Morphology and rheological properties of nanocomposites based on nitrile rubber and organophilic layered silicates

Organo‐montmorillonite/nitrile rubber (NBR) nanocomposites were prepared by a melt intercalation process. The characteristics of NBR nanocomposites were determined by an oscillating disk rheometer and transmission electron microscopy. The cure characteristics were investigated according to the change in clay content and clay types. This study confirmed that organo‐montmorillonite/NBR nanocomposites have various cure characteristics, namely minimum torque, maximum torque, scorch time and curing time, according to the change in clay content and clay types. In particular, as the chain length of the modifier used for the treatment of Na⁺‐MMT following vulcanization increases, scorch time and optimum curing time are reduced. This is because, as the chain length of the modifier increases, organo‐MMT is distributed more equally during the formation of the nanocomposites. As swelling increases, the chain length of the clay modifier expands and then constitutes a better barrier. Copyright © 2003 Society of Chemical Industry     

Characteristics of nitrile–butadiene rubber layered silicate nanocomposites with silane coupling agent

Nanocomposites of organophilic montmorillonite (C18‐MMT), nitrile–butadiene rubber (NBR), and a coupling agent were produced during a melt compounding process at room temperature. During the process, it was clearly observed that organo‐MMT particles were exfoliated into nanoscale layers of approximately 1–30 nm thickness, in addition to their original 40 μm thickness. These MMT layers were uniformly dispersed in the NBR matrix. The effects of a coupling agent such as 3‐(mercaptopropyl)trimethoxy silane in C18‐MMT/NBR nanocomposites were studied. The C18‐MMT/NBR nanocomposites in the presence of the coupling agent were identified and characterized by X‐ray diffraction, transmission electron microscopy, a universal testing machine, thermogravimetric analysis, and IR spectroscopy. It was observed that an additional silane coupling agent, 3‐(mercaptopropyl)trimethoxy silane, enhanced the chemical interaction and was accompanied by the formation of Si? O? Si coupling bonds between C18‐MMT and the coupling agent and Si? C coupling bonds between NBR and the coupling agent. This work resulted in improved properties of organo‐MMT/NBR nanocomposites because of the nanoscale effects and strong interaction of the coupling bonds between NBR and organo‐MMT. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2633–2640, 2003     

Preparation and properties of polypropylene/org-attapulgite nanocomposites

Polypropylene (PP)/org-attapulgite (ATP) nanocomposites were prepared by melt blending in a mixer apparatus. Org-attapulgite was attained by silane coupling agent modification first and then graft-polymerization with butyl acrylate. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the clay morphology and the dispersion of the org-attapulgite, respectively. The changes of crystalline structure for PP nanocomposites were characterized by X-ray diffraction (XRD). The mechanical properties of PP/attapulgite nanocomposites were studied through tensile and impact tests. The thermal and dynamic mechanical properties were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The strength and stiffness of PP/org-ATP nanocomposites were both improved significantly in the presence of organic attapulgite. In addition, the incorporation of org-ATP also gave rise to an increase of the storage modulus and the changes of the glass transition temperature for PP composites. TEM and XRD results revealed the addition of attapulgite did not change the crystal structure of PP, however org-attapulgite acted as nucleating agents for the crystallization of PP.     

Preparation and characteristics of nitrile rubber (NBR) nanocomposites based on organophilic layered clay

The effect of clay modification on organo‐montmorillonite/NBR nanocomposites has been studied. Organo‐montmorillonite/NBR nanocomposites were prepared through a melt intercalation process. NBR nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA) and a universal testing machine (UTM). XRD showed that the basal spacing in the clay increased, which means that the NBR matrix was intercalated in the clay layer galleries. On TEM images, organo‐montmorillonite (MMT) particles were clearly observed, having been exfoliated into nanoscale layers of about 10–20 nm thickness from their original 40 µm particle size. These layers were uniformly dispersed in the NBR matrix. The DMTA test showed that for these nanocomposites the plateau modulus and glass transition temperature (T_g) increased with respect to the corresponding values of pure NBR (without clay). UTM test showed that the nanocomposites had superior mechanical properties, ie strength and modulus. These improved properties are due to the nanoscale effects and strong interactions between the NBR matrix and the clay interface. Copyright © 2003 Society of Chemical Industry     

