Comparison of morphology and mechanical properties of peroxide‐cured acrylonitrile butadiene rubber/LDH composites prepared from different organically modified LDHs

Rubber compounds based on acrylonitrile butadiene rubber (NBR) containing organically modified layered double hydroxides (LDHs) were prepared using peroxide as a curing agent. The LDHs intercalated by organic compounds including sodium styrene sulfonate (SSS) and sodium dodecylbenzene sulfonate (SDBS) were investigated using thermogravimetric analysis (TGA) and X‐ray diffraction (XRD) while the unmodified LDHs were used as contrast. Experimental results from TGA and XRD showed that both SSS‐ and SDBS‐intercalated LDHs were successfully obtained. The morphology of the LDH composites was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and XRD. The chemical structure of NBR/LDHs compounds were measured by Fourier transform infrared spectrum. The thermal properties were measured by TGA and differential scanning calorimetry. Other properties such as mechanical and swelling properties were also investigated. The results showed that a chemical bonding between organically modified LDHs and rubber matrix through SSS was built during vulcanization, which leads to improved interfacial strength of the cured compound. A high‐performance acrylonitrile butadiene rubber/SSS‐modified LDH compound, which has two times higher tensile strength than cured pure rubber without significant loss of elongation, was obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Transport and electrical properties of natural rubber/nitrile rubber blend composites reinforced with multiwalled carbon nanotube and modified nano zinc oxide

As a surface modified zinc oxide, stearic acid‐coated nano zinc oxide (ZOS) has been prepared by sol‐gel method and was used along with N‐benzylimine aminothioformamide‐N‐cyclohexyl benzthiazyl sulfonamide binary accelerator system, multiwalled carbon nanotube (MWCNT) and sulfur for vulcanizing 20/80 natural rubber/nitrile rubber (NR/NBR) blend. Different formulations have been prepared by using 1–7 phr of MWCNT. Solvent transport and electrical properties of the rubber compounds have been investigated. The equilibrium solvent uptake (Q_∞) decreased with increase in concentration of the filler due to the decrease in the free volume and the increase in tortuousity. The conductivities of the vulcanizates increased with increase in the dosage of MWCNT from 1 phr in NBCNT₁ to 7 phr in NBCNT₄ indicating the formation of percolating network of MWCNTs in the NBR/NR matrix. POLYM. COMPOS., 35:956–963, 2014. © 2013 Society of Plastics Engineers     

Enhancement of mechanical strength associated with interfacial tension between barium titanate and acrylonitrile–butadiene rubber with different acrylonitrile contents by surface modification

Acrylonitrile–butadiene rubber (NBR) with different acrylonitrile (ACN) contents was filled with barium titanate (BT) to prepare the polymer dielectrics. The neat NBR, NBR/untreated BT, and NBR/bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (silane coupling agent KH845‐4) modified BT (MBT) composites were prepared. At low ACN content (ACN content 20 wt %), the tensile strength of the NBR/MBT composites increased by 173.6% from 2.69 to 7.36 MPa compared to the neat NBR. The pleasing results were not found in those composites with high ACN content. Both surface modifications of BT and NBR with low ACN content would result in lower interfacial tension between BT and NBR. A strong interfacial adhesion was observed between MBT and NBR with 20 wt % ACN content. The interfacial adhesion had great contribution to the mechanical strength of composites. Moreover, the dielectric properties of composites were also investigated in detail. The addition of BT enhanced the dielectric constant of composites markedly. This study can be applied in manufacturing electronic devices, which are subjected to oily environments for a long time. At the same time, the study can provide some help for researchers to select the polymer matrix and the appropriate surface modification agent of functional filler. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45936.     

