硫酸铜含量对硫酸铜与丁腈橡胶之间配位交联反应的影响

利用丁腈橡胶(NBR)的可配位侧基——腈基(—CN)与金属盐硫酸铜(CuSO4)的铜离子(Cu2+)之间的配位反应制备了一种配位交联CuSO4/NBR.影响该配位交联反应的因素众多,如热压温度、热压时间、增塑剂等等,考察了CuSO4含量对其的影响.通过X射线光电子能谱(XPS)、动态力学分析(DMA)、差示扫描量热分析(DSC)等手段对CuSO4与NBR之间的配位交联反应进行了分析,并对所得配位交联的CuSO4/NBR进行了交联密度及力学性能的测试.结果发现,随CuSO4含量的不断增加,CuSO4与NBR的配位交联程度逐渐增强,且所得配位交联CuSO4/NBR显示出从典型橡胶到韧性塑料再到脆性塑料的力学转变特性.另外,通过扫描电子显微镜(SEM)及X射线能谱仪(EDX)对材料的微观结构进行了分析,发现CuSO4在聚合物基体中不仅充当交联剂的角色,而且还起着增强填料的作用.     

(NBR/PVC)/CuSO_4复合材料中配位交联反应的研究

采用差示扫描量热法(DSC)和傅立叶转换红外光谱(FT-IR)对丁腈橡胶/聚氯乙烯合金/无水硫酸铜((NBR/PVC)/CuSO4)混合物的配位交联反应进行了研究.结果表明,(NBR/PVC)/CuSO4共混物在升温过程中出现两个放热峰,分别归因于腈基(—CN)和CuSO4之间的配位交联反应和体系中NBR/PVC的自交联反应.通过对共混物配位交联反应动力学参数的计算发现,混合物中CuSO4含量的多少并未对体系配位交联反应的进行产生影响.同时共混物中PVC的存在促进了配位交联反应的进行,降低了铜离子(Cu2+)与—CN之间配位交联反应的表观活化能Ea.     

液晶金属配位聚合物的合成及性能

基于国内外最新研究文献 ,系统论述了近年来液晶金属配位聚合物的合成方法、液晶行为及应用前景。指出液晶金属配位聚合物的合成方法可归纳为直接配位法、单体配位法、交联配位法和聚合物反应法四种。液晶金属配位聚合物一般呈现热致液晶行为 ,显示稳定的向列液晶相或近晶液晶相。有些金属配位聚合物还呈现互变性近晶态或单变液晶性。液晶金属配位聚合物具有金属的特殊性质 ,是一种新型高性能磁导、电导和光导材料 ,可望应用于液晶显示材料、磁性信息储存薄膜材料、润滑剂和各向异性催化剂等。     

可变形微区增强丁苯橡胶及其机理

基于丁腈橡胶中腈基与金属离子的配位作用,设计了一种全新的含可变形微区的橡胶,即金属配位交联丁腈橡胶(NBR)作为可变形微区增强丁苯橡胶.随着可变形微区中配位键含量的提升,橡胶的强度和模量快速提高.引入20 wt%的丁腈橡胶,丁苯橡胶的强度和模量分别提升2.6倍和3.2倍.这一体系的增强机理主要是金属配位交联NBR作为强但可变形微区,一方面模量更高的微区由于流体力学效应,使得橡胶整体模量提高;另一方面,在外力作用下,应力通过强的界面相互作用传递到微区,致使其在样品断裂之前发生强迫高弹形变,耗散机械能,从而显著增强橡胶.微区中强迫高弹形变可通过高温松弛回复,从而恢复力学性能.本工作为通过可变形微区的设计实现非极性橡胶的增强提供了一种新途径.     

结晶水对硫酸铜与丁腈橡胶之间配位交联反应的影响

利用动态力学分析(DMA)、差示扫描量热分析(DSC)、扫描电子显微镜(SEM)、平衡溶胀法、力学性能测试等分析手段, 通过研究五水硫酸铜(CuSO4·5H2O)填充的NBR考察了结晶水对CuSO4与NBR之间配位交联反应的影响. 结果表明, 结晶水的存在可以促进该配位交联反应.     

