Interpenetrating polymer networks derived from epoxide-amine adducts in either polymer network

A new type of interpenetrating polymer network was synthesized via photoinitiated free-radical polymerization of α,ω-methacryloyl terminated macromonomers prepared from epoxide-amine-adducts, followed by thermal addition polymerization of bisphenol-A diglycidyl ether and 4,4′-diaminodiphenylsulfone or 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0.^2,6]decane. The interpenetrating polymer networks are optically transparent and show only one glass transition temperature ranging from -10 to 130°C, as a function of the macromonomer/addition polymer mixing ratio. The presence of a single phase was confirmed by scanning electron microscopy (SEM).     

Toughening of epoxy resin by reacting with functional terminated-polyurethanes

Hydroxyl-, amine-, and anhydride-terminated polyurethane (PU) prepolymer which were synthesized from polyether (PTMG) diol, 4,4′-diphenylmethane diisocyanate (MDI), and a coupling agent bisphenol-A, 4,4′-diaminodiphenyl sulfone (DDS), or benzophenonetetracarboxylic dianhydride (BTDA) were used to modify the toughness of bisphenol-A diglycidyl ether epoxy resin (DGEBA) cured with 4,4′-diaminodiphenyl sulfone. From the experimental results, it was shown that the modified resin displayed a significant improvement in fracture energy (G_IC) and also in its interfacial shear strength with polyaramid fiber. It was more enhanced with increase of the PU modifier wt % content. The hydroxyl-terminated PU was found to be the most effective among those three prepolymers. In addition, the toughening mechanism was discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by transmission (TEM) and scanning electron microscopy (SEM) revealed that the modified resin had a two-phase structure. The existence of an unclean fiber surface after its fiber pullout test suggested that a ductile fracture might have occurred. © 1995 John Wiley & Sons, Inc.     

Impact of hexafluoroisopropylidene on the solubility of aromatic‐based polymers in supercritical fluids

Three different supercritical fluids (SCF), CO₂, dimethyl ether (DME), and propane, are investigated as potential solvents for processing two lactide‐based terpolymers and two perfluorocyclobutyl (PFCB) aryl ether polymers. The repeat unit of the lactide‐based terpolymers consists of a 1:1:1 ratio of L ‐lactide, diglycidyl ether of bisphenol A (DGEBA), and, in one case, 4,4′‐hexafluoroisopropylidenediphenol (6F‐Bis‐A) and, in the other case, 4,4′‐isopropylidenediphenol (6H‐Bis‐A). The PFCB‐based polymers are synthesized from 1,1‐bis[4‐[(trifluorovinyl)oxy]phenyl]hexafluoroisopropylidene (6FVE) and from bis(trifluorovinyloxy)biphenyl (BPVE). For both classes of polymer the steric effect of the hexafluoroisopropylidene (6F) group reduces chain–chain interactions, disrupts electronic resonance between adjacent aromatic groups, and improves solubility. The two lactide‐based terpolymers do not dissolve in CO₂ or propane, but dissolve in DME. At room temperature the poly(lactide 6F‐BisA DGEBA) terpolymer dissolves at 700 bar lower pressure in DME compared to the poly(lactide 6H‐Bis‐A DGEBA) terpolymer. Although the 6FVE polymer dissolves in all three SCF solvents, pressures in excess of 800 bar are needed to dissolve this polymer in CO₂ and propane while 6FVE dissolves in DME at pressure below 150 bar. The other PFCB‐based polymer (BPVE) only dissolves in DME, again at low pressure, although BPVE drops out of solution as the system temperature is raised above ～40°C, whereas 6FVE remains in solution in DME for temperatures up to 90°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1736–1743, 2005     

Synthesis and characterization of novel wholly para‐oriented aromatic polyamide‐hydrazides containing sulfone‐ether linkages

