EP Composites Research Articles

Bioderived Bilayer Shell Modification β‐FeOOH Nanorods via Self‐Assembly Technique as Sustainable Flame Retardants for Enhancing Flame Retardancy of Epoxy Resin

AbstractThe design and application of bioderived flame retardants have been widely conducted to meet the concept of green and sustainable development. Here, self‐assembly technique is used to prepare core–shell bioderived additives by using β‐FeOOH as the core and polydopamine (PDA)/tannic acid (TA) bilayer as the shell, following adsorption of nickel ions to enhance the thermal stability, flame retardancy, and mechanical properties of epoxy resin (EP). The molecular structure of biobased resources is rich in hydroxyl groups and carbon content, which can be dehydrated and carbonized during combustion and promote the formation of robust protective char layer. With the addition of 5 wt% β‐FeOOH@PTNi, the EP composites can pass V‐0 rating in the UL‐94 test. The peak heat release rate and total heat release decrease by 28.4% and 17.4% compared with pure EP. The bioderived nanorods can capture the oxygen free radicals, contributing to flame retarding in gaseous phase. Thus, the release of high‐toxic CO and flammable gaseous is significantly suppressed. Besides, the storage modulus of EP composites increases by 16.0% with the addition of 5% β‐FeOOH@PTNi compared with pure EP. This work provides a sustainable methodology for the design of bioderived flame retardants for EP.

Synergistic effect of piperazine pyrophosphate and epoxy-octavinyl silsesquioxane on flame retardancy and mechanical properties of epoxy resin

In order to solve the contradiction between the flame retardancy and mechanical properties of epoxy resin, piperazine pyrophosphate (PAPP) and epoxy-octavinyl silsesquioxane (EOVS) are applied as flame retardants for epoxy resin (EP). With the introduction of PAPP and EOVS, the properties of the EP composites about flame retardancy, mechanical properties and smoke suppression are significantly improved. EP/9 wt% PAPP/1 wt% EOVS (EP3) passes a vertical burning (UL-94) test V-0 rating and acquires the limiting oxygen index (LOI) test value of 32.4%. The results of cone calorimeter (CC) tests confirm that the incorporation of PAPP and EOVS significantly reduces the total heat release (THR), peak heat release (PHRR), total smoke production (TSP) and peak smoke produce rate (PSPR) values, which are respectively decreased by 25%, 81%, 57% and 63% compared with those of pure EP. Scanning electron microscope (SEM), energy dispersive spectrometry (EDS), Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS) and Thermogravimetry-Fourier transform infrared (TG-FTIR) spectroscopy are adopted to analyze the flame-retardant mechanism of PAPP/EOVS flame retardants. These results reveal that the flame retardancy of EP3 is attributed to the excellent charring ability, the dilution effect of non-combustible gases and the flame inhibition of gaseous phosphorous compounds. Besides, the tensile and impact strength of EP3 increase benefitting from the presence of epoxy groups and Si-O bonds in EOVS. This work proposes a new method to prepare the mechanically reinforced and flame-retardant epoxy resin.

Novel [BMIM]PF6 modified flake-ANP flame retardant: Synthesis and application in epoxy resin

A novel ionic liquid-modified flake-NiNH4PO4·H2O (IL-ANP) hybrid material was prepared using a mechanochemical method with weak interactions. Characterization methods, including scanning electron microscope, Fourier transform infrared, X-ray diffraction and thermogravimetric analysis indicated the successful synthesis of IL-ANP. The prepared IL-ANP was incorporated into epoxy resin (EP) to improve the flame retardancy and mechanical properties. The limiting oxygen index (LOI) and cone calorimeter tests showed that IL-ANP enhanced the flame retardancy of EP composites. The 6 part per hundred resin (phr) IL-ANP/EP achieved excellent flame retardancy with the LOI value of 30.3% (that of pure EP was 24.4) and a significant decrease in the peak heat release rate, total heat release rate and the maximum release rates of CO production. This is attributed to the synergistic effect of the condensed phase and gas phase. During combustion, IL-ANP generated an incombustible gas (ammonia gas), nickel phosphate and nickel phosphide. On one hand, the incombustible gas diluted the concentrations of the combustible gas and oxygen in the gas phase. On the other hand, the phosphorus compounds catalyzed the carbonisation of EP to form a stable char layer and accumulated on the char layer surface as a physical barrier to delay the heat release. Additionally, the IL-ANP/EP composites exhibited excellent tensile strength, elongation at break, and impact strength, owing to their good compatibility and dispersion.