辐照交联制备低分子量聚丙烯腈纤维锂硫电池正极材料及其储硫机理

通过γ射线辐照交联异型聚丙烯腈(PAN)纤维解决了低分子量聚丙烯腈半碳化中的熔融坍塌问题, 提高了PAN的半碳化稳定性; 采用傅里叶变换红外光谱、 元素分析及核磁共振波谱确定了辐照交联机理. 同时, 根据辐照产生的不同交联度与PAN硫化后载硫量的变化关系, 探讨了硫化聚丙烯腈(SPAN)锂硫电池正极材料的储硫机理. 利用拉曼光谱及X射线光电子能谱等分析手段表征了SPAN中硫原子的反应位置, 说明PAN主链上的亚甲基所在的碳为与硫化学结合的活性位点, 为探究SPAN结构提供了新的依据. 交联度升高对硫化后所形成的SPAN正极材料的电化学稳定性起促进作用, 容量保持率可提升至98%.     

共聚物配位的钌催化剂及其催化加氢性能研究

在工业中,催化加氢反应由于有重要的应用价值而得到广泛研究,通常这类催化剂以无机材料为活性金属的载体,如活性炭、二氧化硅及一些无机盐类等,有一些研究曾取得了很好的效果[1].然而,这类催化剂存在着普遍的弱点,如:负载于载体表面的活性金属极易形成金属簇从而使催化剂的活性中心减少;载体的结构(孔径、比表面、机械强度等)与性质(与选择反应体系的亲合性)不易改造而限制了上述催化剂的使用效果等.选择含配位原子的高聚物为配体,通过配位的方式使金属均匀地分布在载体的表面,是克服该类催化剂上述弱点的途径之一,有人在这方面进行过一系列的尝试[2～5]. 本文所述的钌配合物催化剂用2-乙烯吡啶(V)和甲基丙烯酸乙二醇双酯(M)的交联共聚物小球为配体,通过配位,还原制成PVMRu催化剂,并对其结构与催化加氢性能进行了研究.     

NBR/CuSO_4混合物的非液相配位交联反应

采用示差扫描量热法(DSC),变温傅立叶转变红外光谱(FT-IR)和X射线光电子能谱(XPS)研究了丁腈橡胶/硫酸铜(NBR/CuSO4)混合物的非液相(聚合物熔融态)配位交联反应.DSC曲线上出现了多个放热峰,并随升温速率提高,峰值一致向高温方向移动;结合XPS和FT-IR的分析表明DSC曲线上的第一个放热峰对应于混合物中发生的铜离子与腈基的非液相配位反应;同时采用非等温法(Kissinger法)及Crane方程计算了NBR/CuSO4混合物非液相配位交联反应的表观活化能和反应级数.     

Diels-Alder反应可控制备交联等规聚丙烯

交联改性可以提升聚合物材料的机械性能、热稳定性及化学稳定性。 含有蒽基团的高质均分子量等规聚丙烯(iPP)可由配位共聚合反应制得,随后通过双官能的马来酰亚胺试剂与iPP中悬挂蒽基团间的Diels-Alder反应可以成功制备交联的iPP膜材料。 材料的交联度可以通过凝胶重量分析及膜红外分析得出,并由制备过程中交联剂的加入量有效地调控。 通过示差扫描量热仪(DSC)与广角X射线衍射仪(WAXD)表征发现,随交联度增加,交联改性限制了分子链的运动,iPP的结晶度逐渐降低、结晶能力逐渐下降。 对交联材料的动态热机械分析仪(DMA)测试表明,随交联度增加,iPP的损耗模量逐渐降低,材料韧性变差。 交联iPP的T_g逐渐升高,说明材料的耐热性得到提升。 由于交联形成了聚合物链间的交联网络,形成了更多受力点并且限制了聚合物链的自由移动,交联材料的拉伸强度随交联度的升高而增加,而断裂伸长率逐渐下降。     

壳聚糖希夫碱金属[Cu(Ⅱ),Mn(Ⅱ)]配合物的合成及其抑菌活性

壳聚糖的氨基与水杨醛发生反应制得壳聚糖希夫碱配体(L);L与铜盐或锰盐发生配位反应制得壳聚糖希夫碱金属[Cu(Ⅱ)和Mn(Ⅱ)]配合物(1和2),其结构经UV,IR,TGA和荧光光谱表征.L的酚亚胺的N原子和酚羟基的O原子同时参与配位.抑菌活性测试结果表明,1和2对大肠杆菌,金黄色葡萄球菌,沙门氏菌和枯草杆菌的抑菌活性较配体和金属盐均有明显提高.     