Four novel wholly para‐oriented aromatic polyamide‐hydrazides containing flexibilizing sulfone‐ether linkages in their main chains have been synthesized from 4‐amino‐3‐hydroxy benzhydrazide (4A3HBH) with either 4,4′‐sulfonyldibenzoyl chloride (SDBC), 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoyl chloride (SODBC), 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoyl chloride (4MeSODBC), or 4,4′‐(1,4‐phenylenedioxy)dibenzoyl chloride (ODBC) via a low‐temperature solution polycondensation reaction. A polyamide‐hydrazide without the flexibilizing linkages is also investigated for comparison. It was synthesized from 4A3HBH and terephthaloyl chloride (TCl) by the same synthetic route. The intrinsic viscosities of the polymer ranged from 2.85 to 4.83 dL g^?1 in N,N‐dimethyl acetamide (DMAc) at 30°C and decreased with introducing the flexibilizing linkages into the polymer. All the polymers were soluble in DMAc, N,N‐dimethyl formamide (DMF), and N‐methyl‐2‐pyrrolidone (NMP), and their solutions could be cast into films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased remarkably by introducing the flexibilizing linkages. The polymers could be thermally cyclodehydrated into the corresponding poly(1,3,4‐oxadiazolyl‐benzoxazoles) approximately in the region of 295–470°C either in nitrogen or in air atmospheres. The flexibilizing linkages improve the solubility of the resulting poly(1,3,4‐oxadiazolyl‐benzoxazoles) when compared with poly(1,3,4‐oxadiazolyl‐benzoxazoles) free from these linkages. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physicomechanical Properties of Carbon Fiber Reinforced Epoxy Composites

Fabrication of carbon fiber reinforced epoxy composites from the matrix resins diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl bis(aminotolyl) cyclohexane (TGBATC) using 4,4′-diaminodiphenyl methane (DDM) as curing agent. The composites were evaluated for their physical and mechanical properties. A significant improvement in the properties was observed on addition of 20 phr of an epoxy fortifier.     

Preparations and properties of a high performance semicrystalline copolyimide and composites reinforced with glass fiber

A semicrystalline copolyimide derived from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA), 1,3‐bis‐(4‐aminophenoxy)benzene (TPER), and 4,4′‐oxydianiline (4,4′‐ODA), end capped with phthalic anhydride (PA), was synthesized. Glass fiber reinforced composite was also prepared by impregnating powdery glass fiber with poly(amic acid) followed by solution imidization techniques. This copolyimide displayed a glass transition temperature of 202°C and a melting temperature of 373°C by differential scanning colorimeter (DSC). Crystallization and melting behaviors were investigated under nonisothermal and isothermal crystallization conditions. Double exothermic peaks were found by DSC when the copolyimide was cooled from the melt and multiple melting behaviors can be observed after the coployimide had been isothermally crystallized at different temperatures. Mechanical properties were investigated by dynamical mechanical analysis (DMA) and tensile experiments. The samples were cured at different temperatures and then tested at different temperatures. Results indicated that the copolyimide and the composite showed excellent mechanical properties. Additionally, this copolyimide also showed lower melt viscosity by rheological analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40345.     

Synthesis and characterization of poly (hydroxyether ketone) and its copolymers

A novel semi‐crystalline polyhydroxyether, poly(hydroxyether ketone) (PHEK), was synthesized via the direct polycondensation between 4,4‐dihydroxybenzophenone and epichlorohydrin. By means of Fourier transform infrared and NMR spectroscopy and gel permeation chromatography (GPC), the structure of PHEK was characterized. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXRD) show that PHEK is a semi‐crystalline polymer with a high rate of crystallization. The polymer possesses a glass transition temperature of 109 °C and a melting temperature of 239 °C. When 4,4′‐isopropylidenediphenol was used as a second bisphenol and was added to copolymerize with a stoichiometric amount of epichlorohydin, a series of polyhydroxyether copolymers were obtained. The copolymers with various compositions were characterized by means of NMR, GPC, WAXRD and DSC. It was found that the crystallinity of the copolymers dramatically decreased with increasing content of 4,4′‐isopropylidenediphenol. The glass transition temperatures of the copolymers are intermediate between those of PHEK and the poly(hydroxyether of bisphenol A) and decreased with increasing content of 4,4′‐isopropylidenediphenol. Copyright © 2007 Society of Chemical Industry     

