Curing Reaction Rate Research Articles

실리콘 수지 혼합비율에 따른 Pre-form 형광체 막 특성 변화에 관한 연구

The effect of the viscosity of phosphor slurry prepared by mixing two types of sil- icone resins with different viscosities in various ratios on the properties of pre-formed phosphor films was investigated. The pre-formed phosphor films manufactured using these phosphor slurries were evaluated for curing characteristics, breaking strength, shear strength, and optical properties. The test results demonstrated that increasing the amount of high-viscosity silicone resin in the composite resin resulted in decreased curing reaction rate, decreased breaking strength, and correlated color temperature, whereas the viscosity and adhesion strength of the composite resin increased. Among seven different mixing ratios of the low- and high-viscosity silicone resins prepared for the composite resin, white- light emission was realized for the ratio 70:30, and the pre-formed phosphor film with this ratio exhibited high breaking strength and low adhesion strength. The breaking strength thus obtained was 24.0 MPa, the adhesion strength was 0.17 MPa, the color temperature was 5,650 K, and the two chromaticity coordinates (CIE(x, y) (1931)) were (0.3293, 0.3251).

Effects of Co-Agents on the Properties of Peroxide-Cured Ethylene-Propylene Diene Rubber (EPDM)

ABSTRACTThe influence of three different co-agents, triallyl isocyanurate (TAIC), trimethylol propane trimethacrylate (TMPTMA) and high vinyl poly(butadiene) (HVPBd), on the curing characteristics, including the cure kinetics, of peroxide-cured EPDM compounds and the mechanical properties of the resulting EPDM vulcanizates were studied. The results showed that the addition of each co-agent could improve the cure extent of the EPDM samples; the hardness and modulus of the EPDM vulcanizates were also improved. In particular, the compound containing TAIC obtained the highest cure extent. However, the addition of TMPTMA negatively affected the scorch safety, especially below 165°C. From the cure kinetics of the EPDM compounds, obtained by using the cure data from a moving die rheometer, it was found that the Deng–Isayev, first-order and Hsich models showed better agreement with experimental data compared to the Kamal–Sourour model. The reaction rate constants were gradually increased with the elevated temperature, and TMPTMA could significantly promote the curing reaction rate, TAIC secondly, while HVPBd showed no effect. In addition, the apparent activation energy of all EPDM compounds, calculated by the Deng–Isayev model, was estimated slightly higher than that of the other three kinetic models. However, due to the addition of the three co-agents, the activation energy of the curing reaction decreased, with the EPDM compound with TAIC showing the lowest activation energy.

Effect of ammonium and aminosilane montmorillonites organo-clays on the curing kinetics of unsaturated polyester (UP) resin nanocomposites

The curing kinetics of UP nanocomposites prepared by incorporating different amounts of two kinds of organo-montmorillonite (organo-MMT): trimethyloctadecacylammonium chloride (TMOA) and aminopropyl-triethoxysilane (APTES) were studied by non-isothermal differential scanning calorimetry (DSC) experiments. small angle X-ray scattering (SAXS) was used for measuring the d-spacings in the modified organo-clays, and no intercalation UP into these clays was observed for the nanocomposites. HRTEM images showed dispersed and agglomerated platelets in UP/APTES 2 and 10wt%. DSC analysis showed two peaks in UP resins and UP/organo-MMT, and a decrease in the exothermal peaks temperature (Tp1 and Tp2) for nanocomposites with the heating rate as compared with those of neat UP system; thus, the higher the heating rate, the higher the curing reaction rate. This effect was more clearly on the UP/MMT-APTES nanocomposites. The effective activation energies (Ea) were determined with the mode-free isoconversional Starik's method. Sesták–Berggren model was chosen to simulate the reaction rate with a good match achieved. Thermal gravimetric analysis showed that the cured UP/APTES at high concentration were slightly more stable than UP and TMOA.

Thermal properties and non-isothermal curing kinetics of carbon nanotubes/ionic liquid/epoxy resin systems

Nanocomposites of multi-wall carbon nanotubes in diglycidyl ether of a bisphenol A epoxy matrix were prepared using ionic liquid [BMIM]PF6 as a dispersion agent and diaminodiphenyl methane as a hardener. The non-isothermal curing kinetics of the neat EP, CNTs/EP and CNTs/ILs/EP were investigated, and the activation energy was calculated using the Kissinger equation. Two-parameter autocatalytic equations of Šesták–Berggren model were constructed to describe the curing reaction rate quantitatively. The reaction orders, pre-exponential factor A and kinetic model f(α) were determined by curve fitting, and the calculated curves described the observed reaction rate well. TGA and DMA were used to measure the thermal properties of the composites. Adding ILs increased the storage modulus of composites, but decreased the thermal stability. Fracture surfaces of CNTs/EP and CNTs/ILs/EP composites were observed by SEM. CNTs showed better dispersion state in CNTs/ILs/EP composites.

