Epoxy/POSS organic–inorganic hybrids: Viscoelastic,mechanical properties and micromorphologies

A series of epoxy resin (EP)/octa(aminpropyl)silsesquioxane (POSS‐NH₂) organic–inorganic hybrid composites (EP/POSS‐NH₂ 100/0, 95/5, 90/10, and 80/20 wt/wt) were prepared by melt casting and then curing. Viscoelastic and mechanical properties of these composites were studied by dynamic mechanical analysis and mechanical testing, respectively. Scanning electron microscopy was used to study of the micromorphologies of the composites and to elucidate the toughening mechanisms of POSS‐NH₂. POSS units incorporated into the epoxy network showed good compatibility with the resin matrix. Phase separation was not observed even at high POSS content (20 wt%). Incorporation of POSS macromer into the epoxy network after curing increased the glass transition temperature, slightly narrowed the temperature range widths of the glass transition, and lowered the intensities of their loss moduli peaks of the resultant composites. The glass transition temperature of EP/POSS‐NH₂ composites increased significantly with increasing POSS content at lower POSS content (<10 wt%), while increased slightly at higher POSS content. Both impact and flexural strengths of the hybrids reached their optimum values when 10 wt% content of POSS was introduced. POLYM. COMPOS., 28:175–179, 2007. © 2007 Society of Plastics Engineers.     

Synthesis,Morphology, and Viscoelastic Properties of Polyhedral Oligomeric Silsesquioxane Nanocomposites with Epoxy and Cyanate Ester Matrices

Octaaminophenyl(T₈)POSS [1, (C₆H₄NH₂)₈(SiO_1.5)₈] and dodecaaminophenyl(T₁₂)POSS [2, (C₆H₄NH₂)₁₂(SiO_1.5)₁₂] were synthesized, characterized and then incorporated into two types of thermoset resins: (1) the bisphenol-F-based cyanate ester resin, PT-15, and (2) epoxy (Epon 828, Shell Chemical Corp.)/4,4′-diaminodiphenylmethane (DDM) resin, respectively, to make two series of nanocomposites. The sum of amino groups in both DDM and POSS were held in a 1:1 mole ratio to the epoxy groups. EPON-828/1/DDM and EPON-828/2/DDM composites (78.63/0/21.37, 77.48/5/17.52, 76.34/10/13.66, 74.05/20/5.95 and 72.28/27.72/0 wt/wt/wt compositions for both series) were prepared. PT-15/1 and PT-15/2 composites (99/1, 97/3 and 95/5 wt/wt compositions for both types) were also prepared. These nanocomposites were characterized by transmission electron microscopy (TEM), dynamic mechanical analysis (DMA), solvent extraction and FT-IR. In all systems, POSS 1 and 2 were chemically bound into the resin matrix and phase-separated POSS particle domains were not observed. Incorporation of both 1 and 2 can dramatically elevate the high temperature bending storage moduli, E′, of epoxy resins.     

Chemical Bonding between Phenolic Resins and Polyhedral Oligomeric Silsesquioxanes (POSS) in Inorganic–Organic Hybrid Nanocomposites