Synthesis of a bio‐based piperazine phytate flame retardant for epoxy resin with improved flame retardancy and smoke suppression

AbstractPiperazine phytate (PIPT), a bio‐based nitrogen‐phosphorus containing flame retardant, was feasibly synthesized by the reaction of piperazine (PI) with phytic acid (PA) in ethanol. The structure and chemical composition of PIPT were systematically characterized by NMR, FTIR, XRD, TEM and EDX. Epoxy resin (EP) composites with PIPT were prepared by utilizing 4, 4′‐diaminodiphenylmethane as a curing agent. The flame retardancy, mechanical performances and thermal decomposition of the EP composites were studied. The results show that the EP composite containing 15 wt% PIPT (sample EP/15PIPT) passes UL‐94 V0 rating with a limiting oxygen index reaching 35.5%. The cone calorimetric tests results demonstrate the peak heat release rate and total smoke release of EP/15PIPT are about 51.4% and 44.9% reduced than which of pure EP, respectively. The morphology of residual char reveals that the EP/ PIPT composites can form good and compact char during the combustion. In comparison with pure EP, the mechanical performances of the EP/PIPT composites decrease slightly as PIPT content increases.

A new recycling strategy for preparing flame retardants from polyphenylene sulfide waste textiles

In this paper, the waste polyphenylene sulfide (PPS) filter bag was converted to waste PPS powder through thermal aging, ball milling and screening, and firstly used as flame retardant to improve the flame retardance of epoxy resin (EP). TG results presented that, it started to decompose at 510.6 °C with 62.08% of residue mass at 800 °C, which showed good charring ability. The UL-94 and cone calorimeter tests showed that waste PPS not only improved the flame retardance of EP but also largely decreased heat and smoke/toxic gases release. Adding 15 wt% waste PPS made EP composites acquire a UL-94 V-1 rating and resulted in a 42.24% reduction in the peak of heat release rate (PHRR). What’ more, the peak of smoke production rate (PSPR) and peak of CO production (PCOP) declined by 27.27% and 45.16%. The morphology of char residue was also observed by scanning electron microscope (SEM), and it was concluded that, introduction of waste PPS indeed improved the compact of char layer, which was be responsible for enhancement in flame retardance. This work provided a new way and theoretical basis for realizing high value recycling of PPS solid waste.

Green self-assembly of h-BN@PDA@MoS2 nanosheets by polydopamine as fire hazard suppression materials

The design of biobased resources to combine two-dimensional (2D) materials organically to design flame-retardant epoxy resin (EP) meets the requirements of green and sustainable development. The pH-switchable characteristics of the polydopamine (PDA) layer are used in this study as a green bridge to prepare the h-BN/MoS2 assembly via electrostatic force (h-BN@PDA@MoS2). The PDA layer containing amine groups at low pH had a positive charge and excluded cations but passed anions, which provided favorable conditions for self-assembly. The chemical structure and morphology were determined by a series of measurements. h-BN@PDA@MoS2 assembly could enhance thermal stability, flame retardancy, and mechanical strength of EP composites significantly. Compared with pure EP, the addition of 2.0 wt% h-BN@PDA@MoS2 resulted in a 32% and 17.8% decrease in peak heat release rate and total heat release of EP composites. The amount of toxic CO and flammable gas production during combustion was also significantly suppressed. PDA as an adhesive could exert the synergistic flame retardant effort of h-BN and MoS2 nanosheets. Moreover, the h-BN@PDA@MoS2 assembly could form strong interactions with the EP matrix and increase the graphitization degree of char residues. This study provided a novel green route to assemble 2D materials efficiently and promoted its application in the high-performance polymer composites.

Superior radical scavenging and catalytic carbonization capacities of bioderived assembly modified ammonium polyphosphate as a mono-component intumescent flame retardant for epoxy resin

Combining biobased resources for fabricating intumescent flame retardant (IFR) systems is an promising approach for producing completely green flame retardants. Herein, ammonium polyphosphate (APP) particles were used as templates in the loading of an ATNi assembly on the basis of the electrostatic interactions among tannic acid (TA), adenine, and Ni2+ for the production of an all-in-one IFR (APP@ATNi). The incorporation of APP@ATNi can form hydrogen bonds in the EP matrix and improve the thermal conductivity and mechanical properties of the composites. When the mass of APP@ATNi reached 15 wt%, the EP composites had an LOI value of 33.5% and a V-0 rating. Total heat release and total smoke production were reduced by 29.1% and 47.2%, respectively. The HRR curves indicated the unique characteristics of the IFR system, and the characterization of condensed and gas phases showed that APP@ATNi formed a protective char layer. The bioderived assembly scavenged oxygen free radicals, catalyzed the formation of the char layer, and generated nonflammable gas, which protected the EP matrix during the combustion process. This study provides guidelines for designing bioderived IFR systems and is expected to promote the application of biobased resources in flame retardant production.