Control of morphologies and mechanical properties of thermoplastic‐modified epoxy matrices by addition of a second thermoplastic

Ternary mixtures based on stoichiometric mixtures of the diglycidyl ether of bisphenol‐A (DGEBA) and 4,4′‐diaminodiphenyl sulfone (DDS) and two miscible thermoplastics, poly(methyl methacrylate) (PMMA) and the poly(hydroxy ether of bisphenol‐A) (phenoxy), were investigated by optical microscopy (OM), atomic force microscopy (AFM) and dynamic mechanical analysis (DMA). Mechanical testing was used to study the ultimate behavior. All the modified epoxy mixtures were heterogeneous. DMA has been shown to be an excellent technique for detecting the morphologies generated after curing when the loss modulus is used for analysis. Morphology varied with the thermoplastic content on the mixtures. The addition of a second thermoplastic in small amounts changed the morphological features from particulated to co‐continuous and from that to phase‐inverted morphologies. A significant increase in fracture toughness was observed above all for the mixtures with some level of co‐continuity within the epoxy‐rich matrix. Phase inversion led to poor strength and also fracture toughness. Copyright © 2003 Society of Chemical Industry     

Synthesis and characterization of novel polyphenol species derived from bis(4‐aminophenyl)ether: Substituent effects on thermal behavior,electrical conductivity,solubility, and optical band gap

In this study, four different Schiff bases namely 4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (2‐HBA), 4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (4‐HBA), 4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (3,4‐HBA), and 4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (HMBA) were synthesized. These Schiff bases were converted to their polymers that have generate names of poly‐4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (P‐2‐HBA), poly‐4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (P‐4‐HBA), poly‐4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (P‐3,4‐HBA), and poly‐4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (PHMBA) via oxidative polycondensation reaction by using NaOCl as the oxidant. Four different metal complexes were also synthesized from 2‐HBA and P‐2‐HBA. The structures of the compounds were confirmed by FTIR, UV‐vis, ¹H and ¹³C NMR analyses. According to ¹H NMR spectra, the polymerization of the 2‐HBA and 4‐HBA largely maintained with C? O? C coupling, whereas the polymerization of the 3,4‐HBA and HMBA largely maintained with C? C coupling. The characterization was made by TG‐DTA, size exclusion chromatography and solubility tests. Also, electrical conductivity of the polymers and the metal complex compounds were measured, showing that the synthesized polymers are semiconductors and their conductivities can be increased highly via doping with iodine ions (except PHMBA). According to UV–vis measurements, the optical band gaps (E_g) were found to be 3.15, 2.06, 3.23, 3.02, 2.61, 2.47, 2.64, 2.42, 2.83, 2.77, 2.78, and 2.78 for 2‐HBA, P‐2‐HBA, 4‐HBA, P‐4‐HBA, 3,4‐HBA, P‐3,4‐HBA, HMBA, PHMBA, 2‐HBA‐Cu, 2‐HBA‐Co, P‐2‐HBA‐Cu, and P‐2‐HBA‐Co, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improvement of Elastic Modulus and Thermal Stability of Epoxy Resin Using New Curing Agents

New curing agents 2,5-diamino-1,3,4-thiadiazole (DATD) and N-(4-hydroxybenzal) N'(4′-hydroxyphenyl) thiourea (HHPT) were synthesised and characterized using FT-IR, 1H-NMR and 13C-NMR analysis. The curing reactions were studied for the epoxy resin diglycidyl ether of bisphenol-A (DGEBA) using new curing agents along with the conventional aromatic diamine 4,4′-diamino diphenyl methane (DDM) for comparison purpose. The curing profiles of DDM, DATD and DATD/HHPT towards DGEBA were examined by Differential Scanning Calorimetry (DSC). Elastic modulus and thermal stability of the cured resins were evaluated using DMA and TGA analysis. When compared with DDM and DATD, the DATD/HHPT curing system accelerated the curing rate due to the presence of phenol molecules in the HHPT. Furthermore, the DATD/HHPT-cured epoxy resin demonstrated higher elastic modulus along with better thermal stability.     