不同粒径氧化锌填充丁腈橡胶的摩擦磨损机制

采用机械共混与热模压工艺制备普通氧化锌(c-ZnO)与纳米氧化锌(n-ZnO)填充丁腈橡胶(NBR)复合材料,并对复合材料的硫化特性、力学性能及摩擦磨损性能进行了对比研究。结果表明,用量相同时,与c-ZnO相比,n-ZnO在硬脂酸与硫黄作用下形成较强硫化剂,可延长胶料的硫化时间,有利于提高胶料的加工安全性与流动性。与加入c-ZnO的胶料相比,n-ZnO/NBR复合材料的撕裂强度提高了11.0%,压缩永久变形减小17.3%,邵尔A硬度略微提高,且在干摩擦、油润滑条件下均表现出优异的耐摩擦磨损性能。c-ZnO/NBR复合材料的磨损机制为磨粒磨损和严重的黏着磨损,n-ZnO/NBR复合材料的磨损机制为磨粒磨损和少量的黏着磨损。     

Natural rubber/cis‐1,4‐polybutadiene nanocomposites: Vulcanization behavior,mechanical properties,and thermal stability

Natural rubber/cis‐1,4‐polybutadiene (NR/BR) blends with two types of layered nanofillers, montmorillonite (MMT) and layered double hydroxide (LDH), both in pristine and organically modified forms are produced and investigated. Faster curing is found for all the NR/BR blends, except for the one containing the unmodified MMT. This effect can be attributed to the groups placed in the interlayer regions of the clays; more precisely to ammonium groups for the organo‐MMTs and to ? OH groups for LDHs. Mechanical properties and thermal stability of rubber compounds are investigated. It has been demonstrated that the performance of the final nanocomposite is significantly affected by the kind of clay. Particularly, the organo‐MMTs provoke an improvement of the mechanical properties and increase the thermal stability of about 4–5° C in respect to the pure NR/BR matrix. On the contrary, the poor compatibility of unmodified MMT and of LDH clays with the rubber blend is evident and no enhancement on the composite performance has been observed. POLYM. ENG. SCI., 2013. © Society of Plastics Engineers     

The influence of filler surface modification on mechanical and material properties of layered double hydroxide‐containing polypropylene composites

The processing and properties of layered double hydroxides (LDHs)‐containing polypropylene (PP) composites have been studied extensively. However, no detailed studies have reported on how stearic acid (SA)‐intercalated and SA‐coated LDHs influence the properties of melt‐processed PP/LDH composites. Here, four different types of LDHs: synthesized (cLDH1) and commercial (cLDH2) SA‐coated LDH, SA‐intercalated LDH (iLDH), and unmodified LDH (nLDH), were used to fabricate composites using a master‐batch‐dilution technique in a twin‐screw extruder. The characterization results showed that microcomposites were formed when cLDH2 and nLDH were used, whereas nanocomposites were formed when iLDH and cLDH1 were used. Strong nucleating behavior was observed for the nLDH‐, cLDH1‐, and cLDH2‐containing composites, whereas iLDH delayed the crystallization process of the PP matrix. A significant improvement in modulus, with a balance of tensile and impact strengths, was observed in the case of the cLDH1‐containing composite, whereas the nLDH‐containing composite showed good improvement in temperature‐dependent load‐bearing capacity. On the other hand, the PP/iLDH composite showed a remarkable improvement in thermal stability and a reduction in the peak‐heat‐release rate. Therefore, this study gives us an opportunity to design PP composites with desired properties by the judicious choice of LDH, which further widens the application of PP matrices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45024.     

Nanomodified fillers in chloroprene‐rubber‐compatibilized natural rubber/acrylonitrile–butadiene rubber blends

Because of the structural dissimilarity, natural rubber (NR) and acrylonitrile–butadiene rubber (NBR) are immiscible, and compatibilizers are used during their blending. Neoprene or chloroprene rubber (CR) has a polar chlorine part and a nonpolar hydrocarbon part. Also, it has many advantageous properties, such as oil resistance, toughness, a dynamic flex life, and adhesion capacity. Hence, it is not less scientific to use CR as a compatibilizer in the blending of NBR with NR. Because many fewer studies on the use of neoprene as a compatibilizer in NR–NBR blend preparation are available, efforts were made to prepare 20:80 NR–NBR blends with CR with the aim of studying the effect of poly(ethylene oxide) (PEO)‐coated nano calcium silicate along with nano N‐benzylimine aminothioformamide and stearic acid coated nano zinc oxide in the sulfur vulcanization of the blends. The optimum dosage of the compatibilizer was derived by the determination of the tensile properties, tear resistance, abrasion resistance, compressions set, and swelling values. The tensile strength, tear resistance, and abrasion resistance of the gum vulcanizates of the blend were improved by the compatibilizing action of CR up to 5 parts per hundred parts of rubber (phr). In the case of the filled vulcanizates, the tear resistance, 300% modulus, hardness, and abrasion resistance increased with increasing dosage of nano calcium silicate. The elongation at break percentage decreased as expected when there was an increase in the modulus. Scanning electron microscopy was used to study the phase morphology of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of imidazolium ionic liquid type on the properties of nitrile rubber composites