Characterization of light‐cured, dental‐resin‐based biocomposites

ABSTRACTThe dependence of the depth of cure (DOC) and degree of conversion (DC) on the depth of experimental and commercial materials were determined according to ISO 4049 procedure and with the use of Raman spectroscopy, respectively. Moreover, an attempt was made to find the correlation between the DOC and DC and the depth of the material. The hypothesis was that curing time recommended by the manufacturers is appropriate for curing both commercial and experimental materials to achieve comparable values of the examined properties. The impact of the filler characteristic was clearly observed. The longer curing time provides a deeper curing (DOC values) and higher reaction rate (DC); however, the dependence between the DC values and DOC values was not visible. Instead, a logarithmic trend in the relation of the DOC and curing time was clearly observed. The results of this study suggest that the experimental materials give some hope for potential clinical applications and should be further investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42812.

Cuprous oxide nanoparticles in epoxy network: Cure reaction, morphology, and thermal stability

Nanosized cuprous oxide filler particles (nCOP) with octahedral morphology were synthesized through hydrazine reduction method and were used to develop a novel nanocomposites based on epoxy resin. The morphology of epoxy–nCOP nanocomposites were analyzed using transmission electron microscopy and scanning electron microscopy. Differential scanning calorimetry analysis showed that the cure reaction rate of epoxy was found to increase with the addition of the nCOP and a plausible cure reaction mechanism was suggested. The activation energy required for the cure reaction reduced by 22% and 13% at the initial (E1) and final stage (E2) of the cure, respectively, by the incorporation of 3 phr nCOP. It was also shown that the kinetically controlled parts of reaction could be expressed well by Kamal's phenomenological model while end of curing process could not be completely expressed by this model as there it was diffusion controlled. The influence of nCOP on glass transition temperature (Tg), mechanical properties, and thermal stability of epoxy matrix was also investigated and the results showed that better characteristics were observed in presence of 3 phr nCOP loading. POLYM. ENG. SCI., 55:2293–2306, 2015. © 2015 Society of Plastics Engineers

Water resistance and curing kinetics of epoxy resins with a novel curing agent of biphenyl-containing amine synthesized by one-pot method

In order to increase thermal stability and decrease water uptake of conventional epoxy resins, the biphenyl structure was introduced through the curing agent. A novel biphenyl-containing amine (BPDP) was synthesized by one-pot method and used as the curing agent for bisphenol-A epoxy resin DGEBA. Thermal property, water uptake and curing kinetics of the co-cured epoxy with diaminodiphenyl methane (DDM) were studied. The introduction of BPDP obviously improved the thermal stability, char yield, and water-uptake of the cured epoxy resins. The glass transition temperature Tg and weight-loss temperature increased with increasing BPDP content in the co-curing agent of BPDP and DDM. BPDP showed lower reactivity toward epoxy DGEBA than DDM with higher apparent activation energy Ea. Curing reaction of the epoxy resins co-cured with BPDP and DDM was investigated by non-isothermal DSC and the curing kinetics was described by a truncated two-parameter autocatalytic equation of the Šesták–Berggren model with experimentally determined parameters, which fitted the observed non-isothermal curing reaction rate quantitatively.

Rheological behaviour and cure kinetic studies of a trifunctional phenylethynyl-terminated imide oligomer

A phenylethynyl-terminated imide oligomer (PETI)was prepared from a triamine and 4-phenylethynylphthalic anhydride. The oligomer can be used to prepare high performance resin-based composite material via resin transfer moulding due to its low melt viscosity. The cured resin also exhibited excellent thermal stability with 5% weight loss at temperature above 531°C and higher glass transition temperature Tg (410°C) than PETI series as a result of the introduction of star-branched units. The rheological properties of the oligomer were measured and numerically fit with the dual Arrhenius model. The curing of the resin was also studied by dynamic and isothermal differential scanning calorimetry measurements. Based on the experimental data, both the curing reaction rate and the curing degree were calculated in the dynamic mode and tested under isothermal conditions.

