Effects of Ultraviolet Radiation,High Temperature and Alkaline Chemicals on Ageing of Silicone Sealants Used in Ballastless Track Expansion Joints

Expansion joints silicone sealants used in high speed railway construction suffer from ultraviolet radiation（UV）, high temperature combined with the alkaline environment. To evaluate the durability and analyse the ageing mechanism, six one-component silicone sealants from different companies were selected and subjected to accelerated ageing tests including UV, thermal and alkali ageing treatments. The ageing effects on the performance of the sealants were evaluated via the appearance and the mechanical property changes. The changes in molecular structure were studied by means of Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC） and thermogravimetry（TG）. This study revealed that different materials displayed different sensibilities to the ageing methods, in which 15 %-20 % decreases of mechanical properties could be observed under UV radiation test, owning the most significant effects. Structure analysis showed that the physical changes of aggregative states were the principal factors to the performance, along with the chemical slight changes. The glossiness dropped significantly in ageing test, which could be used as one of the effective evaluation parameters for ageing conditions in the field.

Evaluation and Selection of Sealants and Fillers Using Principal Component Analysis for Cracks in Asphalt Concrete Pavements

The objective of this paper was to develop a comprehensive evaluation method and index to evaluate the performance of sealants and fillers for cracks in asphalt concrete pavements using the method of principal component analysis. The performance experiments including cone penetration, softening point, flow, resilience and tension at low temperature respectively were conducted by reference of ASTM D5329 for eight sealants and fillers often used in China. There by a principal component model was developed and weight of every index was calculated. The experimental results show that there are significantly different performances for sealants and fillers often used in China. Principal component analysis is an objective method that evaluates and selects the performance of sealants and fillers for cracks in asphalt concrete pavements.

Pancreatic duct disruption and nonoperative management: the SEALANTS approach

Pancreatic-duct disruption (PDD) can be difficult to manage, with diverse etiologies and sequelae in a heterogeneous population. Common etiologies include pancreatitis, iatrogenic injury, and trauma. Sequelae of PDD include pseudocyst, pancreatic ascites,

Synthesis and Application of a Novel Organosilane Modifier for Surface Paintability of Organosiloxane Sealants

A novel organosilane, N-n-butyl-γ-aminopropylmethyldimethoxysilane was synthesized through aminization reaction and the chemical structure of resulting products was characterized by 1HNMR, 13CNMR, FT-IR and elemental analysis. The results of test on probation for this organosilane proved that it was effective to modify surface-paintability of organosiloxane sealants.

Compatibility between glass sealants and electrode materials of solid oxide fuel cells

BaO-CaO-Al2O3-SiO2-La2O3-B2O3 system glass materials were investigated as sealants for a solid oxide fuel cell （SOFC）. The transition temperature （Tg and the crystal temperature （Td） values decrease greatly with the increase of BaCO3 content when the other components do not change. For the thermal expansion coefficient （TEC） values, the trend is inverse. The sealant has superior thermal expansion coefficient matching properties with La（Sr）MnO3 （LSM） cathode, La（Sr）FeO3 （LSF） cathode, Ni-LDC （La doped CeO2） anode, and Ni-YSZ （yttria stabilized zirconia） cermet anode. The sealant also has superior stability, compatibility, and good bonding characteristic with these electrode materials at 800-900℃. The results indicate that the aluminosilicate system glass sealant possesses superior compatibility with electrode materials of the solid oxide fuel cell

