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1.
The effect of wood flour on the cure kinetics of commercial phenol‐formaldehyde resins used as oriented strandboard face and core adhesives was studied using differential scanning calorimetry. The wood flour did not change the cure mechanism of the face resin, but lowered its cure temperature and activation energy and increased its cure reaction order. For the core resin (CR), the wood flour lowered the onset cure temperature, and caused separation of the addition and condensation reactions involved in curing of CR. Compared with neat CR, the addition reaction of CR/wood mixture also followed an nth‐order reaction mechanism but with a lower reaction order, while the condensation was changed from an autocatalytic reaction to an nth‐order one. The addition reaction happened at temperatures lower than 90°C, and the condensation reaction was dominant at temperatures higher than 110°C. The proposed models fitted the experimental data well. Relationships among cure reaction conversion (cure degree), cure temperature, and cure time were predicted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3774–3781, 2006 相似文献
2.
The effect of zinc borate (ZB) on the cure kinetics of commercial phenol–formaldehyde oriented strandboard adhesives was studied using differential scanning calorimetry. ZB caused a separation of the addition and condensation reactions for both face and core resin (CR) systems with lowered cure temperature for the addition reaction. For the face resin, ZB did not change its nth‐order curing mechanism, but retarded the whole cure reactions, and increased the reaction order and the activation energy. Compared with neat CR, the addition reaction of the CR/ZB mixture, which occurred at temperatures lower than 60°C, also followed an nth‐order reaction mechanism. The condensation reaction of the mixture was changed from an autocatalytic reaction to an nth‐order one with the reaction order of about 1. The proposed models fitted the experimental data well. Relationships among cure reaction conversion (i.e., cure degree), cure temperature, and cure time were predicted for various resin/ZB systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3886–3894, 2006 相似文献
3.
In this study, the time–temperature– transformation (TTT) cure diagrams of the curing processes of several novolac resins were determined. Each diagram corresponded to a mixture of commercial phenol–formaldehyde novolac, lignin–phenol–formaldehyde novolac, and methylolated lignin–phenol–formaldehyde novolac resins with hexamethylenetetramine as a curing agent. Thermomechanical analysis and differential scanning calorimetry techniques were applied to study the resin gelation and the kinetics of the curing process to obtain the isoconversional curves. The temperature at which the material gelled and vitrified [the glass‐transition temperature at the gel point (gelTg)], the glass‐transition temperature of the uncured material (without crosslinking; Tg0), and the glass‐transition temperature with full crosslinking were also obtained. On the basis of the measured of conversion degree at gelation, the approximate glass‐transition temperature/conversion relationship, and the thermokinetic results of the curing process of the resins, TTT cure diagrams of the novolac samples were constructed. The TTT diagrams showed that the lignin–novolac and methylolated lignin–novolac resins presented lower Tg0 and gelTg values than the commercial resin. The TTT diagram is a suitable tool for understanding novolac resin behavior during the isothermal curing process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
4.
Differential scanning calorimetry (DSC) was used to study the effect of wood on the curing behavior of two types of commercial oriented‐strand‐board phenolic resins. DSC analysis showed that the curing behavior of the core resin differed significantly from that of the face resin in terms of the peak shape, peak temperature, and activation energy. The addition of wood to the resins moved the two separated peaks in the DSC curves of the core resin adjacent to each other. It also accelerated the addition reactions in the curing processes of both the core and face resins. The two peaks in the DSC curves were the result of the high pH values of the resins. These two peaks became either jointed together or overlapped when the pH value of the resin was reduced. Wood also reduced the activation energies for both the core and face resins by decreasing the pH values of the curing systems. Moreover, the effects of wood on the curing behavior of the resins among the five species studied were similar. The lowest activation energy for a phenolic resin probably appeared at pH 10–11 under alkaline conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 185–192, 2005 相似文献
5.
The curing behavior of synthesized phenol–urea–formaldehyde (PUF) resol resins with various formaldehyde/urea/phenol ratios was studied with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicated that the synthesis parameters, including the urea content, formaldehyde/phenol ratio, and pH value, had a combined effect on the curing behavior. The pH value played an important role in affecting the shape of the DSC curing curves, the activation energy, and the reaction rate constant. Depending on the pH value, one or two peaks could appear in the DSC curve. The activation energy was lower when pH was below 11. The reaction rate constant increased with an increase in the pH value at both low and high temperatures. The urea content and formaldehyde/phenol ratio had no significant influence on the activation energy and rate constant. DMA showed that both the gel point and tan δ peak temperature (Ttanδ) had the lowest values in the mid‐pH range for the PUF resins. A different trend was observed for the phenol–formaldehyde resin without the urea component. Instead, the gel point and Ttanδ decreased monotonically with an increase in the pH value. For the PUF resins, a high urea content or a low formaldehyde/phenol ratio resulted in a high gel point. The effect of the urea content on Ttanδ was bigger than that on the gel point because of the reversible reaction associated with the urea component. Too much formaldehyde could lead to more reversible reactions and a higher Ttanδ value. The effects of the synthesis conditions on the rigidity of the cured network were complex for the PUF resins. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1368–1375, 2005 相似文献
6.
