The boron trifluoride monoethyl amine complex cured epoxy resins

The curing exotherm pattern is affected by the equivalent ratio of curing agent, boron trifluoride monoethylamine complex (BF₃ · MEA), to epoxy resin. The diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) cures more slowly than the diglycidyl ether of bisphenol A (Epon 828). The glass transition temperatures (T_g's) of BF₃ · MEA cured Epon 828 are increased with inceasing concentration of curing agent (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF₃ · MEA (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF₃ · MEA (0.0450 eq./epoxy eq.) cured Epon 828 and DGEBF are almost equivalent 43 and 44 kcal/mol, respectively. DGEBF when added to DGEBA improves the T_g and char yield with the BF₃ · MEA curing system. The T_g of both resin systems can be increased by longer post cure, whereas the char yield does not appear to change significantly. No ester group formation is found for the BF₃ · MEA-cured DGEBF, although this has been previously reported for the DGEBA system. The BF₃ · MEA cure at 120°C is better than at 140°C because of vaporization and degradation of the curing agent at the higher temperature. The rapid gelation of the epoxy resin may be another reason for the lower degree of cure at high temperature.     

Epoxy resin based on 4,4′-dihydroxydiphenysulfone. I. Synthesis and reaction kinetics with 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylsulfone

Epoxy resins based on 4,4′-dihydroxydiphenylsulfone (DGEBS) and diglycidyl ether of bisphenol A (DGEBA) were prepared by alkaline condensation of 4,4′-dihydroxydiphenylsulfone (bisphenol S) with epichlorohydrin and by recrystallization of liquid, commercial bisphenol A-type epoxy resin, respectively. Curing kinetics of the two epoxy compounds with 4,4′-diaminodiphenylmethane (DDM) and with 4,4′-diaminodiphenylsulfone (DDS) as well as T_g values of the cured materials were determined by the DSC method. It was found that the ? SO₂? group both in the epoxy resin and in the harener increases T_g values of the cured materials. DGEBS reacts with the used hardeners faster than does DGEBA and the curing reaction of DGEBS begins at lower temperature than does the curing reaction of DGEBA when the same amine is used. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of diphenylsilanediol modified epoxy resin and curing agent

A series of diphenylsilanediol modified epoxy resins and novel curing agents were synthesized. The modified epoxy resins were cured with regular curing agent diethylenetriamine (DETA); the curing agents were applied to cure unmodified diglycidyl ether of bisphenol A epoxy resin (DGEBA). The heat resistance, mechanical property, and toughness of all the curing products were investigated. The results showed that the application of modified resin and newly synthesized curing agents leads to curing products with lower thermal decomposition rate and only slightly decreased glass transition temperature (T_g), as well as improved tensile modulus and tensile strength. In particular, products cured with newly synthesized curing agents showed higher corresponding temperature to the maximum thermal decomposition rate, comparing with products of DGEBA cured by DETA. Scanning electron microscopy micro images proved that a ductile fracture happened on the cross sections of curing products obtained from modified epoxy resins and newly synthesized curing agents, indicating an effective toughening effect of silicon–oxygen bond.     

New epoxy resins. II. The preparation,characterization, and curing of epoxy resins and their copolymers

A polymer having high aromaticity and/or cyclic ring structures in the chain backbone usually gives high heat resistance and flame resistance. Five glycidyl ether-type epoxy resins are prepared from bisphenol A (DGEBA), 9,9-bis(4-hydroxyphenyl)fluorene (DGEBF), 3,6-dihydroxyspiro-[fluorene-9,9′-xanthane] (DGEFX), 10,10-bis(4-hydroxyphenyl) anthrone (DGEA), and 9,9,10,10-tetrakis(4-hydroxyphenyl)anthracene (TGETA) in order to study structure–thermal stability–flame resistance property relationships. In this study, trimethoxyboroxine (TMB) and diaminodiphenylsulfone (DDS) are employed as the curing agents. The char yield at 700°C under a nitrogen atmosphere and the glass transition temperature (T_g) for the uncured resins decrease according to the sequence TGETA > DGEFX > DGEA > DGEBF > DGEBA. The Tg values for these cured epoxy resins are DGEBA < DGEBF < DGEFX < DGEA. A T_g for the TGETA is not obtainable but would be expected to be the highest. The char yields at 700°C of these cured epoxy resins have the same trend as the uncured resins. DGEBF, DGEFX, DGEA, and TGETA added to the DGEBA system show increases in the char yield, T_g, and oxygen index with increasing concentration of these novel epoxy resins.     

