EP Resin Research Articles

Phenyl, propyl polysiloxane modified epoxy resin II: The co-continuous phase, concurrently strengthening and toughening mechanism

The applications of epoxy resins are restricted in certain areas due to their brittleness, while improving the epoxy toughness always compromises their strength. We reported a phenyl, propyl polysiloxane modified epoxy resins with excellent tensile strength and toughness before. In this study, the mechanism of strengthening and toughening are studied and elaborated. Compared to cured EP resin (EP), cured P/E resin (P/E20) significantly improved the tensile strength, elongation at break, impact strength, and critical strain energy release rate (GIc) by 45 %, 248 %, 18 %, and 512 %, respectively. Fracture analysis of the P/E20 revealed the appearance of parabolic markings, typical and convincing evidence of ductile fracture, indicating good toughness of the resin. AFM height and Young's modulus plots reveal the complex details of the dimples and the co-continuous phases, which provide the strong evidence to explain the reinforcement and toughening mechanism.

Green fabrication for ultra-lightweight polyethersulfone/epoxy foam with excellent thermal insulation

High-performance polymers find extensive applications in heat-resisting materials, aerospace, and automobile manufacturing industry. However, due to their challenging processability, achieving low-density high-performance polymer foams for thermal insulation materials remains a big challenge. Furthermore, the preparation of lightweight special engineering plastic foams has garnered substantial attention in current research. Herein, we have developed polyethersulfone (PES)/bisphenol A epoxy resin (EP) blend foams with ultra-low density and good thermal insulation properties using a facile and environmentally friendly supercritical CO2 (ScCO2) foaming approach. The inherent compatibility between PES and EP resin enhanced the free volume of molecular chain in the matrix, subsequently improving the solubility and diffusion rate of carbon dioxide within the PES matrix. Consequently, in contrast to the maximum expansion ratio of 5.5 observed in pure PES, the PES/EP blend foams achieved an expansion ratio of up to 26 times, along with an improvement of the cell structure of PES and increasing cell density from 2.55 × 109 to 2.96 × 1010 cells/cm3. Furthermore, the thermal conductivity of PES-based foams notably decreased from 0.0667 to 0.0348 W/(m·K) with the addition of EP, possibly resulting from the low density (0.05 g/cm3) and high open-cell content (79.9%) of PES/EP blend foam. Our work presents a novel strategy for producing special engineering plastic foams with ultra-low density for thermal insulation, thereby expanding the potential application of special engineering plastic foam in areas such as biological scaffolds, absorbent material applications, and automotive interior industry.

Degree of Cure, Microstructures, and Properties of Carbon/Epoxy Composites Processed via Frontal Polymerization.

The frontal polymerization (FP) of carbon/epoxy (C/Ep) composites is investigated, considering FP as a viable route for the additive manufacturing (AM) of thermoset composites. Neat epoxy (Ep) resin-, short carbon fiber (SCF)-, and continuous carbon fiber (CCF)-reinforced composites are considered in this study. The evolution of the exothermic reaction temperature, polymerization frontal velocity, degree of cure, microstructures, effects of fiber concentration, fracture surface, and thermal and mechanical properties are investigated. The results show that exothermic reaction temperatures range between 110 °C and 153 °C, while the initial excitation temperatures range from 150 °C to 270 °C. It is observed that a higher fiber content increases cure time and decreases average frontal velocity, particularly in low SCF concentrations. This occurs because resin content, which predominantly drives the exothermic reaction, decreases with increased fiber content. The FP velocities of neat Ep resin- and SCF-reinforced composites are seen to be 0.58 and 0.50 mm/s, respectively. The maximum FP velocity (0.64 mm/s) is observed in CCF/Ep composites. The degree of cure (αc) is observed to be in the range of 70% to 85% in FP-processed composites. Such a range of αc is significantly low in comparison to traditional composites processed through a long cure cycle. The glass transition temperature (Tg) of neat epoxy resin is seen to be approximately 154 °C, and it reduces slightly to a lower value (149 °C) for SCF-reinforced composites. The microstructures show significantly high void contents (12%) and large internal cracks. These internal cracks are initiated due to high thermal residual stress developed during curing for non-uniform temperature distribution. The tensile properties of FP-cured samples are seen to be inferior in comparison to autoclave-processed neat epoxy. This occurs mostly due to the presence of large void contents, internal cracks, and a poor degree of cure. Finally, a highly efficient and controlled FP method is desirable to achieve a defect-free microstructure with improved mechanical and thermal properties.

