Synthesis and separation properties for Cu(II)‐Ni(II) of macroporous crosslinked polystyrene‐supported triethylenetetramine resin using Cu(II) as template

A new method for preparing a novel macroporous chelating resin that has good adsorption capability for Cu(II) and high selectivity for it with the coexistence of Ni(II) was introduced in this article. First, the aminated resin (PS‐TETA) was synthesized by the reaction of crosslinked macroporous chloromethylated polystyrene with triethylenetetramine. Subsequently, PS‐TETA was coordinated with Cu(II) and then PS‐TETA‐Cu was obtained. After the crosslinking reaction of PS‐TETA‐Cu with epoxy chloropropane, the adsorbed Cu(II) was removed by chlorhydric acid, and then the target resin‐Cu(II) template triethylenetetramine crosslinked polystyrene resin was obtained. The selectively sorption tests for Cu(II) showed that the sorption capacity was as high as 1.6 mmol/g and the selectivity coefficient α_{Cu(II)/Ni(II)} could reach to 9.06 with the coexistence of Ni(II). SEM and nitrogen adsorption at 77 K methods were used to characterize the porous structure of the resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 963–967, 2007     

Cure behavior of an interpenetrating diglycidyl ether of bisphenol A/poly(ethylene oxide) miscible system

Differential scanning calorimetry (DSC) was performed to investigate the cure behavior of epoxy networks of diglycidyl ether of bisphenol A/poly(ethylene oxide) (DGEBA/PEO) cured with 4,4'-diaminodiphenyl sulfone (DDS). An interesting miscibility has been recently reported for DGEBA/PEO networks of a semi-interpenetrating structure cured with aromatic amine. This study focused on the cure behavior and effects of miscible polymer diluents on cure kinetics. The physical miscible state between the polymer and epoxy was found to exert no alteration on the cure mechanism, which remained to be autocatalytic for DDS amine-curing of all DGEBA/PEO mixtures as well as the pure DGEBA. The PEO component, being in a miscible state with the epoxy/DDS throughout the cure, acted as a diluent for the reactive DGEBA epoxy and DDS components. The dilution effect could be partially compensated by raising the DDS/epoxy ratio in proportion to increased PEO fraction in DGEBA/PEO/DDS mixtures.     

Cure kinetics of an epoxy/liquid aromatic diamine modified with poly(ether imide)

The cure kinetics and mechanisms of an epoxy oligomer based on diglycidyl ether of bisphenol A (DGEBA), polymerized with a liquid aromatic diamine based on diethyl toluene diamine (DETDA 80), and its blends with poly(ether imide) (PEI) at concentrations of 0–15 wt % were studied with differential scanning calorimetry under dynamic and isothermal conditions. The kinetic analyses were performed with a phenomenological approach. The reaction mechanism of the blends remained the same as that of the neat epoxy. However, the addition of PEI had a marked effect on the cure kinetics in the DGEBA/DETDA 80 system. The rate of reaction decreased with an increase in the thermoplastic content. Diffusion control was incorporated to describe the cure behavior of the blends in the latter stages. Greater diffusion control was observed as the PEI concentration increased and the cure temperature decreased. Polymer blends based on this epoxy/liquid aromatic diamine had not been previously studied from a kinetic viewpoint. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 660–672, 2005     

Cure kinetics and thermal properties of tetramethylbiphenyl epoxy resin/phthalazinone‐containing diamine/hexa(phenoxy)cyclotriphophazene system

Inherently flame retardant epoxy resin is a kind of halogen‐free material for making high‐performance electronic materials. This work describes an inherently flame retardant epoxy system composed of 4,4′‐diglycidyl (3,3′,5,5′‐tetramethylbiphenyl) epoxy resin (TMBP), 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐(4‐(4‐aminophenoxy) phenyl) (2H) phthalazin‐1‐one (DAP), and hexa(phenoxy) cyclotriphophazene (HPCTP). The cure kinetics of TMBP/DAP in the presence or absence of HPCTP were investigated using isoconversional method by means of nonisothermal differential scanning calorimeter (DSC). Kinetic analysis results indicated that the effective activation energy (E_α) decreased with increasing the extent of conversion (α) for TMBP/DAP system because diffusion‐controlled reaction dominated the curing reaction gradually in the later cure stage. TMBP/DAP/HPCTP(10 wt %) system had higher E_α values than those of TMBP/DAP system in the early cure stage (α < 0.35), and an increase phenomenon of E_α ～ α dependence in the later cure stage (α ≥ 0.60) due to kinetic‐controlled reaction in the later cure stage. Such complex E_α ～ α dependence of TMBP/DAP/HPCTP(10 wt %) system might be associated with the change of the physical state (mainly viscosity) of the curing system due to the introduction of HPCTP. These cured epoxy resins had very high glass transition temperatures (202–235°C), excellent thermal stability with high 5 wt % decomposition temperatures (>340°C) and high char yields (>25.6 wt %). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of molecular interactions on spherulite morphology in miscible poly(ethylene oxide)/epoxy network versus poly(ethylene oxide)/poly(4‐vinyl phenol) blend

