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In this study, a novel biobased allyl compound with Schiff-based structure (MPAM) was developed to improve the toughness and thermal properties of 4,4'-bismaleimidodiphenylmethane (BDM). The chemical structure of MPAM was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance ([sup.1]H NMR). A series of BDM/DBA-MPAM blend resins (BD-MPAM resins) were prepared by adjusting the mass ratio of BDM + DBA (BD) to MPAM. The effects of MPAM content on the curing behavior, thermal and mechanical properties of BD-MPAM resins were discussed in details. Compared with BD resin, the thermal stability of modified resins was improved by increasing the content of MPAM. Meanwhile, an increase of 37.1% in flexural strength, and 228 MPa in flexural modulus were obtained for the cured BD-MPAM resin having 10 wt% MPAM loading compared to the BD resin. The impact strength of BD-10 wt% MPAM is of the maximum value (6.6 kJ/[m.sup.2]). Finally, the fracture surface morphology of the BD-MPAM resins was studied by the scanning electron microscope (SEM). KEYWORDS copolymerization, curing behavior, mechanical properties, thermal properties, 1 | INTRODUCTION As one of the well-received key basic resins, bismaleimide resin (BMI) has been generally accepted as commercial raw material in a vast array of cutting-edge fields, including [...]

Quercetin (Q), one of the most abundant molecules in nature, remains relatively unexplored in the realm of bio-based thermosets. In line with the pursuit of sustainability, we report the successful synthesis of a novel bio-based phthalonitrile (PN) monomer (Q-Ph) using Q. The synthesis involved a nitro displacement reaction with 4-nitrophthalonitrile (4-NPN). Confirmation of the monomer's structure utilized hydrogen and carbon nuclear magnetic resonances (1H and 13C NMR), Fourier transform infrared spectra (FTIR), and elemental analysis. Curing characteristics were examined by differential scanning calorimetry (DSC), and polymerization was analyzed using FTIR. The resulting monomers showed a wide processing window and low melt viscosity via rheological analysis. Thermal and thermomechanical properties were assessed using dynamic mechanical analyzer (DMA) and thermogravimetric analysis (TGA), revealing lower curing and polymerization temperatures compared to petroleum-based counterparts. The synthesized resin achieved a high Tg exceeding 400°C, a char yield of 79% at 1000°C, and T5% and T10% values of 564 and 660°C, respectively. The Q-Ph polymer demonstrated superior performance, with evidence of an autocatalytic curing mechanism. These results highlight quercetin as a promising petrochemical replacement for the preparation of self-curable PN thermosets, especially for high-performance applications. [ABSTRACT FROM AUTHOR]

A series of triphenol‐diamine‐type hyperbranched benzoxazines are synthesized by using polyformaldehyde, 1,1,1‐tri(4‐hydroxyphenyl) ethane, and primary amines such as p‐phenylenediamine, 4,4′‐diaminodiphenylmethane, polyetheramine, and bifuranocyclic diamine via Mannich condensation. Then, copolymers with bifunctional benzoxazine (BA‐a) are prepared to obtain superior properties. The polymerization behavior of the copolymers examined using a differential scanning calorimeter and a Fourier transform infrared indicates that the introduction of hyperbranched benzoxazines facilitates the benzoxazine curing reaction, decreasing the onset and peak temperatures of the curing process. Thermogravimetric analysis results suggest the cured hyperbranched benzoxazine demonstrates good thermal stability and can improve the heat resistance of benzoxazine. In addition, dynamic mechanical analysis suggests the glass transition temperature of the copolymers with BA‐a was increased after copolymerization, thus making all the copolymers obtain higher service temperatures. The test results from the universal testing machine and the fracture morphologies of copolymers indicate the hyperbranched benzoxazines with branched structures cause dendritic folds to appear on the surface of copolymers upon polymerization, preventing rapid cracking and spreading of the thermoset resin by dissipating more impact energy through this irregular dendritic appearance, thus obtaining strength and toughness superior to that of BA‐a resins. [ABSTRACT FROM AUTHOR]