Effect of SiC nanoparticles on mechanical and damping properties of epoxy/polysulfide rubber blend composite

Blend polymer matrix composite material are becoming more and more popular due to their promising mechanical properties. In this research, blend polymer mixture was make from epoxy resin (EP) blended with different weight percentages of polysulfide rubber (PSR) (0, 3, 6, 10, 15, and 20%). Then tensile, impact, bending strength and damping ratio were evaluated to get the high quality of mechanical properties for the blend matrix. Due to the requirements to enhance the mechanical properties of this blend; a various weight fraction of carbide silica (SiC) nanoparticle was used as a reinforcement in the ratios of (0, 1, 3, and 5%) by weight to the best ratio of the blended matrix. Tensile, impact, bending and damping ratio tests were also conducted to get the best mechanical properties for the blend materials. Experimental results for the blend matrix showed that adding polysulfide rubber to epoxy resin resulted in a decrease in Young’s modulus, tensile strength, and bending strength; however damping ratio and the impact strength increased. It is found that the weight fraction of 6% of PSR is the Better case, which gave the better mechanical characteristics properties for mixture. Utility of this mixture; it has intermediates between flexible properties of a mixture at the highest rate of PSR and brittle mechanical properties for EP resin. Mechanical and damping properties showed an increasing when the carbide silica (SiC) with a weight fraction of 3% added, then it decreased slightly.

Cyano group‐containing DOPO derivative for improving the flame retardancy, smoke suppression, and mechanical properties of epoxy resins

AbstractIn order to obtain an efficient flame retardant and smoke suppressor without sacrificing mechanical properties of epoxy resin (EP). A cyano group‐containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivative (CP‐DOPO) was proposed and synthesized through one‐step Atherton–Todd reaction between DOPO and 4‐cyanophenol. The comprehensive performance analysis of CP‐DOPO‐based EP composite was conducted by measuring the flame retardancy, smoke suppression, and mechanical properties. The flame‐retardant test findings shows that the EP/4CP‐DOPO sample achieves UL‐94 V‐0 rating with 4 wt% low addition of CP‐DOPO. Moreover, EP/6CP‐DOPO sample presents a LOI of 36.5%, a 28.1% reduction in the peak heat release rate, and a 42.1% substantial decrease in total smoke production, demonstrating its desirable flame retardancy and smoke suppression properties. Significantly, different from the traditionally additive flame retardants, the mechanical properties of EP matrix will not be affected by the incorporation of CP‐DOPO but a 17.7% increasement of flexural properties compared to EP. This research not only provides an ingenious strategy for designing and preparing high‐effective flame retardant but also enhances the comprehensive performance of EP resins in practical applications.

Enhanced thermal conductivity of epoxy resin by incorporating three-dimensional boron nitride thermally conductive network.

Packaging insulation materials with high thermal conductivity and excellent dielectric properties are favorable to meet the high demand and rapid development of third generation power semiconductors. In this study, we propose to improve the thermal conductivity of epoxy resin (EP) by incorporating a three-dimensional boron nitride thermally conductive network. Detailedly, polyurethane foam (PU) was used as a supporter, and boron nitride nanosheets (BNNSs) were loaded onto the PU supporter through chemical bonding (BNNS@PU). After immersing BNNS@PU into the EP resin, EP-based thermally conductive composites were prepared by vacuum-assisted impregnation. Fourier transform infrared spectrometer and scanning electron microscope were used to characterize the chemical bonding and morphological structure of BNNS@PU, respectively. The content of BNNS in BNNS@PU/EP composites was quantitatively analyzed by TGA. The results show that the thermal conductivity of the BNNS@PU/EP composites reaches 0.521 W/m K with an enhancement rate η of 30.89 at an ultra-low BNNS filler content (5.93 wt. %). Additionally, the BNNS@PU/EP composites have excellent dielectric properties with the frequency range from 101 to 106Hz. This paper provides an interesting idea for developing high thermal conductivity insulating materials used for power semiconductor packaging.

