Epoxy resin/poly(ϵ‐caprolactone) blends cured with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane. I. Miscibility and crystallization kinetics

Crystalline thermosetting blends composed of 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane (BAPP)‐cured epoxy resin (ER) and poly(?‐caprolactone) (PCL) were prepared via the in situ curing reaction of epoxy monomers in the presence of PCL, which started from initially homogeneous mixtures of diglycidyl ether of bisphenol A (DGEBA), BAPP, and PCL. The miscibility of the blends after and before the curing reaction was established with differential scanning calorimetry and dynamic mechanical analysis. Single and composition‐dependent glass‐transition temperatures (T_g's) were observed in the entire blend composition after and before the crosslinking reaction. The experimental T_g's were in good agreement with the prediction by the Fox and Gordon–Taylor equations. The curing reaction caused a considerable increase in the overall crystallization rate and dramatically influenced the mechanism of nucleation and the growth of the PCL crystals. The equilibrium melting point depression was observed for the blends. An analysis of the kinetic data according to the Hoffman–Lauritzen crystallization kinetic theory showed that with an increasing amorphous content, the surface energy of the extremity surfaces increased dramatically for DGEBA/PCL blends but decreased for ER/PCL blends. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1085–1098, 2003     

Functionalization of polymeric organolithium compounds with 3,4‐epoxy‐1‐butene: Precursors for diene‐functionalized macromonomers

The functionalization of polymeric organolithiums (PLi) with 3,4‐epoxy‐1‐butene (EPB) in a hydrocarbon solution yielded the corresponding hydroxybutene‐functionalized polymers in high yields (>95%). Three modes of addition of PLi to EPB were observed (1,4, 3,4, and 4,3). The products and chain‐end structures were characterized by ¹H NMR, ¹³C NMR, attached‐proton‐test ¹³C NMR, calculated ¹³C NMR chemical shifts, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The regioselectivity of the addition depended on the PLi chain‐end structure, the reaction conditions, and the addition of lithium salts or Lewis bases. In the absence of additives, the functionalization of poly(styryl)lithium (PSli) produced equal amounts of 1,4‐, 3,4‐, and 4,3‐addition, as determined by quantitative ¹³C NMR analysis. The use of a low temperature (6 °C), inverse addition, the addition of triethylamine (TEA; [TEA]/[PSLi] = 20) as a Lewis base, or dienyllithium chain ends produced polymers with only the 1,4‐addition product. Mild dehydration of the hydroxybutene‐functionalized polymer with p‐toluenesulfonic acid produced the corresponding diene‐functionalized macromonomer, as shown by MALDI‐TOF MS. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 947–957, 2003     

Isothermal cure kinetics of epoxy/phenol‐novolac resin blend system initiated by cationic latent thermal catalyst

The investigation of the cure kinetics of a diglycidyl ether of bisphenol A (DGEBA)/phenol‐novolac blend system with different phenolic contents initiated by a cationic latent thermal catalyst [N‐benzylpyrazinium hexafluoroantimonate (BPH)] was performed by means of the analysis of isothermal experiments using a differential scanning calorimetry (DSC). Latent properties were investigated by measuring the conversion as a function of curing temperature using a dynamic DSC method. The results indicated that the BPH in this system for cure is a significant thermal latent initiator and has good latent thermal properties. The cure reaction of the blend system using BPH as a curing agent was strongly dependent on the cure temperature and proceeded through an autocatalytic kinetic mechanism that was accelerated by the hydroxyl group produced through the reaction between DGEBA and BPH. At a specific conversion region, once vitrification took place, the cure reaction of the epoxy/phenol‐novolac/BPH blend system was controlled by a diffusion‐control cure reaction rather than by an autocatalytic reaction. The kinetic constants k₁ and k₂ and the cure activation energies E₁ and E₂ obtained by the Arrhenius temperature dependence equation of the epoxy/phenol‐novolac/BPH blend system were mainly discussed as increasing the content of the phenol‐novolac resin to the epoxy neat resin. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2945–2956, 2000     