Preparation and properties of nanocomposites based on different polarities of nitrile–butadiene rubber with clay

Nanocomposites were prepared with different grades of nitrile–butadiene rubber (NBR) [with nitrile (CN) contents of 26, 35, and 42%] with organoclay (OC) by a melt‐compounding process. The rubber/clay nanocomposites were examined by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). An increase in the polarity of NBR affected the XRD results significantly. The dispersion level of the nanofiller in the nanocomposites was determined by a function of the polarity of the rubber, the structure of the clay, and their mutual interaction. The intercalated structure and unintercalated structure coexisted in the lower polar of NBR. In addition, a relatively uniformly dispersed state corresponded to a more intercalated structure, which existed in the higher polar of NBR matrix. Furthermore, high‐pressure vulcanization changed the extent of intercalation. The mechanical properties and gas barrier properties were studied for all of the compositions. As a result, an improvement in the mechanical properties was observed along with the higher polarity of NBR. This improvement was attributed to a strong interaction of hydrogen bonding between the CN of NBR and the OH of the clay. Changes in the gas barrier properties, together with changes in the polarity of the rubbers, were explained with the help of the XRD and TEM results. The higher the CN content of the rubber was, the more easily the OC approached to the nanoscale, and the higher the gas barrier properties were. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

硫化方法对橡胶/黏土纳米复合材料黏土片层分散状态的影响

通过熔体插层法以及常压硫化法制备了橡胶/黏土纳米复合材料,并与模压硫化法制备的复合材料进行了对比,研究了硫化方法对橡胶/黏土纳米复合材料微观分散状态的影响。结果表明:采用熔体插层法制备的橡胶/黏土混合物,其受限状态的橡胶大分子链在高温、高压条件下,在黏土片层之间处于一种热力学不稳定状态;模压处理会对橡胶/黏土混合物的分散状态产生不利影响。透射电子显微镜和X光衍射分析表明,采用模压硫化、常压硫化得到的丁基橡胶或丁苯橡胶/黏土纳米复合材料中黏土片层的微观分散状态不同;排除压力的影响,常压硫化有利于提高橡胶/黏土纳米复合材料中黏土片层的分散程度。     

硅烷偶联剂对电场下丁腈橡胶与铁硫化粘接性能的影响

采用电化学反应的作用方法,研究硅烷偶联剂对丁腈橡胶（NBR）与铁（Fe）的热硫化粘接性能的影响。通过对胶接破坏表面进行扫描电镜以及能谱观察分析,明晰了NBR-Fe粘接界面层的结构特征,并对影响粘合性能以及硫化胶物理机械性能的因素进行了研究分析。结果表明,施加的电场强度、导电填料种类以及硅烷偶联剂的用量对粘合性能作用明显;硅烷偶联剂用量变化不仅对粘合性能影响较大,而且影响NBR硫化胶的导电性及物理机械性能。     

Mechanical properties development of high-ACN nitrile-butadiene rubber/organoclay nanocomposites

The nanocomposites of nitrile-butadiene rubber (NBR) with high acrylonitrile content and Cloisite 30B were prepared in the presence of the resorcinol and hexamethylenetetramine (RH) complex as a compatibiliser. The structure of the NBR nanocomposites was characterised by cure characteristics, XRD, TEM and mechanical properties. The mechanical properties of the nanocomposites containing RH were far superior to those of NBR nanocomposites alone. Some hyperelastic models were approved on comparative study of tensile properties and the effect of RH compatibiliser on the material parameters of the models was investigated. The Mori–Tanaka and Halpin–Tsai models were used to estimate the modulus of prepared nanocomposites and compared with experimental results. The effect of RH on the intercalation/exfoliation of silicate layers was investigated from combination of effective particle method and Mori–Tanaka theory. This technique showed that the average number of silicate layers in each effective particle can decrease with RH compatibiliser.     