Toughening of epoxy resin by functional‐terminated polyurethanes and/or semicrystalline polymer powders

Hydroxyl‐, amine‐, and anhydride‐terminated polyurethane (PU) prepolymers, which were synthesized from polyether [poly(tetramethylene glycol)] diol, 4,4′‐diphenylmethane diisocyanate, and a coupling agent, bisphenol‐A (Bis‐A), 4,4′‐diaminodiphenyl sulphone (DDS), or benzophenonetetracarboxylic dianhydride, were used to modify the toughness of Bis‐A diglycidyl ether epoxy resin cured with DDS. Besides the crystalline polymers, poly(butylene terephthalate) (PBT) and poly(hexamethylene adipamide) (nylon 6,6), with particle sizes under 40 μm were employed to further enhance the toughness of PU‐modified epoxy at a low particle content. As shown by the experimental results, the modified resin displayed a significant improvement in fracture energy and also its interfacial shear strength with polyaramid fiber. The hydroxyl‐terminated PU was the most effective among the three prepolymers. The toughening mechanism is discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by the scanning electron microscopy revealed that the modified resin had a two‐phase structure. The fracture properties of PBT‐particle‐filled epoxy were better than those of nylon 6,6‐particle‐filled epoxy. Nevertheless, the toughening effect of these crystalline polymer particles was much less efficient than that of PU modification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2903–2912, 2001     

The Curing Behavior and Properties of Diglycidyl Ether of 4,4′-Bis(4-hydroxybenzoyloxy)-3,3′,5,5′-tetramethylbiphenyl and its Composites with Multi-Wall Carbon Nanotubes

The curing system of a liquid crystalline epoxy monomer, diglycidyl ether of 4,4′-bis(4-hydroxybenzoyloxy)-3,3′,5,5′-tetramethylbiphenyl (DGE-BHBTMBP), and curing agent diaminodiphenylsulfon (DDS) was investigated by means of differential scanning calorimetry (DSC). Physical properties of the cured polymer and its composites with carbon nanotubes were evaluated with dynamic mechanical thermal analysis (DMA). Test of transmission electron microscopy (TEM) showed that oxidated multi-wall carbon nanotubes (OX-MWNT) performed a better dispersion in the cured polymer than untreated MWNT did. The storage modulus of the cured polymer containing OX-MWNT increased, while that containing untreated MWNT decreased. The results also showed that the T_g decreased when the MWNT was filled.     

Viscoelastic behaviour of epoxy resins modified with poly(methyl methacrylate)

The viscoelastic behaviour of a stoichiometric diglycidyl ether of bisphenol-A, (DGEBA), 4,4′-diaminodiphenylmethanes (DDM)s epoxy matrix modified with several amounts of poly(methyl methacrylate) (PMMA) has been studied by dynamic-mechanical analysis. Mixtures pre-cured at 80°C ranged from transparency to opacity as thermoplastic content changed from 5 to 15wt%. These changes have been attributed to variations in the ratio between polymerization rate and phase separation rate when PMMA content increased in the mixtures. When PMMA segregated from the epoxy matrix during curing, it had no influence on the crosslinking density of the epoxy phase. The clear decrease of temperature and activation energy of the β relaxation with respect to those values for the neat matrix, observed for the 5wt% PMMA-containing mixture but not for the 15wt% PMMA-containing one, are proposed to be a consequence of physical interactions between the PMMA chains and some epoxy oligomers. The dissimilar variation of the height of the ω relaxation with frequency when compared to that for the other relaxations studied, outlines the significance of physical factors influencing this relaxation. © 1998 Society of Chemical Industry     