Frontal curing of epoxy resins: Comparison of mechanical and thermal properties to batch-cured materials

The epoxy resin diglycidyl ether of bisphenol F (DGEBF) was cured by the aliphatic amine curing agent Epicure 3371 in a stoichiometric ratio both frontally and in a batch-cure schedule. Glass transition temperatures (T_g) were determined using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DMA also was used for studying the storage modulus (E′) and tan delta (tan δ) of the cured samples. Tensile properties of epoxy samples were tested according to ASTM D638M-93. The properties of the frontally cured epoxy resin were found to be very close to that of batch-cured epoxy resin. Velocity of cure-front propagation was measured for both neat and filled epoxy. Rubber particles (ground tires) were used as a filler. The maximum percentage of filler in the epoxy resin allowing propagation was 30%. Because of convection, only descending fronts would propagate. Advantages and disadvantages of frontal curing of epoxy resins are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1209–1216, 1997     

Synthesis and properties of methyl hexahydrophthalic anhydride‐cured fluorinated epoxy resin 2,2‐bisphenol hexafluoropropane diglycidyl ether

The fluorinated epoxy resin, 2,2‐bisphenol hexafluoropropane diglycidyl ether (DGEBHF) was synthesized through a two‐step procedure, and the chemical structure was confirmed by ¹H n uclear magnetic resonance (NMR), ¹³C NMR, and Fourier transform infrared (FTIR) spectra. Moreover, DGEBHF was thermally cured with methyl hexahydrophthalic anhydride (MHHPA). The results clearly indicated that the cured DGEBHF/MHHPA exhibited higher glass transition temperature (T_g 147°C) and thermal decomposition temperature at 5% weight loss (T₅ 372°C) than those (T_g 131.2°C; T₅ 362°C) of diglycidyl ether of bisphenol A (DGEBA)/MHHPA. In addition, the incorporation of bis‐trifluoromethyl groups led to enhanced dielectric properties with lower dielectric constant (D_k 2.93) of DGEBHF/MHHPA compared with cured DGEBA resins (D_k 3.25). The cured fluorinated epoxy resin also gave lower water absorption measured in two methods relative to its nonfluorinated counterparts. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2801–2808, 2013     

Curing kinetics and properties of epoxy resin-fluorenyl diamine systems

Diglycidyl ether of bisphenol fluorene (DGEBF), 9,9-bis-(4-aminophenyl)-fluorene (BPF) and 9,9-bis-(3-methyl-4-aminophenyl)-fluorene (BMAPF) were synthesized to introduce more aromatic structures into the epoxy systems, and their chemical structures were characterized with FTIR, NMR and MS analyses. The curing kinetics of fluorenyl diamines with different epoxy resins including DGEBF, cycloaliphatic epoxy resin (TDE-85) and diglycidyl ether of bisphenol A (DGEBA) was investigated using non-isothermal differential scanning calorimetry (DSC), and determined by Kissinger, Ozawa and Crane methods. The thermal properties of obtained polymers were evaluated with dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results show that the values of activation energy (E_a) are strongly dependent on the structures of epoxy resin and curing agent. The curing reactivity of epoxy system is restrained by the introduction of rigid fluorene into chain backbone and flexible methyl into side groups. The cured DGEBF/fluorenyl diamine systems exhibit remarkably higher glass transition temperature, better thermal stability and lower moisture absorption compared to those of DGEBA/fluorenyl diamine systems, and display approximate heat resistance and much better moisture resistance relative to those of TDE-85/fluorenyl diamine systems.     

