix itself as shown by FTIR, DSC and DEA analyses; however, some interactions - chemical and/or physical (co-crystallization) - between P-pPDA and borazine 1 cannot be excluded. The microstructure of the composites is characterized by a two phase system consisting of a dispersion of nanosized (10-20 nm) clusters for the lowest borazine 1 concentration (0.5 wt%), evolving towards bigger (100-200 nm), agglomerated clusters for higher borazine 1 concentrations (3 wt%) and finally, continuous, dendritic structures within the P-pPDA matrix for the highest borazine 1 concentration (10 wt%). The benzoxazine composite coating containing 0.5 wt % trimesitylborazine derivative showed a largely increased and durable ability to protect the aluminum substrate. It is shown that a highly capacitive behavior and durable barrier properties can be obtained for P-pPDA coatings containing such a low amount of borazine derivative homogeneously dispersed in the benzoxazine matrix. For concentrations of 3 wt%, as agglomeration took place and dendrites appeared for the highest concentration of borazine derivative (10 wt%), the corrosion resistance decreased with time.

Fillers are widely used to improve the thermomechanical response of polymer matrices, yet often in an unpredictable manner because the relationships between the mechanical properties of the composite material and the primary (chemical) structure of its molecular components have remained elusive so far. Here, we report on a combined theoretical and experimental study of the structural and thermomechanical properties of carbon nanotube (CNT)-reinforced polybenzoxazine resins, as prepared from two monomers that only differ by the presence of two ethyl side groups. Remarkably, while addition of CNT is found to have no impact on the glass-transition temperature ( Tg) of the ethyl-decorated resin, the corresponding ethyl-free composite features a surge by ∼47 °C (50 °C) in Tg, from molecular dynamics simulations (dynamic mechanical analysis measurements), as compared to the neat resin. Through a detailed theoretical analysis, we propose a microscopic picture for the differences in the thermomechanical properties of the resins, which sheds light on the relative importance of network topology, cross-link and hydrogen-bond density, chain mobility, and free volume.

Due to their excellent mechanical, electrical, and thermal properties, carbon nanotubes (CNTs) are considered as the nanofillers of choice to reinforce organic-based materials and to provide additional specific properties that allow a number of exciting potential applications in the energy, electronic, biotechnology, and nanotechnology areas. This chapter presents a review of the most recent progress on the development of polybenzoxazine/CNT-based composites. More specifically, the role of the different CNT functionalization, process dispersion, and benzoxazine-CNT interactions on the resulting material properties are discussed and the key-factors leading to an effective nanoreinforcement of the benzoxazine matrix without losing the physical properties of CNTs are highlighted. This chapter aims to demonstrate the great potential of the benzoxazine/CNT couple, which can lead to unique properties.

A convenient and efficient approach is presented in this study for developing advanced thermosetting composite laminates reinforced or not with 0.5 wt% of pristine CNTs. A highly aromatic benzoxazine monomer was selected as the matrix for the preparation of carbon fiber composites due to its strong intrinsic affinities with CNTs. Fine CNT dispersion was achieved within the whole composite after fabric impregnation leading to a considerable increase of the glass transition temperature of about 50 degrees C. The resulting multiscale composite exibits an improved thermomechanical stability, up to 300 degrees C and its room temperature flexural strength is enhanced from 520 to 700 MPa. Moreover, the confinement of neat CNTs within the whole composite is also found to have a beneficial effect on the fire properties and the water sensitivity of the composite. These promising results highlight that when neat CNTs are able to develop strong interactions with the aromatic resin, the resulting system can provide a new and efficient way to design and improve the properties of composite laminates. (C) 2016 Elsevier Ltd. All rights reserved.

In this paper, the feasibility to apply a laboratory synthesized Phenol-paraPhenyleneDiAmine (P-pPDA) benzoxazine by spin coating on anodized aluminum substrates followed by thermal curing, has been investigated. Prior to coating, sulfo-tartaric anodizing has been carried out aiming at growing porous oxide layers either on 1050 or 2024-T3 aluminum substrates. Optimization of the performance of the benzoxazine coatings to protect the aluminum substrates was achieved by working out conditions preventing delamination of the coatings as observed for non anodized coated substrates and reducing its curing temperature to a level compatible with the requirements of the aerospace industry. Compared to bare substrates coated with P-pPDA, it is shown that highly capacitive and durable barrier properties can be obtained for the same kind of coatings when applied on the anodized substrates. Moreover, in order to respect the thermal sensitivity of aeronautical aluminum substrates, such as 2024-T3, the curing temperature can be limited to 140 degrees C only if the substrates are previously anodized in a sulfo-tartaric acid bath.

From a set of around 30 thermosets (polycyanurates, polybenzoxazines, epoxy and phtalonitrile resins) tested in pyrolysis-combustion flow calorimetry, the contributions to flammability of 14 new chemical groups are calculated using a method previously proposed and validated. The flammability properties include total heat release, heat release capacity and char content. The comparison between these groups allows drawing some consistent conclusions about the best structures in terms of flammability. Especially, the aromaticity, the number of covalent bonds between the considered chemical group and the neighboring groups and the presence of heteroatoms (O, N) in the structure are highlighted.

