纳米碳酸钙影响UF树脂性能的研究

实验对纳米CaCO3对UF树脂固化时间,游离甲醛含量及胶合强度的影响进行研究,结果表明:纳米CaCO3延长了树脂的固化时间,游离甲醛含量随加入量的增加而逐渐减少,纳米CaCO3对胶合板的胶合强度贡献不大。     

The effect of nanosilica on mechanical,thermal and morphological properties of epoxy coating

In this study, nanosilica of very high specific surface area is used as reinforcing filler for preparing an epoxy-based nanocomposite coating. For appropriate dispersion of nanoparticles in the polymer matrix, ultrasound waves were applied after mechanical mixing. The resulting perfect dispersion of nanosilica particles in epoxy coating revealed by transmission electron microscopy ensured the transparency of the nanocomposite. Nanoindentation was used to determine some mechanical properties such as hardness and elastic modulus. The obtained results show 26 and 21% increases in hardness and elastic modulus, respectively for resin filled with 5% nanosilica compared to neat epoxy. DMA results show that the glass transition temperature of samples is increased with increasing silica nanoparticles. The result of TGA shows significant improvement of the thermal decomposition temperature of epoxy coating containing 5% nanosilica compared to neat epoxy. Scanning electron microscopy (SEM) micrographs of fractured surfaces show increased roughness with nanosilica addition.     

UF树脂固化剂研究进展

叙述了UF树脂固化剂研究进展,包括UF树脂性质、UF树脂固化理论以及UF树脂固化剂种类和合理的选择固化剂。     

Assessment of thermal behavior of pre-curing UF resin with different heat treatment

The thermal behavior of pre-curing urea–formaldehyde (UF) resin with different solid content was investigated by different scanning calorimetry (DSC), and the activation energies (E_a) in different pre-curing stage of UF resin were also analyzed by Kissinger method. The results indicated that with pre-curing degree increasing, the DSC curves of pre-curing UF resin shifted to lower temperature, and both the onset and peak temperature decreased. The pre-curing process of UF resin included two stages: In the first stage, the E_a and Z value decreased obviously due to the activity of component increased with water evaporation, and then, these two values increased in the second stage due to pre-curing degree increased even partial resin was cured.     

缩聚条件对脲醛树脂结构的影响

用＾１３ＣＮＭＲ研究脲醛树脂缩聚反应结构形式特征,结果表明：在传统合成工艺条件下,与树脂化反应平行地存在一个较强烈的水解反应;二次缩聚有利于降低树脂中二亚甲基醚的含量,并可提高树脂交联程度;高温缩聚所得的树脂结构简单并有利于降低醚键的含量和提高树脂贮稳定性;降低缩聚阶段的ＰＨ值有利于提高树脂交联程度,降低了甲醛的含量。     

影响改性脲醛树脂性能的因素分析

应用主因子分析法探讨了氧化淀粉改性脲醛树脂的合成工艺中,游离甲醛含量、固含量、贮存稳定性、剪切强度等主要技术指标的影响因素。结果表明:脲醛比、淀粉种类和氧化程度是影响游离甲醛含量和固含量的主要因素;淀粉氧化程度和加入量是影响剪切强度的主要因素;脲醛比、淀粉与水之比及氧化程度是影响稳定性的主要因素。     

终止剂对PVC树脂热稳定性和加工性能的影响

介绍了不同类型终止剂在105 m3聚合釜悬浮法生产SG5型PVC过程中对PVC树脂稳定性和后加工性能的影响.     