COORDINATION CROSSLINKING OF NITRILE RUBBER FILLED WITH COPPER SULFATE PARTICLES

By incorporating copper sulfate(CuSO_4)particles into acrylonitrile butadiene rubber(NBR)followed by heat pressing,a novel vulcanization method is developed in rubber through the formation of coordination crosslinking.This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber.No other vulcanizing agent or additional additive is involved in this process.By analyzing the results of DMA,XPS and FT-IR,it is found that the crosslinking of CuSO_4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups (-CN)and copper ions(Cu~(2 ))from CuSO_4.SEM and EDX results revealed the generation of a core(CuSO_4 solid particle)- shell(adherent NBR)structure,which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover,poly(vinyl chloride)(PVC)and liquid acrylonitrile-butadiene rubber(LNBR)were used as mobilizer to improve the coordination crosslinking of CuSO_4/NBR.The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization.In addition,crystal water in CuSO_4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO_4 and promoted the metal ionization.     

Crosslinking induced by in‐situ coordination in acrylonitrile butadiene rubber/poly(vinyl chloride) alloy,filled with anhydrous copper sulfate particles

Acrylonitrile butadiene rubber (NBR)/poly(vinyl chloride) (PVC) alloy, filled with anhydrous copper sulfate (CuSO₄) particles, was investigated for the first time. The material could be crosslinked in the existence of CuSO₄ by heat pressing, without any other crosslink agents. The crosslinking in the material was induced by in situ coordination between nitrile groups of NBR and solid CuSO₄ particles, which is thoroughly different from the traditional vulcanization of rubber materials. The coordination crosslinking is formed during heat pressing, other than in solutions, which is valuable for practical applications. The resulting material showed excellent tensile properties, and the maximum strength was close to 90 MPa. The CuSO₄ particles act not only as crosslink agents, but also as reinforcing fillers in the polymer matrix. In this work, dynamic mechanical analysis, differential scanning calorimetry, Fourier transform infrared spectrum, X‐ray photoelectron spectroscopy, scanning electron microscope, energy‐dispersive X‐ray spectrum, equilibrium swelling method, and tensile test were performed for the characterization of the material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 378–386, 2006     

XNBR/LDH nanocomposites: Effect of vulcanization and organic modifier on nanofiller dispersion and strain‐induced crystallization

In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Effect of montmorillonite intercalant structure on the cure parameters of natural rubber

Two quaternary phosphonium salts (aromatic and aliphatic) have been used as intercalants for Na-montmorillonite and the effect of intercalant structure on clay morphology and natural rubber vulcanization kinetics was investigated. Due to its lower rigid structure the aliphatic salt was easier to intercalate into the clay galleries giving rise to a higher interlayer distance and facilitating the rubber intercalation obtaining an exfoliated structure in the nanocomposite. The vulcanization process was sensibly accelerated by this organoclay and a higher crosslinking degree was observed in the nanocomposite which gave rise to materials with improved processing and physical characteristics.     

基于金属配位键的自修复、 可重塑聚丁二烯橡胶的合成及性能

橡胶材料通常因经过硫化及补强等工艺处理而呈现出热固性, 因而难以被回收处理, 容易造成严重的资源浪费和环境污染. 本文通过在聚丁二烯上修饰羧酸基团, 再加入锌离子(Zn²⁺)与羧酸配位, 制备了基于金属配位键交联的自修复橡胶(PB-COOH/Zn²⁺). 该橡胶具有良好的机械性能和优秀的自修复及重塑性能, 在70 ℃下修复3 h, 其韧性可以恢复到初始强度, 修复效率可达100%. PB-COOH/Zn²⁺较高的聚合物链段运动能力及配位键交联网络良好的动态性不仅赋予其优异的修复性能, 还使得其在较温和的条件下可以进行多次重塑, 在70 ℃及5 MPa的条件下重塑3次仍能保持原有的机械性能. 此外, 通过在PB-COOH/Zn²⁺中掺杂适量的碳纳米管, 不仅增强了其机械性能, 还使其具备了电致修复及传感能力, 扩宽了PB-COOH/Zn²⁺作为环境友好型材料的应用前景.     