A flame‐retardant phosphate and cyclotriphosphazene‐containing epoxy resin: Synthesis and properties

A novel flame‐retardant epoxy resin, (4‐diethoxyphosphoryloxyphenoxy)(4‐glycidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4‐diethoxyphosphoryloxyphenoxy)(4‐hydroxyphenoxy)cyclotriphosphazene and was characterized by Fourier transform infrared, ³¹P NMR, and ¹H NMR analyses. The epoxy resin was further cured with diamine curing agents, 4,4′‐diaminodiphenylmethane (DDM), 4,4′‐diaminodiphenylsulfone (DDS), dicyanodiamide (DICY), and 3,4′‐oxydianiline (ODA), to obtain the corresponding epoxy polymers. The curing reactions of the PPCTP resin with the diamines were studied by differential scanning calorimetry. The reactivities of the four curing agents toward PPCTP were in the following order: DDM > ODA > DICY > DDS. In addition, the thermal properties of the cured epoxy polymers were studied by thermogravimetric analysis, and the flame retardancies were estimated by measurement of the limiting oxygen index (LOI). Compared to a corresponding Epon 828‐based epoxy polymer, the PPCTP‐based epoxy polymers showed lower weight‐loss temperatures, higher char yields, and higher LOI values, indicating that the epoxy resin prepared could be useful as a flame retardant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 972–981, 2000     

Cure behavior and thermal degradation mechanisms of epoxy and epoxy–cyanate resins

The cure reactions of tetraglycidyl methylene diamine (TGMDA) epoxy cured with tetrasubstituted aromatic diamine on one hand and diglycidyl ether of bisphenol A and diglycicyl ether tetrabromobisphenol A epoxies cured with methylene bis (phenyl‐4‐cyanate) on the other hand are reported. Systematic Fourier transform infrared (FTIR) spectroscopy studies of the cure reaction of epoxy and epoxy–cyanate during thermal cycles are presented. FTIR studies indicate that the reaction of TGMDA monomer is total but the network contains a large amount of primary amine. The cyanate monomer reacts rapidly to form triazine structures. Then the epoxy monomers homopolymerize and crosslink with free cyanate groups. The gas chromatography/mass spectrometry study of volatile products evolved during the polymer thermal degradation shows the dehydration of the epoxy network and the decomposition of the amine structure. The FTIR and solid‐phase ¹³C nuclear magnetic resonance analysis revealed that the ether functions and the amine groups are temperature sensitive but the triazine structure is not. Copyright © 1999 John Wiley & Sons, Ltd.     

Development of toughened bio‐based epoxy with epoxidized linseed oil as reactive diluent and cured with bio‐renewable crosslinker

In the current work, renewable resourced toughened epoxy blend has been developed using epoxidized linseed oil (ELO) and bio‐based crosslinker. Epoxidation of linseed oil was confirmed through FTIR and ¹H NMR spectra. The ELO bio‐resin was blended at different compositions (10, 20, and 30 phr) with a petroleum‐based epoxy (DGEBA) as reactive diluent to reduce the viscosity for better processibility and cured with cardanol‐derived phenalkamine to overcome the brittleness. The flow behavior of the neat epoxy and modified bio‐epoxy resin blend systems was analyzed by Cross model at low and high shear rates. The tensile and impact behavior studies revealed that the toughened bio‐epoxy blend with 20 to 30 phr of ELO showed moderate stiffness with much higher elongation at break 7% to 13%. Incorporation of higher amount of ELO (20 to 30 phr) increases enthalpy of curing without affecting peak temperature of curing. The thermal degradation behavior of the ELO based blends exhibits similar trend as neat epoxy. The higher intensity or broadened loss tangent curve of bio‐epoxy blends revealed higher damping ability. FE‐SEM analysis showed a rough and rippled surface of bio‐based epoxy blends ensuring effective toughening. Reduced viscosity of resin due to maximum possible incorporation of bio‐resin and use of phenalkamine as curing agent leads to an eco‐friendly toughened epoxy and can be useful for specific coating and structural application.     

