Nadic Anhydride Research Articles

Structural design strategy of biobased propargyl ether-functionalized epoxy monomer to access low viscosity resin with excellent heat resistance and mechanical properties for advanced composite via VARTM

High performance biobased epoxy resin with low viscosity is important for preparing fiber-reinforced polymer composites via vacuum-assisted resin transfer molding (VARTM). Herein, a novel biobased propargyl ether-functionalized epoxy monomer (BPBO) with low viscosity (0.07 Pa·s) was designed and synthesized from renewable eugenol, and then it was combined with methyl nadic anhydride (MNA) to produce a new epoxy system (BPBO/MNA) with excellent properties. The curing behaviors and integrated performances were systematically researched and compared with those of petrochemical-based commercial diglycidyl ether of bisphenol A (DGEBA) type epoxy resin (DGEBA/MNA). BPBO/MNA shows better thermal and mechanical properties than DGEBA/MNA. Specifically, the glass transition temperature (Tg) and the flexural strength of BPBO/MNA resin are as high as 242 °C and 176.2 MPa, about 47 °C and 16.8 % higher than those of DGEBA/MNA resin, respectively, and both of them are the highest among those of eugenol-derived epoxy resins reported so far. The nature behind these outstanding integrated performances is attributed to the unique cross-linked structure of BPBO/MNA that originated from the ring opening polymerization of epoxy with anhydride and the polymerization of aryl propargyl ether groups. Moreover, carbon fiber reinforced composite with attractive performance was developed by taking BPBO/MNA as the resin matrix via VARTM process. This work presents a simple and unique strategy to prepare high performance biobased epoxy resin with low viscosity for advanced composites.

Electrical Properties of Alicyclic Epoxy Resins for Application to Varnish of Rotating Machine Winding

Epoxy resins (EP) are commonly used to power apparatus due to their excellent electrical, thermal, and mechanical properties. Two types of EP resins were prepared to develop the varnishes for a rotating machine winding. A bifunctional alicyclic EP were used as an EP main resin, and an acid anhydride [mixture of hexahydro phthalic anhydride and methyl hexahydro phthalic anhydride (HHPA), or methyl nadic anhydride (NMA)] were used as a curing agent. The DC and impulse breakdown strengths of the EP‐HHPA were higher than that of EP‐NMA regardless of the applied voltage waveform and the temperature. The PDIV of the twisted pair sample coated with EP‐HHPA under the surge voltage application was also higher than that of twisted pair sample without the coating with EP resin and that with EP‐NMA. Furthermore, the transferred and/or accumulated charge amount of the EP‐HHAP on bulk and surface properties at high temperatures were superior to that of EP‐NMA. From these results, it is considered that EP‐HHPA may be preferable varnishes materials than EP‐NMA for a rotating machine winding. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Exceptional reactivity of the bridgehead amine on bicyclo[1.1.1]pentane.

Bicyclo[1.1.1]pentane (BCP) has received substantial interest in the field of synthetic chemistry recently for its potential use as a benzene isostere in medicinal chemistry. Whereas bicyclo[2.2.2]octane (BCO) has also been used as a bioisostere of benzene, the condensation of BCP-amine with nadic anhydride is significantly easier than that of BCO-amine. Analyses of the geometries and the frontier molecular orbitals of these amines suggest that the low steric hindrance and high intrinsic nucleophilicity of BCP-amine together contribute to its exceptional reactivity.

Polydicyclopentadiene toughened epoxy resin and its carbon fiber composites via sequential polymerization

AbstractIn this work, a dicyclopentadiene monomer/Grubbs 2 catalyst was added to a mixture of epoxy oligomers and methyl nadic anhydride to obtain a poly‐dicyclopentadiene (DCPD) modified epoxy cross‐linked network via sequential curing. The hybrid resin was used as a matrix for preparing carbon fiber composites. The results indicated that the addition of DCPD monomers significantly reduced the viscosity of the epoxy resin. The toughness and heat resistance of the co‐cured resin was improved without significant loss of strength, which was attributed to the high compatibility between epoxy and the modifier polymer. Regarding the composites, the flexural strength of the hybrid resin‐derived composite first increased and then diminished slightly. Meanwhile, the mode‐I interlaminar fracture toughness continued to increase with the increase of PDCPD content compared to the non‐modified composites. Generally, the change trend of the above properties in the composites was consistent with the change trend of the strength and toughness exhibited in the bulk resin with increasing PDCPD contents, while the change extent was inconsistent due to factors such as fiber volume content and interfacial bonding.Highlights The epoxy/PDCPD hybrid resin system was obtained via sequential curing. The PDCPD as modifier can reduce the viscosity of the epoxy curing system. The toughness and heat resistance of the PDCPD modified epoxy resin was improved. The loss in flexural strength of the hybrid resin system was insignificant. The GIC of the epoxy composites modified with PDCPD improved appreciably.

