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Curing Agent (curing + agent)
Selected AbstractsCuring Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel ComplexesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006Abdollah Omrani Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source] Electroosmotic flow in a poly(dimethylsiloxane) channel does not depend on percent curing agentELECTROPHORESIS, Issue 7-8 2004Aaron R. Wheeler Abstract Poly(dimethylsiloxane) (PDMS) microfluidic devices were prepared from different ratios of "curing agent" (which contains silicon hydride groups) to "base" (which contains vinyl-terminated noncross-linked PDMS), to determine the effect of this ratio on electroosmotic flow (EOF). In fabricating devices for this purpose, a novel method for permanently enclosing PDMS channels was developed. As a supplement to the microfluidic method, the inner walls of capillaries were coated with PDMS formed from varying ratios of curing agent to base. EOF was found to be constant for PDMS formed with each ratio, which implies that the negative surface charges do not arise from chemical species present only in the base or the curing agent. [source] Self-Healing Chemistry: Delivery of Two-Part Self-Healing Chemistry via Microvascular Networks (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Mater. Microvascular self-healing of a brittle coating is accomplished by supplying fluid healing agents from an underlying network of microchannels. Dual independent networks filled with a two-part healing chemistry (epoxy resin and curing agent) that repeatedly heal damage in the coating up to 16 consecutive times are reported by K. S. Toohey et al. on page 1399. [source] Preparation and characterization of epoxy/kaolinite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Xinnian Xia Abstract Epoxy/kaolinite nanocomposites were prepared by adding the organically modified layered kaolinite to an epoxy resin [biphenyl phenol novolac epoxy resin (BPNE)] with 4,4,-diamino biphenyl sulfone (DDS) as a curing agent. The dispersion state of the kaolinite within crosslinked epoxy-resin matrix was examined by X-ray diffraction (XRD) and transmission electron micrograph (TEM). The effects of kaolinite on thermal properties were investigated and discussed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Experimental results show that BPNE/kaolinite nanocomposites exhibit improved thermal than pure BPNE. When the kaolinite content is 5 wt %, the BPNE/kaolinite nanocomposites show the best thermal properties. These results indicate that nanocomposition is an efficient and convenient method to improve the thermal properties of BPNE. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Curing mechanisms and kinetic analysis of DGEBA cured with a novel imidazole derivative curing agent using DSC techniquesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Li Liu Abstract A novel imidazole derivative, 2MI- g -CA, was obtained through the reaction of 2-methylimidazole (2MI) and cyanuric acid (CA) and characterized by means of elemental analysis, FTIR spectroscopy, 1H NMR spectroscopy, and mass spectrometric analysis. The curing mechanisms and kinetics of diglycidyl ether of bisphenol A (DGEBA) using 2MI and 2MI- g -CA as curing agents were studied with differential scanning calorimetry (DSC) under dynamic and isothermal conditions. Both dynamic and isothermal DSC thermograms of DGEBA/2MI system showed two distinct exothermic peaks, whereas those of DGEBA/2MI- g -CA system showed only one distinct exothermic peak. These results indicated that the two systems have different initiation curing mechanisms. The apparent activation energies (Ea) obtained from DSC scanning runs using the Kissinger and Ozawa methods were 79.0, 83.0 kJ/mol and 84.2, 88.8 kJ/mol for DGEBA/2MI and DGEBA/2MI- g -CA systems, respectively. These values suggested the novel curing agent 2MI- g -CA exhibited greater levels of latency during cure or increased the pot life of epoxy resin system. In addition, under the same curing condition, the Tg values of DGEBA/2MI- g -CA system were about 25°C higher than those of DGEBA/2MI system, exhibiting a better thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Glass fiber-reinforced composite based on benzoxazine resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009Hajime Kimura Abstract In this study, we aimed to prepare and characterize glass fiber-reinforced composites (GFRP) based on benzoxazine resins. Therefore, the molten resin from benzoxazine and bisoxazoline with the latent curing agent was used as the matrix resin, and the properties of GFRP based on the molten resins were investigated. The