The synthesis of new methacrylate‐based, curable macromonomers, 4,4′‐bis[2‐hydroxy‐3‐aminopropylmethacrylate] diphenyl ether (BHAPE) and 4,4′‐bis[2‐hydroxy‐3‐aminopropylmethacrylate] diphenyl methane (BHAPM), is reported. BHAPE and BHAPM were prepared by the reaction of glycidyl methacrylate (GMA) with 4,4′‐diaminodiphenyl ether and 4,4′‐diaminodiphenyl methane, respectively. The progress of the reaction was monitored by thin‐layer chromatography (TLC), and the structure of the monomers was characterized by Fourier transform infrared (FTIR) and 1H‐NMR spectroscopy. Thermal curing of the monomers was conducted in a differential scanning calorimeter (DSC) with peroxide as the initiator. Thermal curing of the monomers showed the highest rate at 100°C with the activation energy value in the range 80–90 kJ distilled/mol. The water absorption properties of the cured samples in water, acidic, and basic solutions were studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
7.
The curing reaction kinetics of an epoxy based on the diglycidyl ether of bisphenol A (DGEBA) with an inorganic complex based on nickel(II) chelate with ethylenediamine (en) as a ligand were studied using DSC in dynamic mode. The complex curing agent was synthesized and characterized by the elemental analysis, FT‐IR, and ICP‐Plasma techniques. Thermal dissociation behavior of curing agent was also studied using thermogravimetric (TG) analysis in isolated form. Three kinetic models, Kissinger, Ozawa‐Flynn‐Wall, and Expanded Freeman‐Carrole, were used to determine the kinetic parameters. The effect of hardener concentration on the kinetic parameters and the shape of DSC thermograms of the DGEBA/Ni(en)3Br2 system were investigated. Finally, the previous proposed mechanism by another researcher was used to explain the DSC data in detail. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 265–271, 2005 相似文献
8.
The effect of t‐butyl peroxybenzoate (TBPB) on the cure reaction of QY8911‐3 resin (BMI) was studied by differential scanning calorimetry (DSC) and gel time analysis. The mechanical properties of the resin and the composite were tested and analyzed with the peroxide content. The results showed that TBPB decomposed between 117 and 191°C and the enthalpy was 1123 J/g. TBPB reduced the initial reaction temperature, prompted the reaction speed, and shortened the gel time of the BMI resin. TBPB also increased the bending strength and decreased the impacting strength of the postcured samples. So, the peroxide content should be less than 0.6%. CF/SiO2/BMI composites were prepared from the BMI containing peroxide and their microstructure and properties were better than those of the composites free of peroxide. According to the injection‐molding experiment, the spilling problem was overcome and the forming time was reduced from 2 h to 15 min when peroxide was added. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3769–3773, 2003 相似文献
9.
The characteristics of urea–formaldehyde (UF) resin curing in the presence of wood extracts and a catalyst [ammonium chloride (NH4Cl)] were investigated by differential scanning calorimetry (DSC). The effects of extracts from 16 wood species on resin curing behaviors were evaluated. A model developed in this study, Tp = 53.296 exp(?9.72C) + 93.104, could be used to predict the resin curing rate in terms of the DSC peak temperature (Tp) as influenced by the NH4Cl content (C). The results indicated that the curing rate of UF resin increased as the catalyst content increased and reached a maximum when the catalyst content ranged from 0.5 to 1.0% (solid basis over liquid UF resin weight). Further increases in the catalyst content had no effect on the resin curing rate. The curing rates of UF resin in the presence of wood extracts increased with decreased pH values or increased base buffer capacities. It was also discovered that the activation energy could not fully explain the resin curing behavior when some species of wood extracts were present, and therefore, the pre‐exponential factor had to be taken into account. The concept of the equivalent catalyst content (ECC) of wood extracts to the NH4Cl content was introduced in this study; ECCs ranged from 0.0022 to 0.0331% among the 16 wood species. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
10.
