Preparation and Characterization of Carboxyl-terminated Poly(butadiene-co-acrylonitrile)-epoxy Resin Prepolymers for Fusion-bonded-epoxy Powder Coating

Liquid carboxyl-terminated poly（butadiene-co-acrylonitrile）（CTBN）-epoxy resin（EP） prepolymers were prepared with different contents of CTBN.The chemical reactions between EP and CTBN were characterized by Fourier ransform infrared（FTIR） spectroscopy and gel permeation chromatography（GPC）.The scanning electron micrograph（SEM） and dynamic mechanical analysis（DMA） of curing films showed phase separation,and the rubber particles were finely dispersed in the epoxy matrix.Mechanical properties analysis of curing films showed that impact strength and elongation at break increased significantly upon the addition of CTBN,indicating good toughness of the modified epoxy resins.Thermogravimetric analysis（TGA） showed that the incorporation of CTBN had little effect on the thermal stability of EP.Fusion-bonded-epoxy（FBE） powder coatings modified with CTBN-EP prepolymers were prepared.The experimental results demonstrate the ability of CTBN-EP prepolymers,toughening technology to dramatically enhance the flexibility and impact resistance of FBE coatings without compromising other key properties such as corrosion protection.

Performance of CTBN(carboxyl-terminated poly (butadiene-co-acrylonitrile))-EP(diglycidyl ether of bisphenol-A (DGEBA)) Prepolymers and CTBN-EP/polyetheramine (PEA) System

CTBN-EP prepolymers were synthesized from CTBN and epoxy resin under the catalysis of HTMAB. FTIR analyses indicate the formation of ester group between the carboxyl group of CTBN and the oxirane group of epoxy resin. The viscosity of modified prepolymer increases with CTBN content increasing, but the epoxy value of the prepolymer decreases greatly. DSC analyses verify that CTBN affects the curing process of CTBN-EP/PEA system. Mechanical testing presents the improved toughness of CTBN-EP/PEA curings for the decrease of tensile strength, flexural strength and compressive strength, and increase of impact strength and elongation-at-break with the CTBN content increasing. SEM micrographs show the rubber phase with many holes in diameter about 0.5-1.5 μm is formed when CTBN content is lower than 10 phr. However, the pattern of SEM graph shows some stalactite-like strips when CTBN content is higher than 15 phr. Furthermore, the SEM image of 25 phr CTBN sample forms a kind of co-continuous structure.

氟橡胶的制备方法及研究进展

氟橡胶(FKM)因其结构链的特殊性,具有其他橡胶无法比拟的耐高温、耐化学性以及良好的机械性能。介绍了氟橡胶的发展历程以及氟橡胶/填料复合体系,综述了氟橡胶的制备与改性方法,为进一步改进氟橡胶的性能提供参考。

固相萃取/高效液相色谱-串联质谱法同时测定氟橡胶、氟树脂及其制品中多种全氟和多氟烷基化合物

基于固相萃取/高效液相色谱-串联质谱(HPLC-MS/MS)技术,建立了氟橡胶、氟树脂及其制品中37种全氟和多氟烷基化合物(PFASs)的定量分析方法和19种PFASs的定性分析方法。采用25 mmol·L^(-1)乙酸铵甲醇/乙腈(1∶1,体积比)溶液对氟橡胶类、氟树脂固体类和氟树脂纺织类样品进行超声振荡提取;采用四甲基叔丁基醚(MTBE)对氟树脂液体类样品进行超声振荡提取,提取液经Envi-carb和Oasis WAX柱固相萃取,并用甲醇和0.1%氨水甲醇洗脱。在10 mmol·L^(-1)乙酸铵溶液-乙腈流动相下采用Acquity UPLC BEH C18(2.1 mm×100 mm,1.7μm)色谱柱对目标化合物进行梯度洗脱分离,多反应监测模式(MRM)进行采集,内标法定量。结果表明,在5、10、20 ng·g^(-1)(氟橡胶类)和2.5、5、10 ng·g^(-1)(氟树脂类)加标水平下,氟橡胶类、氟树脂固体类、氟树脂纺织类和氟树脂液体类样品中37种PFASs的回收率分别为81.3%~109%、60.9%~111%、87.8%~125%和88.7%~140%;相对标准偏差(RSD)分别为1.4%~28%、1.5%~22%、1.8%~27%和1.4%~19%;检出限(LOD)分别为0.03~0.3 ng·g^(-1)、0.03~0.8 ng·g^(-1)、0.02~2 ng·g^(-1)和0.04~1 ng·g^(-1);定量下限(LOQ)分别为0.07~0.9 ng·g^(-1)、0.08~2 ng·g^(-1)、0.06~6 ng·g^(-1)和0.1~4 ng·g^(-1)。19种PFASs的回收率为0.300%~208%,适于半定量和定性分析。使用该方法测定10个氟橡胶和氟树脂样品,Σ_(37)PFASs含量为9.73~66.17 ng·g^(-1)。该方法操作简便、灵敏度高且定量准确,可为研究氟橡胶、氟树脂及其制品中PFASs的残留情况及完善我国出口贸易和国内履约执法监测提供技术支撑。