Polycondensation kinetics of poly(phenylene ether sulphone)

The synthesis of poly(phenyl ether sulphone) (from the potassium salts of 4,4′-dihydroxydiphenyl sulphone and 4,4′-dichlorodiphenyl sulphone or 4-chloro-4′-hydroxydiphenyl sulphone) was found to have different reaction kinetics according to the route used. By discriminating between rate constants (between monomer/monomer, monomer/polymer, polymer/polymer) a set of multi-parameter kinetic equations is obtained. Experimental and simulated values of the individual rate constants were in good agreement (for both the reaction rate and molecular weight distribution). The polycondensation reaction can be analysed, in terms of the component reactions.     

Kinetic parameters of the thermoplastic/thermoset epoxy reaction by fourier transform infrared spectroscopy

The melt state reaction, or fusion process of bisphenol-A and the diglycidyl ether of bisphenol-A can produce both linear phenoxy backbone chains and crosslinked network structures. The linear chains can be thought of as thermoplastic polymer, while the crosslinked molecular matrix is a thermoset; therefore, this resin system can be termed a thermoplastic/thermoset epoxy. Fourier transform infrared spectroscopy has been employed to study the chemical kinetics of the urea catalyzed system. The reaction of bisphenol-A and the diepoxide follows first order kinetics with respect to epoxide concentration, through 95 percent consumption of the epoxide for reaction temperatures of 130°C and above while lower temperatures show deviation from first order behavior at 75 percent conversion. When the differential form of the kinetic equation is used for analysis, the system follows first order behavior through 60 percent conversion of the epoxide at which point the order increases to a value of 1.5. Rapid spectral collection techniques have been employed to study this behavior for the temperatures 110 to 160°C. Upon incorporation of 3,4′ bisphenol-A into the system first order behavior still adequately describes the kinetic behavior; however the rate of epoxide consumption and the activation energy are affected. Since the stoichiometric ratio of bisphenol-A to diepoxide was found to affect the rate constant, the reaction mechanisms of linear chain growth and crosslinking cannot be clearly distinguished by the sole use of this technique.     

Thermal,physical and flame-retardant properties of phosphorus-containing epoxy cured with cyanate ester

Two phosphorus-containing advanced epoxy resins were obtained by chain-extension of diglycidyl ether of bisphenol-A epoxy (DGEBA) resin with 2-(6-oxido-6H-dibenz(c,e)(1,2)-oxaphosphorin-6-yl)-1,4-benzenediol (DOPOBQ), at different stoichiometric ratios. The phosphorus-containing advanced epoxy was separately cured with various dicyanate esters to form flame-retardant epoxy/cyanate ester systems. The effects of phosphorus content and dicyanate ester structure were studied, and compared with those of the control (advanced bisphenol-A epoxy) system. The DOPOBQ-containing epoxy/cyanate ester systems exhibited higher glass transition temperatures, better dimensional stability and better thermal stability.     

Poly(ether urethane) flexible cyanate ester resins: Synthesis,characterization, and performance in commercial epoxy and polyurethane applications

A poly(ether urethane)‐based cyanate ester resin (PEUCER) with a biphenyl polyether backbone obtained from polymeric 4,4′‐diphenylmethanediisocyanate, bisphenol A, polyether polyols of three different molecular weights, and cyanogen bromide was synthesized to obtain a polymer with better functional and physical properties, such as adhesion, flexibility, and thermal stability. The synthesis of the poly(ether urethane)‐based 4,4′‐(oxybiphenyl propane) cyanate ester involved three steps: the formation of the poly(ether urethane) NCO‐terminated prepolymer, the formation of the OH‐terminated poly (ether urethane) prepolymer (PEU–PP), and the esterification reaction of cyanate to produce PEUCER. PEUCER was cyclotrimerized to yield a triazine‐ring‐containing polymer, which possessed better adhesion at high temperatures and better impact resistance. PEU–PP and PEUCER were characterized with wet chemical analysis, spectral methods, and thermal methods. PEUCER showed better performance with respect to thermal and adhesion properties with a single‐part polyurethane lamination adhesive and also showed better performance as a toughening agent in a two‐part epoxy laminate system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