Interlayer growth of SiC nanowires in graphene aerogel for thermal conductivity enhancement of epoxy resin and its mechanism

AbstractThe chemical reduction method is a simple and popular way to contrast the graphene network to improve the polymer matrix's thermal conductivity. And hybrid thermal conductive fillers composed of two or more mixed fillers through chemical synthesis usually have better thermal conductivity because of the synergistic effort. In this work, silicon carbide nanowires (SiC NWs) in graphene aerogels are synthesized with the chemical vapor deposition method, acting as bridges for phonon transmission between adjacent graphene sheets. The RGO/SiC NWs aerogel‐endowed EP composites have a high thermal conductivity of 3.79 W/mK at a filler loading of 5.5 wt%, and 4.23 W/mK at a filler loading of 7.5 wt%, which is 1895% and 2126% higher than pure EP resin, respectively. Finite element analysis (FEA) is utilized to analyze the heat conduction mechanism of composites at last.

Influence of epoxy resin species on the curing behavior and adhesive properties of cyanate Ester/Poly(aryl ether nitrile) blends

In this study, four different bisphenol A glycidyl ether epoxy resins (E06, E12, E20, and E44) with varying epoxide equivalents were utilized to investigate their effect on the curing behavior, mechanical, thermal, and adhesive properties of bisphenol A cyanate ester (ACE)/fluorinated poly(aryl ether nitrile) (PFPEN) blends. The differential scanning calorimetry (DSC) results revealed that the use of epoxy resin reduced the curing temperature and activation energy of the modified resin system. The hydroxyl and epoxy groups in the EP resin respectively facilitated the polymerization of cyanate group and the formation of oxazoline and oxazolidone structures, instead of rigid triazine rings. This, in turn, improves the toughness of the cross-linked network structure. Rheological analysis showed that the EP resin could reduce crystallinity in the modified resin and improve low-temperature processing performance. Comparatively, E20/PFPEN/ACE showcased a significant increase in both tensile and impact strength, reaching 74.6 MPa and 19.35 kJ/m2, respectively. Likewise, shear strength and peel strength at room temperature showed an improvement by 18.7% and 20.7%, respectively, when compared to the pure PFPEN/ACE system. Overall, this modified resin exhibits relatively good comprehensive properties and could be used for high-performance adhesives and resin matrix 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.

Tri-source integrated adenosine triphosphate loaded BN in synergy with Cu-MOF to improve the fire safety of epoxy resin

The volume expansion of the char layer during combustion can effectively isolate the external flame and heat. However, the contribution of conventional flame retardants to the volume increase is largely negligible. Adenosine triphosphate (ATP), as a bio-based macromolecule, contains both acidsource, carbon source and gas source groups in its structure, which determines the ability of these groups to synergistically promote the formation of swollen residual carbon at high temperatures, resulting in a good flame retardant effect. Here, a novel and highly efficient organic–inorganic composite flame retardant was achieved by coupling ATP with BN using polydopamine (PDA) as a medium and anchoring Cu-MOF nanoparticles uniformly on its surface. Among them, the high barrier of BN imparted the EP resin and residual carbon excellent heat shielding properties, the presence of ATP facilitated the formation of expanded carbon slag. Besides, the metal ions in Cu-MOF promote the conversion of more cracking products to residual carbon, while the microporous structure of MOF has an appreciable adsorption effect on the flue gas. The results showed that compared to EP, the THR and PHRR for BN/PATP@Cu-MOF/EP decreased by 32.0% and 41.3%, separately. Moreover, the PSRP, TSP, PCOPR and PCO2PR values of BN/PATP@Cu-MOF/EP were visibly lower than those of other specimens, decreasing to 0.226 m2/s, 20.43 m2/s, 0.081% and 0.73%, accordingly, justifying its most optimal fume suppression effect. According to the condensed phase and gas phase flame retardant principle, the synergism of BN, ATP and Cu-MOF leading to the construction of an expanded coal network having greater strength and barrier properties, which is the key to reduce heat release and smoke generation. This study opens the door to new swellable flame retardants and provides a new effective way for flame retardant modification of polymers.