丁腈橡胶/粘土纳米复合材料的阻燃性研究

通过利用自制有机改性粘土，采用插层复合法成功制备了丁腈橡胶（NBR）／粘土纳米复合材料。透射电子显微镜（TEM）结果证实了粘土片层在橡胶基体中的纳米级分散。研究结果表明：纳米复合材料的阻燃性能明显高于炭黑补强胶料的阻燃性能。     

Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams?

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay‐modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide‐angle X‐ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of styrene–butadiene rubber based nanocomposites: The influence of the structural and processing parameters

Rubber‐based nanocomposites were prepared with octadecyl amine modified sodium montmorillonite clay and styrene–butadiene rubber with different styrene contents (15, 23, and 40%). The solvent used to prepare the nanocomposites, the cure conditions, and the cure system were also varied to determine their effect on the properties of the nanocomposites. All the composites were characterized with X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies revealed exfoliation for the modified clay–rubber composites. The TEM photomicrographs showed a uniform distribution of the modified clay in the rubber matrix. The thickness of the particles in the exfoliated composites was around 10–15 nm. Although the FTIR study of the unmodified and modified clays showed extra peaks due to the intercalation of the amine chains into the gallery, the spectra for the rubber–clay nanocomposites were almost the same because of the presence of a very small amount of clay in the rubber matrix. All the modified clay–rubber nanocomposites displayed improved mechanical strength. The styrene content of the rubber had a pronounced effect on the properties of the nanocomposites. With increasing styrene content, the improvement in the properties was greater. Dicumyl peroxide and sulfur cure systems displayed similar strength, but higher elongation and slightly lower modulus values were obtained with the sulfur cure system. The curing of the samples at four different durations at 160°C showed that the cure time affected the properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 698–709, 2004     

Effect of silane coupling agent on the structure and mechanical properties of nano‐dispersed clay filled styrene butadiene rubber

In rubber nanocomposites containing inorganic clay, the reinforcement effect has always been relatively insignificant due to the poor interfacial interaction between the rubber matrix and clay fillers. In this work, the silane coupling agent bis[3‐(triethoxysilyl)propyl]tetrasulfide (Si‐69) was employed through mechanically blending with styrene butadiene rubber (SBR)/clay (100/30) nanocompound that was prepared by combined latex compounding and spray‐drying technique, to serve as the molecular bridge between SBR matrix and clay filler and strengthen the interfacial interaction. TEM and XRD characterization indicated that Si‐69 significantly improved the dispersion of the silicate layers in the SBR matrix. The RPA analysis and the mechanical property study of the SBR/clay nanocomposites revealed that the filler network interaction was weakened while the filler–rubber interaction was strengthened upon the addition of Si‐69. POLYM. COMPOS., 37:890–896, 2016. © 2014 Society of Plastics Engineers     

Effect of single-walled carbon nanotubes on morphology and mechanical properties of NBR/PVC blends