Enhanced interfacial interactions of carbon fiber/epoxy resincomposites by regulatingPEG‐E51and graphene oxide complex sizing at the interface

AbstractA method of using modified epoxy resin (PEG‐E51) and graphene oxide (GO) as sizing agent in different pH has been proposed and applied to improve the interfacial interactions and bonding of carbon fiber (CF) reinforced epoxy resin‐based (EP) composites. The PEG‐E51 and GO complex sizing in different pH is prepared and then coated on CF surfaces homogeneously. The sizing layer forms on the fiber surfaces, and multiple GO sheets are introduced successfully surrounding the CFs. The surface morphologies of CFs change distinctly with different pH. The interfacial shear strength increases from 51.36 MPa for bare fiber‐reinforced EP composites to 66.62 MPa for composites reinforced by CFs coated with GO only. However, a significant improvement is achieved when the pH is adjusted to 10, making the interfacial shear strength grow up to 77.23 MPa. Furthermore, scanning electron microscopy results and interlaminar shear strength test are in agreement with each other, suggesting better interface bonding of composites by regulating pH of PEG‐E51 and GO complex sizing. Besides, the interfacial interaction mechanism in CF reinforced composites is also explored, that is, the positive effects of roughness and specific surface area in complex interfacial layers lead to the improvement of interfacial properties.

Enhanced fire safety and mechanical properties of epoxy resin composites based on submicrometer-sized rod-structured methyl macrocyclic silsesquioxane sodium salt

Facile synthesis of multifunctional macromolecules endowed with low cost has always been a considerable challenge for chemists. Herein, a series of methyl macrocyclic oligomeric silsesquioxane sodium salt (Na-MOSS) were synthesized via the simplified one-pot method. FTIR, NMR, MALDI-TOF MS and XRD results suggested that Na-MOSS endowed with well-defined macrocyclic structure and highly crystalline. The directly obtained Na-MOSS powder crystals were proved to be submicrometer rod-like morphology. TGA results indicated that the initial decomposition temperature and residual weight at 800 °C of Na-MOSS were 427 °C and 89.6%, respectively. These results implied that Na-MOSS enjoyed superior thermal stability. Notably, we firstly discovered that the pyrolysis condensed products of Na-MOSS could react with N2. Thereafter, the synthesized Na-MOSS was introduced into epoxy resin (EP) to improve the fire safety and decrease smoke hazards. Based on the cone calorimeter test results, with the incorporation of 2 wt% Na-MOSS, the peak of smoke production rate (p-SPR) and total smoke production (TSP) of EP/2 wt% Na-MOSS were apparently decreased by 50% and 36% compared with EP. Additionally, the storage modulus, flexural strength and modulus values of EP/Na-MOSS were higher than EP. The incorporation of Na-MOSS can apparently reduce the dielectric constant and loss of composites. These results indicate that EP/Na-MOSS enjoy better flame retardant, dielectric and mechanical properties and is more suitable for practical applications. Overall, our findings provide a class of overwhelmingly promising multifunctional rod-like macrocyclic organic–inorganic hybrid materials. Such materials can alleviate fire hazards and improve mechanical performance of EP composites.

A facile crosslinking strategy endows the traditional additive flame retardant with enormous flame retardancy improvement

With great chemical and physical properties, epoxy resins (EPs) are used almost everywhere in life and engineering, but poor flame-retardant performance hinders them for a wider use. Traditional flame retardants (the most commonly used and researched) usually have dispersion and migration problems (additive ones) or are difficult to synthesize (reactive ones). Herein, a facile crosslinking strategy is used to make traditional additive flame retardants exhibit much better properties. Firstly, a nitrogen/phosphorus containing additive flame retardant with nitrile groups is designed, successfully synthesized, and directly mixed with EP matrix, the secondary crosslinking reaction of nitrile groups inner the flame retardants will occur in cured EP thermosets which was driven by a facile thermal treatment procedure. Then the properties of the flame retardant mixed and crosslinked EP composites are measured by limiting oxygen index (LOI) test, thermogravimetric analyses (TG), UL-94 vertical burning tests, dynamic mechanical analysis and cone calorimeter test, the results show that the crosslink of the additive flame retardant greatly improved the flame-retardant properties, and with 20 wt% loading content of the crosslinked flame retardant, the LOI value reach 46.2% and the peak heat release rate decreases for 77.4% compared with neat EP, furthermore the heat resistance and dynamic mechanical property of the crosslinked samples also get promoted compared with the physical mixed ones.

