Synthesis and properties of an epoxy resin containing trifluoromethyl side chains and its cross-linking networks with different curing agents (2023)

Epoxy resins are well-known adhesive materials, however, the high dielectric constant (D_k) limited their application in microelectronic devices. Additionally, non-degradability is a bottleneck for all thermosetting resins, and the discarded resins posed the great threat to environment. Herein, a bio-based eugenol epoxy was grafted onto the polymethylhydrosiloxane (PMHS-x) main chain via a hydrosilylation reaction to simultaneously lower the D_k and enable degradability. The curing kinetics of bio-based silicone/epoxy hybrid resins with methyl hexahydrophthalic anhydride (MHHPA) or 4,4′-diaminodiphenylmethane (DDM) were studied. The cured resins exhibited low D_k and hydrophobicity by taking advantage of the low polarity, large molecular volume and high dissociation energy of the siloxane segments. The polysiloxane degradation process took place under alkaline conditions, allowing the retrieval of reinforced fibers from the composites. To better illustrate the superiority of the bio-based silicone/epoxy hybrid resins, quartz fiber reinforced composites were prepared. Compared to the commercial epoxy based composite, the impact strength of the PMHS-x with a silicon hydrogen content of 0.8×10^-2 mol·g⁻¹ was increased by 26.5%, meanwhile, the D_k was decreased by 16.7%. The bio-based silicone/epoxy hybrid resins not only alleviated the environmental pollution but also provided a reliable approach for fiber recycling from epoxy composites. The low polarity and degradability were integrated into bio-based silicone/epoxy hybrid resins, which provided a novel way to prepare environment-friendly materials suitable for microelectronic devices.

To explore the high performance epoxy resin with high thermal properties and low dielectric constant and loss for copper clad laminates (CCLs), poly(phenylene oxide) (PPO) with low molecular weight is usually used as a modifier. Toward this end, a fluorinated redistributed poly(phenylene oxide) (F-rPPO) with number-average molecular weight of 3.0~6.2×10³ g/mol was synthesized via the redistribution reaction of commercial PPO with 4,4′-(hexafluoroisopropylidene) diphenol (BPAF) using benzoyl peroxide (BPO) as an initiator. The structure of F-rPPO was characterized by ¹H NMR, ¹⁹F NMR and FT-IR, respectively. F-rPPO was employed in the modification of diglycidyl ether of bisphenol A (DGEBA)/methylhexahydrophthalic anhydride (MeHHPA) epoxy resin, and the effect of F-rPPO on the curing behaviors and resulting thermosets were investigated. The results showed that the cured EP/F-rPPO resins exhibited improved thermal and dielectric properties, as well as lower moisture absorption. At 40 phr F-rPPO (based on DGEBA), the cured EP/F-rPPO resin possessed a higher T_g of 146 ℃ and T_d5% of 363 ℃ than that of 129 ℃ and 321 ℃ for the pristine epoxy resin, respectively. Moreover, EP/F-rPPO exhibited a lower moisture absorption (0.33%), dielectric constant and loss (2.69 and 0.0132 at 12GHz) compared to the pristine epoxy resin (0.48%, 2.93 and 0.0303 at 12GHz, respectively). This work provides an easy and effective solution to fabricate the high performance epoxy resins modified by PPO to better meet the requirement of CCLs.

In this study, a series of sustainable epoxy resin/diatomite composites were prepared by using the synthetic bio-based 2,2′-diglycidyl ether-3,3′-dimethoxy-5,5′-diallyl diphenylmethane (BEF-EP) as the matrix resin and silanized natural diatomite as the reinforcing filler. After cured with methylnadic anhydride and benzimidazole at different proportions of diatomite fillers, the morphology and properties of BEF-EP/diatomite composites were investigated and compared in detail. Due to the good compatibility between the epoxy resin matrix and silanized diatomite, the diatomite is uniformly dispersed in the matrix without large-scale agglomeration. With the addition content of diatomite increasing, the storage modulus of BEF-EP/diatomite composites increased from 2281 to 2983 MPa at 25 °C. The initial degradation temperature (T_d5%) showed an increasing first and then decreasing tendency as the content of diatomite increased, while the T_d50% and T_dmax values of BEF-EP/diatomite composites also increase with the content of diatomite increasing. Especially, BEF-EP/diatomite 20% showed excellent thermal stability with T_d5% of 287 °C, T_d50% of 485 °C, and T_dmax of 412 °C. The results indicated that the mechanical and thermal stability of epoxy resin composites could be significantly improved after the incorporation of diatomite. Furthermore, the bio-based BEF-EP/diatomite composite could be used as the renewable and sustainable alternatives to petroleum-based epoxy resin composites.