Relationships between the spherulite morphology and changes in hydrogen‐bonding interactions between the linear poly(ethylene oxide) (PEO) polymer and a crosslinking epoxy system (diglycidylether of bisphenol‐A resin with 4,4′‐diaminodiphenylsulfone) (DGEBA/DDS) before and after cure have been explored The hydrogen‐bonding interaction is more significant before cure because of the interactions between the ether group of PEO and the amine group of DDS. The interaction between PEO and epoxy/DDS becomes less in the cured network. The morphology of the PEO crystals is, in turn, affected by the contents and chemical structures (functional groups, molecular weights, crosslinks, etc) of crosslinking epoxy/DDS. PEO/poly(4‐vinyl phenol) (PVPh), a thermoplastic non‐curing miscible system with the hydrogen bonding between the ether group of PEO and the ? OH group of PVPh, is also compared. In comparison with the PEO/epoxy/DDS system, the spherulite morphology of PEO/PVPh becomes more extensively spread out, with the extents increasing with the PVPh contents in the PEO/PVPh blend. © 2001 Society of Chemical Industry     

Effects of the complexed moisture in metal acetylacetonate on the properties of the no‐flow underfill materials

A potential no‐flow (compression filling of encapsulant) underfill encapsulant for simultaneous solder joint reflow and underfill cure has been reported by the authors. The encapsulant is based on a cycloaliphatic epoxy/organic anhydride/Co(II) acetylacetonate system. The key of this no‐flow encapsulant is the use of a latent metal acetylacetonate catalyst that provides the solder reflow prior to the epoxy gellation and fast cure shortly after the solder reflow. However, most of the metal acetylacetonates can easily absorp moisture as their ligand. Therefore, it is of practical importance to understand the effect of the complexed water on the properties of the no‐flow material before and after cure. In this paper, differential scanning calorimetry, thermal gravimetric analysis, thermal mechanical analysis, dynamic mechanical analysis, and Fourier transform infrared spectrometry were used to validate the existence of complexed moisture in the Co(II) acetylacetonate. The effects of the complexed water on the curing profile, glass transition temperature, and storage modulus of the cured no‐flow underfill material were studied. A possible catalytic mechanism of the metal acetylacetonate in the cycloaliphatic epoxy/anhydride system was subsequently discussed and proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 103–111, 1999     

Toughening of a trifunctional epoxy system. II. Thermal characterization of epoxy/amine cure

The cure of a trifunctional epoxy resin with an amine coreactant was studied using two thermal analysis techniques: differential scanning claorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). These techniques were used to monitor the development of both the thermal and mechanical properties with cure. Detailed kinetic analysis was performed using a variety of kinetic models: nth order, autocatalytic, and diffusion-controlled. The reaction was found to be autocatalytic in nature during the early stages of cure while becoming diffusion-controlled once vitrification had taken place. By combining the results obtained from DSC and DMTA, the degree of conversion, at which key events such as gelation and vitrification take place, were determined. A TTT diagram was constructed for this epoxy/amine system showing the final properties that can be achieved with the appropriate cure history. © 1996 John Wiley & Sons, Inc.     

Cure kinetics for the ultraviolet cationic polymerization of cycloliphatic and diglycidyl ether of bisphenol‐A (DGEBA) epoxy systems with sulfonium salt using an auto catalytic model

This paper investigates the cure kinetics for the ultraviolet (UV) cationic polymerization for both a cycloaliphatic and diglycidyl ether of bisphenol‐A (DGEBA) epoxy system, using the photoinitiator triarylsulfonium hexafluoroantimonate salt. Using an autocatalytic kinetic cure model, the reaction rate values for both cycloaliphatic and DGEBA epoxy systems were determined for different photoinitiator amount (wt %) added, and at different UV exposure temperatures. The value for the cycloaliphatic epoxy increased significantly with addition of the sulfonium salt, reaching a limiting maximum after 2%. The value for the DGEBA epoxy system also increased, to a limiting maximum after 3%. Addition of the sulfonium salt significantly lowered the activation energy for the cycloaliphatic epoxy at all levels of addition, with the reduction proportional to the amount of salt added. In contrast, the sulfonium salt did not have a major effect on the DEGBA until the addition of at least 3% of the salt. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1587–1591, 2002     