Three classes of inorganic–organic hybrid phenolic resin/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were synthesized. Multifunctional dichloromethylsilylethylheptaisobutyl-POSS (POSS-1), trisilanolheptaphenyl-POSS (POSS-2), and poly(phenylsilsesquioxane) uncured POSS (POSS-3) were employed. Nonfunctional POSS-4 (octaisobuty1-POSS) was blended into the uncured phenolic resin and cured under the same conditions used for the other three nanocomposite classes. Weight ratios of 99/1, 97/3, 95/5 and 90/10 were prepared for the POSS-1, 2 and 4 series and 99/1, 97/3 and 95/5 ratios for the POSS-3 nanocomposites. POSS-1 incorporation into this phenolic resin network increases T _g and broadens the tan peak (DMTA) range. T _g and E′ values at T>T _g both increase with higher POSS-1 content. In contrast, incorporating 5 wt% of POSS-2 into the phenolic resin network lowers T _g to 193 from 213°C for the neat phenolic resin. All values of E′ for POSS-2 composites were higher, than those of the phenolic control in both glassy and rubbery regions. The T _g values of the 1 and 10% POSS-2 systems were higher. Incorporating 10 wt% of POSS-1 or POSS-2 improved the heat distorsion temperature and moduli (E′=123 and 201 GPa at 265°C, respectively, versus 56 GPa for the pure phenolic resin). Increases in E′ for T>T _g and T<T _g were also observed for all POSS-3 nanocomposites. However, the E′ at T>T _g and the T _g values of the POSS-4 composites were lower than those of the control resin. Octaisobutyl POSS-4 cannot form chemical bonds to the resin and could be extracted from its composites with THF. POSS derivatives were not present in residues extracted by THF from the phenolic resins containing POSS-1, 2 or 3, because each of these derivatives were chemically bound within the phenolic resin. Subsequent heating cycles produce much larger increases in T _g and E′ values in the rubbery region for the POSS-1, 2 and 3 composites than for the neat phenolic resin or for the POSS-4 systems. An erratum to this article can be found at     

Preparation of POSS/Quartz fibers/cyanate ester resins laminated composites

Quartz fibers (QFs) and two polyhedral oligomeric silsesquioxane (POSS) (epoxy‐POSS and hydroxy‐POSS) are performed to regulate the dielectric properties, heat resistance, and mechanical properties of cyanate ester (CE) resins. With the introduction of POSS, the dielectric constant and dielectric loss tangent values of the POSS/QFs/CE laminated composites are decreased obviously. The heat resistance properties and flexural strength values of the laminated composites are increased, but the interlaminar shear strength values of the laminated composites are decreased slightly. The EP‐POSS/QFs/CE laminated composites have relatively better dielectric, heat resistance, and mechanical properties than those of HO‐POSS/QFs/CE laminated composites. POLYM. COMPOS., 36:2017–2021, 2015. © 2014 Society of Plastics Engineer     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

Epoxy nanocomposites with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane

The POSS-containing nanocomposites of epoxy resin were prepared via the co-curing reaction between octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) and the precursors of epoxy resin. The curing reactions were started from the initially homogeneous ternary solution of diglycidyl ether of bisphenol A (DGEBA), 4,4′-Diaminodiphenylmethane (DDM) and OpePOSS. The nanocomposites containing up to 40 wt% of POSS were obtained. The homogeneous dispersion of POSS cages in the epoxy matrices was evidenced by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and atomic force microscopy (AFM). Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that at the lower POSS concentrations (<30 wt%) the glass transition temperatures (T_gs) of the nanocomposites almost remained invariant whereas the nanocomposites containing POSS more than 40 wt% displayed the lower T_gs than the control epoxy. The DMA results show that the moduli of the nanocomposites in glass and rubbery states are significantly higher than those of the control epoxy, indicating the nanoreinforcement effect of POSS cages. Thermogravimetric analysis (TGA) indicates that the thermal stability of the polymer matrix was not sacrificed by introducing a small amount of POSS, whereas the properties of oxidation resistance of the materials were significantly enhanced. The improved thermal stability could be ascribed to the nanoscaled dispersion of POSS cages and the formation of tether structure of POSS cages with epoxy matrix.     

Incorporation of metallic POSS,POSS copolymers,and new functionalized POSS compounds into commercial dental resins

An array of polyhedral oligomeric silsesquioxane (POSS) compounds, including metal, methacrylate, and amine functional POSS, and POSS copolymers were incorporated into aromatic and aliphatic dental resins. Heptaphenyl‐propylamine POSS and methacrylate derivatives were synthesized by corner‐capping and Michael addition reactions, respectively. The POSS compounds were tested for solubility in commercial resins at concentrations of 1, 5, 10, and 15 wt %, followed by UV polymerization of all soluble combinations. The POSS compounds generally increased modulus and had an unpredictable effect on T_g. The modulus of the aliphatic resin increased 83% by incorporation of 15 wt % aluminum‐phenyl POSS, while aromatic resins saw a maximum modulus improvement of 18% at 30°C and 72% at 160°C by incorporating 1 wt % of heptaphenyl‐methacrylate POSS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2856–2862, 2006     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