New epoxy resins. I. The stability of epoxy–trialkoxyboroxines triaryloxyboroxine system

A polymer with high aromaticity and/or cyclic ring structures chain backbone usually has high heat, thermal, and flame resistance. Two diglycidyl ethers of bisphenols were prepared from 4,4′ isopropylidenediphenol (DGEBA) and 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) for evaluation. Four boroxines—trimethoxyboroxine (TMB), triethoxyboroxine (TEB), triisopropoxyboroxine (TIPB) and triphenoxyboroxine (TPB)—were used as the curing agents. DGEBA and DGEBF cured with various boroxines indicate that the trend for their respective glass transition temperature (T_g's), degradation temperatures (T_d's), and gel fractions are TMB-cured epoxy ≈ TEB-cured epoxy < TIPB cured epoxy < TPB cured epoxy. The DGEBF system usually has a higher T_g, T_d, gel fraction, oxygen index (OI), and char yield than the related DGEBA system. DGEBF/DGEBA (80/20 mol ratio) shows a synergistic effect in regard to char formation. This effect exists not only in the copolymer system but also in blended homopolymers of the separately cured resins. A modified mechanism for the polymerization of phenyl glycidyl ether (PGE) with TMB has been proposed.     

Preparation,curing kinetics,and thermal properties of bisphenol fluorene epoxy resin

Diglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) was synthesized to introduce more aromatic structures into an epoxy resin system. The structure of DGEBF was characterized with Fourier transform infrared and ¹H‐NMR. 4,4′‐Diaminodiphenylmethane (DDM) was used as the curing agent for DGEBF, and differential scanning calorimetry was applied to study the curing kinetics. The glass‐transition temperature of the cured DGEBF/DDM, determined by dynamic mechanical analysis, was 260°C, which was about 100°C higher than that of widely used diglycidyl ether of bisphenol A (DGEBA). Thermogravimetric analysis was used to study the thermal degradation behavior of the cured DGEBF/DDM system: its onset degradation temperature was 370°C, and at 700°C, its char yield was about 27%, whereas that of cured DGEBA/DDM was only 14%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Epoxy resin containing the poly(sily ether): Preparation,morphology, and mechanical properties

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared through in situ curing reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (T_gs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003     

Toughening epoxy resins with polyepichlorohydrin

Polyepichlorohydrin (PECH) rubbers were found to toughen epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA) and cured with piperidine. The degree of toughening depends on the molecular weight of the PECH and on the curing temperature. Best toughening was achieved with PECH of the highest nominal molecular weight of 3400 (Hydrin 10 × 2). Hydrin 10 × 1 (nominal molecular weight 1700) did not toughen the epoxy resin unless bisphenol A was also added, whereas Hydrin 10 × 2 toughened it in the absence of bisphenol A. Curing resins containing bisphenol A and Hydrin 10 × 1 at 160°C resulted in a slightly more brittle resin than when cured at 120°C. The effect of PECH rubbers on the T_g, modulus, and hot/wet properties is similar to that of carboxy-terminated butadiene-acrylonitrile rubbers (CTBN). Dynamic mechanical thermal analysis (DMTA) and scanning electron micrographs (SEM) of fractured surfaces show that the PECH separates as a discrete phase during curing. © 1993 John Wiley & Sons, Inc.     

Intercalation and exfoliation of clay nanoplatelets in epoxy‐based nanocomposites: TEM and XRD observations

Diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) reinforced with organo‐montmorillonite clay nanoplatelets were investigated using anhydride‐ and amine‐curing agents. The sonication technique was used to process epoxy/clay nanocomposites. The basal spacing of clay nanoplatelets was observed by wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS) techniques, and transmission electron microscopy. It was found that the basal spacing of clay nanoplatelets in epoxy matrix was expanded after mixing with either DGEBA/DGEBF or methyltetrahydrophthalic‐anhydride (MTHPA) curing agent. The sonication technique provided larger d‐spacing of clay nanoplatelets. Because of the different curing temperatures, MTHPA‐cured epoxy/clay nanocomposites produced more expanded d‐spacing of clay nanoplatelets modified with methyl, tallow, bis(2‐hydroxyethyl) quaternary ammonium (MT2EtOH) than triethylenetetramine‐cured nanocomposites. Depending on the selection of curing agent and organic modification for clay nanoplatelets, the d‐spacing was expanded to be up to 8.72 nm. POLYM. ENG. SCI., 46:452–463, 2006. © 2006 Society of Plastics Engineers     