We investigated the influence of hydrophilic and hydrophobic imidazolium ionic liquids on the curing kinetic, mechanical, morphological and ionic conductivity properties of nitrile rubber composites. Two room temperature ionic liquids with a common cation—1‐ethyl‐3‐methylimidazolium thiocyanate (EMIM SCN; hydrophilic) and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI; hydrophobic)—were used. Magnesium–aluminium layered double hydroxide (MgAl‐LDH; also known as hydrotalcite) was added to carboxylated acrylonitrile–butadiene rubber (XNBR) whereas fumed silica Aerosil 380 was used in acrylonitrile–butadiene rubber (NBR) as reinforcing fillers. NBR compounds were vulcanized with a conventional sulfur‐based crosslinking system whereas XNBR compounds were cured with MgAl‐LDH. The optimum cure time reduction and tensile properties improvement were obtained when both ionic liquids were added at 5 parts per hundred rubber (phr). The results revealed that EMIM SCN and EMIM TFSI induced an increase in the AC conductivity of nitrile rubber composites from 10^?10 to 10^?8 and to 10^?7 S cm^?1, respectively (at 15 phr ionic liquid concentration). The presence of ionic liquids in NBR slightly affected the glass transition temperature (T_g) whereas the presence of EMIM TFSI in XNBR contributed to a shift in T_g towards lower temperatures from ?23 to ?31 °C, at 15 phr loading, which can be attributed to the plasticizing behaviour of EMIM TFSI in the XNBR/MgAl‐LDH system. Dynamic mechanical analysis was also carried out and the related parameters, such as the mechanical loss factor and storage modulus, were determined. © 2013 Society of Chemical Industry     

A general approach to rubber–montmorillonite nanocomposites: Intercalation of stearic acid

The effect of stearic acid on the properties of different rubbers/montmorillonite composites was studied. We used alkyl quaternary ammonium modified montmorillonite (organo-montmorillonite), which was additionally modified with stearic acid. Premixed with the montmorillonite, the stearic acid expanded the clay mineral layers, thus permitting the rubber molecules to be more easily intercalated into the montmorillonite. We used several kinds of rubbers with different polarities and molecular structures. Both the X-ray diffraction and infrared spectroscopy studies indicated that the stearic acid propped up interlayer space allowing the intercalation of the rubber chains. Measurement of the physical and dynamic mechanical properties, along with studies of the composite morphology by transmission electron microscopy, very clearly showed that mixing the montmorillonite clay with stearic acid yielded various rubber nanocomposites with a high amount of intercalated and exfoliated montmorillonite particles. Either complete intercalation or increased nanostructure formation yielded as compared to the standard rubber–clay mineral composites prepared with a normal dose (2 parts per hundred of rubber) of stearic acid, can be achieved by adding a large amount of stearic acid (10 parts per hundred of rubber in our case) to non-polar rubbers (e.g. natural rubber (NR), ethylene propylene rubber (EPDM), etc.) that are not known to form totally exfoliated structures by simple melt mixing of montmorillonite and rubber.     