后固化工艺对T700/PTA2复合材料耐热性能影响

试验研究了后固化处理温度及时间对T700/聚三唑(PTA2)复合材料耐热性和热稳定性(Td5)的影响。结果表明,当后固化处理温度从160℃提高到220℃时,复合材料的玻璃化转变温度(Tg)增加了28℃;延长后固化处理时间对复合材料Tg的影响不显著;PTA2树脂的Td5是由分子中最弱的化学键所决定的,后固化处理温度的提高对复合材料的Td5影响不大。     

丙烯酸-脲醛树脂交联共混改性乳白胶

研究了以丙烯酸和醋酸乙烯酯共聚合生成乳液胶,加入脲醛树脂共混得改性乳白胶的工艺方法。实验确定了乳液聚合时引发剂、乳化剂、交联剂丙烯酸及共混时脲醛树脂的加入量。所获乳白胶具有耐水、耐寒、胶液稳定、抗剪强度高等特点。     

硅树脂对硅橡胶耐热性能的影响

用硅树脂对硅橡胶进行改性 ,研究了硅树脂及其含量对硅橡胶耐热性能的影响。通过热空气老化试验及热重法—差热分析表明 :其力学性能与热空气老化性能显著提高。经过 30 0℃× 48h热空气老化后 ,加入硅树脂的试样仍非常柔软 ,性能保持率达 80 %。     

Influence of nanosilica particles on the cure and physical properties of an epoxy thermoset resin

Measurements are reported on the cure and physical properties of an epoxy resin created using a functionalised nanosilica filler. The filled bisphenol A epoxy (Nanopox A410) contained 40 wt% silica nanoparticles and was blended with two bisphenol A resins of molecular weights of 355 and 1075 g mol^?1, respectively. Cure was achieved using 3,3‐diaminodiphenylsulfone. The functionality of the mixture containing the epoxy nanoparticles was determined using NMR analysis. Cure times showed a progressive decrease with increasing silica level. Dynamic mechanical thermal analysis showed a decrease in the value of the glass transition temperature (T_g) with increasing silica level. T_g was further studied using differential scanning calorimetry. The ability of the nanosilica to create a stable network structure was demonstrated by the variation of the high‐temperature modulus with silica composition. Thermomechanical analysis carried out below and above T_g showed a progressive decrease in the expansion coefficients with increasing silica level, indicating the effectiveness of the functionalised silica nanoparticles in forming a network. The network formed during cure in the nano‐modified epoxy is unable to undergo the densification possible in the pure resin material and explains the observed lowering of T_g with increasing nanosilica content. Copyright © 2009 Society of Chemical Industry     

The effect of a CNT interface on the thermal resistance of contacting surfaces

Experimental and theoretical analyses were used to study the effect of thermal contact resistance in two materials, aluminum and graphite. Experimental investigation included the use of a modern laser flash device to measure the effective thermal conductivity of each material for three different cases: in direct contact, with a graphite coating and with a thin sheet of carbon nanotube (CNT) thermal interface material (TIM). For both materials total thermal resistance values were determined corresponding to different cases for same contact pressure. Results showed that the CNT TIM produced the minimum thermal contact resistance. A theoretical study was carried out to compare the experimental results with thermal resistance models from the literature. Based on the surface roughness of the materials tested, two models were used. Both models showed reasonable agreement with the experimental results with an error of less than 6.5%. The results demonstrate the effectiveness of CNT materials in improving the thermal conductance of contacting surfaces.     

低温合成聚乙烯醇改性脲醛树脂的研究

探讨了低温弱酸性条件下聚乙烯醇改性脲醛树脂的合成,研究了聚乙烯醇加入量、加入的顺序对脲醛树脂胶粘剂的影响。结果表明,甲醛与尿素的摩尔比F/U=1.87,pH=4.5和温度40℃的反应条件下,加入聚乙烯醇量为0.2 g时,脲醛胶质量最好,游离甲醛含量低至0.64%,耐水时间为14 h,且稳定性好。而传统高温工艺的游离甲醛含量为1.14%,耐水时间3.4 h。本工艺节能环保,提高生产效率。     

乙二醛-尿素树脂提高脲醛树脂固化速率和性能的研究

在酸性介质中合成了一种无F(甲醛)的环保型GU(乙二醛-尿素树脂),并探讨了其用作UF(脲醛树脂)固化剂的可行性。研究结果表明:GU含有共轭结构、大量的氨基和羟基等活性基团,并且其Mr(相对分子质量)分布较宽且比较零散,主要以加成产物和低聚物为主;当m(GU)∶m(UF)=5∶95时,不另加固化剂而制备的胶合板之干态胶接强度和F释放量,均满足GB/T 9846.3—2004标准中的指标要求。     