Evaluation of Ion Release from Four Dental Sealants

The purpose of this study was to determine the ion release from four commercially available pit-and-fissure sealants [3M Clinpro, 3M ConciseTM, BeautiSealant （BS）, and GI FX-Ⅱ）]. With each brand, 18 specimens were prepared. Their fluoride release in de-ionized water was measured by fluoride electrode, while the release of silicate （Si）, aluminum （A1）, sodium （Na）, calcium （Ca）, strontium （Sr）, and phosphorus （P） was measured by inductively coupled plasma atomic emission spectroscopy （ICP-AES） on days 1, 3, 7, 14, 21, and 28. The result showed that fluoride was not released from 3M ConciseTM. GI FX-II displayed the largest fluoride release, which, however, dropped rapidly on day 3.3M Clinpro exhibited less fluoride release than GI FX-II and BS did. At any time during the 28-day experimental period, GI FX-II released more Na than the other sealants （P〈0.001）. BS ranked the second in Na release, and a small amount of Na ions was released from the 3M Clinpro and 3M ConciseTM samples. Al ions were only detected from BS and GI FX-Ⅱ, but not from the 3M Clinpro and 3M ConciseTM. Additionally GI FX-II had the largest Si release among the four brands at any time during the experimental period （P〈0.001）. Ca ions were detected from 3M Clinpro and 3M ConciseTM, but not from GI FX-Ⅱ. BS released more Sr than the other sealants at any time during the experimental period （P〈0.001）. All the samples released similar amounts of P continuously during these 28 days. In conclusion, based on the type and the amount of ion release, BS is the best pit-and-fissure sealant among the four brands.

High-temperature glassy-ceramic sealants SiO_2-Al_2O_3-BaO-MgO and SiO_2-Al_2O_3-ZrO_2-CaO-Na_2O for solid oxide electrochemical devices

Glasses of the SiO_2-Al_2O_3-BaO-MgO and SiO_2-Al_2O_3-ZrO_2-CaO-Na_2O systems were synthesized in the perspective to apply them as sealants in SOFC at operating temperatures of 700-900 °C. Thermal properties of the chosen glass compositions and their compatibility with the SOFC materials(YSZ-electrolyte and alloy-interconnector Crofer22 APU, 15Х25Т) were investigated by means of synchronic thermal analysis and high-temperature dilatometry. The elemental analysis was performed by atomic emission spectroscopy. The average values of the temperature coefficients of the linear extension are 10.0×10^(-6) °С^(-1) for glass 45%SiO_2-15%Al_2O_3-25%BaO-15%MgO and 9.5×10^(-6) °С^(-1) for glass 60%SiO_2-10%Al_2O_3-10%ZrO_2-5%CaO-15%Na_2O. The gluing microstructure in YSZ/glass/Crofer22 APU was studied by scanning electron microscopy. The crystallization process of silicate phases was revealed to occur in the SiO_2-Al_2O_3-BaO-MgO glass. The analysis of the crystallization products was performed by Raman spectroscopy and X-ray diffraction. Glassy ceramics was proved to possess better parameters in comparison with amorphous glass to be used as a sealant in electrochemical sensors and oxygen sensors. The SiO_2-Al_2O_3-ZrO_2-CaO-Na_2O low-temperature amorphous glass can be applied in SOFC.

Bilayered Glass-Ceramics as Sealants for SOFCs

Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferritic stainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties, especially in terms of thermal expansion. A bilayered glass-ceramic system was developed to overcome the mismatch in coefficients of thermal expansion (CTE) between ferritic steel and YSZ. Therefore, two different glass-ceramics with slightly different CTEs were developed, one with good bonding characteristics to the ferritic steel and the other to the YSZ electrolyte. Steel and electrolyte components were coated with a layer of their corresponding glass sealant paste and heated up to form a sandwich sample. During the heat treatment of the sealing process, the glasses are crystallized into glass-ceramics. The resulting interface between the two glass-ceramics is of special interest. Cross-sections of the sandwich samples were cut, polished and investigated using SEM. The glass-ceramics show continuous, gap-free layers and excellent bonding to both steel and YSZ. Energy release rates are measured for single and bilayered glass sealants by mechanical testing. The designed bilayered glass-ceramics fulfill the special requirements of ferritic steel and YSZ. They show excellent potential to become a new outstanding sealant for SOFCs.

