甲基丙烯酸镁增强氢化丁腈橡胶的结构与形态和性能

用不同份量的甲基丙烯酸镁(MgMA)作增强剂,过氧化二异丙苯(DCP)作硫化剂,通过混炼和硫化过程的原位聚合制备了氢化丁腈橡胶/聚甲基丙烯酸镁(HNBR/PMgMA)纳米复合材料,用XRD、FTIR1、3C-NMR、SEM、TEM、DMA和交联密度分析等方法研究了其结构、形态和性能,并阐述了MgMA改性HNBR的相关机理.结果表明,MgMA在混炼过程中粒径明显变小,部分达到纳米级.硫化过程中发生原位自由基聚合,并部分接枝到HNBR分子链上,HNBR硫化胶和PMgMA有可能形成接枝互穿聚合物网络(接枝IPN).随着MgMA用量的增加,纳米复合材料硫化胶的定伸应力、拉伸强度、扯断伸长率、撕裂强度和热氧老化性能逐渐提高.当MgMA含量为30份时,体系的拉伸强度和扯断伸长率分别为38.5MPa和545%,并具有优异的热空气老化性能.MgMA能明显增加HNBR复合材料的储能模量,并降低其损耗因子.随着MgMA用量的增加,纳米复合材料硫化胶的总交联密度(Ve)和离子键交联密度(Ve2)增加,而共价键交联密度(Ve1)下降,表明离子键对HNBR/PMgMA纳米复合材料的力学性能起重要作用.     

Effect of organo-modified clay on accelerated aging resistance of hydrogenated nitrile rubber nanocomposites and their life time prediction

Organically modified clay - reinforced hydrogenated nitrile rubber vulcanizate was subjected to accelerated heat aging to estimate its long-term thermo-oxidative stability and its useful lifetime was compared with that of the virgin polymer for the first time. Changes in technical properties such as tensile strength, modulus and elongation at break were studied as a function of time and temperature of aging. The infrared spectroscopic analysis of the degraded products revealed that under aerobic hot aging conditions, hydrogenated nitrile rubber (HNBR) compounds undergo cross-linking reactions that lead to embrittlement and ultimately failure. Incorporation of clay filler, however, resulted in significant improvement of the degradation profile of the nanocomposite at elevated temperatures. Loss of ductility during aging of the nanocomposite was also milder, relative to the unfilled polymer, indicating a restricted degradation by the clay filled rubber, thus prolonging the durability. From the scanning electron microscopy and atomic force microscopy studies, it was found that nanofillers protected the elastomer from surface rupture that took place on oxidation. Life prediction of both virgin elastomer and the nanocomposite indicated a three-fold increase in the effective service temperature range of the HNBR using 8 parts organically modified nanoclay.     

Solvent‐free fabrication of proton‐conducting membranes based on commercial elastomers

Five different types of elastomers were examined as the matrix materials in the preparation of non‐fluorinated proton exchange membranes utilizing a solvent‐free route via the in situ reaction of sodium 4‐styrenesulfonate (NaSS). The morphology of the elastomer/NaSS vulcanizates was studied to evaluate the effect of polarity, viscosity and saturation degree of the elastomer matrixes. Much better dispersion of NaSS was found in chlorosulfonated polyethylene rubber (CSM) and hydrogenated nitrile butadiene rubber (HNBR) matrixes than in the other three types of elastomer matrixes. For CSM/NaSS and HNBR/NaSS proton exchange membranes, distinctive membrane properties were observed and correlated with their different structure and morphologies. The CSM/NaSS membranes exhibited the proton conductivity as high as ~0.03 S cm^?1 and the selectivity (the ratio of proton conductivity to methanol permeability) higher than that of Nafion. Copyright © 2015 John Wiley & Sons, Ltd.     

The morphology of zinc dimethacrylate reinforced elastomers investigated by SEM and TEM

The morphologies of various ZDMA-reinforced elastomers, including styrene butadiene rubber (SBR), ethylene-propylene-diene monomer (EPDM), nitrile-butadiene rubber (NBR), ethylene-propylene monomer (EPM), poly(α-octylene-co-ethylene) elastomer (POE) and hydrogenated nitrile-butadiene rubber (HNBR), were studied by using SEM and TEM. The observation on the compounds showed that during the compounding process, the dimension of ZDMA particles reduced, and could even form dispersion structures with nanometer size (<100 nm). It is shear stress of compounds during mixing rather than polarity of matrix rubber that plays the most important role to determine dispersion state of ZDMA in compounds. High shear stress facilitates dispersion of ZDMA. Only in elastomers having the lower shear stress such as POE and EPM, original dimension features of ZDMA particles make considerable effects on dispersion level of ZDMA in compounds. The observation on cured composites displayed that there are two kinds of micro-dispersed structures: micron dispersion—residual ZDMA particles and nano-dispersion—the aggregate of poly-ZDMA. The higher saturation and polarity of rubbers and the better dispersion level of ZDMA in compounds benefit in situ polymerization of ZDMA, resulting in the lower amount of residual ZDMA particles (micron dispersion). In the elastomer with higher saturation such as POE, EPM, EPDM and HNBR, the dimensions of nano-dispersions are slightly larger. For the ZDMA/POE, formula effect on morphology of the composite was also discussed. It was found that the loading of ZDMA and peroxide impact remarkably on the amount and dimension of nano-particles in the composite.     