Enhancements in LOX compatibility and fracture toughness of carbon fiber/epoxy composite for liquid oxygen cryotank by simultaneously introducing Al(OH)3 and phosphorous-nitrogen flame retardants

Simultaneously enhancing the liquid oxygen (LOX) compatibility and fracture toughness at the cryogenic temperature of carbon fiber reinforced epoxy (CFRE) composites is critical for their successful application in LOX cryotanks. Herein, based on our previous work on optimizing the phosphorous-nitrogen containing organic flame retardant (TAD) content in epoxy resin for achieving the best LOX compatibility, the EP resins and CFRE composites modified with further incorporating inorganic flame retardant Al(OH)3 were fabricated. Specifically, the effects of introducing Al(OH)3 particles on the LOX compatibility and mechanical performances particularly at 90 K were thoroughly investigated. The results indicate that the Al(OH)3/TAD-EP resin (hence CFRE composite) with 4 phr Al(OH)3 exhibits an outstanding LOX compatibility without any impact reaction of burning, explosion, flash and charring observed in 20 samples. Moreover, the mode II fracture toughness of CFRE composites at room temperature and 90 K is improved by 27.3% and 16.7%, respectively with the addition of 4 phr Al(OH)3. Benefited with the simultaneous incorporation of 15 phr TAD and 4 phr Al(OH)3, the CFRE composite is promising for application in LOX tanks.

Synthesis of silylamine and siloxyamine compounds: A novel approach to flame retardancy of polypropylene and Epoxy resins

A series of innovative flame retardants containing N-Si and N-O-Si bonds have been synthesized. Their chemical structures were verified by nuclear magnetic resonance (NMR) spectroscopy and thermal stabilities determined by thermogravimetric analysis (TGA). The results indicate that their thermal and hydrolytic stabilities could be adjusted by fine tuning their silylamine (N-Si) and siloxyamine (N-O-Si) skeletons. Thus, the substituents bonded to the phthalimides, such as diphenylmethylsilyl, dimethylphenylsilyl, diphenyl‑tert-butylsilyl, triisopropylsilyl or diphenylmethylsiloxy; whichever was attached to the imide played a significant role on its thermal and hydrolytic properties. Upon thermal dissociation, the N-Si and N-O-Si compounds were shown to yield aminyl, silyl and oxygen-centered radicals that provided fire proofing effect in polypropylene (PP) films alone and a synergistic effect in combination with conventional phosphorous flame retardant in PP, linear low-density polyethylene (LLDPE) and epoxy resins (EP). Their efficacy as flame retardants alone in thin PP films were evaluated according to the DIN4102-B2 test. Both N-Si and N-O-Si significantly slowed down the burning of PP films. Moreover, their potential as adjuvants with a conventional phosphorous based flame retardant, i.e., spirocyclic phosphonate (AFLAMMIT® PCO 900) in PP and EP resins was evaluated according to the UL-94 V fire standard. A synergistic effect was observed when the phosphorous flame retardant was combined with either N-Si or N-O-SI containing compounds, since none of the flame retardants by themselves could provide V-0 rating in the UL94-V test in PP, LLDPE or EP resins even at much higher loadings. The thermogravimetric analysis carried out under inert atmosphere revealed enhanced and earlier onset of decomposition and thermal activation of phosphorous based flame retardant in the presence of N-Si or N-O-Si in comparison to spirocyclic phosphonate, N-Si or N-O-Si used alone, respectively. The interaction of the phosphorus flame retardant with N-Si was verified by 31P NMR.

Novel multifunctional microcapsule and its cyanate ester resin composites with self‐healing ability and gamma radiation shielding ability

AbstractResin‐based composites used in spacecraft face risks from space debris and high‐energy charged particles during their long‐term service in the space environment. This work proposes a novel microcapsule (MC) and its cyanate ester (CE) resin‐based composites (CE/MCs) with self‐healing ability and gamma radiation shielding ability. The multifunctional epoxy/lead tungstate (EP@PWO) microcapsules are developed through self‐assembly method and in‐situ precipitation method. These microcapsules and curing agent 4,4′‐diaminodiphenylsulfone (DDS) are incorporated into the CE resin to form resin‐based composites with low curing temperature, self‐healing ability, and gamma radiation shielding ability. Various approaches including chemical characterizations (X‐ray diffractometer, fourier‐transform infrared, energy dispersive spectrometer), microscopy (optical microscope, scanning electronic microscope), and thermal analysis (differential scanning calorimeter, thermogravimetric analysis) are utilized to demonstrate the successful encapsulation of the EP resin by PWO shell and good thermal stability of this material. The mechanical property, self‐healing ability, and gamma radiation shielding property are investigated via fracture toughness test and using a NaI (Tl) spectrometer. In comparison with pure CE resin, the fracture toughness of the CE/MCs composites can increase by 66.5%, and the self‐healing efficiency can reach up to 56%, indicating that the microcapsules have good toughening and self‐healing abilities. The microcapsules and their composites also exhibit good gamma radiation shielding properties.