A novel biobased benzoxazine monomer containing additional allyl functionality was synthesized using a solventless approach from the reaction of a natural occuring phenol: chavicol, para-phenylene diamine and formaldehyde. The chemical structure of this functionalized benzoxazine monomer was confirmed by H-1 NMR and FTIR. Its polymerization was investigated and monitored by DSC showing two well defined exotherms allowing the selective ring-opening polymerization of benzoxazine functions and the preservation of the allyl functionality. The network crosslink density could be further increased via the controlled polymerization of allyl functionalities with a post-cure in order to adjust the thermo-mechanical properties. When both networks were polymerized, the thermoset presented an excellent thermo-mechanical stability with a T alpha higher than 350 degrees C as measured by DMTA. This exceptional behavior for a potentially biobased benzoxazine resin will allow the preparation of sustainable high performance biocomposite materials. (C) 2016 Elsevier Ltd. All rights reserved.

This work presents a scalable and solventless synthesis of two fully bio-based bis-benzoxazine resins derived from resorcinol, hydroquinone and furfurylamine. The structures of the two synthesized precursors have been studied by H-1 NMR and FTIR spectroscopies and SEC. The polymerization and degradation of the precursors have been investigated and monitored by DSC and TGA. The properties of the resulting polybenzoxazine networks were found to be dependent on the precursor molecular structure. In both cases, an excellent thermomechanical behavior associated with high charring ability were obtained which highlights the great potential of these fully bio-based resins as new matrices for the preparation of structural composites following a sustainable approach. (C) 2016 Elsevier Ltd. All rights reserved.

A novel benzoxazine monomer containing a carbohydrate moiety was synthesized using a solventless approach from the reaction of arbutin, a naturally occurring phenolic compound, furfurylamine and formaldehyde. The chemical structure of this fully bio-based benzoxazine monomer was confirmed by H-1 NMR and FTIR. Its polymerization has been investigated and monitored by DSC showing the ring opening polymerization of benzoxazine functions with a network densification thanks to the reaction of the furan group. The high hydroxyl content of the monomer allows its easy solubilisation in water paving the way to a wide range of possible "environmentally friendly" applications especially in the fields of coatings, paintings and adhesives.

Aluminum alloys are widely used in aircraft applications, especially series 2xxx (Cu) and 7xxx (Ti). Those alloys offer improved mechanical properties compared to pure aluminum, but are strongly sensitive to corrosion. Chromic anodizing combined with chromate containing epoxy primer was used as an efficient system to prevent corrosion. Nevertheless, due to health and environmental issues, this treatment is going to be forbidden. Alternative solutions have to be developed to reach aircraft standards considering health and environmental concerns. This work aims at proposing an alternative protective system, consisting in an oxide layer obtained from sulfotartaric anodizing (TSA) and coated with benzoxazine organic layers. Benzoxazine resins offer high chemical resistance and low shrinkage and so are very good candidates for coating applications. Investigated layers have been prepared on both bare and clad Al-2024 T3 substrates. The morphology and the thickness of coating systems were determined using Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Electrochemical Impedance Spectroscopy (EIS) was used to characterize the electrochemical behaviour of obtained systems and separated layers in order to emphasize synergetic effects. The AC/DC/AC electrochemical tests were carried out to evaluate the cathodic disbonding sensitivity of these new coating systems. The results were fitted by Equivalent electrical circuits to model the electrochemical properties of different layers and the evolution of their properties over immersion time in an aggressive saline solution and during AC/DC/AC cycles. The results confirmed the strong potential of such systems for future corrosion protection applications.

In this communication, we highlight the remarkable and unexpected mechanical and electrical properties of new porous nanohybrid materials as readily obtained by a two-step preparation procedure. Neat multi-wall carbon nanotube (CNT)-reinforced benzoxazine nanocomposites were first produced. At a CNT content of 5 wt%, pyrolysis of the nanocomposites allowed for recovering porous monolithic nanohybrid materials exhibiting outstanding mechanical resistance (elastic modulus of ca. 50 MPa) for an electrical conductivity as high as 30 S cm(-1). Interestingly, long CNTs were found to build up an internal scaffold limiting the deformation of the foamed structure and preserving the geometric shape and dimensional integrity of the sample along the pyrolysis process. The concept of this novel approach paves the way for the production of a very promising choice of viable (nano) materials for use as domains as versatile as in energy storage, catalysis, or shielding applications.

Polybenzoxazine coatings were elaborated by dip coating of a solution, prepared from a commercial bisphenol A benzoxazine (BA-a), on a 1050 aluminum alloy. The monomer was dissolved in acetone and the influence of the different application parameters (withdrawal speed and viscosity of the solution) on the wet coating thickness was evaluated. A heat treatment was then performed on the coating to polymerize the benzoxazine monomer by a ring opening mechanism attested for by Fourier Transform Infrared spectroscopy (FT-IR) and followed by Differential Scanning Calorimetry (DSC). Dielectric Analysis (DEA) and Thermogravimetric Analysis (TGA) showed a particular behavior related to a partial decomposition taking place at 180 degrees C and associated with the creation of intermediary ionic and volatile species. Finally, the barrier protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) for 30 days in sodium chloride solution (0.1 M). The results showed an improvement of the impedance modulus from 10(4) Omega cm(2) for an uncoated aluminum to,a value as high as 10(9) Omega cm(2) with a 10-mu m thick polybenzoxazine coating. (C) 2014 Elsevier B.V. All rights reserved.