properties of GFRP were estimated by mechanical properties, heat resistance, and flame resistance. As a result, it was found that GFRP based on the molten resins from benzoxazine and bisoxazoline with the latent curing agent showed good heat resistance, flame resistance, and mechanical properties compared with those of the conventional GFRP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Effect of rheological behavior of epoxy during precuring on foamingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Osamu Takiguchi Abstract In this study, the effect of rheological behavior of epoxy during precuring on foaming was investigated. Dynamic time sweep test of epoxy/curing agent (100/1, w/w) was conducted. The viscosities as a function of time showed extremely rapid increase from the order of 102,103 to 106Pa · s at a certain time, followed by slow increase of the viscosities. Dynamic frequency sweep test of precured epoxy with curing agent was conducted at 90°C. The critical gelation time was obtained by using rheological criterion proposed by Winter and Chambon. We found that the slopes of G,(,) and G,(,) decreased with increasing precuring time. Correspondingly, tan , showed a change from negative to positive slope at a critical time. By using the results, the critical gelation time was determined as t = 895,935 s. Samples of epoxy/curing agent/blowing agent (100/1/0.5) were precured for 960,1620 s. And then precured samples were foamed at 230°C for 300 s to decompose chemical blowing agent. The formed bubble size distribution becomes sharp with increase of the precuring time. There are roughly two sizes of bubbles when precured for relatively short time (t < 1080 s) before foaming: large bubbles (>100 ,m) and small ones (,30 ,m). On the other hand, foams precured for long time (t > 1200 s) before foaming, large bubbles disappear, and the average diameter of the bubble becomes small while the porosity is low. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal degradation kinetics of epoxy/organically modified montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Ivan Brnardi Abstract Nanocomposites based on a commercial epoxy resin and organically modified montmorillonites (OMMTs), containing 5 and 10 phr OMMT, were prepared and characterized. Poly(oxypropylene) diamine (Jeffamine D400) and octadecylamine were used as organic modifiers. Another poly(oxypropylene) diamine (Jeffamine D230) was used as a curing agent. The thermal degradation kinetics of the neat resin system and nanocomposites were investigated by thermogravimetric analysis. The dispersion of silicate layers within the crosslinked epoxy matrix was verified by transmission electron microscopy. The activation energy of degradation for the investigated systems was determined by the isoconversional Kissinger,Akahira,Sunose method. The thermal behavior of the neat resin systems and nanocomposites was modeled with an empirical kinetic model. The influence of organic modifiers and the OMMT loading on the thermal stability of the nanocomposites was discussed. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008 [source] New type of phenolic resin,The curing reaction of bisphenol A based benzoxazine with bisoxazoline and the properties of the cured resin.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Abstract The curing reaction of a bisphenol A based benzoxazine [2,2-bis(3,4-dihydro-3-phenyl-1,3-benzoxazine) propane (Ba)] and bisoxazoline with a latent curing agent and the properties of the cured resins were investigated. With a latent curing agent, the ring-opening reaction of the benzoxazine ring occurred more rapidly, and then the phenolic hydroxyl group generated by the ring-opening reaction of the benzoxazine ring also reacted with the oxazoline ring more rapidly. The cure time of molten resins from Ba and bisoxazoline with a latent curing agent was reduced, and the cure temperature was lowered, in comparison with those of resins from Ba and bisoxazoline without a latent curing agent. The melt viscosity of molten resins from Ba and bisoxazoline with a latent curing agent was kept around 50 Pa s at 80°C even after 30 min, and molten resins from Ba and bisoxazoline with a latent curing agent showed good thermal stability below 80°C. However, above 170°C, the curing reaction of Ba with bisoxazoline with a latent curing agent proceeded rapidly. Cured resins from Ba and bisoxazoline with a latent curing agent showed good heat resistance, flame resistance, mechanical properties, and electrical insulation in comparison with cured resins from Ba and bisoxazoline without a latent curing agent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Mechanical