Transparent, flame retardant, mechanically strengthened and low dielectric EP composites enabled by a reactive bio-based P/N flame retardant

• A reactive bio-based P/N flame retardant (named VTP) as a multifunctional additive was prepared successfully. • VTP simultaneously improved the flame retardancy, glass-transition temperature and dielectric properties of EP. • EP/VTP composites exhibited the excellent smoke suppression and improved mechanical properties. With the application of epoxy resin (EP) in high-end fields such as electronics and appliances, 5 G communication, rail transit interior decoration and so on, the requirements of flame retardant, lightweight and high performance are also put forward for EP products. Thus, it is of great significance to prepare EP composites with excellent comprehensive properties. For the sake of achieving this target, we synthesized a reactive bio-based P/N flame retardant (named VTP) as a multifunctional additive to develop high-performance EP composites with excellent flame retardance, mechanical properties, transparency and thermal oxidation stability. As expected, VTP possessed excellent flame-retardant efficiency thanks to the synergism of tetrazoles, phosphaphenanthrene and vanillin, only 5 wt% of which made EP/VTP-5% sample achieve UL-94 V-0 rating, increased limiting oxygen index (LOI) value to 30.5%, and reduced the peak of heat release (PHRR) and total smoke production (TSP) by 36.1% and 37.9% respectively. Besides, the tensile strength and glass transmission temperature (T g ) of EP/VTP composites were increased as compared to unmodified EP, as well as high transparency was retained. This work provided a very good idea and experimental basis for the preparation of high-performance EP resin.

Nanoarchitectonics of BN/AgNWs/Epoxy Composites with High Thermal Conductivity and Electrical Insulation.

To promote the construction of the thermal network in the epoxy resin (EP), a certain proportion of silver nanowires (AgNWs) coupled with the hexagonal boron nitride (BN) nanoplates were chosen as fillers to improve the thermal conductivity of EP resin. Before preparing the composites, BN was treated by silane coupling agent 3-aminopropyltriethoxysilane (KH550), and AgNWs was coated by dopamine hydrochloride. The BN/AgNWs/EP composites were prepared after curing, and the thermal conductivity and dielectric properties of the composites was tested. Results showed that the AgNWs and BN were uniformly dispersed in epoxy resin. It synergistically built a thermal network and greatly increased the thermal conductivity of the composites, which increased 9% after adding AgNWs. Moreover, the electrical property test showed that the addition of AgNWs had little effect on the dielectric constant and dielectric loss of the composites, indicating a rather good electrical insulation of the composites.

High-strength and toughness carbon nanotube fiber/resin composites by controllable wet-stretching and stepped pressing

Carbon nanotubes (CNTs) have been used as reinforcements for various composites due to their excellent mechanical properties. However, CNTs have widely suffered from heterogeneous distribution and poor alignment in the composites. To tackle these issues, we herein report an effective strategy towards preparing highly orientated CNT/epoxy (EP) composites from CNT fibers. That is, CNT fibers were continuously soaked and stretched in an EP resin solution and winded into a film on a drum. During this process, the EP resin was infiltrated and the CNTs were aligned simultaneously, leading to a highly uniform and orientated composite. Stepped pressing before formal curing was further utilized to improve the distribution of the EP resin, the densification and thus the internal bonding strength of the composite. The final CNT/EP composite showed a high tensile strength (3.5 GPa) and toughness (80.2 J cm−3), appearing superior to those for previous CNT and carbon fiber reinforced composites.

Toughening of epoxy resin with balanced performance by in situ constructing interfacial bonding and elastic segments into epoxy network

Solid rubber-toughened epoxy resin (EP) has important theoretical and application value. However, the compatibility between solid rubber and EP is usually poor, leading to severe phase separation and consequently poor toughening effect. In this work, ethylene-glycidyl methacrylate-vinyl acetate solid rubber (EGVA) was functionalized with carboxyl groups (EGVA-COOH) and amino groups (EGVA-NH2), which was confirmed by 1H NMR, and used as reactive tougheners for EP systems. All functionalized EGVA rubbers can react with EP molecules to form the EGVA-g-EP, resulting in better compatibility between the EP matrix and the EGVA. Furthermore, the functionalized EGVA can react with EP matrix to incorporate into the final EP network to form a co-network, which greatly improve the compatibility between the EP matrix and EGVA. As a consequence, the EGVA particle size was reduced by a factor of 71.4%, and the impact toughness of EP resin with 5 phr EGVA-NH2 was increased by 130% without sacrificing the tensile strength and heat resistance. Theoretical analysis indicated that critical stress intensity factor (KIc) and critical strain energy release rate (GIc) of EP were 158% and 341% higher than that of neat EP, respectively. Therefore, this work provided a novel route for producing EP-based thermosets with balanced strength and toughness by in situ constructing interfacial bonding and elastic segments into epoxy network, which could broaden the application range of solid rubber in the field of epoxy toughening.