New organo‐soluble aromatic polyimides based on 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and aromatic diamines

New aromatic tetracarboxylic dianhydride, having isopropylidene and bromo‐substituted arylene ether structure 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride, was synthesized by the reaction of 4‐nitrophthalonitrile with 3,3′,5,5′‐tetrabromobisphenol A, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). The novel aromatic polyetherimides having inherent viscosities up to 1.04 dL g⁻¹ were obtained by either a one‐step or a conventional two‐step polymerization process starting from the bis(ether anhydride) and various aromatic diamines. All the polyimides showed typical amorphous diffraction patterns. Most of the polyimides were readily soluble in common organic solvents such as N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), pyridine, and even in less polar solvents like chloroform and tetrahydrofuran (THF). These aromatic polyimides had glass transition temperatures in the range of 256–303°C, depending on the nature of the diamine moiety. Thermogravimetric analysis (TGA) showed that all polymers were stable, with 10% weight loss recorded above 470°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1673–1680, 1999     

Flame‐retardant epoxy resins with high glass‐transition temperatures. II. Using a novel hexafunctional curing agent: 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐yl‐tris(4‐aminophenyl) methane

We synthesized a novel phosphorus‐containing triamine [9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐yl‐tris(4‐aminophenyl) methane (dopo‐ta)] from the nucleophilic addition of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide and pararosaniline chloride, using triethylamine as an acid receiver. We confirmed the structure of dopo‐ta by IR, mass, and NMR spectra and elemental analysis. dopo‐ta served as a curing agent for diglycidyl ether of bisphenol A (DGEBA) and dicyclopentadiene epoxy (hp7200). Properties such as the glass‐transition temperature (T_g), thermal decomposition temperature, flame retardancy, moisture absorption, and dielectric properties of the cured epoxy resins were evaluated. The T_g's of cured DGEBA/dopo‐ta and hp7200/dopo‐ta were 171 and 190 °C, respectively. This high T_g phenomenon is rarely seen in the literature after the introduction of a flame‐retardant element. The flame retardancy increased with the phosphorus content, and a UL‐94 V‐0 grade was achieved with a phosphorus content of 1.80 wt % for DGEBA/dopo‐ta/diamino diphenylmethane (DDM) systems and 1.46 wt % for hp7200/dopo‐ta/DDM systems. The dielectric constants for DGEBA/dopo‐ta and hp7200/dopo‐ta were 2.91 and 2.82, respectively, implying that the dopo‐ta curing systems exhibited low dielectric properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5971–5986, 2005     

Epoxy resin/poly(ϵ‐caprolactone) blends cured with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane. II. Studies by Fourier transform infrared and carbon‐13 cross‐polarization/magic‐angle spinning nuclear magnetic resonance spectroscopy

Crystalline thermosetting blends composed of 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane‐crosslinked epoxy resin (ER) and poly(?‐caprolactone) (PCL) were investigated by means of Fourier transform infrared (FTIR) spectroscopy and high‐resolution solid‐state NMR spectroscopy. FTIR investigations indicated that there were specific intermolecular interactions between ER and PCL and that the intermolecular hydrogen‐bonding interactions were weaker than the self‐association in pure epoxy. The intermolecular hydrogen bonding was considered to be the driving force for the miscibility of the thermosetting blends. For the examination of the miscibility of the thermosetting blends at the molecular level, high‐resolution solid‐state ¹³C cross‐polarity/magic‐angle spinning (CP‐MAS) NMR spectroscopy was employed. The line width of ¹³C CP‐MAS spectra decreased with increasing PCL contents, and the chemical shift of the carbonyl carbon resonance of PCL shifted to a low field with an increasing epoxy content in the blends. The proton spin–lattice relaxation experiments in the laboratory frame showed that all the blends possessed identical, composition‐dependent relaxation times (i.e., the proton spin–lattice relaxation times in the laboratory frame), suggesting that the thermosetting blends were homogeneous on the scale of 20–30 nm in terms of the spin‐diffusion mechanism, and this was in a good agreement with the results of differential scanning calorimetry and dynamic mechanical analysis. For the examination of the miscibility of the blends at the molecular level, the behavior of the proton lattice relaxation in the rotating frame was investigated. The homogeneity of the thermosetting blends at the molecular level was quite dependent on the blend composition. The PCL‐lean ER/PCL blends (e.g., 70/30) displayed a single homogeneous amorphous phase, and the molecular chains were intimately mixed on the segmental scale. The PCL‐rich blends displayed biexponential decay in experiments concerning the proton spin–lattice relaxation times in the rotating frame, which was ascribed to amorphous and crystalline phases. In the amorphous region, the molecular chains of epoxy and PCL were intimately mixed at the molecular level. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1099–1111, 2003     