Sustainable and recyclable thermosets with performances for high technology sectors. An environmental friendly alternative to toxic derivatives

This study focuses on the development of environmentally friendly and chemically recyclable thermosets using or a renewable based monomer, the triglycidyl ether of phloroglucinol (TGPh), or a commercial non-toxic tris(4-hydroxyphenyl) methane triglycidyl ether (THPMTGE) monomer. The recyclable polyester thermosets were prepared by crosslinking the two monomers with hexahydro-4-methylphthalic anhydride (HMPA) or methyl nadic anhydride The TGPh-based formulations exhibited lower reaction temperatures and narrower reaction intervals. Additionally, these systems showed higher tan δ values (189°C–199°C), higher crosslinking densities (7.6–7.8 mmol cm−3) and compact networks, crucial for high-performance industries. Tensile tests demonstrated the remarkable mechanical properties of the thermosets, including high Young modulus (1.3–1.4 GPa), tensile stress (55–69 MPa), and an elongation at break around 3%–8%. Moreover, the thermosets exhibited complete dissolution at a temperature of 170°C, with depolymerization times of approximately 2.5 h for TGPh-based resins and 4.5 h for THPMTGE-based formulations. In conclusion, this study shows that sustainable and eco-friendly thermosets with excellent physico-chemical and thermo-mechanical properties, low hydrophilicity, and rapid dissolution capacity can be developed. These thermosets offer a viable alternative to non-recyclable and toxic resins in high-end industrial applications.

Experimental study on Diels-Alder addition of conjugated dienes directly from cracking C5 fraction by continuous micro-channel reactors

Diels-Alder reactions of cyclopentadiene, isoprene, and trans-1,3-pentadiene in the cracking C5 fraction with maleic anhydride were gradually carried out by step-heating in a continuous-settling reactor and a micro-channel reactor. Kinetic experiments (effects of temperature, reaction time, and molar ratio) and response surface analysis of three Diels-Alder reactions were carried out, and kinetic equations were fitted. The conditions of nadic anhydride preparation in a continuous-settling reactor, such as residence time and temperature, and that of 3/4-methyltetrahydrophthalic anhydride synthesis in a micro-channel reactor, such as temperature, feed ratio, and residence time, were optimized. The conversion rate of CPD to more than 92%, IP and T-PD to more than 97% has been achieved.

Preparation of lignin-based epoxy resins with tunable properties through constructing a partially ordered crosslinking network

In this work, lignin-based epoxy resins with tunable thermomechanical properties were prepared through constructing a partially ordered crosslinking network, which is designed on the curing behavior of phenyl glycidyl ether (PGE) and phenolated lignin-based epoxy resin (PLBER) with methyl nadic anhydride. Curing kinetics analysis illustrated that the introduction of PLBER could substantially reduce the activation energy (Ea) of curing reaction, indicating that PLBER have higher reactivity than PGE. Epoxy resins exhibited improved flexural strength, impact toughness, storage modulus, and glass transition temperature with the increase in lignin content. Based on the atomic force microscopic images of the thermosets, the highly crosslinked lignin-based epoxy resin was embedded in the epoxy matrix to form a heterogeneous network structure, which confirms that PGE reacted with PLBER as an active monomer to form a partially ordered crosslinked network, where PLBER represents the high-density region in the epoxy network. Moreover, the incorporation of lignin decreased the initial degradation temperature (Td5%) of epoxy resins, whereas Td50% (the temperature at 50% weight loss), Tmax (the temperature at the maximum rate of weight loss), and char yield (Char800) were improved with the increase in lignin content. This result may be attributed to the abundant β–O–4 bonds in lignin, which are degraded rapidly to form a protective carbon layer at the initial stage of decomposition, thereby slowing down the decomposition rate of epoxy resins.