Dynamically vulcanized thermoplastic elastomer based on Nitrile butadiene-rubber (NBR)/PVC with functionalized single-walled carbon nanotubes (f-SWNTs) and non-functionalized single-walled carbon nanotubes (SWNTs) were prepared using a brabender internal mixer. Effects of two types of SWNTs (functionalized and non-functionalized) on morphology and mechanical properties of NBR/PVC blends were studied. Results showed that the mechanical properties of NBR/PVC/SWNTs nanocomposites improved with the increasing of SWNTs content and in particular with the increase of f-SWNTs content. Moreover, the enhancement of mechanical properties of NBR/PVC blends reinforced with functionalized SWNT was higher than that of NBR/PVC blends with non-functionalized SWNT. Dispersion of SWNTs and morphology of NBR/PVC/SWNT nanocomposites were determined by scanning electron microscopy and transmission electron microscopy (TEM) techniques. TEM images illustrated that f-SWNTs were dispersed uniformly in NBR/PVC matrix while non-functionalized SWNTs showed much aggregation. Dynamic mechanical thermal analysis of NBR/PVC/SWNTs nanocomposites was also studied. The outcomes indicated that in the case of f-SWNTs, the intensity of tan ?? peak was lower than that in the case of non-functionalized SWNTs. Meanwhile, the intensity of tan ?? peak reduced when the content of f-SWNTs was increased.     

The influences of silane coupling agents on rheological properties of bentonite/nitrile butadiene rubber nanocomposites during curing process

In the present work, the influences of different silane coupling agents (SCA) on the rheological behaviors of Bent/NBR nanocomposites during the curing process were investigated. The nanocomposites were prepared with a green method which is simple and free of organic solvents. The dispersion state and filler–polymer interfaces were analyzed with XRD, TEM, and SEM while rheological behaviors of the nanocomposites were explored with a rubber processing analyzer (RPA). (3‐Mercaptopropyl)trimethoxysilane (MPTMS) and bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPT) both improved the dispersion state of bentonite in the matrixes significantly. MPTMS increased the crosslinking density by forming single sulfur bonds while TESPT worked as a plasticizer and delayed the formation of crosslinking during curing process. [3‐(2‐Aminoethylamino)propyl]triethoxysilane (AEAPTMS) led to reversible filler–rubber interactions, which was the main reason for the low elastic torque of the vulcanized nanocomposites. J. VINYL ADDIT. TECHNOL., 25:236–242, 2019. © 2018 Society of Plastics Engineers     

Effects of clay dispersion on the foam morphology of LDPE/clay nanocomposites

Intercalated and exfoliated low‐density polyethylene (LDPE)/clay nanocomposites were prepared by melt blending with and without a maleated polyethylene (PE‐g‐MAn) as the coupling agent. Their morphology was examined and confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of clay content and dispersion on the cell morphology of nanocomposite foams during extrusion foaming process were also thoroughly investigated, especially with a small amount of clay of 0.05–1.0 wt%. This research shows the optimum clay content for achieving microcellular PE/clay nanocomposite foams blown with supercritical CO₂. It is found that < 0.1 wt% of clay addition can produce the microcellular foam structure with a cell density of > 10⁹ cells/cm³ and a cell size of ～ 5 μm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2129–2134, 2007     

NBR/OMMT纳米复合材料的性能研究

通过机械共混法制备了丁腈橡胶/有机蒙脱土（NBR/OMMT）纳米复合材料。利用X射线衍射（XRD）、透射电镜（TEM）对复合材料的结构进行表征。研究了OMMT用量对复合材料硫化性能、交联密度的影响。结果表明,少量的OMMT（5份）缩短了正硫化时间（t90）,提高了交联密度。随着OMMT用量的增加（5～20份）,t90逐渐延长,交联密度逐渐减小。对照炭黑的增强机理,对OMMT对橡胶的增强机理进行了初步探讨。从力学性能的变化趋势可以看出,随着OMMT用量的增加,拉伸强度提高。由此可知,OMMT对橡胶的增强机理是OMMT片层对橡胶大分子链的吸附作用。同时还研究了复合材料的热空气老化性能和热稳定性能。     

Surface‐activated nanosilica treated with silane coupling agents/polypropylene composites: Mechanical,morphological, and thermal studies