and morphological properties of organic,inorganic, hybrid, clay-filled, and cyanate ester/siloxane toughened epoxy nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007S. Nagendiran Abstract Organic,inorganic hybrids involving cyanate ester and hydroxyl-terminated polydimethylsiloxane (HTPDMS) modified diglycidyl ether of bisphenol A (DGEBA; epoxy resin) filled with organomodified clay [montmorillonite (MMT)] nanocomposites were prepared via in situ polymerization and compared with unfilled-clay macrocomposites. The epoxy-organomodified MMT clay nanocomposites were prepared by the homogeneous dispersion of various percentages (1,5%), and the resulting homogeneous epoxy/clay hybrids were modified with 10% HTPDMS and ,-aminopropyltriethoxysilane as a coupling agent in the presence of a tin catalyst. The siliconized epoxy/clay prepolymer was further modified separately with 10% of three different types of cyanate esters, namely, 4,4,-dicyanato-2,2,-diphenylpropane, 1,1,-bis(3-methyl-4-cyanatophenyl) cyclohexane, and 1,3-dicyanato benzene, and cured with diaminodiphenylmethane as a curing agent. The reactions during the curing process between the epoxy, siloxane, and cyanate were confirmed by Fourier transform infrared analysis. The results of dynamic mechanical analysis showed that the glass-transition temperatures of the clay-filled hybrid epoxy systems were lower than that of neat epoxy. The data obtained from mechanical studies implied that there was a significant improvement in the strength and modulus by the nanoscale reinforcement of organomodified MMT clay with the matrix resin. The morphologies of the siloxane-containing, hybrid epoxy/clay systems showed heterogeneous character due to the partial incompatibility of HTPDMS. The exfoliation of the organoclay was ascertained from X-ray diffraction patterns. The increase in the percentage of organomodified MMT clay up to 5 wt % led to a significant improvement in the mechanical properties and an insignificant decrease in the glass-transition temperature versus the unfilled-clay systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Synthesis of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine and its application as latent curing agentsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Jun Gao Abstract A kind of new compound of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine was successfully synthesized by addition,condensation reaction of phenyl aldehyde and ,-hydroxylethanolamine and purified by vacuum distillation. Its purity was examined by gas chromatographic analysis. Its structure was confirmed by 13C NMR and FTIR. When this compound was added as a latent curing agent in single-component moisture-curable polyurethane system (SPU), bubbles of SPU formed during curing was obviously restrained, and the elongation at break of the cured SPU contained a certain content of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine was increased to 16 times when compared with that uncontained this oxazolidine derivative. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Amar Boukerrou Abstract The morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite (MMT) nanocomposites were investigated with wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), tensile testing, and dynamic mechanical thermal analysis. An ultrasonicator was used to apply external shearing forces to disperse the silicate clay layers in the epoxy matrix. The first step of the nanocomposite preparation consisted of swelling MMT in a curing agent, that is, an aliphatic diamine based on a polyoxypropylene backbone with a low viscosity for better diffusion into the intragalleries. Then, the epoxy prepolymer was added to the mixture. Better dispersion and intercalation of the nanoclay in the matrix were expected. The organic modification of MMT with octadecylammonium ions led to an increase in the initial d -spacing (the [d001] peak) from 14.4 to 28.5 Å, as determined by WAXS; this indicated the occurrence of an intercalation. The addition of 5 phr MMTC18 (MMT after the modification) to the epoxy matrix resulted in a finer dispersion, as evidenced by the disappearance of the diffraction peak in the WAXS pattern and TEM images. The mechanical and viscoelastic properties were improved for both MMT and MMTC18 nanocomposites, but they were more pronounced for the modified ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3547,3552, 2007 [source] Nonisothermal cure kinetics of DGEBA with novel aromatic diamineJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007M. Ghaemy Abstract The effect of the molar ratio of diglycidyl ether of a bisphenol-A based epoxy (DGEBA) and