The curing kinetics and mechanisms of diglycidyl ether of bisphenol A (DGEBA) using imidazole (H‐NI) and 1‐methyl imidazole (1‐MI) as curing agents are studied with differential scanning calorimetry (DSC) under isothermal (90–120°C) and dynamic conditions (50–250°C). The isothermal DSC thermograms of curing DGEBA with H‐NI and 1‐MI curing agents show two exothermic peaks. These peaks are assigned to the processes of adduct formation and etherification. These results indicate that there is no difference in the initiation mechanism of 1‐unsubstituted (H‐NI) and 1‐substituted (1‐MI) imidazoles in the curing reaction with epoxy resin. A kinetic analysis is performed using different kinetic models. The activation energies obtained from DSC scanning runs using the Ozawa and Kissinger methods are similar and in the range of 75–79 and 76–82 kJ/mol for DGEBA/H‐NI and DGEBA/1‐MI systems, respectively. These values compare well with the activation energies obtained from isothermal DSC experiments using the autocatalytic method (74–77 kJ/mol). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2634–2641, 2006 相似文献
11.
Shin‐Shiao Yang Tar‐Hwa Hsieh Hsiaotao T Bi Ko‐Shan Ho Tsung‐Han Ho Ho‐Ruei Chen Shi‐Hao Ye Yu‐Chen Chang 《应用聚合物科学杂志》2009,114(4):2373-2377
12.
Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to detect and simulate the cure behavior of unsaturated polyester (UP), phenol, and UP/phenol blends and to calculate and predict the cure rate, cure temperature, conversion, and changes in the glass‐transition temperature along with various cure orders in order to obtain the optimum parameters for processing. With dynamic scanning and isothermal DSC procedures and Borchardt–Daniels dynamic software, cure data for the UP resin were obtained, 90% of the conversion rate at 100°C being achieved after 15 min. However, for the phenol and UP/phenol blends, gradually increasing the temperature was found to be best for curing according to the DSC and DMA test results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1041–1058, 2004 相似文献
13.
The curing behavior of two kinds of commercial powdered resol phenolic resins was studied by differential scanning calorimetry. Liquid‐state 13C‐NMR spectroscopy was used to aid in understanding the curing behavior by detecting the structure of powdered resins. The reaction mechanism was interpreted with the dependency of activation energy on the degree of conversion. The results indicate that there are differences in the curing mechanism between core and face phenolic resins. The curing process of core resin was faster than that of face resin at the same reaction temperature. The water added in the curing system played an important role of plasticizer or diluent according to different curing stages and water content. In the initial curing stage, water mainly diluted the system and retarded the curing reactions. However, at the higher degrees of conversion, water played the role of plasticizer to decrease the effect of diffusion on the curing reactions to make the curing reactions more complete. The excess water added in the curing system played the role of diluent at almost all stages during the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1371–1378, 2003 相似文献
14.
15.
Three novel aromatic phosphorylated diamines, i.e., bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl} pyromellitamic acid (AP), 4,4′‐oxo bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AB) and 4,4′‐hexafluoroisopropylidene‐bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AF) were synthesized and characterized. These amines were prepared by solution condensation reaction of bis(3‐aminophenyl)methyl phosphine oxide (BAP) with 1,2,4,5‐benzenetetracarboxylic acid anhydride (P)/3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride (B)/4,4′‐(hexafluoroisopropylidene)diphthalic acid anhydride (F), respectively. The structural characterization of amines was done by elemental analysis, DSC, TGA, 1H‐NMR, 13C‐NMR and FTIR. Amine equivalent weight was determined by the acetylation method. Curing of DGEBA in the presence of phosphorylated amines was studied by DSC and curing exotherm was in the temperature range of 195–267°C, whereas with conventional amine 4,4′‐diamino diphenyl sulphone (D) a broad exotherm in temperature range of 180–310°C was observed. Curing of DGEBA with a mixture of phosphorylated amines and D, resulted in a decrease in characteristic curing temperatures. The effect of phosphorus content on the char residue and thermal stability of epoxy resin cured isothermally in the presence of these amines was evaluated in nitrogen atmosphere. Char residue increased significantly with an increase in the phosphorus content of epoxy network. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2235–2242, 2002 相似文献
16.