Cancer detection by ubiquitin carboxyl-terminal esterase L1 methylation in pancreatobiliary fluids

AIM:To evaluate the utility of measuring epigenetic alterations in pancreatic and biliary fluids in determining molecular markers for pancreatobiliary cancers.METHODS:DNA was extracted from undiluted pancreatic and biliary fluids.As a surrogate for a genomewide hypomethylation assay,levels of long interspersed nuclear element-1(LINE-1) methylation were analyzed using bisulfite pyrosequencing.CpG island hypermethylation of 10 tumor-associated genes,aryl-hydrocarbon receptor repressor,adenomatous polyposis coli,calcium channel,voltage dependent,T type α1G subunit,insulin-like growth factor 2,O-6-methyl-guanine-DNA methyltransferase,neurogenin 1,CDKN2A,runt-related transcription factor 3(RUNX3),secreted frizzled-related protein 1,and ubiquitin carboxyl-terminal esterase L1(UCHL1),was analyzed using MethyLight.To examine the role of CpG methylation and histone deacetylation in the silencing of UCHL1,human gallbladder carcinoma cell lines and pancreatic carcinoma cell lines were treated with 2 or 5 μmol/L 5-AZA-dC for 72 h or 100 nmol/L Trichostatin A for 24 h.After the treatment,UCHL1 expression was analyzed by real-time reverse transcription-polymerase chain reaction.RESULTS:Pancreatobiliary cancers exhibited significantly lower LINE-1 methylation levels in pancreatic and biliary fluids than did noncancerous pancreatobiliary disease(58.7% ± 4.3% vs 61.7% ± 2.2%,P = 0.027;53.8% ± 6.6% vs 57.5% ± 1.7%,P = 0.007);however,LINE-1 hypomethylation was more evident in pancreatic cancer tissues than in pancreatic fluids(45.4% ± 5.5% vs 58.7% ± 4.3%,P < 0.001).CpG island hypermethylation of tumor-associated genes was detected at various frequencies,but it was not correlated with LINE-1 hypomethylation.Hypermethylation of the UCHL1 gene was cancer-specific and most frequently detected in pancreatic(67%) or biliary(70%) fluids from patients with pancreatobiliary cancer.As a single marker,hypermethylation of the UCHL1 gene in pancreatic and biliary fluids was most useful for the detection of pancreatic and pancreatobiliary cancers,respectively(100% specificity).Hypermethylation of the UCHL1 and RUNX3 genes in pancreatic and biliary fluids was the most useful combined marker for pancreatic(87% sensitivity and 100% specificity) and pancreatobiliary(97% sensitivity and 100% specificity) cancers.Treatment with a demethylating agent,5-AZA-2'-deoxycytidine,restored UCHL1 expression in pancreatobiliary cancer cell lines.CONCLUSION:Our results suggest that hypermethylation of UCHL1 and RUNX3 in pancreatobiliary fluid might be useful for the diagnosis of pancreatobiliary cancers.

Microstrueture and Properties of Fluoroelastomer/Butadiene-Acrylonitrile Rubber Interpenetrating Polymer Networks

Interpenetrating polymer networks （IPNs） based on fluoroelastomer/butadiene-acrylonitrile rubber （FKM/NBR） by molten blending at a high temperature and chemical cross-linking of two components were prepared. The influence of the two networks component on the mechanical properties and thermostabilities was studied. The experimental results show that the mechanical properties of the IPNs are superior to those of the individual FKM and NBR networks due to forming the case of interpenetrating and intercross-linking between the two networks, the mechanical properties and thermal resistance exhibit higher values when 80/20 （w/w） FKM and NBR is blended and respectively cured simultaneously. The co-continuous morphology of the IPNs in the blends of 80/20 （w/w） FKM/NBR is found by transmission electron microscopy （TEM）, the differential scanning calorimetry （DSC） determination shows that the blends of 80/20 （w/w） FKM/NBR have better compatibility, and the glass transition temperature of the elastomer is -21.5 ℃.