Synthesis of a Flame Retardant for Epoxy Resins: Thermal Stability, Flame Retardancy, and Flame-Retardant Modes

Abstract A polyphosphonate (PDPA) flame retardant that contains phenyl phosphonic dichloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide groups, has been synthesized. The flame retardant was introduced into epoxy resins (EP) and cured by 4,4’-diamino diphenylmethane. The vertical burning, limited-oxygen index and cone calorimeter tests reveal that the PDPA can enhance the flame-retardant properties of the EP significantly. With only a 4 wt% PDPA loading, the EP composites achieved a limited-oxygen index value of 33.4% and a V-0 rating in the vertical burning test, and the peak heat release rate and total heat release were decreased by 40.9% and 24.6%, respectively. The thermal properties and gas pyrolysis products of the EP composites were evaluated by thermogravimetric analysis and thermogravimetric analysis-Fourier transform infrared spectroscopy, and the morphology and structure of residual char were characterized by scanning electron microscopy, Flourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. To explain the combined effects of the condensed and gas phases, modes of the flame-retardant action are proposed.

A phosphate covalent organic framework: Synthesis and applications in epoxy resin with outstanding fire performance and mechanical properties

To prepare epoxy resin (EP) with satisfied fire performance and mechanical properties, a novel phosphoric acid modified triazine covalent organic framework (PCOF) was successfully synthesized. The structure and microtopography of PCOF were fully characterized. By the presence of 12wt% PCOF, the limiting oxygen index value of EP composite was increased from 24.8% to 28.6%, and V-0 rating was achieved in UL-94 vertical burning test. The cone calorimeter test showed that the peak heat release rate and total heat release of the 12PCOF-EP sample were decreased sharply by 78.9% and 68.9% compared with that of the control EP. The flame retardant effect was maintained after soaked in 75 °C for 168 h, indicating an excellent water resistance. The thermogravimetric analysis of the composites indicated that more char residue was formed, especially at a high-temperature range. Moreover, both the tensile and impact properties of EP composites were improved by adding appropriate amount of PCOF. By analyzing the products formed during combustion, it was proposed that PCOF took effects in both gas and condensed phase.

Improvement in the charge dissipation performance of epoxy resin composites by incorporating amino-modified boron nitride nanosheets

To restrain the surface charge accumulation of the epoxy resin (EP) applied in the high-voltage power field, one of the efficient methods is to dissipate the charges on the EP surface by incorporating inorganic filler. In this work, we employed amine-functionalized boron nitride nanosheets (mBNNS) based on liquid-phase exfoliation and urea modification to prepare EP composites. Owing to the existence of –NH2 groups on the exfoliated mBNNS platelets, the uniform filler dispersion and good filler-matrix compatibility were achieved in the EP composites. As compared to the pure EP, the EP/mBNNS composites exhibited better charge dissipation performance, comparable dielectric constant and higher breakdown strength. The best charge dissipation performance was achieved in the EP composite by adding only 1.0 wt% mBNNS with the surface potential decreased by 65.5% in 1200 s, much higher than pure EP (28.1%).

Phosphorylated cardanol-formaldehyde oligomers as flame-retardant and toughening agents for epoxy thermosets