It is a longstanding bottleneck for epoxies applied in high-tech fields to obtain integrated performances, including excellent thermal mechanical and stability properties, hydrophobicity, low permittivity and curing activation energy. A novel epoxy monomer with stiff tetrafluorophenyl backbone and robust intramolecular/intermolecular forces is expected to fundamentally break through this challenge. Herein, three model epoxy monomers with different symmetrical para-hexatomic ring blocks were synthesized, including tetrafluorophenyl-based (FEP), phenyl-based (TEREP) and cyclohexyl-based (CEP), followed by curing with methylhexahydrophthalic anhydride (MeHHPA) and polyetheramine (D230), respectively. As expected, TEREP showed better thermal mechanical properties than CEP due to closer stacking density and electronic effect. Noticeably, FEP self-consistently showed the best comprehensive properties among three resins, which mainly benefited from the introduced C–F bonds and the unique electronic effect caused by tetrafluorophenyl. Moreover, the exhilarating results of tetrafluorophenyl para-hexatomic ring provide an efficient guideline for building epoxy-based material genomes to better design future-oriented engineering materials.

Firstly, a benzoxazine-type silane coupling agent (BS) was synthesized using 3-aminopropyltriethoxysilane (KH-550), 3-N-pentadecylphenol and paraformaldehyde. Subsequently, modified amorphous zirconia (ZrO₂) nanoparticles (NPs) were obtained through sol-gel method in ethanol with zirconium-butoxide (Zr(OBu)4) and the synthesized BS as dispersant. FTIR spectra confirmed the existence of BS structure on the surface of the synthesized ZrO₂ particle. The results of DLS showed that the modified NPs possessed small particle size of 20–70 mm with low polydispersity index and stable dispersion performance which was consistent with the morphology observed in TEM. The zeta potential was proportional to the addictive BS amount and reached the maximum when the BS loading rate was 30 mol%. Bisphenol A epoxy resin (DGEBA) was cured with Bisphenol A benzoxazine and the modified ZrO₂ NPs were incorporated to prepare the epoxy/benzoxazine/ZrO₂ composite. Homogeneous dispersion of the modified NPs was observed in the cured composite which was in deep contrast with the unmodified one. The results of tensile test showed that the cured polymer with the BS modified NPs possessed promoted tensile strength. The maximum of tensile strength was 105.7 MPa derived from the BS3-3 group while that for the U3 group with the same content of unmodified ZrO₂ NPs was just 73.5 MPa. The critical point of the tensile stress moved toward higher NPs content for the composites including the BS modified NPs and the standard deviation of the results, especially for the tensile stress, decreased remarkably which mean more stable mechanical behavior. DMA results were in good consistence with the tensile test that the composites with the BS-modified NPs possessed higher glassy modulus and T_g value.

Over the past several decades, producing materials from fossil-based sources has become a serious problem because such action continues to contribute to global warming and contamination of the ecosystem. Thus, it is highly desirable to address this issue through producing functional materials via green chemistry such as the use of renewable compounds. In this paper, the preparation of hydrophobic coatings based on isosorbide, a derivative of polysaccharides, is reported. The inherently hydrophilic thermoset derived from isosorbide was made hydrophobic through the use of the hydrophobic curing agent F8815. The influence of the F8815 concentration on the decomposition temperature, glass transition temperature and storage modulus of the biobased samples was explored using TGA, DSC and DMA, respectively. The results showed that, despite of its poor mechanical and thermal properties, incorporation of F8815 served to improve the thermal and mechanical properties of the isosorbide-based polymers. Deconvolution analysis of FTIR spectra and SEM images provided insightful information on the participation of F8815 in the polymer network.