Reaction kinetics,thermal properties of tetramethyl biphenyl epoxy resin cured with aromatic diamine

Epoxy resins, 4, 4′‐diglycidyl (3, 3′, 5, 5′‐tetramethylbiphenyl) epoxy resin (TMBP) containing rigid rod structure as a class of high performance polymers has been researched. The investigation of cure kinetics of TMBP and diglycidyl ether of bisphenol‐A epoxy resin (DGEBA) cured with p‐phenylenediamine (PDA) was performed by differential scanning calorimeter using an isoconversional method with dynamic conditions. The effect of the molar ratios of TMBP to PDA on the cure reaction kinetics was studied. The results showed that the curing of epoxy resins contains different stages. The activation energy was dependent of the degree of conversion. At the early of curing stages, the activation energy showed the activation energy took as maximum value. The effects of rigid rod groups and molar ratios of TMBP to PDA for the thermal properties were investigated by the DSC, DMA and TGA. The cured 2/1 TMBP/PDA system with rigid rod groups and high crosslink density had shown highest T_g and thermal degradation temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis of a novel phosphorus‐containing dicyclopentadiene novolac hardener and its cured epoxy resin with improved thermal stability and flame retardancy

A novel phosphorus‐containing dicyclopentadiene novolac (DCPD‐DOPO) curing agent for epoxy resins, was prepared from 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and n‐butylated dicyclopentadiene phenolic resin (DCPD‐E). The chemical structure of the obtained DCPD‐DOPO was characterized with FTIR, ¹H NMR and ³¹P NMR, and its molecular weight was determined by gel permeation chromatography. The flame retardancy and thermal properties of diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with DCPD‐DOPO or the mixture of DCPD‐DOPO and bisphenol A‐formaldehyde Novolac resin 720 (NPEH720) were studied by limiting oxygen index (LOI), UL 94 vertical test and cone calorimeter (CCT), and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. It is found that the DCPD‐DOPO cured epoxy resin possess a LOI value of 31.6% and achieves the UL 94 V‐0 rating, while its glass transition temperature (T_g) is a bit lower (133 °C). The T_g of epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 increases to 137 °C or above, and the UL 94 V‐0 rating can still be maintained although the LOI decreases slightly. The CCT test results demonstrated that the peak heat release rate and total heat release of the epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 decrease significantly compared with the values of the epoxy resin cured by NPEH720. Moreover, the curing reaction kinetics of the epoxy resin cured by DCPD‐DOPO, NPEH720 or their mixture was studied by DSC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44599.     

Azo initiator selection to control the curing order in dimethacrylate/epoxy interpenetrating polymer networks

Differential Scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) spectroscopic studies have been undertaken of the cure of interpenetrating polymer networks (IPNs) formed with imidazole‐cured diglycidyl ether bisphenol‐A (DGEBA) and with either diethoxylated bisphenol‐A dimethacrylate (DEBPADM) or bisphenol‐A diglycidyl dimethacrylate (bisGMA), polymerized by a range of azo initiators (AIBN64, VAZ088, VR110 and AZO168). Due to the differing decomposition rates of the azo initiators, the neat dimethacrylate resin either cured faster than (with AIBN64 and VAZO88), or similar to (VR110), or slower than (AZO168), the neat epoxy resin. In the neat DGEBA/1‐methyl imidazole (1‐MeI), DEBPADM/AIBN64, DEBPADM/VAZO88 and DEBPADM/VR110 resins, close to full cure was achieved. For the neat, high‐temperature DEBPADM/AZO168 resin, full cure was not attained, possibly due to the compromise between using a high enough temperature for azo decomposition while avoiding depolymerization or decomposition of the methacrylate polymer. IPN cure studies showed that, by appropriate initiator selection, it was possible to interchange the order of cure of the components within the IPN so that either the dimethacrylate or epoxy cured first. In the isothermal cure of the 50:50 DEBPADM/AIBN64:DGEBA/1‐Mel IPN system, the cure rate of both species was less than in the parent resins, due to a dilution effect. For this system, the dimethacrylate cured first and to high conversion, due to plasticization by the unreacted epoxy, but the subsequent cure of the more slowly polymerizing epoxy component was restricted by the high crosslink density developed in the IPN. After post‐curing, however, high conversion of both reactive groups was observed and the fully cured IPN exhibited a single high‐temperature T_g, close to the T_g values of the parent resins. In the higher‐temperature, isothermal cure of the 50:50 DEBPADM/VR110:DGEBA/1‐Mel IPN system, the reactive groups cured at a similar rate and so the final conversions of both groups were restricted, while in the 50:50 DEBPADM/AZO168:DGEBA/1‐Mel system it was the epoxy which cured first. Both of these higher‐temperature azo‐initiated IPN systems exhibited single T_gs, indicating a single‐phase structure; however, the T_gs are significantly lower than expected, due to plasticization by residual methacrylate monomer and/or degradation products resulting from the high cure temperature. Copyright © 2004 Society of Chemical Industry     