Epoxy‐functionalized polyhedral oligomeric silsesquioxane/cyanate ester resin organic–inorganic hybrids with enhanced mechanical and thermal properties

A series of cyanate ester resin (CE) based organic–inorganic hybrids containing different contents (0, 5, 10, 15 and 20 wt%) of epoxy‐functionalized polyhedral oligomeric silsesquioxane (POSS‐Ep) were prepared by casting and curing. The hybrid resin systems were studied by the gel time test to evaluate the effect of POSS‐Ep on the curing reactivity of CE. The impact and flexural strengths of the hybrids were investigated. The micromorphological, dynamic mechanical and thermal properties of the hybrids were studied by SEM, dynamic mechanical analysis (DMA) and TGA, respectively. Results showed that POSS‐Ep prolonged the gel time of CE. CE10 containing 10 wt% POSS‐Ep displayed not only the optimum impact strength but the optimum flexural strength. SEM results revealed that the improvement of mechanical properties was attributed to the large amount of tough whirls and fiber‐like pull‐outs observed on the fracture surfaces of CE10. DMA results indicated that POSS‐CE tended to decrease E′ of the hybrids in the glassy state but to increase E′ of the hybrids in the rubbery state. TGA results showed that CE10 also possesses the best thermal stability. The initial temperature of decomposition (T_i) of CE10 is 426 °C, 44 °C higher than that of pristine CE. © 2013 Society of Chemical Industry     

Phenolic resin-trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) hybrid nanocomposites: Structure and properties

The structure and properties of organic-inorganic hybrid nanocomposites prepared from a resole phenolic resin and a POSS mixture containing >95 wt% trisilanolphenyl POSS was investigated by POM (polarized optical microscopy), SEM, TEM, WAXD, FT-IR, DSC, and TGA techniques. Composites with 1.0-10.4 wt% of POSS were prepared by dissolving the POSS and the phenolic resin into THF, followed by solvent removal and curing. Both nano- and micro-sized POSS filler aggregates and particles were shown to be heterogeneously dispersed in the cured matrix by POM, TEM, SEM, and X-EDS. POSS was found everywhere, including in both dispersed phase domains and in the matrix. The nanocomposite morphology appears to form by a multi-step POSS aggregation during the process of phase separation. Both the matrix and dispersed ‘particulate’ phase domains are mixtures of phenolic resin and POSS. POSS micro-crystals act as the core of the dispersed phase. The bigger dispersed domains consist of smaller particles or aggregates of POSS molecules that exhibit some order but regions of matrix resin are interspersed. A WAXD peak at 2θ∼7.3° indicates crystalline order in the POSS aggregates. This characteristic peak's intensity increases with an increase in POSS loading, suggesting that more POSS molecules have aggregated or crystallized. FT-IR spectra confirm that hydrogen bonding exists between the phenolic resin and POSS Si-OH groups. This increases their mutual compatibility, but H-bonding does not prevent POSS aggregation and phase separation during curing. TGA measurements in air confirmed the temperature for 5% mass loss in increases with increase of POSS loading and at T>550° the thermal stability increases more sharply with POSS loading. The nanocomposite glass transition temperatures (T_g) are only slightly be affected by the POSS filler.     

Synthesis,characterization, and properties of multifunctional naphthalene-containing epoxy resins cured with cyanate ester

Multifunctional naphthalene-containing epoxy resins derived from 2,7-dihydroxylnaphthalene were synthesized and the intermediates were characterized by Fourier transform infrared spectroscopy, elemental analysis, and mass spectrometry. The cured products from naphthalene-containing epoxy resin and the dicyanate ester of bisphenol A (DCBA) exhibited a better T_g and a lower coefficient of thermal expansion than those of the commercial epoxy system. The glass transition temperature, thermal stability, and moisture absorption were found to increase with the epoxy functionality when naphthalene-containing epoxy resins were cured with DCBA. Thermogravimetric analyses revealed that the DCBA-cured system had a better thermal stability than that of the 4,4′-diaminodiphenylsulfone (DDS)-cured system. The addition of a metallic catalyst into the epoxy resin/cyanate ester system not only facilitated the cyclotrimerization of the cyanate ester but also the polyetherification of the epoxy resin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1611–1622, 1999     