不同氢化度氢化丁腈橡胶的结构表征与分子模拟

通过核磁共振波谱(¹H NMR)、 红外光谱(IR)及热分析等方法研究了不同氢化度氢化丁腈橡胶(HNBR)分子结构之间的差异, 结果表明, 在丁腈橡胶(NBR)加氢过程中, 聚丁二烯上的乙烯基加氢速率最快, 其次是反式1,4结构, 顺式1,4结构的加氢速率最慢, 而腈基基本不发生氢化反应. 采用核磁共振谱法对不同氢化度HNBR中不同链段的含量进行定量分析, 依据此结果建模并进行分子模拟计算, 得到不同氢化丁腈橡胶的密度、 内聚能密度(CED)和玻璃化转变温度(T_g)等参数, 模拟值与实验结果吻合. 实验结果表明, 随着氢化度的增加, HNBR的热氧化稳定性逐渐增加, 这主要是由于氢化度增加后分子链中双键含量逐渐减少而CED增加的缘故. 分子模拟可以有效地计算出多种结构参数, 为共聚橡胶材料的制备与加工提供基础数据及理论指导.     

One-step Synthesis of End-Functionalized Hydrogenated Nitrile-Butadiene Rubber by Combining the Functional Metathesis with Hydrogenation

End-functionalized hydrogenated polymers obtained from nitrile-butadiene rubber (NBR) yield new materials with suitable properties for a number of applications as sealing material and adhesives. We investigated the one-step synthesis of ester end-functionalized hydrogenated nitrile-butadiene rubber (EF-HNBR) by combining the functional metathesis with the hydrogenation of NBR in the presence of the 2^nd generation Grubbs catalyst and a functionalized olefin as a chain transfer agent (CTA). We established the operating conditions for the effective production of saturated functional polymers with a high degree of hydrogenation, high chemo-selectivity and moderate molecular weight. The structures of the products were confirmed by FT-IR and ¹H-NMR spectroscopy, rubber molecular weight, and distribution determined by using gel permeation chromatography (GPC); their thermal properties were determined by thermo-gravimetric analysis (TGA) and different scanning calorimetry (DSC).     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Multifunctional action of in situ formed Zn-salt of monoallylmaleamic acid

Monoallylmaleamic acid (CH₂=CH-CH”2-NH-CO-CH=CH-CO-OH; MAMA) when used in combination with zinc basic carbonate (ZBC) shows multifunctional action during processing and peroxide curing of hydrogenated nitrile rubber (HNBR). It follows from the lower viscosity, higher crosslinking degree and higher tensile strength of samples prepared from HNBR, MAMA, ZBC and peroxide, compared with the HNBR cured with the peroxide only. This kind of activity of the such system is connected with the in situ formation of very small particles of Zn-MAMA salt dispersed in the rubber matrix and in part chemically bound to the rubber.     

Elastic recovery after compression in HNBR at low and moderate temperatures: Experiment and modelling

Elastic recovery after compression or compression set is one of the key indicators of elastomer performance in sealing applications, such as O-rings in flange joints. In this work, findings of a study of the compression set property of a hydrogenated nitrile butadiene rubber (HNBR) at temperatures above and below the glass transition temperature T_g are presented. The compression set in the elastomer is found to increase with cooling up to 100% at the glass transition temperature and decrease with time after unloading even at temperatures below T_g. The effects of reinforcing filler (carbon black) and the initial compression time are also considered. Equivalence of time and temperature effects on the compression set of the elastomers is then demonstrated. A viscoelastic model describing the time-temperature variation of the compression set is proposed and verified by finite element analysis (FEA) and experimental results. It is shown that modelling captures well the experimental behaviour of the elastic recovery of the studied HNBR at ambient and low temperatures.     