Synthesis of a novel DPPA‐containing benzoxazine to flame‐retard epoxy resin with maintained thermal properties

The flame‐retarded epoxy resin with improved thermal properties based on environmentally friendly flame retardants is vital for industrial application. Hereby, a novel reactive‐type halogen‐free flame retardant, 10‐(3‐(4‐hydroxy phenyl)‐3,4‐dihydro‐2H‐benzo[e] [1,3] oxazin‐4‐yl)‐5H‐phenophosphazinine 10‐oxide (DHA‐B) was synthesized via a two‐step reaction route. Its structure was characterized using ¹H, ¹³C, and ³¹P NMR and HRMS spectra. For 4,4′‐diaminodipheny ethane (DDM) and diglycidyl ether of bisphenol A (DGEBA)‐cured systems, the epoxy resin with only 2 wt% loading of DHA‐B passed V‐0 rating of UL‐94 test. Significantly, its glass transition temperature (T_g) and initial decomposition temperature (T_5%) were as high as 169.6°C and 359.6°C, respectively, which were even higher than those of the corresponding original epoxy resin. Besides, DHA‐B decreased the combustion intensity during combustion. The analysis of residues after combustion suggested that DHA‐B played an important role in the condensed phase.     

Phase structure and thermomechanical properties of primary and tertiary amine‐cured epoxy/silica hybrids

Several kinds of organic–inorganic hybrids were synthesized from an epoxy resin and a silane alkoxide with a primary amine‐type curing agent or tertiary amine curing catalyst. In the hybrid systems cured with the primary amine‐type curing agent, the storage modulus in the high‐temperature region increased, and the peak area of the tan δ curve decreased. Moreover, the mechanical properties were improved by the hybridization of small amounts of the silica network. However, these phenomena were not observed in the hybrid systems cured with the tertiary amine catalyst. The differences in the network structures of the hybrid materials with the different curing processes were characterized with Fourier transform infrared (FTIR). In the hybrid systems cured with the primary amine‐type curing agent, FTIR results showed the formation of a covalent bond between silanol and hydroxyl groups that were generated by the reaction of an epoxy group with an active hydrogen of the primary amine. However, this phenomenon was not observed in the hybrids cured with the tertiary amine. The hybrids with the primary amine showed a homogeneous microstructure in transmission electron microscopy observations, although the hybrids cured with the tertiary amine showed a heterogeneous structure. These results mean that the differences in the interactions between the organic and inorganic phases significantly affect the properties and microstructures of the resultant composites. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1071–1084, 2001     

The epoxy–polycarbonate blends cured with aliphatic amine—I. Mechanism and kinetics