Buildings and civil engineering works-Sealants-Determination of changes in cohesion and appearance of elastic weatherproofing sealants after exposure of statically cured specimens to artificial weathering and mechanical cycling

Foreword ISO(the International Organization for Standardization)is a worldwide federation of national standards bodies(ISO member bodies).The work of preparing International Standards is normally carried out through ISO technical committees.Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee.

水性环氧树脂改性的建筑结构密封胶缓凝性能研究

为研究水性环氧树脂建筑结构密封胶缓凝性能,选用水性环氧树脂、水性环氧树脂固化剂、MS聚合物、硅烷偶联剂、纳米碳酸钙以及不同填料等试剂,以MS聚合物质量为标准设定试剂比例,分别制备A组分与B组分,将2组分依照1∶1质量比混合配比,由此获取不同配比条件下的改性密封胶样本。结果显示,在偶联剂用量达到2%以上时,密封胶样本的适用期符合建筑结构密封胶应用的适用期标准;水性环氧树脂用量为25%,密封胶样本硬度最优;当密封胶样本内不同填料质量比达到3.4∶20∶66∶16时,密封胶样本不会发生流淌现象;不同MS聚合物具有不同特征。

纳米银/有机硅密封胶的制备及性能研究

本文采用水热合成法成功合成了纳米银颗粒,然后以聚二甲基硅氧烷为硅油基质,采用物理共混法制备了纳米银/有机硅密封胶。研究了纳米银/有机硅密封胶的微观形貌结构、耐热性能、力学性能以及抗菌性能。结果表明,在纳米银颗粒的质量分数为10%时,所制备的密封胶显示了出色的拉伸强度(4.22 MPa)和高达157.1%的断裂伸长率。同时,该密封胶还表现出卓越的抗菌性能,并且在室温下放置40 d后仍具有良好的抗菌效果,表现出优异的耐久性能。该工作为绿色、健康和清洁的密封应用提供了一种新的思路。

不同用量外科用封合剂对急性Stanford A型主动脉夹层患者手术止血的安全性及有效性影响

目的评估不同用量的Coseal■外科用封合剂对急性Stanford A型主动脉夹层患者手术止血的安全性及有效性影响。方法单中心前瞻性观察性研究。对2021年4月至2022年6月四川大学华西医院行急性Stanford A型主动脉夹层手术的患者依据使用Coseal■外科用封合剂的用量分为12 ml组(32例)和16 ml组(68例),观察术后体外循环时间、手术时间、术中止血时间、血制品用量、止血药物使用情况、术后24 h引流量、重症监护室驻留时间及患者早期不良事件。结果16 ml组较12 ml组的体外循环时间、手术时间、止血时间、术中Ⅶ因子用量及术后24 h引流量均显著下降或减少(均为P<0.05)。本研究中因引流量增加再次开胸止血的患者,12 ml组多于16 ml组(9.4%比1.5%),但差异无统计学意义(P=0.095)。再次手术患者出血点分布位置:12 ml组分别在人工血管与主动脉吻合处1例,人工血管与人工血管吻合处1例,以及主动脉根部1例;16 ml组出血点位于胸骨后。术后12 ml组患者因肺部感染死亡1例,16 ml组患者因心室颤动和脑卒中死亡各1例。结论对于Stanford A型夹层患者,相比Coseal■外科用封合剂12 ml的基础用量,16 ml的用量对于术中减少体外循环时间、手术时间、止血时间均有积极作用,且有助于降低术后早期引流量及再次开胸止血的风险。