International Journal of Hydrogen Energy, Volume 44, Issue 12, 2019, pp. 6136-6147

In this work, the organic-inorganic hybrid membranes were prepared. The synthesis and properties of the hybrid membranes were investigated. The sulfonated poly(arylene ether ketone sulfone) containing amino groups (Am-SPAEKS) was synthesized by nucleophilic polycondensation. The sol-gel method was used to prepared functional titania inorganic particles (L-TiO₂). The ¹H NMR and FT-IR were performed to verified the structure of Am-SPAEKS and L-TiO₂. The organic-inorganic hybrid membranes showed both good thermal stabilities and mechanical properties than that of Am-SPAEKS. The L-Am-15% membrane exhibited the highest Young's modulus (2262.71MPa) and Yield stress (62.09MPa). The distribution of L-TiO₂ particles was revealed by SEM. Compared to Am-SPAEKS, the hybrid membranes showed higher proton conductivities. The L-Am-15% exhibited the highest proton conductivity of 0.0879Scm⁻¹ at 90°C. The results indicate that the organic-inorganic hybrid membranes have potential for application in proton exchange membrane fuel cells.

Reactive and Functional Polymers, Volume 111, 2017, pp. 7-13

A synthetic approach to poly(arylene ether ketones) grafted with super-acidic perfluoroalkyl-sulfonic-acids is reported. A series of iodo-containing poly(arylene ether ketone)s derived from a 4-iodophenylated hydroquinone monomer were synthesized by aromatic nucleophilic substitution (SNAr). The iodo-containing polymers were functionalized via the Ullmann reaction to give poly(arylene ether ketone)s grafted with perfluoroalkyl-sulfonic-acid. The perfluoroalkyl-sulfonic-acid functionalized aromatic polymers were investigated as proton exchange membranes (PEM). The membranes had good overall properties of thermal-oxidative stability, mechanical strength, methanol permeability and proton conductivity. A membrane with IEC ~1.37meqg⁻¹ had a proton conductivity of 0.088Scm⁻¹ at 100°C, which was higher than many sulfonated hydrocarbon PEMs with similar IEC values.

Thermochimica Acta, Volume 590, 2014, pp. 251-258

A multifunctional silicone–phenyl contained aliphatic polyamine, PSPA, was originally synthesized and employed to cure bisphenol A epoxy resin (DGEBA) isothermally, and the curing reactions of DGEBA/PSPA were systematically investigated by DSC measurement at 55, 60, 65 and 70°C. The model fitting kinetic analysis confirmed that the reaction rate could be simulated with an autocatalytic Kamal model from start to initiation of diffusion control stage. Taking the diffusion effects into account, the extended Kamal model was applied to fit the experimental reaction rate, and acquired good agreement results. The multi-frequency dynamic mechanical analysis shows that the cured DGEBA/PSPA appears at a β relaxation in low temperature and at an α relaxation in higher temperature interval (>80°C). The relaxation activation energies for the α and β relaxations are 80.51 and 832kJ/mol, separately.