Reaction mechanism of the PC–epoxy blends cured by aliphatic amine has been investigated by varying PC contents in the blends. The transamidation reaction tends to convert nearly all the carbonates into N-aliphatic aromatic carbamates even at ambient temperature before normal curing. The remaining amine proceeds the normal curing with epoxy at a higher temperature (80°C). For the PC–epoxy/aliphatic amine blend containing 6 wt % PC, the yielded N-aliphatic aromatic carbamate further reacts with amine to produce the urea structure. The urea undergoes substitution reaction with the hydroxyl formed from the normal curing to give the N-aliphatic aliphatic carbamate. For the blend containing 12 wt % PC, the N-aliphatic aromatic carbamate converts into the N-aliphatic aliphatic carbamate via two different routes. For the blend containing lower molecular weight of the aliphatic amine, the N-aliphatic aromatic carbamate reacts with hydroxyl to form the N-aliphatic aliphatic carbamate directly. For the blend containing higher molecular weight of aliphatic amine, the N-aliphatic aromatic carbamate decomposes into the aliphatic isocyanate accelerated by the presence of the residual oxirane. The isocyanate formed then reacts with hydroxyl to yield the N-aliphatic aliphatic carbamate. The activation energy (E_a) and preexponential factor (A) of the PC–epoxy/POPDA blends decrease with the increase of the PC content. Kinetic study by thermal analysis by the method of autocatalyzed model is able to correctly predict oxirane conversion vs. time relationship for the neat epoxy/aliphatic amine and the PC–epoxy/aromatic amine systems because the dominant reaction is the normal curing reaction between amine and oxirane. The model fails to predict the PC–epoxy/aliphatic amine system because the system is complicated by several other reactions besides the normal curing reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2169–2181, 1997     

Synthesis and characterization of itaconic‐based epoxy resins

A trifunctional epoxy resin from itaconic acid (TEIA) was synthesized from a renewable resource‐based itaconic acid by allylation of itaconic acid to form diallyl itaconate by using m‐chloroperoxybenzoic acid as oxidizing agents followed by epoxidation of allylic C═C bond of diallyl itaconate methylhexahydropthalic anhydride as curing agent in the presence of 2‐methyl imidazole as a catalyst. The chemical structure of the synthesized resins was confirmed by Fourier transform infrared and nuclear magnetic resonance (¹H‐NMR and ¹³C‐NMR) spectroscopy analysis. The mechanical, thermal, and rheological performances of the TEIA were also investigated and compared with diglycidyl ether of bisphenol A and a plant‐based epoxidized soybean oil bioresin cured with the same curing agent. The higher epoxy value of 1.02, lower viscosity (0.96 Pa s at 25°C), higher mechanical, and higher curing reactivity toward methylhexahydropthalic anhydride of TEIA as compared with epoxidized soybean oil and comparable with diglycidyl ether of bisphenol A demonstrated significant evidence to design and develop a novel bio‐based epoxy resin with high performance to substitute the petroleum‐based epoxy resin.     

Properties of methyltetrahydrophthalic anhydride‐cured epoxy resin modified with MITU

Methylimidazole‐terminated chain‐extended urea (MITU) containing polypropylene oxide spacer was synthesized and employed to modify epoxies composed of a diglycidyl ether of bisphenol‐A (E‐51) and methyltetrahydrophthalic anhydride (MTHPA). The curing behavior, viscoelastic property, impact response, and fracture surface morphology of the curing systems were systematically investigated. Differential scanning calorimeter (DSC) analysis reveals that the curing reactivity of the epoxy system is greatly enhanced with the addition of MITU. From the dynamic mechanical analysis, besides the low‐temperature β relaxation, shoulder at higher temperature side appears for the MITU‐modified systems. Meanwhile, the addition of MITU leads to the increase of loss factor (tan δ) over the temperature range of 0–75°C. Impact tests show that the modifier can be effective in toughening the epoxy resin at relatively low loading, and the scanning electron microscope (SEM) images of the fracture surface for the modified systems display signs of ductility. Copyright © 2008 John Wiley & Sons, Ltd.     

