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1.
K. Siimer T. Kaljuvee P. Christjanson I. Lasn 《Journal of Thermal Analysis and Calorimetry》2006,84(1):71-77
TG-DTA
analysis method was used to study the curing behaviour of urea-formaldehyde
(UF) adhesive resins in the presence of a wood substrate. The cure process
was followed using a Setaram labsysTM instrument
in flowing nitrogen atmosphere by varying the ratio of resin and wood. Resin
cure was catalysed with 2% of NH4Cl. Curing tests were
performed in the open standard platinum crucibles and in the sealed glass
capsules. To characterise the reactivity of curing system, the peak temperatures
in DTA curve and the mass loss values in TG curve were taken as the apparent
indices. The main attention was paid to phenomena which actually take place
in curing of UF resins during manufacturing of particleboards. Reactivity
of the curing system depends mostly on methylol content of resin and can be
adequetly evaluated by the maximum temperature of exothermic peak. The wood
substrate has a substantial influence on the resin and water diffusion in
system causing the changes in water/resin separation and water evaporation
conditions. The water movement in curing adhesive joint was a confusing parameter
in determining the peak positions. The rate of mass loss on a wood substrate
is higher as compared to curing UF resin alone. 相似文献
2.
选用过氧化二异丙苯(DCP)和偶氮二异丁腈(AIBN)分别引发含乙烯基液态聚碳硅烷(VHPCS)聚合。采用非等温差示扫描量热法(DSC)研究VHPCS/DCP、VHPCS/AIBN两种体系的固化反应动力学,通过Kissinger方程和Crane方程确定相关动力学参数,并由此得出体系的n级固化模型。同时通过β-T外推法确定体系的固化工艺温度,并对体系交联机理及产物热性能进行分析。研究结果表明:VHPCS/DCP、VHPCS/AIBN二体系的活化能分别为72.17kJ/mol、94.11kJ/mol,反应级数分别为0.92、0.93。β-T外推法确定:当升温速率为0℃/min时二体系的近似凝胶化温度均为55℃,峰值温度分别为110℃、107℃,终止温度分别为129.5℃、134℃。FTIR结果表明,VHPCS的交联固化主要是通过双键的自聚合实现,交联后样品的陶瓷产率有所提高。 相似文献
3.
以原位红外加热附件(in situ FTIR)跟踪二胺型苯并噁嗪树脂的交联固化过程,用二维红外相关光谱(2D-IR)研究其固化机理.In situ FTIR系列图谱显示苯并噁嗪发生热开环反应后,生成的中间体以两种形式存在,含有C N键的中间体不再继续链的增长,其中一部分在高温下发生裂解反应,生成含有亚胺正离子C N+的Schiff碱;含有碳正离子的中间体继续发生交联聚合反应,生成含有羟基、三取代芳香醚和Mannich桥结构的自聚产物.通过2D-IR的分析,进一步给出固化过程中关键基团的变化顺序,确定了二胺型苯并噁嗪树脂的自聚产物结构含有三取代芳香醚和Mannich桥结构. 相似文献
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A. A. Shimkin S. A. Ponomarenko R. R. Mukhametov 《Russian Journal of Applied Chemistry》2016,89(2):263-270
Curing of diphthalonitrile resin was studied by IR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. Polymerization of the resin yields triazine and phthalocyanine structures, but the main structural components of the cured matrix are polyimines/isoindolenines. 相似文献
6.
Abstract Printing inks, paints, and other coatings are applied as a liquid or paste but must change to a solid and nontacky state before the painted or coated article can be used. The change is known as curing or drying. Sometimes it occurs by physical means, the evaporation of a solvent or dispersion medium for example, and sometimes by chemical changes such as polymerization and cross-linking. These chemical processes connect the many relatively small molecules of the original liquid or paste into a large molecular network or insoluble solid, which may be either rigid or rubbery in consistency depending upon the requirements of a particular application. Among traditional materials, gravure inks and many lacquers dry by solvent evaporation while paints and inks based upon linseed oil “dry” by chemical cross-linking promoted by oxygen in the air. Considerable time is usually required for curing in both methods, and the evaporation of solvents can result in air pollution and potential fire hazards. There is also a tendency of the media to dry upon presses, brushes, sprayers, and other application equipment. The long cure time requirement raises difficulties in modern production lines; the other factors have become more acute since the rapid rise of petroleum prices and the advent of air pollution legislation. 相似文献
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Cristina Leonelli Massimo Messori Francesco Pilati Paolo Veronesi 《Macromolecular Symposia》2005,228(1):229-236
Infrared and microwave curing of organic–inorganic hybrid materials was studied, in order to achieve the maximum conversion without detrimental effects due to the overheating or to the long-time permanence at high temperature. Partially cured poly(ethylene oxide)/silica hybrids were prepared by hydrolysis and subsequent condensation of precursors for 30 minutes isothermal heat treatment at 70°C. The conversion after the preliminary treatment is still low and requires an additional heating to complete the reaction. Three different thermal treatments were investigated: conventional heating, infrared heating and microwave heating. DSC characterisation of the obtained samples evidenced a drastic reduction of the treatment time when microwaves were used, requiring only a few seconds, compared to the hours-lasting conventional treatments. 相似文献
11.