Bismaleimide (BMI) resins is widely used in the aerospace field because of its excellent properties, but its poor toughness limits the possibility of its application in a wider range of fields. Therefore, a novel bio‐compound, 4‐(allyloxy)‐3‐methoxy‐N‐(3‐(triethoxysilyl)propyl)benzamide (AMTPM), was designed and synthesized from renewable vanillin, which has Schiff‐base structure, silico‐oxygen bond structure, and allyl structure. The chemical structure of AMTPM has been characterized and validated by Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance (1H NMR). It was found that the addition of AMTPM can effectively promote the curing behavior of BD resins (BMI and diallyl bisphenol A (DBA) was mixed and cured at the ratio of 1:0.87, named BD resins). AMTPM can affect the thermal stability and improve the mechanical properties of BD‐AMTPM resins (BD resins modified by AMTPM in different addition), and the detailed discussion was conducted. With the increase of AMTPM content, the thermal stability of BD‐AMTPM resins was deteriorated while the residual weight percentage at 800°C (Yc) was increased. When the content of AMTPM reached 12 wt%, the results showed that Yc achieved the values at a magnitude of 37.57%. Meanwhile, the glass transition temperature (Tg) achieved 320°C. Among the BD‐AMTPM resins system, the BD‐6 wt% AMTPM has the best toughness and mechanical properties. The impact strength was increased by 29.2%, the tensile strength was increased by 22.1% and the elongation at break was increased by 44%. The fracture morphology of BD‐AMTPM resins was also studied by scanning electron microscopy (SEM) to support the mechanical experimental conclusions. This study provides a more environmentally friendly and convenient modifier, which is of great significance for expanding the application of bismaleimide resin. Highlights: A bio‐based modifying agent (AMTPM) was designed and successfully synthesized.AMTPM has both Si‐O and Schiff‐base structures.AMTPM can effectively improve the toughness of BD‐AMTPM resins through impact and tensile tests. [ABSTRACT FROM AUTHOR]

This present investigation reports, for the first time, the properties of the polybenzoxazine bio-based furfurylamine reinforced using the hybrid short carbon fibers and tungsten particles. The results revealed good compatibility between the matrix and the filers using scanning electron microscopy, due to the use of the silane treatment that led to enhanced interfacial bonding. In addition, the mechanical data disclosed that the bending and impact values were respectively increased to 210 MPa and 9 KJ/m2 for the composites containing 20%wt of the short carbon fibers and 20%wt tungsten particles. The hybrid composite shielding properties were evaluated using the cobalt-60 as an irradiation source, and the nuclear results depicted that the half-value length and the tenth-value length were increased as compared to those of the pure polymers. Based on the thermal stability studies, the reinforced hybrid composites also showed excellent thermal resistance. [ABSTRACT FROM AUTHOR]

In an attempt to make polybenzoxazines more sustainable, a novel bio-based benzoxazine monomer namely Q-Bz was synthetized via the Mannich condensation reaction utilizing Quercetin, paraformaldehyde and aniline. The chemical structure of the monomer was confirmed by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopies (FTIR). The curing behaviour was studied by differential scanning calorimetry (DSC) and the polymerization process was investigated by FTIR. The obtained results showed very low melting and polymerization temperatures (73 and 183°C, respectively) and the disappearance of the oxazine ring absorption bands due to the ring opening polymerization of the monomers. Afterwards, the cured bio-based thermoset, referred to as PQ-Bz, was obtained and its thermal stability and thermo-mechanical properties were also assessed by DSC and thermogravimetric analysis (TGA). As expected the newly developed thermoset exhibited high thermal stability along with excellent processability. Indeed, the results showed that PQ-Bz had a relatively high Tg of approximately 280°C, with a 53% char yield at 800°C, 5% and 10% weight reduction temperature (T5% and T10%) values of 349 and 373°C, respectively. These findings demonstrate the potential of the novel bio-based benzoxazine monomer as a sustainable alternative to traditional petroleum-based thermosets in high performance applications. [ABSTRACT FROM AUTHOR]

The development of novel nanomaterials with superior reflection loss (RL), thin thickness, wide bandwidth, and low density has recently received significant attention in an effort to increase their effectiveness in electromagnetic (EM) microwave absorption while maintaining an easy manufacturing process. Naturally, using conventional materials with magnetic or dielectric loss makes it difficult to achieve the last criterion and limitations the thickness of the absorber and mass production. In this work, microwave nanocomposites samples were prepared on epoxy resin with different percentages of the nanoparticles of aluminum oxide (epoxy/Al2O3) with surfaces treated by amino propyl and silane. The surface treatment was carried out to improve the adhesion, morphology, and EM properties of the samples to enhance the microwave absorption and the Shielding Effectiveness (SE). Therefore, the treated sample can be considered as potential candidate for high frequency EM absorption applications. Then, the study is followed by structural, morphological, thermal, and electrical characterization of the prepared samples in order to enhance the performances of the latters. The EM absorption and the shielding effectiveness were done in the X band frequency (8 GHz-12 GHz). The obtained results confirmed that the nanocomposites treated samples exhibit higher EM absorption performance and better electrical characteristics. Overall, these results put forward the role played by the addition of the nanoparticles films as high-performance materials in electronic devices and EM applications. [ABSTRACT FROM AUTHOR]