Synthesis and characterization of the novel meta‐modified aramid fibers with liquid crystalline properties

To improve the interfacial adhesion between the meta‐aramid fibers and the matrix, the new method of interfacial polymerization was used to complete the aramid's surface modification. Two new kinds of grafted fibers which had liquid crystalline properties were prepared. The structure and properties of the aramid fibers before and after modification were characterized by scanning electron microscope (SEM), Fourier transform infrared, differential scanning calorimetry, and polarizing optical microscope. The surface of grafted aramid fibers was very rough. The range of liquid crystalline phase of the grafted fibers AF‐1 and AF‐2 on the cooling scan, respectively, is from 147 to 209°C and from 163 to 221°C. It was novel that the grafted fibers with rigid‐rod structure had typical nematic texture. The grafted aramid fibers as the ideal substitute material of asbestos were used as reinforcing fibers in nitrile butadiene rubber (NBR) matrix. Combining with NBR, the composites reinforced with the unmodified and grafted aramid fibers were synthesized. The micrographs of the composites' fractured surface were studied by SEM. The mechanical properties of the grafted fibers/NBR composites were superior to the unmodified fibers/NBR composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of nanostructures of modified clay–carbon black on physico‐mechanical,electrical, and acoustic properties of elastomer‐based composites

Elastomeric composites based on nitrile rubber (NBR), carbon black (CB), and organically modified nanoclay (NC) were prepared using a laboratory two‐roll mixing mill. Influences of the hybrid filler system (CB+NC) on various properties of NBR compound were analyzed. It was found that the addition of hybrid filler (CB+NC) over only carbon black enhances various properties. It was also found that the addition of nanoclay to the rubber matrix effectively improved key properties. Acoustics and electrical properties were modified with reduced water absorption because of layered clay platelets. The lower volume resistivity of NBR composites reflected better electrical conductivity attributed to the presence of nanoclay leading to effective filler connectivity. X‐ray diffraction and transmission electron microscopy measurements revealed that nanoclays were mostly intercalated and were uniformly dispersed. Use of calcium stearate facilitated dispersion of nanoclay in the rubber matrix which was observed through the formation of nanostructures including “nano” and “halo” units. Time temperature superposition in dynamic mechanical analysis test of the composites indicated lower mechanical loss in the frequency range of interest. The advantages accruing due to overall property enhancement, including lower water absorption, and better electrical and excellent acoustic properties of NBR composites make it suitable as underwater acoustic transparent materials for transducer encapsulation application. POLYM. COMPOS., 37:1786–1796, 2016. © 2014 Society of Plastics Engineers     

Structure and dynamic properties of nitrile‐butadiene rubber/hindered phenol composites

Crosslinked nitrile‐butadiene rubber (NBR)/hindered phenol composites were successfully prepared by mixing tetrakis [methylene‐3‐(3‐5‐ditert‐butyl‐4‐hydroxy phenyl) propionyloxy] methane (AO‐60) into NBR with 35% acrylonitrile mass fraction. The structural and mechanical properties of the NBR/AO‐60 composites were systematically investigated by using differential scanning calorimeter, XRD, Fourier transform infrared, scanning electronic microscope, dynamic mechanical analyzer, and tensile testing. The results indicated that the AO‐60 changed from crystalline form into amorphous form, and most of the AO‐60 molecules could be uniformly dispersed in the NBR matrix. The glass transition temperature (T_g) of NBR/AO‐60 composites increased gradually with increasing content of AO‐60. The increase in T_g could be attributed to the formation of a strong hydrogen bonding network between the AO‐60 molecules and the NBR matrix. Unlike the pure NBR, the NBR/AO‐60 rubber composites had only one transition with a high loss factor. With increasing content of AO‐60, the loss peak shifted to the high temperature region, the loss factor increased from 1.45 to 1.91, and the area under the tan δ versus temperature curve (TA) also showed a significant increase. All these results were ascribed to the good compatibility and strong intermolecular interactions between NBR and AO‐60. Furthermore, all NBR/AO‐60 composites exhibited higher glass transition temperatures and tensile strength than NBR, and they had other desirable mechanical properties. They have excellent prospects in damping material applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of ZnO type and concentration on the mophology,thermal, and mechanical properties of poly(ether ester)/ZnO composites