Young‐Kyu Lee Dae‐Jun Kim Hyun‐Joong Kim Teak‐Sung Hwang Miriam Rafailovich Jonathan Sokolov 《应用聚合物科学杂志》2003,89(10):2589-2596
The thermal behavior, thermal degradation kinetics, and pyrolysis of resol and novolac phenolic resins with different curing conditions, as a function of the formaldehyde/phenol (F/P) molar ratio (1.3, 1.9, and 2.5 for the resol resins and 0.5, 0.7, and 0.9 for the novolac resins) were investigated. The activation energy of the thermal reaction was studied with differential scanning calorimetry at five different heating rates (2, 5, 10, 20, and 40°C/min) between 50 and 300°C. The activation energy of the thermal decomposition was investigated with thermogravimetric analysis at five different heating rates (2, 5, 10, 20, and 40°C/min) from 30 to 800°C. The low molar ratio resins exhibited a higher activation energy than the high molar ratio resins in the curing process. This meant that less heat was needed to cure the high molar ratio resins. Therefore, the higher the molar ratio was, the lower the activation energy was of the reaction. As the thermal decomposition of the resol resins proceeded, the activation energy sharply decreased at first and then remained almost constant. The activation energy of the thermal decomposition for novolac resins with F/P = 0.5 or F/P = 0.7 was almost identical in all regions, whereas that for novolac resins with F/P = 0.9 gradually decreased as the reaction proceeded. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2589–2596, 2003 相似文献
17.
We studied the curing behavior of heterocyclic‐based epoxy‐terminated resins using diaminodiphenyl ether, diaminodiphenyl sulfone, benzophenone tetracarboxylicdianhydride, and the commercial hardener of Ciba‐Geigy's two‐pack Araldite as curing agents. The adhesive strength of the adhesives was measured by various ASTM methods such as lap‐shear, peel, and cohesive tests on metal–metal, wood–wood, and wood–metal interfaces. All of these results were compared with those of an epoxy resin prepared from bisphenol‐A and epichlorohydrin resin with an epoxy equivalent value of 0.519. The thermal stability of both the virgin resin and its cured form was also studied by thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3520–3526, 2002 相似文献
18.
The cure of a novolac‐type cyanate ester monomer, which reacts to form a polycyanurate network, was investigated by using differential scanning calorimeter. The conversions and the rates of cure were determined from the exothermic curves at several isothermal temperatures (513–553 K). The experimental data, showing an autocatalytic behavior, conforms to the kinetic model proposed by Kamal, which includes two reaction orders, m and n, and two rate constants, k1 and k2. These kinetic parameters for each curing temperature were obtained by using Kenny's graphic‐analytical technique. The overall reaction order was about 1.99 (m = 0.99, n = 1.0) and the activation energies for the rate constants, k1 and k2, were 80.9 and 82.3 kJ/mol, respectively. The results show that the autocatalytic model predicted the curing kinetics very well at high curing temperatures. However, at low curing temperatures, deviation from experimental data was observed after gelation occurred. The kinetic model was, therefore, modified to predict the cure kinetics over the whole range of conversion. After modification, the overall reaction order slightly decreased to be 1.94 (m = 0.95, n = 0.99), and the activation energies for the rate constants, k1 and k2, were found to be 86.4 and 80.2 kJ/mol. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3067–3079, 2004 相似文献
19.
Curing of fiber‐reinforced thermoset polymer composites requires an elevated temperature to accelerate the crosslinking reaction and also hydrostatic pressure to consolidate the part and suppress the formation of voids. These processing conditions can be provided by autoclaves of appropriate size, but these are expensive and sometimes difficult to schedule. Ultrasonic debulking followed by oven cure is an attractive alternative to autoclave cure. In this technique a movable “horn” driven at ultrasonic frequency is applied to the surface of the uncured part. This generates pressure and at the same time produces heating by viscoelastic dissipation. The part can be debulked to net shape and staged through the action of the ultrasound. There are a large enough number of experimental parameters in ultrasonic debulking and staging to make purely empirical process optimization difficult, and this paper outlines numerical simulation methods useful in understanding and developing the process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1609–1615, 2004 相似文献
20.
Suping Bao Shijun Shen Guodong Liang Hongbo Zhai Weibing Xu Pingsheng He 《应用聚合物科学杂志》2004,92(6):3822-3829
The nanocomposite of epoxy resin/tung oil anhydride/organic montmorillonite was prepared by casting and curing. The distance of the clay gallery rose and the exfoliated nanocomposite was formed. The exfoliation behaviors of the nanocomposite had been investigated by X‐ray diffraction (XRD). The curing mechanism and kinetics of epoxy resin with the different amounts of organic montmorillonite were studied using isothermal and dynamic methods by differential scanning calorimetry (DSC). Some parameters, the activation energy and reaction orders, were calculated by the modified Avrami equation in analysis of the isothermal experiment. The total curing mechanism and kinetics of curing reaction were also analyzed by the Flynn–Wall–Ozawa method. It was noted that the instantaneous activity energy during the curing process could be obtained by the Flynn–Wall–Ozawa method and the trend of the results was in agreement with those obtained from the modified Avrami equation. These results show that the activity energy decreases with the addition of organic montmorillonite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3822–3829, 2004 相似文献