Synthesis and characterization of bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane/epoxy/glass fiber composites

Bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane was prepared by treating CNBr with bis(4‐hydroxy‐3,5‐dimethylphenyl)anisylmethane and blended with commercial epoxy resin in different ratios and cured at 120°C for 2 h, 180°C for 1 h, and postcured at 220°C for 1 h using diamino diphenyl methane as curing agent. Castings of neat resin and blends were prepared and characterized. The composite laminates were also fabricated with glass fiber using the same composition. The tensile strength of the composites increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m², for neat epoxy resin, to 0.8615 kJ/m², for 9% cyanate ester‐modified epoxy system. The 10% weight loss temperature of pure epoxy (358°C) was increased to 390°C by the incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% in the epoxy resin increases the T_g from 143 to 147°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

环氧树脂/石英纤维透波复合材料制备

为改善环氧树脂的介电性能及提升石英纤维的界面性能,使用缩水甘油醚基笼型倍半硅氧烷(G-POSS)和γ-氨丙基三乙氧基硅烷(KH-550)分别对环氧树脂和石英纤维进行改性.利用差示扫描量热法研究改性后环氧树脂的固化过程,并通过外推法确定了其固化工艺,根据固化工艺制备环氧树脂/石英纤维复合材料,分别对该复合材料的热稳定性、...     

Thermal and mechanical properties of liquid‐like trisilanol isobutyl‐polyhedral oligomeric silsesquioxanes (POSS) derivative/epoxy nanocomposites

Liquid‐like trisilanol isobutyl polyhedral oligomeric silsesquioxanes derivative (L‐POSS‐D) was synthesized with γ‐(2,3‐epoxypropoxy)propytrimethoxysilane (KH560) as corona and polyetheramine M1000 as canopy. Its structure and properties were characterized by FTIR, XPS, TGA and Rheology data. Epoxy nanocomposites with 0.0, 0.5, 1.0 and 2.0 wt% content of L‐POSS‐D were prepared. T _g of the nanocomposites improved 47.6°C higher than pure epoxy resin. Mechanical properties, including flexural strength and impact toughness, were improved markedly with L‐POSS‐D. The morphologies of impact fracture were studied by SEM. POLYM. COMPOS., 38:691–698, 2017. © 2015 Society of Plastics Engineers     

Modification of cyanate ester resin by poly(ethylene phthalate) and related copolyesters

Aromatic polyesters were prepared and used to improve the brittleness of the cyanate ester resin. The aromatic polyesters include poly(ethylene phthalate) (PEP) and poly(ethylene phthalate‐co‐1,4‐phenylene phthalate). The polyesters were effective modifiers for improving the brittleness of the cyanate ester resin. For example, inclusion of 20 wt % PEP (MW 19,800) led to a 120% increase in the fracture toughness (K_IC) with retention in flexural properties and a slight loss of the glass transition temperature compared to the mechanical and thermal properties of the unmodified cured cyanate ester resin. The microstructures of the modified resins were examined by scanning electron microscopy and dynamic viscoelastic analysis. The thermal stability of the modified resins was lower than that of the unmodified resin as determined by thermogravimetric analysis. The water absorptivity of the modified resin increased significantly, compared to that of the unmodified cured cyanate ester resin. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified cyanate ester resin system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 208–219, 2000     

Graphite-Filled Polyethylene/Epoxy Blend for High-Conductivity Applications: The Immiscibility Edge

ABSTRACT

Polyethylene (PE)/epoxy blends filled with graphite were prepared and studied in this work. The in-plane and through-plane conductivities of the composites increased from 11.68 Scm^?1 to 73.11 Scm^?1 and 0.20 Scm^?1 to 4.12 Scm^?1, respectively, as graphite content increased from 30 to 80 wt%. Phase bonding effect of the compatibilizer and reinforcing effect of the filler enhanced the flexural modulus and strength of the composites up to 70 wt% filler content. The electrical conductivities attained by these composites being significantly higher than comparable composite formulations in literature show the edge of immiscible PE/epoxy blend for achieving high-conductivity polymer composites.     