Keith F. Chater 《Chemistry & biology》2013,20(10):1199-1200
12.
M. C. Jovičić R. Ž. Radičević J. K. Budinski-Simendić 《Journal of Thermal Analysis and Calorimetry》2008,94(1):143-150
An alkyd/melamine resin mixtures are mainly used in industrial baking enamels. The aim of this work was to study the curing
behaviour of alkyds based on dehydrated castor oil and soybean oil with melamine resin by differential scanning calorimetry
(DSC). The kinetic parameters obtained by the transformation of dynamic DSC results into isothermal data through Ozawa kinetic
model are in good agreement with those determined by the isothermal DSC experiments. The apparent degree of curing, determined
by DSC measurements and sol/gel method, has a pronounced effect on the hardness of the resultant coating film. 相似文献
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Johannis Ch. Simitzis Loukas Th. Zoumpoulakis Spiridon K. Soulis Leonidas N. Mendrinos 《Mikrochimica acta》2001,136(3-4):171-174
Unsaturated polyesters are synthesized by means of polyesterification, often with catalysts like strong acids, metal oxides
and metal-organic salts. Most often, the catalysts used cannot be separated from the bulk of the polyester. Also, some organic
or inorganic additives – called fillers – which are used with the polyester in order to decrease cost, affect the curing of
the polyester. In this work the effect of residual catalyst on the curing of unsaturated polyester is studied. Unsaturated
polyesters were prepared using propylene glycol with a 10% molar excess over stoichiometry and a mixture of dicarboxylic acids,
namely maleic acid (unsaturated) adipic acid (saturated) and phthalic anhydride (saturated) at a molar ratio 1:2:2. Lead dioxide,
p-toluenesulfonic acid and zinc acetate were used as catalysts, at 0.1% w/w. After the polyesterification, the polymers were
diluted with styrene at a proportion of 100:30 w/w. The resins were cured by using MEKP (methylethylketone peroxide) as initiator
and CoNp (cobalt naphthenate) as accelerator. Catalysts affect the final color of the polyester. The kinetics of curing of
the resins was studied by DSC analysis based on the exothermic peak due to the double bonds breaking to give crosslinked macromolecules.
The heat released ΔH is decreased by the presence of catalyst, while activation energy, the frequency factor and the order of reaction are increased. 相似文献
15.
M. Sangermano E. Amerio A. Di Gianni A. Priola D. Pospiech B. Voit 《Macromolecular Symposia》2007,254(1):9-15
Summary: A wide range of hyperbranched polymers (HBP) was synthesized and investigated as additives in cationic photopolymerization of epoxy systems. The HBP were inserted into the polymeric network either by a copolymerization or through a chain transfer reaction involving the phenolic hydroxyl groups. By varying the type and concentration of HBP a modification of the bulk properties of photocured films was induced. An increase of toughness properties together with a flexibilization was obtained without affecting the processability and the viscosity of the photocurable mixture. In the presence of fluorine-containing HBP, a surface modification was induced. 相似文献
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C. Maes J. Devaux R. Legras I. W. Parsons 《Journal of polymer science. Part A, Polymer chemistry》1995,33(12):1943-1955
A monofunctional maleimide-ended model compound was synthesized and purified. The thermal curing of this compound was followed by size exclusion chromatography and the molecular masses of the oligomers formed during the curing reaction were determined by mass spectroscopy. It was found that high molecular mass species were not thermally stable. At high temperature and after enough time, a strong decrease in the polydispersity of the oligomers and a significantly preferential formation of trimer were observed. From 13C-NMR characterization, a five membered ring structure was found for the trimer, which explains the thermal stability of this species. © 1995 John Wiley & Sons, Inc. 相似文献
18.
David N. Vincent 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):485-499
Abstract The effect of chlorine and polynuclear structures on the thermal degradation of polyphenylene has been examined. The thermal dehalogenation reaction has been utilized to cross-link the polymer. Composites stabilized in this manner were evaluated by exposure to an oxyacetylene torch. 相似文献
19.
C. Carfagna E. Amendola M. Giamberini A. G. Filippov R. S. Bauer 《Liquid crystals》1993,13(4):571-584
By endcapping mesogenic rigid rod molecules with reactive epoxy groups a novel class of liquid-crystalline thermoset has been obtained. In fact is has been shown that the nematic molecular arrangement is sustained over the crosslinking reaction of liquid-crystalline epoxy resins when the curing reaction is carried out in the thermal stability range of the liquid-crystalline phase. Calorimetric analysis was used in characterizing the isothermal cure. An unsophisticated model is proposed for evaluating the activation energies of the crosslinking reaction. For liquid-crystalline epoxy resins lower activation energies result with respect to the cure reactions for non liquid-crystalline epoxy resins. 相似文献
20.
A method for synthesis and purification of polydimethylboronzirconiumsiloxane, which is used as a component in a curing system for single-component organosilicon compositions applied in technologies for manufacturing of microelectronics products, is developed. It is shown that the introduction of heterosiloxane polymer allows one to obtain electroinsulating corrosion-passive coatings that possess high adhesion to structural materials and operate in a wide temperature range under conditions of increased humidity. 相似文献