Curing kinetics and shape-memory behavior of an intrinsically toughened epoxy resin system

A diglycidylether of propoxylated bisphenol-A with two oxypropylene units (DGEBAPO-2) was prepared, and the structure was characterized by FTIR, 1H NMR, and ESI–MS, and a flexible curing agent 2-methyl-1,5-pentanediamine (MPDA) was used to obtain an intrinsically toughened network for potential shape-memory application. The curing kinetics of DGEBAPO-2/MPDA was systematically investigated by using both non-isothermal and isothermal DSC methods; in addition, the dynamic mechanical property, mechanical property, and shape-memory property were investigated by DMA, tensile experiment, and quantitative shape-memory evaluation method. The results showed that Sestak-Berggren model and Kamal model were able to well describe the non-isothermal curing reaction rate and isothermal curing reaction rate, respectively. Tensile test at 49 °C indicated that the cured DGEBAPO-2/MPDA combined a relatively large elongation at break of 95.53 ± 2.27 % with a relatively large tensile stress of 6.33 ± 0.11 MPa. Quantitative shape-memory evaluation revealed good shape-memory properties of cured DGEBAPO-2/MPDA with shape fixity of 98.88 ± 0.04 % and shape recovery of 96.67 ± 6.91 %.

Flame retardant, mechanical properties and curing kinetics of DOPO-based epoxy resins

A halogen-free flame retardant epoxy resin was prepared consisting of DOPO-based glycidyl ether of cresol formaldehyde novolac and diglycidyl ether of bisphenol A cured by micronized dicyandiamide with accelerator U-52. The optimized epoxy resin formula contained 1.5 wt% of phosphorus and achieved UL-94 V-0 grade and LOI of 32%, with high tensile strength and impact strength of 48 MPa and 14.5 kJ/m2, respectively. Curing reaction kinetics for the DOPO-containing epoxy with 1.5 wt% of P was investigated by DSC through both non-isothermal and isothermal scanning. A two-parameter autocatalytic equation of the Šesták–Berggren model was constructed with experimentally determined kinetics parameters, which described the non-isothermal curing reaction rate quantitatively. For the isothermal curing kinetics, the Kamal–Sourour model was adopted to express the autocatalytic effect. The parameters of the reaction rate constant and reaction order were evaluated by curve fitting, and the calculated curve described the observed reaction rate fairly well. The determined kinetics parameters reflected the characteristics of the autocatalytic reaction for the curing of the phosphorus-containing epoxy system.

Comparative Study of Silicone Resin Cured with a Linear and a Branched Cross-Linking Agent

The molecular structure of hydropolysiloxane curing agents is expected to greatly affect the curing reaction and properties of the cured species, but the exact influence still remains somewhat misunderstood. Herein, we choose two representative cross-linking agents: a linear polysiloxane with the Si–H group (LPHS for short) and a branched polysiloxane with the Si–H group (TPHS for short) and a kind of high refractive index of polysiloxane resin with the vinyl-end group (short for MPSR) which was successfully synthesized in laboratories. The curing behaviors, dynamic mechanical properties, optical and electrical properties, and thermal stability of two kinds of curing systems (MPSR/TPHS and MPSR/LPHS) were systematically investigated and compared. The effect of molecular architecture of two different cross-linking agents on the curing activation energy, reactivity, and reaction rate has been studied by DSC and online FT-IR spectroscopy. The results confirm that the MPSR/TPHS system shows lower effective ac...

Curing Kinetics of Phenol Formaldehyde Resin Modified with Sodium Silicate

The curing kinetics of PF resin modified with sodium silicate had been investigated by differential scanning calorimetry (DSC). The kinetic analysis was performed at heating rates of 5, 10, 15, and 20°C/min，respectively. The kinetic parameters such as reaction order and activation energy were solved by Kissinger and Crane equation. The relationship between curing temperature and heating rate was also investigated. The activation energy and the curing reaction order，which were obtained by kinetic calculation, are 83.00kJ/mol and 0.917, respectively. The curing reaction kinetics equations were built by the obtained best curing temperature, reaction order, pre-exponential factor and reaction rate constant.