High‐performance epoxy hybrid nanocomposites containing organophilic layered silicates and compatibilized liquid rubber

A mixture of two epoxy resins, tetraglycidyl 4,4′‐diaminodiphenyl methane and bisphenol‐A diglycidylether, cured with 4,4′‐diaminodiphenyl sulfone, was used as matrix material for high‐performance epoxy hybrid nanocomposites containing organophilicly modified synthetic fluorohectorite and compatibilized liquid six‐arm star poly(propylene oxide‐block‐ethylene oxide) (abbreviated as PPO). The hydroxy end groups of the poly(propylene oxide‐block‐ethylene oxide) were modified, yielding a six‐arm star PPO with an average of two pendant stearate chains, two phenol groups, and two hydroxy end groups. The alkyl chains of the stearate end groups played an important role in tailoring the polarity of the polymer. Its phenol end groups ensured covalent bonding between liquid polymer and epoxy resin. Two different organophilic fluorohectorites were used in combination with the functionalized PPO. The morphology of the materials was examined by transmission electron microscopy. The hybrid nanocomposites were composed of intercalated clay particles as well as separated PPO spheres in the epoxy matrix. As determined by dynamic mechanical analysis, the prepared composites possessed glass‐transition temperatures around 220°C. Although the tensile moduli remain unaltered, the tensile strengths of the hybrid materials were significantly improved. The relatively high fracture toughness of the neat resin, though, was not preserved for the hybrid resins. Scanning electron microscopy of the fracture surfaces revealed extensive matrix shear yielding for the neat resin, whereas the predominant fracture mode of the hybrid nanocomposites was crack bifurcation and branching. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3088–3096, 2004     

New polymer syntheses: II. Preparation of aromatic poly(ether ketone)s from silylated bisphenols

Bulk condensations of 4,4′-difluorobenzophenone and various silylated bisphenols were carried out at 220°–320°C, with caesium fluoride as catalyst. Silylated bisphenol-A, tetramethylbisphenol-A, 1,1-bis(4-hydroxyphenyl)cyclohexane or 4,4′-dihydroxydiphenylsulphone as monomers and glassy polymers were soluble in several organic solvents. Their glass transitions were determined by differential scanning calorimetry (d.s.c.) and their number molecular weights ($\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$) determined by means of vapour pressure osmometry. M_n's up to 10 000 were obtained. When silylated hydroquinone, 4,4′-dihydroxydiphenyl, 2,7-dihydroxynaphthalene or 4,4′-dihydroxydiphenylsulphide undergo polycondensation the resulting poly (ether ketone)s form crystals. It is demonstrated that transesterification does not take place and that block copoly(ether ketone-ether sulphone)s are synthesized. Furthermore, the thermostability of the poly(ether ketone)s in air was investigated.     

Correlation between stress-whitening and fracture toughness in rubber-modified epoxies

Fracture toughness of rubber modified epoxy systems was evaluated in relation to stresswhitening. The epoxy systems consisted of diglycidyl ethers of bisphenol A (DGEBA)-based epoxy resin, 4,4′ diaminodiphenyl sulphone (DDS) as curing agent, and carboxylterminated butadiene-acrylonitrile (CTBN) rubber. It was found that a peak value of fracture toughness occurs at a small amount of rubber content (∼ 4 phr) and closely corresponds to that of stress-whitening size. Other properties such as flexural strength and flexural modulus were also found to display maxima at a similar amount of rubber content. © 1996 John Wiley & Sons, Inc.