精氨酸改性Clinpro^(TM)窝沟封闭剂对其性能的影响

目的:将精氨酸添加到Clinpro^(TM)窝沟封闭剂中进行改性,比较改性对窝沟封闭剂性能的影响。方法:配制出精氨酸浓度分别为3%、5%、10%的窝沟封闭剂(Arg3组、Arg5组、Arg10组),比较不同窝沟封闭剂的表面硬度、聚合转化率、界面微渗漏。扫描电镜观察固化后窝沟封闭剂的形貌。用液相色谱质谱法测定不同时间点窝沟封闭剂中精氨酸的释放情况。结果:各组窝沟封闭剂的表面硬度、聚合转化率没有显著性差异。Arg10组的界面渗漏率明显高于其他组(P<0.05),其余各组间无明显差异。扫描电镜观察精氨酸改性后的窝沟封闭剂均有不同程度的离子团聚现象。在24 h内的各个时间段Arg5组比Arg3组释放的精氨酸量要多,差异均有统计学意义(P<0.05)。结论:添加5%精氨酸不会影响Clinpro^(TM)窝沟封闭剂的性能及界面微渗漏,Arg5组具有好的精氨酸释放能力。

一种填料优化改性的建筑外墙密封胶性能研究

密封胶的质量与性能对装配式建筑外墙接缝处理具有直接影响,利用密封胶填补接缝,可以防止水分渗透,避免结构材料的破坏,从而延长建筑物的使用寿命。研究制备一种装配式建筑外墙接缝用改性密封胶,将其用于装配式建筑外墙接缝过程,为装配式建筑外墙提供加固支撑。通过进行装配式建筑伸缩缝的嵌缝处理,完成装配式建筑伸缩缝的养护后,对伸缩缝粘接性能、硬度性能、拉伸性能进行测试。实验发现,在碳酸钙填料的质量分数占比2.5%时,制备得到的改性密封胶具有最佳的力学性能和加固性能等,更适用于装配式建筑外墙接缝的实际应用。

一种适用羽毛球拍的抗菌有机硅密封胶性能测试研究

为提升羽毛球拍专用有机硅密封胶的抗菌性能,提出了一种融合C18-QAS抗菌剂的抗菌功能性有机硅密封胶材料。在聚硅氧烷基材的基础上导入C18-QAS抗菌剂,再通过硫化处理的方式制备出抗菌功能性有机硅密封胶。为验证抗菌功能性有机硅密封胶的综合性能,运用邵氏硬度计、拉力材料试验仪以及测角仪等设备对该材料的力学性能和亲疏水性能进行测试,通过乙酰接触法和甲苯平衡溶胀法对该材料的表干性能和交联密度进行测试,并根据测试结果来确定C18-QAS抗菌剂的合理掺量。经试验研究发现,当C18-QAS抗菌剂掺量为3%时,抗菌性有机硅密封胶的综合性能最为理想,可满足羽毛球拍在粘接密封工艺阶段的使用需求。

铝箔纸进行建筑密封材料质量测试可行性分析

在当今建筑业中,密封材料的热失重特性测试是确保建筑性能和节能减排目标达成的关键环节。鉴于国家及国际标准对此类测试所规定的周期较长,围绕简化和加速热失重测试过程展开。通过深入分析GB 16776—2005标准下的热失重测试方法,并对比其他几种材料的测试手段,提出了一种便捷高效的检测方案,旨在为企业内部质量监控提供切实可行的技术支持。考虑到成本和实施的便利性,探索了使用铝箔纸代替传统金属环进行测试的可能性。铝箔纸的选用基于其660℃的高熔点和良好的化学稳定性——铝在空气中可迅速形成一层防护性氧化膜,此膜在高温下能有效阻隔化学反应,保证测试的准确性。此外,铝箔纸的低成本也大幅度降低了测试的经济负担。通过系列实验验证,不仅证明了铝箔纸在密封材料热失重测试中的可行性,还为其在实际应用中的推广提供了科学依据。