STUDIES ON SELF-VULCANIZING FLUOROELASTOMER/PHENOL HYDROXY SILICONE RUBBER BLENDS

Self-vulcanizing blends of phenol hydroxy silicone rubber (PHSR) and fluoroelastomer (FPM) were prepared. Vulcanized rubbers with lower glass transition temperature (T(g)) were successfully obtained. The results of dynamic mechanical analysis (DMA) show that the vulcanized FPM/PHSR (10 phr) blend has only one T(g) temperature, demonstrating the well compatibility between FPM and PHSR. The thermogravimetric analysis (TGA) demonstrates that the PHSR do little damage to the thermal stability of FPM. The vulcanization characteristics of the FPM/PHSR blends were analyzed by using oscillating disc rheometer (ODR). The results show that FPM/PHSR blends have smaller S(min) values and longer scorch time than that of FPM with the same level of bisphenol AF curing agent. It means that FPM/PHSR blends have better processability and curing security. Better mechanical properties can be gained for FPM/PHSR blends at appropriate level of PHSR.

Study of intumescent flame-resistant fluoroelastomer

The efficiency of different intumescent flame-retardant （IFR） formulations designed to improve the flame resistance of fluoroelastomer （ FKM ） composites was studied. The proportion of ammonium polyphosphate （APP） with charring-foaming agent （CFA） in IFR systems, and the addi- tion of synergists zinc borate （ZB） and ketonealdehyde resin （ KR120 ） were investigated to show their effect on flame resistance of FKM. According to flame resistance tests, when the mass ratio of APP to CFA was 4：1 as well as the loadings of IFR, ZB, KR120 were 83 parts per hundred resin （phr）, 13phr, 25phr, respectively, the FKM-KR120/IFR-ZB composites had good synergetic flame resistant effect. TGA data showed that IFR and synergists could obviously lower the maximum weight loss rate of FKM composites and effectively increase the char residue at high temperature. The morphological structures of the composites observed by scanning electron microscopy （SEM） demonstrated that the addition of ZB and KR120 could clearly reduce the cracks in char residue and make the char layer structure more integrated and compact.

Preparation and Mechanical Properties of Micro- and Nano-sized SiC/Fluoroelastomer Composites

Microand nano-sized SiC/fluoroelastomer （FKM） composites were prepared by a mechanical mixing method. These composites were first characterized by a rotorless rheometer. Then the effects of micro- and nano-sized SiC on hardness, static and dynamic mechanical properties of the composites were investigated. The increasing amount of the SiC filler increased the curing efficiency of the biphenyl curing system, which was evident from the rheometric properties of the resulting composites. The tensile properties of composite increased with the increasing of micro- and nano-sized SiC content. When the micro- and nano-sized SiC content was higher than 20 phr, the composites showed almost unchanged tensile properties. The increasing of the tensile property was mainly attributed to the well dispersed micro- and nano-sized SiC particles characterized by SEM images. Compared to pure FKM, the composites exhibited a higher glass transition temperature and lower tan peak value.

碳纳米管改性氟橡胶的性能研究

开展了碳纳米管材料对氟橡胶复合材料的改性研究,探究碳纳米管含量对氟橡胶复合体系物理性能、热性能、微观结构形貌、透气性以及宏观力学性能的影响。在此基础上模拟高温高压条件进行老化试验,对老化试验前后材料的硬度变化、体积变化、拉伸性能、撕裂性能和压缩永久变形量进行了测量与分析。结果表明,拉伸强度和撕裂强度随碳管含量增加表现增加的规律,基于脆断表面和热失重断面证实了本文实现了高含量碳纳米管的均匀分散,并且一维纳米材料构筑的碳纳米管网络结构有助于氟橡胶复合材料气体阻隔性能提升;基于老化前后的性能对比数据,表明碳纳米管的存在有助于老化后氟橡胶宏观性能的保持。

硼氢化钠/Ziegler-Natta稀土催化剂组成的还原体系用于还原液体端羧基氟橡胶

以液体端羧基氟橡胶(LTCFs)为原料,硼氢化钠/Ziegler-Natta稀土催化剂(NaBH_4/Ziegler-Natta)为还原体系,采用一锅法将液体端羧基氟橡胶还原为液体端羟基氟橡胶(LTHFs).采用傅里叶变换红外光谱(FTIR)、核磁共振氢谱(~1H NMR)、核磁共振氟谱(~(19)F NMR)和化学滴定法对液体端羧基氟橡胶和液体端羟基氟橡胶的分子链结构和官能团含量进行了表征.结果表明,液体端羧基氟橡胶中的碳碳双键(—C=C—)和端羧基官能团(—COOH)均被高效地还原为碳碳单键(—C—C—)和端羟基(—OH).与传统硼氢化钠/催化剂还原体系相比,硼氢化钠/Ziegler-Natta催化剂还原体系对LTCFs的还原效果具有催化剂用量小、反应时间短、反应温度低及对—COOH还原能力强等优点.