Functionalized graphene with Platelet-like magnesium hydroxide for enhancing fire safety, smoke suppression and toxicity reduction of Epoxy resin

With the rapid development of Graphene based hybrid materials, various of them were fabricated to improve the fire safety of EP. However, the effect of GO content in the hybrid material on flame retardancy of EP composites is rarely reported. In order to find the optimal ratio of GO/Mg(OH)2, platelet-like Mg(OH)2 functioned graphene (GPM) were synthesized with diverse content GO substance and then presented into EP resin for improving its fire retardancy. Various characterizations confirmed its composition, structure and morphology. The incorporation of GPM contains about 1% GO increased the tensile strength by 31.6% compared to that of untreated Mg(OH)2. The GPM contains about 5% GO exhibited the finest fire safety in various EP composites. The fire-retardant assessments illustrated that the limiting oxygen index (LOI) of EP composite with 3 wt% GPM progressed to 27.8% compared with virgin EP (24.4%). In parallel, compared to virgin EP, the peak heat release rate, peak smoke production rate, total smoke production and peak CO production rate of EP/5GPM were diminished by 50.9%, 44.0 %, 25.5% and 53.1%, separately. The mechanism investigation revealed that the prominent flame retardancy and smoke suppression were attributed to the physical barrier of GO, the endothermic decomposition of Mg(OH)2, the barrier effect of MgO and synergistic effect between GO and Mg(OH)2 toward the optimized carbonization. In perspective, hierarchical platelet structure with synergistic effect offered an effective approach for the fire-safe polymer.

The Dielectric Properties and Thermal Conductivities of Epoxy Composites Reinforced by Titanium Dioxide

To improve the dielectric properties and thermal conductivities of epoxy resins (EP), titanium dioxide superfine powders with microspheres structure (S-TiO2) were prepared via a hydrothermal process based on the sodium dodecyl benzene sulfonate and hydroxyl silicate. The different content of S-TiO2 was then employed as modifiers to add into EP resin to prepare the S-TiO2/EP composites. The structure and morphology of the prepared S-TiO2 was observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and influences of different addition of S-TiO2 on the thermal conductivity of S-TiO2/EP composites are researched, while their dielectric constant and dielectric loss are also studied. The results suggested that the reasonable content of S-TiO2 can endow the S-TiO2/EP composites with higher dielectric constant without excessive increase their dielectric loss even under the high frequency. Furthermore, the thermal conductivity of S-TiO2/EP are also be improved, which can be attributed to the good thermal conductivity of S-TiO2 itself and the thermal conductivity path formed by S-TiO2 inside the EP matrix.

Effect of gamma and neutron irradiation on properties of boron nitride/epoxy resin composites

Improving the radiation resistance of epoxy resin (EP) is pivotal for the reliability of equipment and the safety of facilities in the nuclear industry. Hexagonal boron nitride (h-BN) is attractive in the preparation of radiation-resistant materials due to its good radiation stability and neutron shielding capability. In this work, h-BN/EP composites with enhanced radiation resistance were fabricated by solution blending. The tensile strength and thermal properties of the composites after γ-ray and neutron irradiation were investigated. The results showed that the addition of h-BN improved the mechanical property and the glassy transition temperature of the resin. The presence of low-level h-BN was favorable to enhance the radiation resistance of EP. As for composites with the 0.05% mass percentage of h-BN, the absorbed dose required to decrease relative tensile strength by 50% was about 300 kGy, which was higher than that of neat EP. The intrinsic mechanism of radiation resistance was attributed to the oxygen barrier effect as investigated by XPS and EPR. Then, benefiting from the absorbing neutrons capability of boron atoms, an addition of 0.55% h-BN to the EP resin could reduce the neutron transmittance of the resin by 5.6%. This study demonstrates that the blending with h-BN can increase the radiation-resistant property of EP resin, meanwhile augmenting the neutron shielding ability.