PHASE-SEPARATION BEHAVIOR IN POLY(ETHER IMIDE)-MODIFIED EPOXY BLENDS

Phase-separation behavior of aromatic amine-cured diglycidyl ether of bisphenol-A (DGEBA) epoxy oligomer and poly(ether imide) (PEI) engineering thermoplastic-modifier mixtures was investigated by means of small-angle light scattering (SALS) and optical microscopy. The starting reactant mixtures comprising epoxy, PEI, and the curing agents, namely diamino diphenyl sulfone (DDS) and methylene dianiline (MDA), were found to be single phase. During curing, phase separation occurred in the epoxy/PEI/DDS system, whereas no phase separation took place in MDA-cured epoxy/PEI blends. The difference between the two systems has been attributed to thermodynamic and kinetic aspects of cure reaction in thermoplastic-modified thermosetting (TMT) polymeric blends. Spinodal decomposition as characterized by an increase of scattered intensity, shift of the peak angle to a smaller scattering angle, and development of a regularly phase-separated structure followed by coarsening was found to be the dominant mechanism of reaction-induced phase separation in DDS-cured epoxy/PEI blend compositions.     

Epoxy resin cure. II. FTIR analysis

Fourier transform infrared (FTIR) spectroscopy is used to determine the cure rate of an epoxy resin consisting of Tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and diaminodiphenylsulfone (DDS). Cure rates at 120 and 160°C are shown to increase noticeably when 1% BF₃–MEA is added to either TGDDM to TGDDM plus DDS. Fluoroboric acid is shown to increase the cure rates even more than the BF₃–MEA. These Results combined with the NMR results in the accompanying article indicate that BF₃–MEA is not a catalyst for epoxy resin cure. Instead it is rapidly hydrolyzed to fluoroboric acid which acts as the catalyst.     

Non-isothermal curing kinetics of epoxy/mechanochemical devulcanized ground rubber tire (GRT) composites

The curing behavior of diglycidyl ether of bisphenol A (DGEBA) epoxy and specially ground mechanochemical devulcanized ground rubber tire system (GRT) in the presence of polyoxyalkyleneamine curing agent was investigated by non-isothermal differential scanning calorimetry technique at different heating rates. Scanning electron microscopic-energy dispersive X-ray spectroscopy, and attenuated total reflection infrared spectroscopy were used to characterize the GRT particles. The kinetic parameters of curing process were determined by isoconversional method given by Málek. The average activation energy E _a was found to be 52.3–60.7 and 45–59.2 kJ/mol for neat epoxy amine (Epo am 31) and epoxy/amine with GRT (5 Epo am 31) systems, respectively. It was observed that the presence of GRT in epoxy/amine promotes the curing. A two parameter (m, n) autocatalytic model (SB equation) was found to be the most adequate to describe the cure kinetics of the studied epoxy/GRT system. A dominant catalyzing effect of GRT on the curing reaction was observed which is attributed to the complexity of the reaction at later stages of curing, therefore, it was not possible to model the reaction over the whole range of degree of conversion.     

Curing kinetics and reaction‐induced homogeneity in networks of poly(4‐vinyl phenol) and diglycidylether epoxide cured with amine

Mixtures of diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin with poly(4‐vinyl phenol) (PVPh) of various compositions were examined with a differential scanning calorimeter (DSC), using the curing agent 4,4′‐diaminodiphenylsulfone (DDS). The phase morphology of the cured epoxy blends and their curing mechanisms depended on the reactive additive, PVPh. Cured epoxy/PVPh blends exhibited network homogeneity based on a single glass transition temperature (T_g) over the whole composition range. Additionally, the morphology of these cured PVPh/epoxy blends exhibited a homogeneous network when observed by optical microscopy. Furthermore, the DDS‐cure of the epoxy blends with PVPh exhibited an autocatalytic mechanism. This was similar to the neat epoxy system, but the reaction rate of the epoxy/polymer blends exceeded that of neat epoxy. These results are mainly attributable to the chemical reactions between the epoxy and PVPh, and the regular reactions between DDS and epoxy. Polym. Eng. Sci. 45:1–10, 2005. © 2004 Society of Plastics Engineers.     