Polymer Degradation and Stability, Volume 99, 2014, pp. 27-34

In this study, a maleimido-substituted aromatic s-triazine (TMT) was synthesized successfully via the nucleophilic substitution reaction between cyanuric chloride and N-(4-hydroxyphenyl) maleimide (HPM) formed from paraaminophenol and maleic anhydride; and its structure was characterized by flourier transform infrared spectroscope (FT-IR), ¹H and ¹³C nuclear magnetic resonance (NMR), and elemental analysis (EA). The studied flame-retarded epoxy resins were obtained via thermal curing reactions among 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) modified epoxy prepolymer (DOPOER), 4,4′-diaminodiphenyl ethane (DDM) and TMT. Cure kinetics, flame-retardant, thermal and mechanical properties of the cured epoxy resins were characterized by differential scanning calorimeter (DSC), thermogravimeric analysis (TGA), limited oxygen index (LOI) measurement, UL 94 vertical burning test and mechanical test. The results indicate that TMT can promote the curing reaction of epoxy resins and decrease its apparent activation energy (E_a). Introduction of TMT can greatly improve flame-retardant, thermal and mechanical properties of the cured epoxy resins. Compared with the DOPOER/DDM system without TMT, LOI value of the cured epoxy resin can increase from 36.4% to 51.8%, and all samples can pass UL 94 V-0 rate when TMT content ranges from 1.98wt% to 7.44wt%. Its initial degradation temperature and glass transition temperature (T_g) can increase maximally by 37.6°C and 12.6°C, respectively when TMT content is 3.88wt%.

Materials Today Communications, Volume 26, 2021, Article 101984

Diglycidyl ethers of N,N'-bis(5-hydroxy-1-naphthyl)pyromellitimide (BNIDE) and polyethylene glycol (PEGDE) were binarily cured by N,N'-bis(5-amino-1-naphthyl)pyromellitimide (BNIDA) curing agent. Three homogenized mixtures of BNIDE and PEGDE resins with different mole ratios (75/25, 50/50 and 25/75) were isothermally reacted with the stoichiometric amounts of the curing agent. For comparison purposes, each diglycidyl ether was also cured separately with the same condition. The exothermic phase transitions associated with the curing processes were specified in the dynamic differential scanning calorimetry (DSC) traces of BNIDEBNIDA, BNIDE:PEGDEBNIDA, and PEGDEBNIDA mixtures. The completion of the curing processes was confirmed using Fourier transform-infra red (FT-IR) spectra and DSC traces of the isothermally cured resins. Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and T_g value of binarily cured epoxy resins was investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Both thermal stability and T_g value of the imide-epoxy thermoset films significantly increases with BNIDE resin. Instead, when PEGDE resin was cured by BNIDA, the prepared films showed more flexibility and pliability. These important characteristics were appropriately balanced by employing three binary mixtures of BNIDE and PEGDE resins.

Polymer, Volume 217, 2021, Article 123460

A phosphaphenanthrene-containing vanillin-derived compound (VDG) was synthesized by a one-pot nucleophilic addition reaction from vanillin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and 3,5‐diamino‐1,2,4‐triazole. The molecular structure of VDG was characterized by Fourier transform infrared (FTIR), and ¹H, ¹³C, and ³¹P nuclear magnetic resonance (NMR) spectrometer. Various loadings of VDG were incorporated into diglycidyl ether of bisphenol A (DGEBA) as a co-curing agent together with 4, 4′-diaminodiphenylmethane (DDM) to produce an epoxy thermoset. The thermomechanical, thermal and fire-retardant properties of EP thermosets were evaluated by dynamic mechanical analyzer (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94, and cone calorimetry. The results showed that a linear decrease in glass transition temperature with increasing loading of VDG owing to the declined cross-linking density. The cured DGEBA/DDM system with 2.0wt% of VDG exhibited super anti-flammability in terms of a high LOI value of 37.0% and UL-94 V-0 rating, whereas the cured DGEBA/DDM and DGEBA/DDM with 2.0wt% of DOPO systems showed no rating in UL-94 test. In addition, cone calorimetry test showed that the cured DGEBA/DDM system with 2.0wt% of VDG exhibited a reduction of up to 47.5% and 34% for peak heat release rate and total heat release, respectively, compared to the cured DGEBA/DDM system. The enhanced flame-retardant property was attributed to the formation of the compact and continual structure of char layer residue with good thermo-oxidative stability. In addition to good anti-flammability, the cured DGEBA/DDM/VDG thermoset showed antibacterial property against E. coli, with an inhibition zone diameter of 10mm. Thus, this bio-based co-curing agent could impart flame-retardant and antibacterial performance to epoxy for developing high performance functional thermosetting materials.