In Situ Modification to Reinforce Isoprene Rubber by Sacrificial Bonds

Functionalization and reinforcement of polymers by introducing dynamic sacrificial bonds have attracted increasing attention. In this contribution, the in situ modification of isoprene rubber by the formation of sacrificial bonds during vulcanization has been investigated. The sacrificial bonds were formed by in situ introduction of hydrogen bonds and metal–ligand motifs, which became part of the vulcanized isoprene rubber network by reaction of the former with the vulcanizing agent. The introduction of three-component modifiers (nadic anhydride (NA), 2-aminopyrimidine (AP), and ZnCl2) and the molar ratio of these components can greatly affect the tensile strength and modulus of the vulcanized rubber. Under the external load, the sacrificial bonds preferentially rupture prior to the covalent network and facilitate rubber chain orientation, resulting in high fracture energy. In addition, the dynamic behavior of the sacrificial bonds and the hysteresis behavior of the vulcanized rubbers were studied.

Polyester-based epoxy vitrimer integrating spent coffee ground as a natural filler

Coffee is a widely consumed beverage, but approximately 80% mass of coffee cherry is discarded as waste. In this study, spent coffee grounds (SCG) were recycled and used as a natural filler in a polyester-based epoxy matrix made from reactions of diglycidyl ethers of Bisphenol A and polyethylene glycol with methyl nadic anhydride. The properties of SCG/epoxy composites with various SCG contents up to 40% w/w were evaluated using various techniques such as FT-IR spectroscopy, tensile testing, optical microscopy, differential scanning calorimetry, and rheology. The SCG filled polyester-based epoxy matrix demonstrated excellent dimensional stability and retained a permanently crosslinked network, but re-shaping was possible at ∼150 °C through transesterification, which occurred due to a dynamic chain exchange reaction between the ester group of the epoxy matrix and the hydroxyl group of the SCG fillers. The transesterification also improved the interfacial adhesion between the matrix and SCG fillers, resulting in tensile strength of over 20 MPa and a modulus of around 2.5 GPa, even with high SCG contents up to 40% w/w. While neat, cured epoxy shows thermoset behavior, filling the matrix with SCG enables reforming and origami-inspired spontaneous change in shape.

Highly Thermally Stable, Reversible, and Flexible Main Chain Type Benzoxazine Hybrid Incorporating Both Polydimethylsiloxane and Double-Decker Shaped Polyhedral Silsesquioxane Units through Diels-Alder Reaction.

This work synthesizes a new bifunctional furan derivative (PDMS-FBZ) through a sequence of hydrosilylation of nadic anhydride (ND) with polydimethylsiloxane (PDMS), reaction of the product with p-aminophenol to form PDMS-ND-OH, and its subsequent Mannich reaction with furfurylamine and CH2 O. Then, the main chain-type copolymer PDMS-DABZ-DDSQ is prepared through a Diels-Alder (DA) cycloaddition of PDMS-FBZ with the bismaleimide-functionalized double-decker silsesquioxane derivative DDSQ-BMI. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirm the structure of this PDMS-DABZ-DDSQ copolymer; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) reveal it to have high flexibility and high thermal stability (Tg = 177 °C; Td10 = 441 °C; char yield = 60.1 wt%); contact angle measurements reveal a low surface free energy (18.18 mJ m-2 ) after thermal ring-opening polymerization, because the inorganic PDMS and DDSQ units are dispersed well, as revealed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This PDMS-DABZ-DDSQ copolymer possesses reversible properties arising from the DA and retro-DA reactions, suggesting its possible application as a functional high-performance material.

Fully bio-based furan/maleic anhydride epoxy resin with enhanced adhesive properties