Hybrids from HNBR and in situ polymerizable cyclic butylene terephthalate (CBT): Structure and rolling wear properties

Hybrids composed of peroxide-curable hydrogenated acrylonitrile-butadiene rubber (HNBR) and cyclic butylene terephthalate oligomers (CBT) were produced. CBT was expected to polymerize in situ when curing the HNBR. Extraction, differential scanning calorimetry (DSC), dynamic-mechanical thermal analysis (DMTA), wide-angle X-ray scattering (WAXS) and atomic force microscopy (AFM) were adopted to investigate the CBT conversion and the phase structure of the hybrids before (T = 190 °C; HNBR-(p)CBT) and after annealing (T = 250 °C; HNBR-pCBT). Unlubricated rolling wear properties of the related compounds with different CBT contents were assessed in orbital rolling ball (steel)-on-plate (rubber) test rig (Orbital-RBOP). The dynamic coefficient of friction and the specific wear rate were determined. Both (p)CBT and pCBT improved the rolling wear resistance of the hybrids compared to plain HNBR. However, the polymerized CBT (pCBT) improved the wear properties more than the unpolymerized CBT ((p)CBT). The wear mechanisms were identified by inspecting the worn surfaces in scanning electron microscope (SEM) and are discussed as a function of (p)CBT/pCBT modification. Changes in the structure and properties of the hybrids caused by the annealing-induced polymerization of CBT were analyzed.     

Preparation of facile separable homogeneous Rhodium catalyst and its application for the catalytic hydrogenation of nitrile butadiene rubber and styrene-butadiene rubber

Poly(propylene imine) dendrimer (G2-PPI) terminated by nitrogen-containing triolefinic macrocycle on the periphery (G2-M) was synthesized by a nucleophilic substitution reaction. The structure and composition of G2-M were characterized by FT-IR, ¹H-NMR and elemental analysis. The Rh³⁺ dendrimer-stabilized catalyst (G2-M(Rh³⁺)) was prepared by utilizing G2-M as stabilizer and analyzed by UV–Vis spectroscopy, ¹H-NMR spectrometry, XPS and XRD. G2-M(Rh³⁺) demonstrates excellent catalytic activity and selectivity for the hydrogenation of nitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR), and Rh residue contents for HNBR and HSBR are only 35 and 13 ppm, respectively, without any post treatment.     

乙丙橡胶的分子链结构及其加工性质

研究了乙丙橡胶的组成、分子量、分子量分布、单体序列分布及组成和值分别随分子量之分布等对其特性粘数、门尼粘度、断裂强度、包辊性和动态力学性质等方面的影响,并对微观结构的特征作了初步探讨。     

Superior heat‐resistant and oil‐resistant blends based on dynamically vulcanized hydrogenated acrylonitrile butadiene rubber and polyamide 12

High‐performance thermoplastic vulcanizates (TPVs) are the new generation of TPVs that provide superior heat and oil aging behavior. TPVs based on hydrogenated acrylonitrile butadiene rubber and polyamide 12 (PA12) have been first developed by the dynamic vulcanization process, in which selective cross‐linking of the elastomer phase during melt mixing with the thermoplastic phase (PA12) was carried out simultaneously. In this present investigation, hydrogenated acrylonitrile butadiene rubber (HNBR)/PA12 and partially hydrogenated carboxylated acrylonitrile butadiene rubber (XHNBR)/PA12 with blend ratio of 50:50, 60:40, and 70:30 wt% were prepared at 185°C at a rotor speed of 80 rpm for 5 min. Di‐(2‐tert‐butyl peroxy isopropyl) benzene was chosen as the suitable cross‐linking peroxide to pursue the dynamic vulcanization. TPV based on 50:50 HNBR/PA12 and XHNBR/PA12 show better physico‐mechanical properties, rheological behavior, thermal stability, dynamic mechanical analysis, and creep behavior among all the TPVs. Morphology study reveals that dispersed phase morphology has been formed with an average dimension of the rubber particles in the range of 0.8–1.5 µm. For aging test, TPVs were exposed to air and ASTM oil 3, respectively. Air aging tests were carried out in hot air oven for 72 hr at 125°C, while the oil aging tests were carried out after immersion of the samples into the oils in an aging oven. After aging, there is only slight deterioration in the physico‐mechanical properties of the TPVs. In case of 50:50 blends of HNBR/PA12 and XHNBR/PA12, the retention of the properties upon after aging was found excellent. These TPVs are designed to find potential application in automotive sector especially for under‐hood‐application, where high‐temperature resistance as well as high oil resistance is of prime importance. Copyright © 2016 John Wiley & Sons, Ltd.     

Network characteristics of hydrogenated nitrile butadiene rubber networks obtained by radiation crosslinking by electron beam

The effects of high-energy radiation on hydrogenated nitrile butadiene rubber (HNBR) copolymer structure and properties were studied. Characterization by FTIR spectroscopy, swelling and mechanical measurements of irradiated and un-irradiated sample permit us to correlate the change in structure with properties. The modifications obtained are dependent on the radiation dose of the incident electron beam. FTIR spectroscopy in absorption mode shows that irradiation of HNBR first induces trans-vinylene bond formation and secondly small amounts of carbonyl (CO) groups. Moreover, more significant changes were observed with swelling method and mechanical behaviour showing the effect of crosslinking on the elastomer.     