synthesized 4-phenyl-2,6-bis(4-aminophenyl)pyridine (PAP) as curing agent during nonisothermal cure reaction by the Kissinger, Ozawa, and isoconversional equations was studied. The cure mechanism was studied by FTIR analysis. Kinetic analysis of the curing reaction of DGEBA at two different concentrations (42 and 32 phr) of the curing agent was studied by using DSC analysis. With an increasing PAP content, the pre-exponential factor increased by increasing collision probability between epoxide and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of crosslink density. The activation energies obtained from three equations were in good agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3076,3083, 2007. [source] Liquid-crystalline thermosets by the curing of dimeric liquid-crystalline epoxyimine monomers with 2,4-toluene diisocyanateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2003David Ribera Abstract We studied the curing processes of several series of dimeric liquid-crystalline epoxyimine monomers with 2,4-toluene diisocyanate (TDI) alone or with added catalytic proportions of 4-(N,N -dimethylamino)pyridine. We obtained isotropic materials or liquid-crystalline thermosets with different degrees of order, which depended on the structures of the monomers. To fix ordered networks, we had to do the curing in two steps when TDI was used alone as the curing agent. However, when a tertiary amine was added in catalytic proportions, the ordered networks were fixed in just one step. In this way, we were able to fix both nematic and smectic mesophases. The significance of the polarization of the mesogen for obtaining liquid-crystalline thermosets was demonstrated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2521,2530, 2003 [source] Synthesis, characterization, and thermal properties of ladderlike polyepoxysiloxanesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Yuhui Lin Abstract Starting from trichlorosilanes and using 1,4-phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl- co -alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, 1H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215,2222, 2001 [source] Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel ComplexesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006Abdollah Omrani Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source] Effect of different types of peroxides on properties of vulcanized EPDM + PP blendsPOLYMER COMPOSITES, Issue 10 2010Witold Brostow Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [source] Cure kinetics and conductivity of rigid rod epoxy with polyaniline as a curing agentPOLYMER COMPOSITES, Issue 10 2009Tiezhu Fu The samples of rigid rod epoxy resin (4,4,-diglycidyl (3,3,,5,5,-tetramethylbiphenyl) epoxy resin (TMBP)) with different weight contents of polyaniline (PANI) as a curing agent were prepared. The kinetics of curing reaction between TMBP and PANI was analyzed by dynamic differential scanning calorimetry in the temperature range of 25,300°C. The results showed that the heat of cure reaction of TMBP/PANI sample with 10 wt% PANI was larger than those of others. The active energies with different curing conversions of TMBP/PANI sample with 10 wt% PANI were calculated by iso-conversional method using the Coats-Redfern approximation. The results showed that the activation energy was dependent on the degree of conversion. The morphology of the cured samples was detected by scanning electron microscopy measurements. The relationship between morphology and conductivity of cured samples was researched. The conductivities increased from 2.7 × 10,4 to 9.5 × 10,4 S/cm with the increase of PANI from 5 to 20 wt% in cured samples. The thermal stabilities of cured TMBP/PANI samples were examined by thermogravimetric analysis. The results showed that the cured TMBP/PANI can be promising to use as a conducting adhesive. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Effect of bifunctional modifiers of the clay on the morphology of novolac cured epoxy resin/clay nanocompositesPOLYMER COMPOSITES, Issue 10 2008Tsung-Yen Tsai Montmorillonite type clay, (PK-802) is modified by the bifunctional modifiers (2-phenylimidazole/benzalkonium chloride, PI/BEN or 2-methylimidazole/benzalkonium chloride, MI/BEN) with different ratio, which contain a curing agent, BEN, and the promoters/accelerator (PI and MI). These two modifying agents are simultaneously intercalated into the gallery space of pure PK-802. The novolac cured epoxy nanocomposites are prepared with this modified clay by crosslinking polymerization reaction. Wide-angle X-ray diffraction is used to measure the resulting d -spacing of modified PK-802 and