Effect of oxirane groups on curing behavior and thermal stability of vinyl ester resins

The effects of oxirane groups in vinyl ester (VE) resin and reactive diluent on curing characteristics and thermal behavior of cured resins are described. Stoichiometric (0.5:1, sample A) as well as nonstoichiometric (0.5:0.85, sample B) ratios of the diglycidyl ether of bisphenol-A (DGEBA) and methacrylic acid (MA) were used for the synthesis of VE resins. Resin sample B had more residual epoxy groups because of the stoichiometric imbalance of the reactants. VE resins thus obtained were diluted with methyl methacrylate (MMA; 1:1, w/w), and controlled quantities of epoxy groups were introduced by partial replacement of MMA with glycidyl methacrylate (GMA), keeping the overall ratio of resin and reactive diluent constant. Increase of GMA content in resin A or B resulted in a decrease in gel time, indicating that the curing reaction is facilitated by the presence of epoxy groups. An increase in initiator content also reduced the gel time. In the differential scanning calorimetry (DSC) scans, a sharp curing exotherm was observed in the temperature range 107 ± 3–150 ± 1 °C. The onset temperature (T_onset) and peak exotherm temperature (T_exo) decreased with increase in GMA content. Heat of curing (ΔH) also increased with increase in GMA content. A broad exotherm was observed after the initial sharp exotherm that was attributed to the etherification reaction. Cured VE resins were stable up to 250–260 °C, and started losing weight above this temperature. Rapid decomposition was observed in the temperature range 400–500 °C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 416–423, 2001     

ToF‐SIMS investigation of epoxy resin curing reaction at different resin to hardener ratios

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and principal components analysis (PCA) were used to analyze diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) epoxy resin blend cured with isophorone diamine (IPD) hardener at different resin to hardener ratios. The aim was to establish correlations between the hardener concentration and the nature and progress of the crosslinking reaction. Insights into the cured resin structure revealed using ToF‐SIMS are discussed. Three sets of significant secondary ions have been identified by PCA. Secondary ions such as C₁₄H₇O⁺, CHO⁺, CH₃O⁺, and C₂₁H₂₄O₄⁺ showed variance related to the completion of the curing reaction. Relative intensities of C_xH_yN_z⁺ ions in the cured resin samples are indicative of the un‐reacted and partially reacted hardener molecules, and are found to be proportional to the resin to hardener mixing ratio. The relative ion intensities of the aliphatic hydrocarbon ions are shown to relate to the cured resin crosslinking density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel adamantane‐containing epoxy resin