Characterization of diene monomers as healing agents for autonomic damage repair

For effective autonomic healing of damaged polymers and composites, it is essential to understand how the encapsulated healing agent behaves during and after cure. In this study, two different diene monomers [dicyclopentadiene (DCPD), 5‐ethylidene‐2‐norbornene (ENB)] and their blends were investigated as candidate self‐healing agents, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DSC experiments for samples showed that DCPD has a melting transition while the blends and ENB have no melting in the temperature range measured. Samples for DMA were prepared and tested by two different methods in the presence of Grubbs catalyst. In the first case (method I), monomers were mixed with the catalyst directly. In the second case (method II), the catalyst was mixed with an epoxy/amine system and cured into a film that was polished to expose the catalyst. The cure behavior of monomer samples was examined on the epoxy/catalyst film. Method II is considered to be a simulative experiment, which can occur in a real situation for damaged epoxy matrix composite. It was found that acceleration of cure reaction and reduction of catalyst concentration is possible by blending DCPD with ENB from method I. Storage modulus (G′) value after cure in method II showed that a DCPD : ENB blend ratio of 1 : 3 reached the highest G′ value at shorter cure time and lower catalyst levels than other monomer combinations. DCPD and ENB are presumably responsible for increases in rigidity and reactivity, respectively. This may improve the healing efficiency in autonomic damage repairing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1266–1272, 2006     

Characterization of epoxy resins by photochemical hole burning (PHB) spectroscopy

The phonon frequencies, E_s, measured as the energy differences between zerophonon hole peak and pseudophonon side hole peak in photochemical hole burning (PHB) spectra, were studied for tetraphenylporphin (TPP) in epoxy resin films under various conditions of sample preparation and annealing. The values of phonon frequency, E_s, reflecting low energy excitation modes of the matrix epoxy resins were about 13 to 16 cm^?1. They decreased when the epoxy resin was cured at relatively low temperatures and vice versa. At the same cure temperatures the sample quenched to liquid nitrogen showed a lower value than that of the annealed sample. These results are in agreement with the results of qualitative free volume measurements. The thermal stability of holes burned at 20 K was also tested, and the results were compared with the extent of cure and glass transition temperature of the resins.     

In-process control of epoxy composite by microdielectrometric analysis. Part II: On-line real-time dielectric measurements during a compression molding process

The curing of a fiberglass epoxy composite based on diglycidyl ether of bisphenol A (DGEBA) with dicyanodiamide (DDA) as the hardener and imidazole as the catalyst agent was analyzed using microdielectrometry. The curing behavior of thick epoxy composite parts was examined in a production environment for compression molding process. The particular focus of this paper is to present the method used to collect on-line real-time conversion measurements during an epoxy/fiberglass composite cure. For this purpose, temperature and ionic conductivity profiles during industrial moldings of a thick epoxy part were recorded. Corresponding conversion profiles were deducted from a previous empirically established correlation and discussed in terms of cure gradients as a function of the through-the-thickness location and of the cure cycle time.     

Phase separation,cure kinetics,and morphology of epoxy/poly(vinyl acetate) blends

Epoxy based on diglycidyl ether of bisphenol A + 4,4′diaminodiphenylsulfone blended with poly(vinyl acetate) (PVAc) was investigated through differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and environmental scanning electron microscopy (ESEM). The influence of PVAc content on reaction induced phase separation, cure kinetics, morphology and dynamic‐mechanical properties of cured blends at 180°C is reported. Epoxy/PVAc blends (5, 10 and 15 wt % of PVAc content) are initially miscible but phase separate upon curing. DMTA α‐relaxations of cured blends agree with T_g results by DSC. The conversion‐time data revealed the cure reaction was slower in the blends than in the neat system, although the autocatalytic cure mechanism was not affected by the addition of PVAc. ESEM showed the cured epoxy/PVAc blends had different morphologies as a function of PVAc content: an inversion in morphology took place for blends containing 15 wt % PVAc. The changes in the blend morphology with PVAc content had a clear effect on the DMTA behavior. Inverted morphology blends had low storage modulus values and a high capability to dissipate energy at temperatures higher than the PVAc glass‐transition temperature, in contrast to the behavior of neat epoxy and blends with a low PVAc content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1507–1516, 2007     

Co(II) and Ni(II) Concentration,and Co(II) Purification with Microbiological Collectors (Saccharomyces cerevisiae)

Abstract

Co(II) and Ni(II) can be concentrated quantitatively using a microbiological collector consisting of a Saccharomyces cerevisiae strain suspended in a glucose containing phosphate buffer. Optimal conditions for such accumulation as regards pH, time, and concentration have been studied. The influence of some complexing agents on the accumulation of a mixture of Co(II) and Ni(II) has also been investigated. By adapting the Saccharomyces cerevisiae strain to Co(II), separation of Co(II) from Ni(II) in dilute solution has been achieved.     