the nanocomposites. Thermo-gravimetric analysis is used to characterize the thermal properties of the nanocomposites. The morphology of the nanocomposites is investigated using transmission electron microscopy techniques. Well dispersion of clay into the novolac cured epoxy-clay nanocomposites resulted when simultaneously both the modifying agents with 5:5 mole ratios are used to modify the clay instead of using single modified agent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] The electrical behavior of thermosetting polymer composites containing metal plated ceramic fillerPOLYMER COMPOSITES, Issue 1 2005Hedva Bar This paper describes the electrical behavior of a thermosetting system, based on epoxy resin, containing metal plated fillers. Ceramic fillers such as chopped glass fibers and mica flakes were coated with copper by electroless plating and incorporated into an epoxy resin based on di-glycidyl ether of bisphenol A (DGEBA) with tri-ethylenetetramine (TETA) curing agent. The percolation threshold in these systems is obtained at very low copper contents of 0.11,0.44 vol%. The epoxy/copper coated mica system is characterized by an extremely large positive temperature coefficient (PTC) effect, which is not followed by a negative temperature coefficient (NTC) effect. Increasing the copper coated mica concentration raises the PTC temperature of the first temperature cycle, and exposing the material to continuous heating-cooling cycles results in a decrease in the PTC temperature and an increase of its room temperature resistivity. Inverse relations were found between the coefficient of thermal expansion and the PTC temperature. Accordingly, the mechanism governing the PTC effect in the epoxy/copper coated mica composite is based on a larger thermal expansion coefficient of the matrix compared with the ceramic filler. POLYM. COMPOS., 26:12,19, 2005. © 2004 Society of Plastics Engineers. [source] The role of a third component on the conductivity behavior of ternary epoxy/Ag conductive compositesPOLYMER COMPOSITES, Issue 4 2002W. Jia Conductive adhesives, based on highly filled silver particles dispersed in a liquid epoxy resin, with an aliphatic amine [diethyltriamine (DETA)] as a curing agent, were investigated. A third component was added to the epoxy/Ag system to obtain composites of better conductivity, or similar conductivity but at lower silver contents, to modify the conductive adhesive properties, and also to reduce cost. Epoxy/Ag/carbon black (CB), epoxy/Ag/carbon fibrils (CF), epoxy/Ag/SiO2 and epoxy/Ag/dispersant composites were thus studied. The effect of high curing temperature on the uniformity and resulting conductivity level was also studied. The studied systems, excluding the epoxy/Ag/CB composite, exhibited enhanced conductivities. The microstructure of most of the systems was studied by scanning electron microscopy (SEM). The micrographs produced have served to establish structure-property relations for better understanding of the observed phenomena. [source] Reactive blending of functionalized acrylic rubbers and epoxy resinsPOLYMER ENGINEERING & SCIENCE, Issue 9 2001C. Dispenza A high molecular weight acrylonitrile/butadiene/methacrylic acid (Nipol 1472) rubber is chosen to control processability and mechanical properties of a TGDDM (tetra glycidyl diphenyl methane) based epoxy resin formulation for aerospace composite applications. The physical blend of rubber and epoxy resin, achieved by dissolution of all the components in a common solvent, forms a heterogeneous system after solvent removal and presents coarse phase separation during cure that impairs any practical relevance of this material. A marked improvement of rubberepoxy miscibility is achieved by reactive blending (,pre-reaction') the epoxy oligomer with the functional groups present in the rubber. The epoxy-rubber ,adduct' so obtained appears as a homogeneous system at room temperature and also after compounding with the curing agent. Depending on the nature and extent of interactions developed between the rubber and the epoxy resin during ,pre-reaction,' materials with different resin flow characteristics, distinctive morphologies and mechanical properties after curing were obtained. The effect of ,pre-reaction' on the resin cure reaction kinetics has been also investigated. [source] Curing of diglycidyl ether of bisphenol-A epoxy resin using a poly(aryl ether ketone) bearing pendant carboxyl groups as macromolecular curing agentPOLYMER INTERNATIONAL, Issue 8 2009Fuhua Liu Abstract BACKGROUND: Reactive thermoplastics have received increasing attention in the field of epoxy resin toughening. This paper presents the first report