Presently, flammability and brittleness are two major problems for EP which has restricted its development and application in industrial. Under the global advocacy of green and sustainable development, developing bio-based flame-retardant and toughening agents which can endow epoxy resins with high fire resistance and satisfactory mechanical properties is of significant demand for its industrial applications. Herein, three kinds of phosphorylated cardanol-formaldehyde oligomers (CF-PO(OPh)2, CF-POPh2, and CF-PPh2) were synthesized and introduced into epoxy thermosets. The incorporation of CF-PO(OPh)2, CF-POPh2, and CF-PPh2 can remarkably improve the mechanical performance of EP composites, especially the tensile strength and elongation at break. With 10 wt% of CF-PO(OPh)2, CF-POPh2, and CF-PPh2, the tensile strength of epoxy thermosets reached 67.1, 74.5, and 70.3 MPa, respectively; the elongation at break of epoxy thermosets was raised by 133.3%, 162.5%, and 150.0%, respectively, as compared to neat EP. EP composites containing CF-PO(OPh)2, CF-POPh2, and CF-PPh2 also exhibited remarkably enhanced flame retardancy simultaneously. Besides, CF-PO(OPh)2 exhibited the best flame-retardant efficiency by comparison with CF-POPh2 and CF-PPh2, and the results manifested that epoxy composite with only 2.5 wt% CF-PO(OPh)2 could pass the UL-94 V-0 rating as well as a high LOI value of 28%, and the LOI value of EP/CF-PO(OPh)2–10 reached up to 32%. Moreover, CF-PO(OPh)2 also displayed an excellent catalytic charring effect and great suppression effect on heat and smoke release. The cone calorimeter test results showed that EP composite containing 10 wt% CF-PO(OPh)2 exhibited the most significant PHRR reduction which was 53.8% lower than pure EP, and the char yield of EP/CF-PO(OPh)2–10 after the cone calorimeter test was 14.0% which was much higher than that of pure EP (5.7%). This work opens a new vision for the synthesis of bio-based flame-retardant and toughening agents with a special oligomeric structure combining rigidity with flexibility, and contributes to the production of high-performance epoxy thermosets.

Preparation of the organic–inorganic double‐shell microencapsulated aluminum hypophosphite and its improved flame retardancy and mechanical properties of epoxy resin composites

AbstractTo develop the functional particles with better flame‐retardant and compatibility with epoxy resin (EP) matrix, organic–inorganic double‐shell microencapsulated aluminum hypophosphite (MSiAHP) was prepared by situ polymerization. The water contact angles of MSiAHP (62.4°) is significantly larger than that of aluminum hypophosphite (34.4°), which shows that the organic shell material of MSiAHP endows excellent hydrophobicity and water resistance. With the incorporation of MSiAHP, EP/30%MSiAHP composite exhibits limiting oxygen index value of 27.3% and V‐0 rating. Furthermore, the cone calorimetry test reveals that MSiAHP reduces the peak heat release rate, total heat release and total smoke release of EP matrix by 33.3%, 24.4% and 56.6%, respectively. Besides, due to the unique organic–inorganic double‐shell structure of MSiAHP particles, EP/30%MSiAHP composite achieves greater thermal stability and higher char yields than pure EP. The investigation of the products in the gas and condensed phase demonstrates that MSiAHP is beneficial to the generation of a high‐density and compact carbon layer structure with a high graphitization degree, and delay the generation time of pyrolysis products in the gas phase, which can improve the fire safety of EP composites effectively. Furthermore, preeminent dispersion and compatibility of MSiAHP lead to EP/MSiAHP composites with excellent mechanical properties.

Grafting multi‐elements hybrid polymer brushes on graphene oxide for epoxy composite with excellent flame retardancy

AbstractIn this paper, a silicon‐oxygen coupling agent (MPS) with a double bond is hydrolyzed with graphene oxide (GO) to obtain MPS‐GO. The polymerization of MPS‐GO with the phosphorus‐containing monomer (HEPO) is initiated with 2,2′‐Azobis(2‐methylpropionitrile) (AIBN) to obtain multi‐elements hybrid polymer brushes grafting graphene oxide (HM‐GO). As a flame retardant, different amounts of HM‐GO are added to obtain EP composites. In this system, the properties of composite flame retardant obviously increase with the increasing of HM‐GO. The limiting oxygen index (LOI) value of composites with 4 wt% addition of HM‐GO is 31.0%, while the LOI value of EP‐0 is only 23.9%. And the peak heat release rate (PHRR) value is reduced from 515.8 W g−1 of pure epoxy resin to 376.9 W g−1. In addition, with the increase of HM‐GO addition, the Tg value, flexural strength and flexural modulus of EP composites are improved. Through calculation, it is proved that the rising of Tg was due to the increase of crosslink density of the system. The flame retardant performance and mechanical properties of the composite materials are steadily improved, indicating that such flame retardants are dispersed well in the epoxy resin. HM‐GO is an efficient macromolecular modified graphene oxide halogen‐free flame retardant, which can improve both flame retardant properties and mechanical properties.