Epoxy resins are widely used in a variety of application fields, thanks to their good mechanical strength, chemical resistance and adhesion to several substrates. Nowadays, the quite majority of epoxy resins are based on derivatives of bisphenol A (BPA), which poses serious health concerns. This issue is pushing the research towards suitable bio-based alternatives to this product, being furan-based epoxies very promising in this respect. In a previous work, 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) was cured with methyl nadic anhydride (MNA), and successfully used as tinplate coating. Herein, in a view of increasing the sustainability of these epoxy resins, we have replaced MNA with maleic anhydride (MA), which can be derived from vegetable feedstocks, thus obtaining a fully bio-based epoxy resin. This latter has then been used as adhesive for carbon fiber-reinforced thermosetting plastics (CFRP). The curing process of the resin was monitored by differential scanning calorimetry (DSC) and chemo-rheological analysis. The results highlighted the significantly higher reactivity of BOMF towards MA compared to the diglycidyl ether of BPA (DGEBA). The crosslinked samples were characterized in their thermal, mechanical and adhesive properties. In comparison to DGEBA/MA and BOMF/MNA, BOMF/MA showed higher ultimate strain and slightly lower glass transition temperature, tensile modulus and ultimate strength. Interestingly, BOMF/MA displayed outstanding adhesive strength on CFRP joints, outperforming the DGEBA-based counterpart by three times. Indeed, by properly selecting the anhydride curing agent, a highly ductile fully bio-based material was developed for high performance adhesive applications. The overall results demonstrate that the properties of BOMF-based epoxy resins can be tailored to meet technical and safety requirements of downstream applications, representing a sustainable alternative to traditional systems containing DGEBA.

Epoxidized and Maleinized Hemp Oil to Develop Fully Bio-Based Epoxy Resin Based on Anhydride Hardeners

The present work aims to develop thermosetting resins using epoxidized hemp oil (EHO) as a bio-based epoxy matrix and a mixture of methyl nadic anhydride (MNA) and maleinized hemp oil (MHO) in different ratios as hardeners. The results show that the mixture with only MNA as a hardener is characterized by high stiffness and brittleness. In addition, this material is characterized by a high curing time of around 170 min. On the other hand, as the MHO content in the resin increases, the mechanical strength properties decrease and the ductile properties increase. Therefore, it can be stated that the presence of MHO confers flexible properties to the mixtures. In this case, it was determined that the thermosetting resin with balanced properties and high bio-based content contains 25% MHO and 75% MNA. Specifically, this mixture obtained a 180% higher impact energy absorption and a 195% lower Young's modulus than the sample with 100% MNA. Also, it has been observed that this mixture has significantly shorter times than the mixture containing 100% MNA (around 78 min), which is of great concern at an industrial level. Therefore, thermosetting resins with different mechanical and thermal properties can be obtained by varying the MHO and MNA content.

Development of a novel epoxy resin based on epoxidized chia oil as matrix and maleinized chia oil as bio‐renewable crosslinker

AbstractIn this work novel thermosetting resins with high bio‐based content have been developed derived from chia seed oil (CO). Epoxidized chia seed oil (ECO) was used as bio‐based epoxy matrix with different mixtures of crosslinker agents, that is, methyl nadic anhydride (MNA) as petroleum‐derived and maleinized chia seed oil (MCO) as bio‐based crosslinker. The chemically modified oils from CO, that is, ECO and MCO, and MNA were analyzed by titration and FT‐IR. Additional 1H NMR analysis was performed to characterize MCO structure. Two different behaviors were observed using the mixtures of crosslinkers. On one hand, MNA increases the rigidity with bio‐based content of 54.2%. On the other hand, the addition of MCO provides higher ductility with bio‐based content up to 98%. The same trend was observed by DMTA analysis. The novel cured resins were successfully crosslinked as demonstrated by the mechanical properties, FT‐IR analyses, and gel content. Based on the results, it is concluded that MCO presents higher reactivity than MNA, decreasing curing time with possible energy saving at industrial level. In general, the results showed that adding the appropriate amount of MCO, green thermosetting resins with the desired thermal and mechanical properties can be manufactured with high bio‐based content.

Curing Kinetics of Bioderived Furan-Based Epoxy Resins: Study on the Effect of the Epoxy Monomer/Hardener Ratio

The potential of furan-based epoxy thermosets as a greener alternative to diglycidyl ether of Bisphenol A (DGEBA)-based resins has been demonstrated in recent literature. Therefore, a deep investigation of the curing behaviour of these systems may allow their use for industrial applications. In this work, the curing mechanism of 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) with methyl nadic anhydride (MNA) in the presence of 2-methylimidazole as a catalyst is analyzed. In particular, three systems characterized by different epoxy/anhydride molar ratios are investigated. The curing kinetics are studied through differential scanning calorimetry, both in isothermal and non-isothermal modes. The total heat of reaction of the epoxy resin as well as its activation energy are estimated by the non-isothermal measurements, while the fitting of isothermal data with Kamal's autocatalytic model provides the kinetic parameters. The results are discussed as a function of the resin composition. The global activation energy for the curing process of BOMF/MNA resins is in the range 72-79 kJ/mol, depending on both the model used and the sample composition; higher values are experienced by the system with balanced stoichiometry. By the fitting of the isothermal analysis, it emerged that the order of reaction is not only dependent on the temperature, but also on the composition, even though the values range between 0.31 and 1.24.