Cure kinetics and thermal stability of micro and nanostructured thermosetting blends of epoxy resin and epoxidized styrene‐block‐butadiene‐block‐styrene triblock copolymer systems

AbstractThe compatibility of styrene‐block‐butadiene‐block‐styrene (SBS) triblockcopolymer in epoxy resin is increased by the epoxidation of butadiene segment, using hydrogen peroxide in the presence of an in situ prepared catalyst in water/dichloroethane biphasic system. Highly epoxidized SBS (epoxy content SBS >26 mol%) give rise to nanostructured blends with epoxy resin. The cure kinetics of micro and nanostructured blends of epoxy resin [diglycidyl ether of bisphenol A; (DGEBA)]/amine curing agent [4,4′‐diaminodiphenylmethane (DDM)] with epoxidized styrene‐block‐butadiene‐block‐styrene (eSBS 47 mol%) triblock copolymer has been studied for the first time using differential scanning calorimetry under isothermal conditions to determine the reaction kinetic parameters such as kinetic constants and activation energy. The cure reaction rate is decreased with increasing the concentration of eSBS in the blends and also with the lowering of cure temperature. The compatibility of eSBS in epoxy resin is investigated in detailed by Fourier transform infrared spectroscopy, optical and transmition electron microscopic analysis. The experimental data of the cure behavior for the systems, epoxy/DDM and epoxy/eSBS(47 mol%)/DDM show an autocatalytic behavior regardless of the presence of eSBS in agreement with Kamal's model. The thermal stability of cured resins is also evaluated using thermogravimetry in nitrogen atmosphere. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Effect of Montmorillonite Modified by Poly(oxypropylene) Amines on Curing Process of Epoxy Nanocomposites

Five kinds of Montmorillonite (MMT) modified by poly(oxypropylene) (POP) amines were prepared. Each of these modified MMT (O-MMT) was added into epoxy (EP) E51 and hardener POP amine D400 to yield an EP/MMT mixture. Differential scanning calorimetry (DSC) was used to investigate effect of these five MMTs modified by POP amines on epoxy curing process at a heating rate of 10 ℃/min. Then isothermal curing kinetics of neat epoxy and an EP/D400-T5000-MMT mixture was studied by DSC at dif- ferent temperatures (130, 140, 150 and 160 ℃). Kamal model was used to calculate the kinetics parameters of the isothermal curing of these two EP systems. The results show that the cure process of EP was found to be influenced by the presence of MMT modified with POP amines. Compared with that of neat EP, exo- thermic peak of DSC curve of EP/O-MMT shifted to higher temperature, while co-intercalation of POP amine D400 weakened the effect of POP amine D2000 and T5000 on EP curing. At the same isothermal curing temperature, two curing rate constants, k1 and k2, and curing reaction order m of the EP/D400-T5000-MMT mixture were smaller than that of neat EP system, but curing reaction order n and the overall reaction order m+n of the EP/D400-T5000-MMT mixture were larger than that of neat EP system. Thus means that D400-T5000-MMT decreases the rate of epoxy curing reaction. In addition, compared with that of neat EP system, the curing reaction activation energy of EP/D400-T5000-MMT mixture increased

Preparation of Hexaphenylamine Cyclotriphosphazene and its Green Flame Retardance on Epoxy Molding Compound for Large-Scale Integrated Circuit Packaging

The hexaphenylamine cyclotriphosphazene (HPACTPZ) was synthesized using titrating technology of hexachlorocyclotriphosphazene solution and the synthesis parameters were investigated, and the structure of HPACTPZ was analyzed by FTIR and NMR in this paper. Using HPACTPZ synthesized in the work as flame retardant, the epoxy molding compound(EMC) for packaging of large-scale integrated circuits with halogen-free flame retardance was prepared. The results have shown that the flame retardance of EMC flame-retardanced by HPACTPZ was up to UL 94 V0 rating(3.2mm) and the oxygen index of the EMC was up to 35.8%, which indicates that HPACTPZ has much better flame retardance for EMC than traditional halogen flame-retardants. Meanwhile, HPACTPZ accelerated the curing reaction rate of EMC, which can be used for manufacturing the quick-curing EMCs or afterward-curing-free EMCs.

Kinetic study of the novolac resin curing process using model fitting and model-free methods

The curing behavior of novolac type phenolic resin was studied through differential scanning calorimetry (DSC) using model fitting and model-free (isoconversion) kinetic methods. For the model fitting kinetic study, a piecewise fitting approach was developed to describe the dependence of cure reaction rate on temperature and curing degree. The piecewise model displayed excellent modeling ability. In the model-free kinetic study, Friedman, and Kissinger–Akahira–Sunose methods were used to calculate the curing activation energy. The dependence curve of activation energy on conversion and the piecewise model fitting results both displayed a change in the kinetic reaction mechanism from the autocatalytic to n-order regime. According to the isothermal prediction results, the model-free kinetic methods show much better prediction ability, compared with the model fitting methods. Also, Friedman and Kissinger–Akahira–Sunose methods were found to show similar results in predicting the isothermal curing behavior of this novolac resin.