Solvent-Extraction Behavior of Cobalt(II), Nickel(II), Copper(II), and Palladium(II) with Tri-n-butylphosphate

Abstract

A systematic study of the extraction behavior of cobalt(II), nickel(II), copper(II), and palladium(II) with TBP from thiocyanate system in various ranges of acid concentrations has been performed. The thiocyanate medium leads to enhanced extractions in all these cases compared to those in the previously used chloride medium. For palladium, the chloride and nitrate systems have been critically examined. Sixty-two per cent extraction occurs from 4 M hydrochloric acid using 100% TBP in a single run and the extraction becomes quantitative (>99%) after four successive equilibrations. A simpler method has been proposed for rapid extraction of palladium(II) as the thiocyanate complex. Quantitative extraction occurs in the presence of 1.2% thiocyanate solution from 0.5 to 2 M hydrochloric acid (initial) up to pH 8.0. The extractable species of cobalt(II), nickel(II), copper(II), and palladium(II) from thiocyanate medium are probably similar and of the type [M(CNS)₄]^2? [K·TBP·3H₂O]₂ ⁺ (buffer solution) and [M(CNS)₄]^2? [H·TBP·3H₂O]⁺ ₂ (acid solution). A simple extraction scheme has been worked out for the separation of palladium(II) from iron(III), cobalt(II), nickel, manganese(II), copper(II), and platinum.     

Cure kinetics of several epoxy–amine systems at ambient and high temperatures

Epoxy-crosslinker curing reactions and the extent of the reactions are critical parameters that influence the performance of each epoxy system. The curing of an epoxy prepolymer with an amine functional group may be accompanied by side reactions such as etherification. Commercial epoxy prepolymers were cured with different commercial amines at ambient as well as at elevated temperatures. Singularly, only epoxy–amine reactions were observed with diglycidyl ether of bisphenol-A (DGEBA)-based epoxides in our research even upon post-curing at 200°C. Etherification side reaction was found to occur at a cure temperature of 200°C in epoxides possessing a tertiary amine moiety. A combined goal of our research was to understand the effect of tougheners on the cure of epoxy–amine blend. To discern the effect of tougheners on the cure, core–shell rubber (CSR) particles were incorporated into the epoxy–amine blend. It was observed that CSR particles did not restrict the system from proceeding to complete reaction of epoxy moieties. Besides, CSR particles were found to accelerate the epoxy-amine reaction at a lower level of epoxy conversion. The lower activation energy of epoxy–amine reaction of CSR incorporated system compared to control supported the catalytic effect of CSR particles on the epoxy-amine reaction of epoxy prepolymer and amine blends.     

Investigation of readily processable thermoplastic-toughened thermosets. II. Epoxy toughened using a reactive solvent approach

The fracture toughness of epoxy thermosets was increased by up to 220% using very low-molecular-weight (∼ 1000 g/mol) imide thermoplastic. The objective was to produce a low-viscosity prepolymer that could be easily autoclave-processed to give a tough thermoset. Here, an homogenous epoxy prepolymer was prepared by first synthesizing very low-molecular-weight linear aromatic imide (∼ 1000 g/mol) directly in a liquid allyl phenol reactive solvent, followed by dissolution of the epoxy (Epon® 825) and the cure agent (DDS) directly in the thermoplastic solution. The allyl phenol both cures into the epoxy network, through phenol functional groups, and accelerates the cure. The viscosity of the pure epoxy was 1.4 Pa · S at 30°C. The prepolymer formulations ranged from ∼ 5–33 Pa · S at 30°C, but all reduced to less than 1 Pa · S at 90°C. The onset of cure is well above 90°C so the prepolymer viscosity is within the range for autoclave processing. The cured resin plaques were not transparent, but phase-separated domains were not found by scanning electron microscopy, indicating that the domain size is below the detection limit of the instrument. The reactive solvent causes a decrease in both the T_g and the high temperature modulus of the thermoset. Introduction of the thermoplastic results in partial recovery of the T_g and modulus. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 935–942, 1998