of using a novel polyaryletherketone bearing one pendant carboxyl group per repeat unit to cure the diglycidyl ether of bisphenol-A epoxy resin (DGEBA). The curing reactions of DGEBA/PEK-L mixtures of various molar ratios and with different catalysts were investigated by means of dynamic differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy methods. RESULTS: FTIR results for the DGEBA/PEK-L system before curing and after curing at 135 °C for different times demonstrated that the carboxyl groups of PEK-L were indeed involved in the curing reaction to form a crosslinked network, as evidenced by the marked decreased peak intensities of the carboxyl group at 1705 cm,1 and the epoxy group at 915 cm,1 as well as the newly emerged strong absorptions of ester bonds at 1721 cm,1 and hydroxyl groups at 3447 cm,1. Curing kinetic analysis showed that the value of the activation energy (Ea) was the highest at the beginning of curing, followed by a decrease with increasing conversion (,), which was attributed to the autocatalytic effect of hydroxyls generated in the curing reaction. CONCLUSION: The pendant carboxyl groups in PEK-L can react with epoxy groups of DGEBA during thermal curing, and covalently participate in the crosslinking network. PEK-L is thus expected to significantly improve the fracture toughness of DGEBA epoxy resin. Copyright © 2009 Society of Chemical Industry [source] Layered silicate/epoxy nanocomposites: synthesis, characterization and propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004Nehal A. Salahuddin Abstract Novel epoxy-clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T-403), primary polyethertriamine (Jeffamine T-5000) and three types of polyoxypropylene diamine (Jeffamine D-230, D-400, D-2000) with different molecular weight were used to treat Na-montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na+ in MMT with the organic ammonium group in Jeffamine compounds. X-ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine-MMT intercalates. Jeffamine D-230 was used as a swelling agent for the organoclay and curing agent. It was established that the d001 spacing of MMT in epoxy-clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000-MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5,nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140,nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three-fold increase in the energy required for breaking the test specimen was found for T5000-MMT/epoxy containing 7,wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Formation of zinc protoporphyrin IX in Parma-like ham without nitrate or nitriteANIMAL SCIENCE JOURNAL, Issue 2 2009Jun-ichi WAKAMATSU ABSTRACT Zinc protoporphyrin IX (ZPP) is a characteristic red pigment in meat products that are manufactured without the addition of a curing agent such as nitrate or nitrite. To examine the effects of impurities such as mineral components in sea salt on the formation of ZPP, we manufactured Parmatype dry-cured hams that were salted with refined salt or sea salt and examined the involvement of oxidation-reduction potential (ORP) in the formation of ZPP. The content of ZPP was increased drastically after 40 weeks. Microscopic observation showed strong fluorescence caused by ZPP muscle fiber after 40 weeks. Conversely, heme content varied considerably during processing. ORP increased during processing. However, there was no obvious difference between ham salted with refined salt and that salted with sea salt. Therefore, it was concluded that impurities in sea salt were not involved in the formation of ZPP. [source] Delivery of Two-Part Self-Healing Chemistry via Microvascular NetworksADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Kathleen S. Toohey Abstract Multiple healing cycles of a single crack in a brittle polymer coating are achieved by microvascular delivery of a two-part, epoxy-based self-healing chemistry. Epoxy resin and amine-based curing agents are transported to the crack plane through two sets of independent vascular networks embedded within a ductile polymer substrate beneath the coating. The two reactive components remain isolated and stable in the vascular networks until crack formation occurs in the coating under a mechanical load. Both healing components are wicked by capillary forces into the crack plane, where they react and effectively bond the crack faces closed. Healing efficiencies of over 60% are achieved for up to 16 intermittent healing cycles of a single crack, which represents a significant improvement over systems in which a single monomeric healing agent is delivered. [source] Curing mechanisms and kinetic analysis of DGEBA cured with a novel