High-performance naphthalene epoxy resins cured by catalyst for packaging materials

Epoxy resins are widely used for electronic packaging materials due to their good performance. A common way to cure epoxy is to add anhydride as a hardener, to this, we added a less used curing method, catalytic curing, to study their effect on the curing system and curd samples. Polymers containing naphthalene rings usually have low moisture absorption, good thermal stability, dimensional stability, and dielectric properties. Here, we used two naphthalene epoxy monomers (1,6- naphthalene diglycidyl ether (1,6-NDE) and 2,7-NDE) and cured them with two methods (anhydride (methyl nadic anhydride, MNA) / accelerator (Tris(dimethylaminomethyl)phenol, DMP-30) curing system and catalyst (DMP-30) curing system). We obtained four types of epoxy resins and compared the differences in their structure and performance. All epoxy resins had excellent tensile properties at around 100 MPa tensile strength. Catalyst cured resins had better thermal stability and higher glass transition temperature that close to 180 ˚C (T g -DMA), compared with anhydride cured resins. Meanwhile, 1,6-naphthalene epoxy resins had better performance than 2,7-naphthalene epoxy resins in high glass transition temperature and high crosslink density. Overall, all naphthalene epoxy resins had good performances, and catalyst-cured resins performed better and provided an additional method. Herein, these types of naphthalene epoxy resins have potential applications in the field of electronic packaging. • Molecular arrangement inferred from mode layer spacing and crosslink density. • Spatial resistance affects the cross-linking density and the performance of the resins. • Better thermal stability and solvent resistance of catalyst cured resins.

Newly designed polydicyclopentadiene and its continuous carbon fiber composites: Preparation and mechanical properties assessment

In this work, the tackified PDCPD (PDCPD-T) specialized for vacuum assistant resin infusion process (VARI) was developed. The epoxy resin and methyl nadic anhydride (NMA) was subsequently added to the PDCPD-T to improve the interfacial bonding with the carbon fibres. The results showed that the introduction of NMA-cured epoxy undermined the mechanical properties of the PDCPD-T owing to the agglomeration of the tackifier particles. Nonetheless, the mechanical properties of the CFRCs based on the co-cured blends of the PDCPD-T and the NMA-cured epoxy were comprehensively improved compared to the composites based on the PDCPD-T. The improvement was that a part of NMA-cured epoxy in the co-cured blends would phase separate on the surface of the carbon fibre, which formed the “bridge” connecting the matrix and the carbon fibre. In addition, the degree of the tackifier agglomeration would also decrease due to the decrease in the surrounding epoxy concentration.

Effect of Dielectric Relaxation of Epoxy Resin on Dielectric Loss of Medium-Frequency Transformer

Epoxy resin (EP) is a typical and widely used insulating material for medium-frequency transformers (MFTs). The dielectric loss of EP is one of the key variables in the design and operation of MFT. In this article, six types of epoxy/anhydride systems are prepared, and the dielectric loss of MFT is calculated by finite element method (FEM) analysis based on broadband dielectric spectroscopy measurements. The material dependence of the dielectric loss of MFT is investigated using dielectric spectroscopy and molecular dynamics simulations over a wide temperature and frequency range. The results show that the variation of dielectric loss with output power is attributed to the temperature characteristics of the imaginary part ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{\prime \prime }$ </tex-math></inline-formula> ) of complex permittivity. Compared to the dielectric loss at no-load state, the one at rated power is reduced by 5–10 W. The anhydride hardener containing benzene ring or a methyl substituent has an inhibitory effect on dielectric loss, and the EP cured by methyl nadic anhydride (MeNA) has the lowest dielectric loss (16.2 W) at rated power. The dielectric loss and overload characteristics of MFT are closely related to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -relaxation of EP, respectively. The acid anhydride curing agent containing benzene ring or a methyl substituent reduces the temperature corresponding to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation peak by more than 50 °C compared to the one without. The increased rigidity of the chain segment of EP makes the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation move to the low-temperature side, which is beneficial to suppress the dielectric loss. This article not only serves as a bridge among dielectric loss of MFT, dielectric spectroscopy, and molecular structure of EP but also lays a solid foundation for the selection of insulating materials for MFT.