Effect of carbon nanofibers on mechanical and electrical behaviors of acrylonitrile‐butadiene rubber composites

Recently, carbon nanofibers have become an innovative reinforcing filler that has drawn increased attention from researchers. In this work, the reinforcement of acrylonitrile butadiene rubber (NBR) with carbon nanofibers (CNFs) was studied to determine the potential of carbon nanofibers as reinforcing filler in rubber technology. Furthermore, the performance of NBR compounds filled with carbon nanofibers was compared with the composites containing carbon black characterized by spherical particle type. Filler dispersion in elastomer matrix plays an essential role in polymer reinforcement, so we also analyzed the influence of dispersing agents on the performance of NBR composites. We applied several types of dispersing agents: anionic, cationic, nonionic, and ionic liquids. The fillers were characterized by dibutylphtalate absorption analysis, aggregate size, and rheological properties of filler suspensions. The vulcanization kinetics of rubber compounds, crosslink density, mechanical properties, hysteresis, and conductive properties of vulcanizates were also investigated. Moreover, scanning electron microscopy images were used to determine the filler dispersion in the elastomer matrix. The incorporation of the carbon nanofibers has a superior influence on the tensile strength of NBR compared with the samples containing carbon black. It was observed that addition of studied dispersing agents affected the performance of NBR/CNF and NBR/carbon black materials. Especially, the application of nonylphenyl poly(ethylene glycol) ether and 1‐butyl‐3‐methylimidazolium tetrafluoroborate contributed to enhanced mechanical properties and electrical conductivity of NBR/CNF composites.     

PPC／NBR弹性体的结构与性能

本文研究了聚丙撑碳酸酯(PPC)/丁腈橡胶(NBR)弹性体结构形态、动态力学性能、力学性能、耐油、耐热氧老化及耐化学介质稳定性。发现PPC/NBR弹性体呈现IPN结构特征,加入PPC使NBR拉伸强度、扯断伸长率大幅度提高。PPC/NBR弹陸体具有优良的耐油及耐热氧老化稳定性。     

Mineral oxides and layered minerals in combination with itaconic acid as coagents for peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer

The aim of this work was to study the activity of nanosized calcium and magnesium oxides and layered minerals (boehmite, hydrotalcite) as coagents in the crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) with dicumyl peroxide. The surfaces of the mineral oxides and layered minerals were modified with unsaturated acid (itaconic acid) to ensure their activity during the crosslinking process. The efficiency of modification process was estimated, based on thermogravimetric analysis and zeta potential measurements of obtained coagents. In this article, we discuss the effect of coagents on the crosslinking density and mechanical properties of vulcanisates. Application of nanosized mineral oxides and layered minerals together with itaconic acid decreased the optimal vulcanisation time of rubber compounds and improved the crosslinks density as well as the tensile strength of the vulcanisates due to formation of additional ionic crosslinks in the elastomer network. It is important from technological reasons.     

NBR/CuSO4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.     

Polymers used as viscosity index improvers: A comparative study

Ethylene-propylene copolymers and hydrogenated styrene-diene copolymers were used for a comparative study aiming at their application as viscosity index improvers in multigrade engine oils. The variation of viscosity with temperature has been evaluated as a function of the polymer concentrations. The thickening effect of different viscosity index improvers and the dependence of reduced viscosities on temperature were determined. At concentrations lower than 3% (w/w) the viscosity/temperature characteristic suggested the occurrence of polymer coil expansion with temperature for hydrogenated styrene-diene copolymer. The direct dependence of mechanical stability on the copolymer molecular weight was observed.     

Interfacially modified LDPE/GTR composites with non-polar elastomers: From microstructure to macro-behavior

This paper provides some new insights into the mechanism of interaction and modifications in thermoplastic composites based on low density polyethylene (LDPE), ground tire rubber (GTR) and non-polar elastomer. The composites were prepared using a co-rotating twin-screw extruder at variable LDPE/GTR ratio and constant elastomer content. Two types of commercial elastomer were applied: styrene-butadiene-styrene (SBS) block copolymers (Kraton^®) with different topologies (linear/branched) and partially cross-linked butyl rubbers (Kalar^®) with different Mooney viscosities. Processing characteristics, static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties and morphology of the resulting thermoplastic composites were investigated. Microstructure analysis shows that modification of LDPE/GTR composites with non-polar elastomers caused encapsulation of GTR particles within the elastomer phase. This phenomenon has significant influence on macro-behavior of thermoplastic composites based on LDPE/GTR blends. The results indicate that SBS copolymer improves interfacial interactions between GTR and LDPE, which enhances mechanical and thermal properties of the composites. On the other hand, cross-linked butyl rubber showed partial compatibility with LDPE and low compatibility with GTR particles.