环保型亲水聚氨酯防渗封堵剂的研制

以大分子量多官能度亲水聚醚多元醇为软段、甲苯二异氰酸酯(TDI)为预聚物封端剂、二苯基甲烷二异氰酸酯(MDI)为游离异氰酸酯、三亚乙基二胺(A33)为催化剂、二乙二醇二甲醚(GDC)为亲水剂,开发了环保型亲水聚氨酯防渗封堵剂,研究了TDI和MDI用量对聚氨酯封堵剂固结体性能的影响。结果表明:在TDI中异氰酸酯基团与聚醚多元醇中羟基摩尔比(n_(T-NCO)∶n_(OH))为1.6、MDI中异氰酸酯基团与聚醚多元醇中羟基摩尔比(n_(M-NCO)∶n_(OH))为6、GDC质量分数为20%、催化剂A33质量分数为0.5%条件下,制备的亲水聚氨酯防渗封堵剂具有黏度低、包水倍率高、反应活性高的特点,聚氨酯防渗封堵剂浆液黏度为800mPa·s左右,遇水凝胶时间可控制在50s左右,反应后固结体发泡率大于400%,包水倍率超过30g/g,遇水膨胀率约为57%。

室温快速固化耐温型环氧树脂的制备及改性密封胶的性能研究

以邻苯二甲酸酐和环氧氯丙烷为原料合成邻苯二甲酸二缩水甘油酯(PADE),并将其作为一种基体树脂制备了双组分密封胶。对PADE的结构以及双组分密封胶的表干时间、硬度、力学性能、热性能、热稳定性和微观形貌进行测定或表征。研究结果表明:(1)通过FT-IR和1H-NMR对产物进行了结构表征,产物的环氧值为0.58 mol/100 g,室温(25℃)下的黏度为2 245 mPa·s。(2)PADE-10%密封胶比未添加PADE的密封胶表干时间缩短了30 min。(3)随着PADE掺入量的增大,环氧密封胶的拉伸强度、断裂伸长率、弯曲强度和冲击强度先上升后下降,当PADE添加量为10%时,综合力学性能较好;PADE-10%密封胶在不同的老化时间下拉伸剪切强度均高于PADE-0的密封胶,说明此胶粘剂具有一定的耐老化性。(4)发现PADE具有催化作用,降低了活化能,提高了反应速度;并且随着PADE的加入,体系的Tg不断降低,从93.1℃降低到81.6℃。(5)PADE-0(纯E-51)密封胶的T10%和Tmax均小于PADE-10%密封胶,说明PADE的掺入形成高交联网络,使得固化物结构更加致密。适量添加PADE,可提高密封胶的耐热性,使密封胶具备更优异的力学性能。(6)通过研究掺入PADE后对改性E-51环氧密封胶粘接机制的影响发现,E-51固化物断裂面呈现脆性断裂特征,而掺入10%PADE时环氧密封胶的断裂表面显示出有序的能带结构,并伴随着大量细小的银纹出现,表现为韧性断裂特征,表明PADE具有增强增韧的作用。

专利视角下硅烷改性聚醚密封胶的研究进展

本文首先从研究方向、技术区域和申请人情况等维度分析了近些年硅烷改性聚醚密封胶的专利申请情况,然后从申请的专利中梳理出硅烷改性聚醚的合成、硅烷改性聚醚密封胶的制备以及对硅烷改性聚醚密封胶性能的改进(粘接性、机械性、透光性、模量、阻燃、耐热性以及固化性能等)和应用(建筑、汽车等)等方面研究进展,并对未来发展进行了展望。

建筑幕墙密封用多孔硅酮密封胶的制备及保温性能研究

以硅橡胶为基料,多孔硅藻土为填料,制备建筑幕墙密封用多孔硅酮密封胶,并研究其保温性能。结果表明:在一定程度上增大多孔硅藻土用量和延长养护时间会增大多孔硅酮密封胶的表观密度,当多孔硅藻土用量为15份、养护时间为14 d时多孔硅酮密封胶的表观密度较大,孔隙结构调控到了相对较佳状态,保温性能较好;过度延长养护时间、采用水光试验箱养护方式和增大含水率会增大多孔硅酮密封胶的热导率,降低保温性能,当普通养护1~10 d时多孔硅酮密封胶的热导率较小,具有较为理想的保温效果。