A novel adamantane‐containing epoxy resin diglycidyl ether of bisphenol‐adamantane (DGEBAda) was successfully synthesized from 1,3‐bis(4‐hydroxyphenyl)adamantane by a one‐step method. The proposed structure of the epoxy resin was confirmed with Fourier transform infrared, ¹H‐NMR, gel permeation chromatography, and epoxy equivalent weight titration. The synthesized adamantane‐containing epoxy resin was cured with 4,4′‐diaminodiphenyl sulfone (DDS) and dicyandiamide (DICY). The thermal properties of the DDS‐cured epoxy were investigated with differential scanning calorimetry and thermogravimetric analysis (TGA). The dielectric properties of the DICY‐cured epoxy were determined from its dielectric spectrum. The obtained results were compared with those of commercially available diglycidyl ether of bisphenol A (DGEBA), a tetramethyl biphenol (TMBP)/epoxy system, and some other associated epoxy resins. According to the measured values, the glass‐transition temperature of the DGEBAda/DDS system (223°C) was higher than that of the DGEBA/DDS system and close to that of the TMBP/DDS system. TGA results showed that the DGEBAda/DDS system had a higher char yield (25.02%) and integral procedure decomposition temperature (850.7°C); however, the 5 wt % degradation temperature was lower than that of DDS‐cured DGEBA and TMBP. Moreover, DGEBAda/DDS had reduced moisture absorption and lower dielectric properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of 4‐(4‐hydroxyphenoxy)phenol diglycidyl ether with improved toughness behavior

A high‐performance difunctional epoxy resin, 4‐(4‐hydroxyphenoxy)phenol diglycidyl ether (DHPOP), was synthesized by a two‐step method. The curing behavior of DHPOP was investigated by nonisothermal differential scanning calorimetry method and the curing kinetics results revealed that the introduction of ether linkage could improve the activity of epoxy groups, leading to a lower curing temperature and apparent activation energy compared with that of the commercial bisphenol‐A diglycidyl ether (DGEBA). A series of copolymers were then prepared by varying the mass ratio of DHPOP and DGEBA, which were cured with 4,4′‐diaminodiphenyl methane. The effect of DHPOP contents on thermal and mechanical properties and fracture morphology was studied. As expected, with the increase of DHPOP in the network, the impact strength and char yield were significantly enhanced, while the glass transition temperature (T_g) remained unchanged because of the increase of crosslink density. The excellent toughness endows the DHPOP with the promising potential for the application as high‐performance resin matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46458.     

Syntheses of epoxy‐bridged polyorganosiloxanes and the effects of terminated alkoxysilanes on cured thermal properties

A series of epoxy‐bridged polyorganosiloxanes have been synthesized by reacting multifunctional aminoalkoxysilanes with diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The reactions of trifunctional 3‐aminopropyltriethoxysilane (APTES), difunctional 3‐aminopropylmethyldiethoxysilane (APMDS), and monofunctional 3‐aminopropyldimethylethoxysilane (APDES) with DGEBA epoxy have been monitored and characterized by FTIR, ¹H NMR, and ²⁹Si NMR spectra in this study. The synthesized epoxy‐bridged polyorganosiloxanes precursors, with different terminated alkoxysilane groups, are thermally cured with or without the addition of curing catalysts. Organometallic dibutyltindilaurate, and alkaline tetrabutylammonium hydroxide have been used as curing catalysts to investigate the thermal curing behaviors and cured properties of epoxy‐bridged polyorganosiloxanes precursors. The maximum exothermal curing temperatures of epoxy‐bridged polyorganosiloxanes precursors are found to appear around the same region of 120°C in DSC analysis. The addition of catalysts to the epoxy/APTES precursor shows significant influence on the cured structure; however, the catalysts exhibit less influence on the cured structure of epoxy‐APMDS precursor and epoxy/APDES precursor. Curing catalysts also show significant enhancement in increasing the thermal decomposition temperature (T_d50s) of cured network of trifunctional epoxy‐bridged polyorganosiloxane (epoxy/APTES). High T_d50s of 518.8 and 613.6 in the cured hybrids of epoxy/APTES and epoxy/APMDS precursors are also observed, respectively. When trialkoxysilane‐terminated epoxy‐bridged polyorganosiloxanes precursor are cured, with or without the addition of catalyst, no obvious T_g transition can be found in the TMA analysis of cured network. The cured network of trialkoxysilane‐terminated epoxy‐bridged polyorganosiloxanes also exhibits the lowest coefficient of thermal expansion (CTE) among the three kinds of alkoxysilane‐terminated epoxy‐bridged polyorganosiloxanes investigated. The organic–inorganic hybrid, from epoxy‐bridged polyorganosiloxanes after the thermal curing process, shows better thermal stability than the cured resin network of pure epoxy‐diaminopropane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3491–3499, 2006