环保型脲醛树脂胶粘剂的合成研究——三聚氰胺聚乙烯醇改性UF胶

介绍了三聚氰胺,聚乙烯醇(PVA)在脲醛树脂胶粘剂(UF胶)合成过程中所起的改性作用,研究了甲醛与尿素的摩尔比、PVA和三聚氰胺用量以及加料顺序、反应温度、pH值、反应时间对脲醛树脂胶性能的影响。结果表明,甲醛与尿素的摩尔比为1.4∶1,PVA和三聚氰胺的用量分别为尿素总量的1.5%和4%时,合成的脲醛树脂胶粘剂综合性能良好,游离甲醛含量低,达到了绿色环保的要求。     

玻纤薄毡用水溶性脲醛树脂的开发及应用

脲醛树脂的原料来源丰富,价格便宜,在粘合剂与处理剂方面有广泛应用.水性脲醛树脂又分为水乳型(外观乳白)和水溶性(外观透明).     

多官能度环氧树脂对共混体系耐热性能的影响

为了研究多官能度环氧树脂(AFG-90)对环氧树脂共混体系耐热性能的影响,通过动态机械分析仪测试了其不同加入量的共混树脂固化物的玻璃化转变温度(Tg)。结果表明:AFG-90和普通环氧树脂有很好的相容性,其固化物的Tg随AFG-90加入量的增加而增加,并表现出1个最佳值范围;而固化物的初始模量基本保持不变。     

Investigation on curing reaction of phthalonitrile resin with nanosilica and the properties of their glass fiber-reinforced composites

In this work, Phthalonitrile containing benzoxazine (BA-ph) and Bisphenol A based cyanate ester (CE) were chosen as the matrix resin. Various amount of nano-SiO₂ was incorporated into BA-ph/CE and their glass fiber-reinforced composite laminates were fabricated. Curing reaction and processability of BA-ph/CE/SiO₂ blends were studied by differential scanning calorimetry and dynamic rheological analysis. Results showed that BA-ph and CE exhibited good processability and curing reaction of BA-ph/CE was not obviously affected by SiO₂. Scanning electron microscope images of the composites showed that SiO₂ particles were well dispersed in BA-ph/CE matrix. Moreover, SiO₂ could act as physical crosslinking points and diluent in matrix as well as between the glass fibers to improve the mechanical properties of composite laminates. As the results of dynamic mechanical analysis and thermogravimetry analysis, composite laminates possessed satisfactory T_g and good thermal stability. With incorporation SiO₂ particles into matrix resin, dielectric constant and dielectric loss of BA-ph/CE/SiO₂/GF composites were increased and showed frequency dependence.     

Thermal and photocuring of an acrylate-based coating resin reinforced with nanosilica particles

A macromonomer, 1,3-bis[(2-hydroxy-3-acrylate)propyloxy]2-hydroxypropane (BHAPP) was prepared by the reaction of acrylic acid with diglycerol diglycidyl ether (DGE) in the presence of triethyl amine as a catalyst. The progress of the reaction was followed by measuring the decrease in intensity of the epoxide absorption peak at 915?cm^?1, and structure of BHAPP was characterized by FTIR and ¹H NMR spectroscopy. The effect of nanosilica (NS) particles as catalyst on thermal and photocuring of BHAPP was studied. The photopolymerization was carried out with the visible light using camphorquinone and N,N-dimethylaminoethylmethacrylate (DMAEM) as the photoinitiating system. The kinetic parameters of thermal curing were obtained using nonisothermal differential scanning calorimeter (DSC), and the data indicated that NS particles catalyzed the cure reaction by shifting the exothermic peak toward lower temperatures, decreasing the activation energy (E _a), and increasing the rate constant value. The absorption properties of the cured nanocomposites were also studied in different exposure conditions.     

脲醛树脂制造所用的尿素与甲醛的供应和计量

尿素及甲醛的计量、质量及价格对纤维板的质量及经济效益影响很大,建议购置名牌产品,从大型生产企业定点进货,有条件的单位可考虑使用散装尿素。