Evaluation of Natural and Modified Castor Oil Incorporation on the Melt Processing and Physico-Chemical Properties of Polylactic Acid

Bio-based plasticizers derived from renewable resources represent a sustainable replacement for petrochemical-based plasticizers. Vegetable oils are widely available, non-toxic and biodegradable, resistant to evaporation, mostly colorless and stable to light and heat, and are a suitable alternative for phthalate plasticizers. Plasticized poly(lactic acid) (PLA) materials containing 5 wt%, 10 wt%, 15 wt% and 20 wt% natural castor oil (R) were prepared by melt blending to improve the ductility of PLA. Three castor oil adducts with maleic anhydride (MA), methyl nadic anhydride (methyl-5-norbornene-2,3-dicarboxylic anhydride) (NA) and hexahydro-4-methylphthalic anhydride (HA), previously synthesized, were incorporated in a concentration of 15 wt% each in PLA and compared with PLA plasticized with natural R. The physico-chemical properties of PLA/R blends were investigated by means of processability, chemical structure, surface wettability, mechanical, rheological and thermal characteristics. The addition of natural and modified R significantly improved the melt processing by decreasing the melt viscosity by ~95%, increased the surface hydrophobicity, enhanced the flexibility by ~14 times in the case of PLA/20R blend and ~11 times in the case of PLA/15R-MA blend as compared with neat PLA. The TG/DTG results showed that the natural R used up to 20 wt% could significantly improve the thermal stability of PLA, similar to the maleic anhydride-modified R. Based on the obtained results, up to 20 wt% natural R and 15 wt% MA-, HA- or NA-modified R might be used as environmentally friendly plasticizers that can improve the overall properties of PLA, depending on the intended food packaging applications.

Double-Decker-Shaped Polyhedral Silsesquioxanes Reinforced Epoxy/Bismaleimide Hybrids Featuring High Thermal Stability.

In this study, we synthesized bismaleimide into a functionalized double-decker silsesquioxane (DDSQ) cage. This was achieved by hydrosilylation of DDSQ with nadic anhydride (ND), reacting it with excess p-phenylenediamine to obtain DDSQ-ND-NH2, and treating with maleic anhydride (MA), which finally created a DDSQ-BMI cage structure. We observed that the thermal decomposition temperature (Td) and char yield were both increased upon increasing the thermal polymerization temperature, and that these two values were both significantly higher than pure BMI without the DDSQ cage structure since the inorganic DDSQ nanoparticle could strongly enhance the thermal stability based on the nano-reinforcement effect. Based on FTIR, TGA, and DMA analyses, it was found that blending epoxy resin with the DDSQ-BMI cage to form epoxy/DDSQ-BMI hybrids could also enhance the thermal and mechanical properties of epoxy resin due to the organic/inorganic network formation created by the ring-opening polymerization of the epoxy group and the addition polymerization of the BMI group due to the combination of the inorganic DDSQ cage structure and hydrogen bonding effect. The epoxy/DDSQ-BMI = 1/1 hybrid system displayed high Tg value (188 °C), Td value (397 °C), and char yield (40.4 wt%), which was much higher than that of the typical DGEBA type epoxy resin with various organic curing agents.

Mechanical and thermal properties of synergistic modification of bismaleimide polymer composites with nano‐SiO2 and hyperbranched polyimide

AbstractBismaleimide resin (BMI) is a thermosetting resin with excellent properties. However, due to its poor toughness as a cured product, this paper uses hyperbranched polyimide (HBPI) and nano‐SiO2 in a synergistic manner to improve the performance of BMI. Isophorone diisocyanated tripolymer (IPDI trimer) and methyl nadic anhydride (MNA) were used to synthesize HBPI, and then we investigated the effect of the synergistic modification on the mechanical and thermal properties and the modification mechanism of HBPI and nano‐SiO2. The experiments showed that the most significant improvements were achieved at the addition of 40 and 3 wt% of HBPI and nano‐SiO2 respectively, with the impact strength of the materials increasing by 97.2%, fracture toughness indexes GIC and KIC increased by 36.7% and 34.6% respectively and glass transition temperature (Tg) was reduced. The SEM results showed that the nanoparticles were uniformly dispersed and further validated the synergistic modification mechanism.