Synthesis of Phosphazene Flame Retardant and its Application in Epoxy Molding Compound for Large-Scale Integrated Circuit Packaging

The tri(o-phenylenediamine) cyclotriphosphazene (TPCTP) was synthesized using titrating technology of hexachlorocyclotriphosphazene solution and the synthesis parameters were investigated, and the structure of TPCTP was analyzed by FTIR in this paper. Using TPCTP synthesized in the work as flame retardant, the epoxy molding compound(EMC) for packaging of large-scale integrated circuits with halogen-free flame retardance was prepared. The results have shown that the flame retardance of EMC flame-retardanced by TPCTP was up to UL 94 V0 rating(1.6mm) and the oxygen index of the EMC was up to 34.5%, which indicates that TPCTP has much better flame retardance for EMC than traditional halogen flame-retardants. Meanwhile, TPCTP accelerated the curing reaction rate of EMC, which can be used for manufacturing the quick-curing EMCs or afterward-curing-free EMCs.

Study on the Curing Characteristics of MUF Co-Polymerization Resin

Curing is the key to the bonding, this paper considered the production practice, studied the curing properties of different MUF resin under the different curing agent with DSC. The experimental results show that: The characteristics temperature of curing reaction is closely related to the β. With the increase of β, the initial and peak temperature is moving to the high-temperature, the curing time became shorter; the range of curing temperature became much wider. At the same time, the curing peaking temperature was decreased and the Enthalpy integral of curing reaction was reduced first then increased with the increased of the amount of curing agent. When the amount of curing agent occupied 4.0%-6.0% of the MUF resin, the pH was decreased mostly, and the curing reaction rate run up quickly Along with the increasing of n (F): n (U1), the To, Tp and Ti are going ahead distinctly after hardening. At the same time, both activation energy and reaction order are all decreased, absorbed heat is dropping too. So, curing technics became easily.

Study on the Cure Kinetic Behavior of Thermosetting Polyurethane Solids and Foams: Effect of Temperature, Density, and Carbon Nanofiber

Cure kinetic behavior was studied for both thermosetting polyurethane (PU) solids and foams. The effects of cure temperature, foam density, and carbon nanofiber (CNF) contents were examined. Cure studies were performed experimentally by measuring the evolution of complex shear modulus as a function of time using an advanced polymer analyzer operating in dynamic shear mode. Isothermal cure behavior of PU solid and foams was investigated at four different temperatures, namely, 25°C, 45°C, 60°C, and 80°C and at three different amounts of CNF, namely, 0.01%, 0.05%, and 0.1% by weight. The cure data were analyzed by using an autocatalytic cure kinetic model. The cure behavior of both solid and foam was found to be temperature dependent. Addition of CNF was also found to affect the cure behavior of the PU foam. It was observed that the PU foam with 0.1% CNF shows the highest polymerization reaction compared with the neat foam. It was also observed that the reaction rate constants follow an Arrhenius dependence on temperature, whereas the reaction orders remain fairly constant. A simple predictive model using the reaction orders indicated that the maximum cure reaction rate was occurred at 37.5% conversion.

Synthesis and Characterisation of Epoxy Resins Reinforced with Carbon Nanotubes and Nanofibers

Epoxy nanocomposites were fabricated using two kinds of nanofiller, amino-functionalized multi-walled carbon nanotubes (CNTs) and non-treated long carbon nanofibers (CNFs). The non-cured mixtures were analysed through viscosity measurements. The effect of the nanoreinforcement on the curing process was determined by differential scanning calorimetry. Finally, the characterisation of cured nanocomposites was carried out studying their thermo-mechanical and electrical behaviour. At room temperature, the addition of CNTs causes a viscosity increase of epoxy monomer much more marked than the introduction of CNFs due to their higher specific area. It was probed that in that case exists chemical reaction between amino-functionalized CNTs and the oxirane rings of epoxy monomer. The presence of nanoreinforcement induces a decrease of curing reaction rate and modifies the epoxy conversion reached. The glass transition temperature of the nanocomposites decreases with the contents of CNTs and CNFs added, which could be related to plasticization phenomena of the nanoreinforcements. The storage modulus of epoxy resin significantly increases with the addition of CNTs and CNFs. This augment is higher with amino-functionalized CNTs due, between other reasons, to the stronger interaction with the epoxy matrix. The electrical conductivity is greatly increased with the addition of CNTs and CNFs. In fact, the percolation threshold is lower than 0.25 wt% due to the high aspect ratio of the used nanoreinforcements.