硅橡胶/氟橡胶并用胶的制备及力学性能

硅橡胶和氟橡胶作为国防、航天等重要领域的耐热材料一直被人们青睐,但其有着各自地优缺点且价格昂贵,本文尝试将这两种橡胶制成并用胶以解决氟橡胶不耐低温和加工性差的问题,以期增大其使用温度范围。采用机械共混法制备硅橡胶/氟橡胶并用胶,研究了硅橡胶和氟橡胶的混炼工艺、并用比、共硫化体系和硫化条件对并用胶力学性能的影响。结果表明,当硅橡胶/氟橡胶的质量比为10∶90,共硫化体系为3~#硫化剂/过氧化二异丙苯(DCP),一段硫化温度为170℃、硫化压力为10MPa、硫化时间为30min,二段硫化温度为200℃、硫化时间为6h时,并用胶的力学性能达到最好。     

Enhanced thermal conductivity and mechanical properties of polymeric composites through formation of covalent bonds between boron nitride and rubber chains

Hexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN-PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN-PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of N? C═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as-prepared 30 vol% BN-PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN-PRd platelets was 880% times of pure NBR. The 30 vol% BN-PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large-scale industrial production of high thermally conductive composites.     

A novel nitrile butadiene rubber/zinc chloride composite: Coordination reaction and miscibility

In this work, an inorganic metal salt, zinc chloride (ZnCl₂), was mechanically mixed with nitrile butadiene rubber (NBR) to prepare a novel crosslinkable NBR/ZnCl₂ composite. ZnCl₂ was found to dissolve into NBR upon heating to a designed temperature, which was considered as a result of dissolution process induced by the occurrence of coordination reaction. Consequently, the morphology of the composite could change from an obvious two-phase structure to a macro-homogeneous phase structure. The determination of the coordination bonding in NBR/ZnCl₂ composite was done by Fourier transform infrared spectroscopy. The crosslinking procedure of the composite was investigated by dynamic mechanical analysis and differential scanning calorimetry. A Kissinger’s method was used to calculate the active energy. Other characterizations including scanning electron microscopy, elemental analysis, X-ray Diffraction and polarized microscope with a hot stage were used to investigate the morphology of the composite. Furthermore, the resulting material possessed special and excellent tensile properties.     

Effects of cellulose nanocrystals on the vulcanization of natural rubber/cellulose nanocrystals nanocomposite and corresponding regulating strategies

Vulcanization is a vital process in rubber processing, it endows rubber with valuable physical and mechanical properties, making rubber a widely used engineering material. In addition to vulcanization agent, reinforcing fillers play a non-ignorable influence on the vulcanization of rubber nanocomposites. Herein, the effects of cellulose nanocrystals (CNCs) on the vulcanization of natural rubber (NR)/CNCs nanocomposite was studied. It was found that even though the addition of CNCs can effectively improve the dispersion of ZnO in NR matrix, the vulcanization of NR was inhibited. This may be attributed to the CNCs' adsorption of vulcanizing agents (DM, ZnO) and the acidic chemical environment on the surface of CNCs. In order to improve the vulcanization properties of NR/CNCs nanocomposite, tetramethyldithiochloram (TMTD) and triethanolamine (TEOA) were used as a combination accelerator and curing activator, respectively, and polyethylene glycol (PEG) was introduced to screen hydroxyl groups on the surface of CNCs to prohibit the CNCs' adsorption of vulcanizing agents. The results indicate that TMTD and TEOA effectively improved the vulcanization rate of NR/CNCs nanocomposite and increased the crosslink density by an order of magnitude. Subsequently, the tensile strength, tear strength, and so forth. of NR/CNCs nanocomposite were significantly improved. However, PEG hardly help to improve the vulcanization properties of NR/CNCs nanocomposite. In addition, the control samples without CNCs were prepared and characterized, the comparation between NR and NR/CNCs nanocomposite shows that the synergistic effect of crosslink density and CNCs' reinforcement more effectively improve mechanical properties of NR. This work not only elucidates the inhibiting mechanisms of CNCs on the vulcanization of NR, but also provides practical strategies for improving the vulcanization and properties of NR/CNCs nanocomposite. It may accelerate the application of CNCs as rubber reinforcing filler.