Poly(ether ester) (PEE) copolymers were synthesized in a two‐stage process involving transesterification and polycondensation. The synthesized copolymer and the zinc oxide (ZnO) were used in composite preparation by melt compounding. The influence of ZnO type and concentration on the morphology, thermal and mechanical properties of the composites were studied. DSC and XRD analyses indicated that crystallinity of composites was slightly reduced with ZnO content. Homogeneous dispersion of fillers in the polymer matrix was observed through morphological analyses. While in general tensile strength and elongation at break values of the composites decreased with increasing ZnO content, elastic modulus values increased with the addition of ZnO. Moreover, ZnO particles were modified with poly(N‐vinyl pyrrolidone) and a slight improvement in mechanical properties was observed, respectively over the composites containing unmodified particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

硫化助剂及促进剂用量对异戊橡胶性能的影响

以吉林石化公司研究院生产的高顺式稀土异戊橡胶(JH-01)为生胶,研究了氧化锌、硬脂酸及促进剂等硫化助剂的用量对硫化橡胶物理机械性能的影响,探索了性能变化规律,确定了各助剂最佳使用量。在基础胶及炭黑用量不变的前提下,改变氧化锌、硬脂酸及促进剂用量,采用相同的混炼工艺及硫化工艺制成硫化胶试片,进行物理机械性能测试。结果表明,得到的硫化橡胶各项物理机械性能变化幅度较大。如需调整异戊橡胶的应力应变性能及撕裂强度可适当调整氧化锌、硬脂酸及促进剂的用量。     

The influence of zinc ferrites nanoparticles on the thermal,mechanical, and magnetic properties of rubber nanocomposites

The interest to ferrite nanoparticles (NPs) is thriving because of their unique applications in life industry. Doping of rubber composites by nanoparticles results in a novel characteristics which is not exist either in the ferrite or rubber alone. In this study, zinc ferrite NPs have been synthesized via sol–gel technique. These nanoferrites embedded into acrylonitrile butadiene rubber (NBR) at different concentrations. The morphology and structure of zinc ferrite and zinc ferrite NPs doped NBR were investigated using X‐ray diffraction and transmission electron microscopy. The influence of zinc ferrite NPs loading on the thermal stability showed that the zinc ferrite enhanced the thermal stability and reduced the rate of thermal degradation of rubber nanocomposites. The effect of zinc ferrite NPs on the mechanical properties of NBR showed that the hardness, tear strength, and tensile stress are improved. The magnetic measurements of these nanocomposites showed that the saturation magnetization is enhanced as the concentration of zinc ferrite NPs increased into NBR nanocomposites. The EPR spectra of zinc ferrite NPs doped NBR indicated that the increase in zinc ferrite NPs content resulted in an increase in the g‐factor and line width. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Enhanced oil resistance and mechanical properties of nitrile butadiene rubber/lignin composites modified by epoxy resin

This is probably the first report on developing nitrile butadiene rubber (NBR) composites with enhanced performance s via lignin bridged epoxy resin in the rubber matrix. NBR/lignin masterbatch has been prepared through latex‐compounding method, and then epoxy resin (F51) was added in the NBR/lignin compounds by the melt compounding method. Lignin‐epoxy resin networks were synthesized in situ during the curing process of rubber compounds through epoxide?hydroxyl reactions. Compared with lignin filler, lignin‐F51 networks showed an improved oil resistance ability and led to increased mechanical properties, crosslinking density, and thermal stability of the rubber composites. This method provides a new insight into the fabrication of novel interpenetrating polymer networks in rubber composites and enlarges the potential applications of lignin in high performance rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42922.     