Morphological,mechanical and thermal properties of cyanate ester/benzoxazine resin composites reinforced by silane treated natural hemp fibers

This present study deals with the reinforcement of thermosetting resin blends composed of cyanate ester (CE) and benzoxazine (BOZ) resins with natural hemp fibers (NHFs). These NHFs were initially treated by using a silane coupling agent (SCA) in order to chiefly enhance their distributions as well as adhesions within the CE/BOZ resin matrix, then incorporated with various weight amounts ranging from 5 wt% to 20 wt% with a regular interval of 5 wt%. The obtained results showed that at the maximum treated fiber loading (20 wt%), distinctive enhancements in the mechanical properties in terms of flexural strength and microhardness were obtained. Besides, the thermal stability and glass transition temperature (T_g) were appreciably enhanced and were higher than those of the pure CE/BOZ resin properties. With respect to the astonishing properties of the NHFs, these enhancements could be possibly due to the good dispersion and adhesion of the treated NHFs inside the CE/BOZ resin achieved upon using the SCA. Therefore, we believe herein that these renewable and cheap NHFs have considerable potential to be used as reinfocer materials for CE/BOZ resin composites to be used in various industrial sectors.     

Mechanical,thermal, and viscoelastic response of novel in situ CTBN/POSS/epoxy hybrid composite system

The present study focuses on the preparation of a novel hybrid epoxy nanocomposite with glycidyl polyhedral oligomeric silsesquioxane (POSS) as nanofiller, carboxyl terminated poly(acrylonitrile‐co‐butadiene) (CTBN) as modifying agent and diglycidyl ether of bisphenol A (DGEBA) as matrix polymer. The reaction between DGEBA, CTBN, and glycidyl POSS was carefully monitored and interpreted by using Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). An exclusive mechanism of the reaction between the modifier, nanofiller, and the matrix is proposed herein, which attempts to explains the chemistry behind the formation of an intricate network between POSS, CTBN, and DGEBA. The mechanical properties, such as tensile strength, and fracture toughness, were also carefully examined. The fracture toughness increases for epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems with respect to neat epoxy, but for hybrid composites toughening capability of soft rubber particles is lost by the presence of POSS. Field emission scanning electron micrographs (FESEM) of fractured surfaces were examined to understand the toughening mechanism. The viscoelastic properties of epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems were analyzed using dynamic mechanical thermal analysis (DMTA). The storage modulus shows a complex behavior for the epoxy/POSS composites due to the existence of lower and higher crosslink density sites. However, the storage modulus of the epoxy phase decreases with the addition of soft CTBN phase. The T_g corresponding to epoxy‐rich phase was evident from the dynamic mechanical spectrum. For hybrid systems, the T_g is intermediate between the epoxy/rubber and epoxy/POSS systems. Finally, TGA (thermo gravimetric analysis) studies were employed to evaluate the thermal stability of prepared blends and composites. POLYM. COMPOS., 37:2109–2120, 2016. © 2015 Society of Plastics Engineers     

A study on rheological behavior of MWCNTs/epoxy composites

Rheological behaviors of multiwalled carbon nanotubes (MWCNTs)/epoxy composites with various MWCNT contents were investigated by using a time sweep and frequency sweep experiment with oscillatory rheometry. The functional groups on the acid-treated MWCNTs were investigated by fourier transfer-infrared spectroscopy (FT-IR). The composites containing acid-treated MWCNTs exhibited faster gel time than pure epoxy resins. The storage (G′) and loss (G″) moduli of the composites showed solid-like behavior owing to interaction between the MWCNTs and the epoxy resins. The 1.0 wt% MWCNT composites had the highest crosslinking activation energy (E_c) due to good dispersion and strong interfacial bonding. These results imply that three-dimensional crosslinking might take place among the hydroxyl group in epoxy resins and the carbonyl or hydroxyl group in acid-treated MWCNTs.