imidazole derivative curing agent using DSC techniquesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Li Liu Abstract A novel imidazole derivative, 2MI- g -CA, was obtained through the reaction of 2-methylimidazole (2MI) and cyanuric acid (CA) and characterized by means of elemental analysis, FTIR spectroscopy, 1H NMR spectroscopy, and mass spectrometric analysis. The curing mechanisms and kinetics of diglycidyl ether of bisphenol A (DGEBA) using 2MI and 2MI- g -CA as curing agents were studied with differential scanning calorimetry (DSC) under dynamic and isothermal conditions. Both dynamic and isothermal DSC thermograms of DGEBA/2MI system showed two distinct exothermic peaks, whereas those of DGEBA/2MI- g -CA system showed only one distinct exothermic peak. These results indicated that the two systems have different initiation curing mechanisms. The apparent activation energies (Ea) obtained from DSC scanning runs using the Kissinger and Ozawa methods were 79.0, 83.0 kJ/mol and 84.2, 88.8 kJ/mol for DGEBA/2MI and DGEBA/2MI- g -CA systems, respectively. These values suggested the novel curing agent 2MI- g -CA exhibited greater levels of latency during cure or increased the pot life of epoxy resin system. In addition, under the same curing condition, the Tg values of DGEBA/2MI- g -CA system were about 25°C higher than those of DGEBA/2MI system, exhibiting a better thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Impact of curing temperature on microstructures and properties of isobutylene,isoprene rubber/clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Yong-Lai Lu Abstract In this work, the influence of curing temperature on microstructures of isobutylene,isoprene rubber/clay nanocomposites (IIRCNs) prepared by melt compounding was characterized using wide-angle X-ray diffraction and TEM. The gas barrier and tensile properties of IIRCN cured under different temperature were examined. The results reveal that high pressure, curing reactions, and reactions of amine intercalants with curing agents together play important roles on determining the final microstructures of cured IIRCNs. Changing curing temperature would dramatically alter intercalated structure, dispersion homogeneity, filler,rubber interaction strength, and crosslinking density of obtained IIRCN, resulting in great difference in final properties. Finally, some suggestions for the preparation of successful RCNs were proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Structure and metal type effects on cure kinetics of DGEBA with benzil bisthiosemicarbazone complexesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Mousa Ghaemy Abstract The curing reaction kinetics of the diglycidyl ether of bisphenol A- (DGEBA) based epoxy was investigated according to the change of curing agents. Complex curing agents based on Ni(II) and Cu(II) chelates with benzil bisthiosemicarbazone (LH6) as a ligand was studied using differential scanning calorimetry. The curing reaction was characterized by high-activation energies (Ea), cure onset (Ti), and peak maximum (Tp) temperatures. Dynamic kinetic parameters were calculated by using Kissinger and Ozawa methods. For the NiLH6Cl2, CuLH6Cl2, and LH6 the average values of Ea were calculated to be 165.16, 165.92, and 115.75 kJ/mol, respectively. For the NiLH6Cl2 systems, their activation energies at 40 and 30 phr are equal. The Ti and Tp of the DGEBA/NiLH6Cl2 system are lower than those of DGEBA/CuLH6Cl2 system. These results indicate that NiLH6Cl2 has a higher reactivity toward epoxy resin at the beginning of the curing reaction. The effect of hardener concentration, heating rate, and type of metal ion on the cure kinetic parameters and the shape of DSC thermograms were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine and its application as latent curing agentsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Jun Gao Abstract A kind of new compound of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine was successfully synthesized by addition,condensation reaction of phenyl aldehyde and ,-hydroxylethanolamine and purified by vacuum distillation. Its purity was examined by gas chromatographic analysis. Its structure was confirmed by 13C NMR and FTIR. When this compound was added as a latent curing agent in single-component moisture-curable polyurethane system (SPU), bubbles of SPU formed during curing was obviously restrained, and the elongation at break of the cured SPU contained a certain content of 2-phenyl-3-hydroxyethanyl-1,3-oxazolidine was increased to 16 times when compared with that uncontained this oxazolidine derivative. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] | |||||||||||||