A Mo‐based metal‐organic framework toward improving flame retardancy and smoke suppression of epoxy resin

In this work, a Mo‐based metal‐organic framework (Mo‐MOF) was first used as flame retardant for epoxy resin (EP). It was found that Mo‐MOF particles showed an excellent dispersion state and good compatibility in the EP matrix. Burning test results showed that the flame retardancy and smoke suppression of EP were obviously improved due to the introduction of Mo‐MOF. Compared with pure EP, 6 wt% Mo‐MOF reduced the values of peak heat release rate (pHRR), peak smoke production rate (pSPR), total smoking production (TSP) and peak CO production rate (pCOP) by 44.7%, 21.8%, 25.1%, and 42.9%, respectively. Moreover, the limited oxygen index (LOI) value of the composites increased from 24.8% to 32.8% compared with the pure EP, and UL‐94 reached V2 rating with no dripping in the vertical burning test. The combustion products of EP composites were also detected and analyzed to obtain the possible flame retardant and smoke suppression mechanisms of Mo‐MOF.

Preparation of silver-plated carbon nanotubes/carbon fiber hybrid fibers by combining freeze-drying deposition with a sizing process to enhance the mechanical properties of carbon fiber composites

A facile method to prepare silver-plated carbon nanotubes (CNTs)/carbon fiber (CF) hybrid fibers that shows significant mechanical properties enhancement functions was proposed. In this method, abundant CNTs were evenly deposited on the CF surface by freeze-drying deposition and tightly attached to the CF surface by the following sizing process. The Ag@CNTs network on the CF surface significantly enhanced the wettability of the hybrid fibers and increased the interfacial mechanical interlocking between the fiber and matrix, thus significantly enhancing the properties of the CFRP composites. Compared with the untreated CF/EP composites, the interlaminar shear strength (ILSS), flexural strength, impact strength, thermal conductivity, and the electrical conductivity in the thickness direction of the C-CF-Ag@CNTs/EP composites were increased by 54.7%, 62.7%, 107.2%, 37.5% and 385.8%, respectively. Such a simple and effective method of preparing silver-plated CNTs/CF hybrid fibers provides great potential in industrial applications.

Synergetic effect of fly ash cenospheres and multi‐walled carbon nanotubes on mechanical and tribological properties of epoxy resin coatings

AbstractThe multiform wear of friction pair components is the main cause of marine equipment failure and epoxy resin (EP) coatings have been widely used in this field. Fly ash cenospheres (FACs) and multi‐walled carbon nanotubes (MWCNTs) were used to reinforce the tribological properties of EP coatings. The synergetic effects of FACs and MWCNTs on the mechanical and tribological properties of EP coatings were studied. Experimental results show that the tensile and flexural properties of FACs‐MWCNTs/EP composites are significantly reinforced. The tribological performance of EP composite coatings under seawater conditions is improved by the synergetic effect of FACs and MWCNTs, especially, the 10 wt.% FACs‐1 wt.% MWCNTs/EP coatings behave the most excellent tribological properties. It indicates that FACs can increase the hardness of EP coatings and provide a smoother surface for the water film formation, which decreases the friction coefficient and wear volume. MWCNTs can increase the elasticity modulus of EP, and act as a rope to prevent EP matrix and FACs from being desquamated.

Facile synthesis of carbon microspheres/tin ethylenediamine tetramethylene phosphonate hybrid for improving the mechanical, flame‐retardant, and thermal properties of epoxy resin

A botryoidal carbon microspheres/tin ethylenediamine tetramethylene phosphonate hybrid (CMS@TETP) was fabricated via a self‐assembly method and was applied to modify epoxy resin (EP) in order to simultaneously improve its mechanical, flame‐retardant, and thermal properties. The mechanical tests' results show that the addition of 1.0 wt% CMS@TETP endows EP with an increase in tensile and impact strengths of 24.4% and 23.1%, respectively, relative to the values of pure EP. The cone calorimeter test results reveal that CMS@TETP has better flame retardancy in EP than either CMS or TETP at the same loading level. In comparison with those of pure EP, the mean heat release rate, peak heat release rate, total heat release, and effective heat of combustion of the EP composite containing 3.0 wt% CMS@TETP (EP/CMS@TETP‐3) are respectively reduced by 49.5%, 59.1%, 47.0%, and 46.1%. The glass transition temperatures of EP/CMS@TETP composites are slightly increased than that of pure EP, indicating an increase in the thermal resistance. Thermogravimetric analysis results provide evidence that CMS@TETP has good char‐forming capacity in EP.