Advances in layered double hydroxide (LDH)-based elastomer composites

This article reviews the advances in layered double hydroxide (LDH) materials and the synthesis of LDH-based elastomer composites. The potential of tuning the structure of LDH materials for desired properties and applications has attracted both academic and industrial interest in recent years. The modification of LDH materials and the use of such materials in the synthesis of composites with different elastomer matrices have been critically analyzed. Emphasis has been given to the use of Mg-Al LDHs and Zn-Al LDHs with different elastomers. The use of modified LDHs with elastomers substantially improves their mechanical, thermal and optical properties. Even “smart properties” of elastomers, such as reversible thermotropic optical characteristics, have been realized with the use of LDH-based multifunctional additives in rubber formulations. The flame retardance of some elastomer composites has also been enhanced with the use of modified LDHs. The possibility of replacing ZnO with LDH during rubber compounding has also been discussed, which would lead to drastic interventions in the well-established rubber processing technologies. LDH materials have also been reported to be biocompatible. Therefore, among the various possible applications of LDHs in different material development processes, their use in rubber technology offers the potential for environmentally friendly rubber products, even tires. Throughout this article, the structure, synthesis, properties and applications of elastomer/(LDH) composites are discussed, including suitable examples taken from the relevant literature.     

Using Mg‐Al‐layered double hydroxide intercalated with chiral dicarboxylic acid for the reinforcement of isoleucine amino acid containing poly(amide‐imide)

A series of bionanocomposite (BNC) materials based on isoleucine containing poly(amide‐imide) (PAI) and modified MgAl‐layered double hydroxide (LDH) were prepared by solution intercalation method for the first time. An optically active PAI was synthesized by direct polycondensation reaction of N,N'‐(pyromellitoyl)‐bis‐isoleucine with 3,5‐diamino‐N‐(thiazol‐2‐yl)benzamide under green conditions. Organically modified LDH was prepared via ion exchange reaction of MgAl‐LDH in a solution of N,N'‐(pyromellitoyl)‐bis‐l‐ isoleucine in distilled water. X‐ray diffraction (XRD) results of modified LDH show an increase in interlayer distance as compared to the unmodified one. The obtained polymer and modified LDH were used to prepare chiral and high‐performance hybrid materials. Fourier transform infrared spectroscopy, XRD, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis (TGA) techniques were used to study the morphology and thermal properties of the obtained hybrid materials. TGA data indicated an increase in thermal stability of the BNCs as compared to the pure polymer. POLYM. COMPOS., 37:3288–3295, 2016. © 2015 Society of Plastics Engineers     

The influence of surface modification on the structure and properties of a zinc oxide‐filled poly(ethylene terephthalate)

Hydrophobic zinc oxide (ZnO) nanoparticles were successfully prepared by a one‐step precipitation reaction in an aqueous solution of zinc sulfate and sodium hydroxide with stearic acid as the modifying agent. Poly(ethylene terephthalate) (PET)/ZnO nanocomposites were prepared by further in situ polymerization of purified terephthalic acid, ethylene glycol and the ZnO nanoparticles. The surface modification of ZnO and the microstructure and properties of the nanocomposites were investigated using relative contact angle measurements, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission and scanning electron microscopies, thermogravimetric analysis and differential scanning calorimetry. Measurements of relative contact angle indicated that the surface‐treated ZnO was hydrophobic. Compared to the nanocomposite filled with unmodified ZnO, a significant improvement in thermal stability and crystallinity was observed with the addition of 2 wt% surface‐treated ZnO. The experimental results also suggested that the properties of the nanocomposites were correlated with the dispersion of ZnO in PET and the interfacial interactions between ZnO and PET matrix. © 2012 Society of Chemical Industry     

改性石墨烯对天然橡胶/丁腈橡胶复合材料热性能的影响

采用超声辅助超临界CO2方法制备石墨烯,经3-氨丙基三乙氧基硅烷(APTES)改性后,采用"预混合"的方法,得到硬脂酸/石墨烯母料。通过机械共混法制备天然橡胶(NR)/改性石墨烯(GNs)与丁腈橡胶(NBR)/GNs复合材料。通过分析复合材料的导热性能、热管理性能和压缩生热性能的变化情况,验证石墨烯的性能与硬脂酸/石墨烯"预混合"对石墨烯分散的影响。结果表明,添加3份GNs时,NRC-3、NBRC-3的导热性能分别提升了108%和194%,压缩温升降低了8. 9℃和9. 9℃。该方法制备的石墨烯导热性能优秀,硬脂酸/石墨烯的"预混合"有效改善了石墨烯在聚合物中的分散性。