Diglycidyl ether of bisphenol‐A epoxy resin modified using poly(ether ether ketone) with pendent tert‐butyl groups

Bisphenol‐A‐based difunctional epoxy resin was modified with poly(ether ether ketone) with pendent tert‐butyl groups (PEEKT). PEEKT was synthesized by the nucleophilic substitution reaction of 4,4′‐difluoro benzophenone with tert‐butyl hydroquinone in N‐methyl‐2‐pyrrolidone. Blends with various amounts of PEEKT were prepared by melt‐mixing. All the blends were homogeneous in the uncured state. The glass transition temperature of the binary epoxy/PEEKT blends was predicted using several equations. Reaction‐induced phase separation was found to occur upon curing with a diamine 4,4′‐diaminodiphenyl sulfone. The phase morphology of the blends was studied using scanning electron microscopy. From the micrographs, it was found that PEEKT‐rich phase was dispersed in a continuous epoxy matrix. The domain size increased with the amount of PEEKT in the blends. The increase in domain size was due to the coalescence of the domains after phase separation. Dynamic mechanical analysis of the blends gave two peaks corresponding to epoxy‐rich phase and thermoplastic‐rich phase. The tensile strength and modulus of the blends remained close to that of the unmodified resin, while the flexural properties decreased with the addition of PEEKT to epoxy resin. The fracture toughness of the epoxy resin increased with the addition of PEEKT. Investigation of the fracture surfaces revealed evidences for local plastic deformation of the matrix, crack pinning, crack path deflection, and ductile tearing of PEEKT‐rich phase. Thermogravimetric analysis revealed that the initial decomposition temperature of the blends were close to that of the unmodified resin. Finally, the properties of the blends were compared with other modified PEEK/epoxy blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2481–2496, 2007     

Near‐infrared spectroscopic studies on the cure behaviors of the CAE/DGEBA blend system initiated by a thermal latent catalyst

The latent properties and cure behaviors of an epoxy blend system based on cycloaliphatic epoxy (CAE) and diglycidyl ether of bisphenol A (DGEBA) epoxy containing N‐benzylpyrazinium hexafluoroantimonate (BPH) as a thermal latent initiator were investigated with near‐infrared (N‐IR) spectroscopy. The assignments of the latent properties and cure kinetics were performed by the measurements of the N‐IR reflectance for epoxide and hydroxyl functional groups at different temperatures and compositions. As a result, this system showed more than one type of reaction, and BPH was an excellent thermal latent catalyst without any coinitiator. The cure behaviors were identified by the changes in the absorption intensity of the hydroxyl groups at 7100 cm⁻¹ with different composition ratios. Moreover, characteristic N‐IR band assignments were used to evaluate the reactive kinetics and were shown to be an appropriate method for studying the cure behaviors of the CAE/DGEBA blend system containing a thermal latent catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 326–331, 2001     

Mechanistic study of ring‐opening copolymerization of ɛ‐caprolactam with epoxide: Development of novel thermosetting epoxy resin system

We investigated the mechanism of the ring‐opening copolymerization of ?‐caprolactam (?‐CL) with glycidyl phenyl ether (GPE) to afford poly(?‐CL‐co‐GPE) as a model reaction of the thermal curing of certain epoxy resins with ?‐CL. The reaction of ?‐CL and GPE proceeded efficiently in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) at 170^°C for 2 h. The monomer reactivities r₁ of ?‐CL and r₂ of GPE calculated according to the Fineman‐Ross method and the Kelen‐Tüdös method were 0.58 and 5.52, respectively. These values indicate that poly(?‐CL‐co‐GPE) has a pseudo‐block gradient copolymer. Based on these results, we examined the thermal curing reactions of certain epoxy resins with ?‐CL. The corresponding novel cured products were obtained quantitatively, and each of them showed a high glass transition temperature and high thermal stability, presumably due at least in part to a pseudo‐block gradient primary structure resembling that of poly(?‐CL‐co‐GPE). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2220–2228     

Thermal properties and flame retardancy of novel epoxy based on phosphorus‐modified Schiff‐base