氟橡胶/改性乙丙橡胶并用胶的热稳定性

采用热分析技术考察了氟橡胶及氟橡胶(FPM)/改性乙丙橡胶(MEPDM)并用胶在氮气中的热稳定性,通过微分法与积分法两种动力学方法计算出了FPM及FPM/MEPDM并用胶的热分解活化能E和指前因子A.结果表明,并用胶的热分解温度稍高于纯的氟橡胶,但热分解活化能略低于氟橡胶,FPM、FPM/MEPDM(5%)和FPM/MEPDM(10%)的热分解活化能分别为251.74、244.98和219.60kJ·mol-1;热分解反应级数n均为0.95.随着失重百分率的增大,热分解活化能增大.

石墨和二硫化钼填充氟橡胶的摩擦磨损特性研究

研究了石墨和二硫化钼填充量对氟橡胶(FKM)的摩擦磨损性能的影响,并用扫描电子显微镜和热重分析仪分析了石墨和二硫化钼填充氟橡胶(FKM)的磨损表面和热稳定性。结果表明,石墨和二硫化钼的加入提高了FKM的摩擦磨损性能与热稳定性;随着石墨和二硫化钼用量的增大,复合材料的摩擦因数和磨损量先降后升;当石墨和二硫化钼质量分数分别为3%和5%时,复合材料的摩擦磨损性能最佳;当二硫化钼填充量为10%时,氟橡胶的热分解温度比未添加润滑剂的氟橡胶提高了7℃左右。

热氧老化对特种氟橡胶交联结构及力学性能的影响

采用加速老化实验方法对特种氟橡胶密封材料的热氧老化性能进行了研究,获得了不同老化温度及老化时间对特种氟橡胶力学性能和交联结构的影响规律。研究结果表明,氟橡胶在热空气中老化时随老化温度的升高和老化时间的延长,材料的拉伸强度、硬度降低,100%定伸应力先增加后减小,拉断伸长率先减小后增大,回弹性和压缩永久变形增大。材料的交联密度先增加后减少,表明氟橡胶在热氧老化初期以交联为主,在老化后期以降解为主。

氟橡胶性能、应用及我国氟橡胶工业发展现状

本文介绍了氟橡胶的性能和应用 ,对我国氟橡胶工业发展现状进行了概述 。

氟弹性体的分类及主要应用

针对当前氟弹性体材料种类增多、应用日益广泛的现状,主要以美国材料与试验协会ASTM D1418标准为依据,详细解释了FKM、FFKM和FEPM三类氟弹性体的划分方法及相关应用,并介绍了氟弹性体在汽车、航空航天、石油天然气等领域中的相关应用。对中国相关领域的科研人员更好地了解和掌握国外先进氟弹性体技术,发展和应用方向有一定借鉴作用。

空气和液压油环境中氟橡胶老化性能研究

为了解氟橡胶密封件在液压系统中的贮存寿命,在两种介质环境中对氟橡胶开展了加速老化试验。结果表明,氟橡胶耐热、耐介质、耐老化性能优异,在90℃下加速老化120 d后,压缩回弹性能、物理力学性能保持率均在80%以上,评估其具有20年的贮存寿命。

PPA在LLDPE/LDPE农膜加工中的应用

本工作以LLDPE／LDPE为基料，添加氟弹性体加工改性剂DynamarPPA，采用LDPE挤出机加工农膜。结果表明，挤出机加工LLDPE的能力大幅度地提高，使共混物中LLDPE含量从原来的40％增加到80％，薄膜的物理机械性质亦有明显改善，而主机电流和挤出量未见变化。在添加无滴剂母料条件下，可加工LLDPE总含量达95％的无滴膜，且该膜的力学性质和光学性质均住。

碳纳米管表面处理对碳纳米管/氟橡胶复合材料形貌及界面作用的影响

采用溶液浇注法制备了碳纳米管(CNTs)/氟橡胶纳米复合材料,并对不同表面状态的碳纳米管(原始碳纳米管、酸处理碳纳米管、CF4等离子体处理碳纳米管)在复合材料中的分散以及碳纳米管与氟橡胶的界面作用进行了研究。研究结果表明,经CF4等离子体处理后的碳纳米管在氟橡胶中的分散性明显优于混酸处理碳纳米管,激光显微拉曼分析结果表明,在与氟橡胶共混后,部分表面吸附所产生的不稳定的F原子从氟化碳纳米管表面离开,与氟橡胶发生界面化学接枝反应,说明CF4等离子体处理能明显提高碳纳米管与氟橡胶的相容性。

国内外氟橡胶生产消费现状及发展趋势

概述了氟橡胶的特性和分类。详细介绍了世界FKM、FSR和FFKM三类氟橡胶的生产消费现状及预测;同时对氟橡胶研发技术进展进行了归纳梳理。指出目前中国氟橡胶产能虽居世界第一,但已显现出低端过剩、无序竞争局面,今后应从技术创新入手,在产品品种和质量提升、开拓市场等方面进行结构性调整。