Through addition reaction of Schiff‐base terephthalylidene‐bis‐(p‐aminophenol) ( DP‐1 ) and diethyl phosphite (DEP), a novel phosphorus‐modified epoxy, 4,4'‐diglycidyl‐(terephthalylidene‐bis‐(p‐aminophenol))diphosphonate ether ( EP‐2 ), was obtained. An modification reaction between EP‐2 and DP‐1 resulted in an epoxy compound, EP‐3 , possessing both phosphonate groups and C?N imine groups. The structure of EP‐2 was characterized by Fourier transform infrared (FTIR), elemental analysis (EA), ¹H, ¹³C, and ³¹P NMR analyses. The thermal properties of phosphorus‐modified epoxies cured with 4,4'‐diaminodiphenylmethane (MDA) and 4,4'‐diaminodiphenyl ether (DDE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The activation energies of dynamic thermal degradation (E_d) were calculated using Kissinger and Ozawa's methods. The thermal degradation mechanism was characterized using thermogravimetric analysis/infrared spectrometry (TG‐IR). In addition, the flame retardancy of phosphorus‐modified epoxy thermosets was evaluated using limiting oxygen index (LOI) and UL‐94 vertical test methods. Via an ingenious design, phosphonate groups were successfully introduced into the backbone of the epoxies; the flame retardancy of phosphorus‐modified epoxy thermosets was distinctly improved. Due to incorporation of C?N imine group, the phosphorus‐modified epoxy thermosets exhibited high thermal stabilities; the values of glass‐transition temperatures (T_gs) were about 201–210°C, the values of E_d were about 220–490 kJ/mol and char yields at 700°C were 49–53% in nitrogen and 45–50% in air. These results showed an improvement in the thermal properties of phosphorus‐modified epoxy by the incorporation of C?N imine groups. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and Properties of a Novel Cycloaliphatic Epoxide

The novel cycloaliphatic epoxide 3,4‐epoxycyclohexylmethyl‐2′,3′‐epoxycyclohexyl ether ( II ) containing an unsymmetrical epoxycyclohexyl moiety linked via an ether bond, and its precursor 3‐cyclohexene‐1‐methyl‐2′‐cyclohexene ether ( I ) were synthesized. Their structure was confirmed by means of elemental analysis, FT‐IR and ¹H NMR spectroscopy. Compared with commercial epoxide ERL‐4221, the newly synthesized epoxide II shows a higher epoxy value (0.85 eq/g) and lower viscosity (86 mpa·s/25°C). The cured product, based on epoxide II and curing agent hexahydro‐4‐methylphthalic anhydride (HMPA), showed higher glass transition temperature (162°C), higher storage modulus at the glass transition region (2.95 GPa), higher crosslinking density (1.60×10^–3 mol/cm³) and a lower coefficient of thermal expansion (6.22×10^–5/°C).     

Recyclable carbon fiber‐reinforced plastics (CFRP) containing degradable acetal linkages: Synthesis,properties, and chemical recycling

Two epoxy resins containing degradable acetal linkages were synthesized by the reaction of cresol novolak‐type phenolic resin (CN) with vinyl ethers containing a glycidyl group [cyclohexane dimethanol vinyl glycidyl ether (CHDMVG) and 4‐vinyloxybutyl glycidyl ether (VBGE). Carbon fiber‐reinforced plastics (CFRPs) were prepared by heating laminated prepreg sheets with CN‐CHDMVG resin (derived from CN and CHDMVG) and CN‐VBGE resin (derived from CN and VBGE), in which carbon fibers are impregnated with epoxy resins containing curing agents [dicyandiamide (DICY)] and curing accelerator [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU)]. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs exhibited almost the same tensile strength as the conventional bisphenol‐A‐based CFRPs. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs underwent smooth breakdown with the treatment of hydrochloric acid in tetrahydrofuran at room temperature for 24 h to regenerate strands of carbon fibers. The surface conditions of the recovered carbon fibers had little changes during degradation and recovery processes on the basis of scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The recovered carbon fibers exhibited almost the same tensile strength as virgin carbon fibers and hence would be reused for the production of CFRPs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1052–1059