This work reports the mechanical, morphological, and thermal properties of the polypropylene (PP) nanocomposites containing nanosilica (nano‐SiO₂) which were treated by different functional group silane coupling agents. Four types of silane coupling agents namely aminopropyltriethoxy silane (APTES), glycidyloxypropyltrimethoxy silane (GPTMS), trimethoxysilylpropyl methacrylate (TMPM), and dichlorodimethyl silane (DCMS) were used to modify the surface‐activated nanosilica. To enhance the effectiveness of the coupling, nanosilica was chemically activated and analyzed through FTIR and X‐ray photo electron spectroscopy (XPS). The highest tensile strength was recorded by the activated nanocomposites treated with APTES followed by nanocomposite treated with GPTMS, TMPM, and DCMS, respectively. The addition of silane coupling agents into nano‐SiO₂/PP system further improved the tensile modulus of the PP nanocomposites. From the transmission electron microscopy (TEM) analysis, activated nanosilica treated with APTES showed better nanosilica dispersion in the PP matrix and lesser agglomeration occurred when compared with the other silane coupling agents which were used in this study. Surface activation process does not effectively increase the degree of crystallinity and thermal stability on the PP nanocomposites. However, with the assistance of the surface treatment, it was found that the thermal behavior of the PP nanocomposites had been enhanced. POLYM. COMPOS., 2011. © 2011 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.     

Properties of silica/clay filled heavy‐duty truck tire thread formulation

A tire thread formulation for heavy‐duty trucks containing SBR/BR rubber blend and varying proportions of silica/clay fillers including a silane‐coupling agent have been investigated. The various mixes were compounded in a Banbury ‘O’ mixer and vulcanized using the EV‐system. Silica/clay (80/0) served as the control mix. The oscillating disc rheometer (ODR) was used in determination of cure characteristics. Substitution of silica (80 phr) with china clay up to 40 phr increased the cure rate of the rubber blend mixes as well as their maximum torque level (T_max). T_max was observed to be highest at a filler blend ratio of 40/40 phr. Synergism between silica and clay at this filler blend mixture is suggested to be responsible for the observation. The heat buildup was reduced from 43 to 20°C as the clay content increased. Results also showed that the rubber blend compound containing silica/clay (60/20) filler blend in the stated ratio exhibited the best balance of properties in the critical parameters such as the absolute torque level (69.5 dNm), heat buildup (39°C), and abrasion resistance (0.574 mg.loss/1,000 rev). The rate of depreciation of abrasion resistance of rubber blend compound as the clay content increased was found to be 0.035 mg loss/1,000 rev as silica is substituted with one part of china clay phr. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1024–1028, 2004     

Phenolic resin‐crosslinked natural rubber/clay nanocomposites: Influence of clay loading and interfacial adhesion on strain‐induced crystallization behavior

Nanocomposites of natural rubber (NR) and pristine clay (clay) were prepared by latex mixing, then crosslinked with phenolic resin (PhOH). For comparative study, the PhOH‐crosslinked neat NR was also prepared. Influence of clay loading (i.e., 1, 3, 5, and 10 phr) on mechanical properties and structural change of PhOH‐crosslinked NR/clay nanocomposites was studied through X‐ray diffraction (XRD), transmission electron microscopic (TEM), wide‐angle X‐ray diffraction (WAXD), tensile property measurement, and Fourier transform infrared spectroscopy (FTIR). XRD and TEM showed that the clay was partly intercalated and aggregated, and that the dispersion state of clay was non‐uniform at higher clay loading (>5 phr). From tensile test measurement, it was found that the pronounced upturn of tensile stress was observed when the clay loading was increased and a maximum tensile strength of the PhOH‐crosslinked NR/clay nanocomposites was obtained at 5 phr clay. WAXD observations showed that an increased addition of clay induced more orientation and alignment of NR chains, thereby lowering onset strain of strain‐induced crystallization and promoting crystallinity of the NR matrix during tensile deformation. FTIR investigation indicated a strong interfacial adhesion between NR matrix and clay filler through a phenolic resin bridge. This suggested that the PhOH did not only act as curative agent for crosslinking of NR, but it also worked as coupling agent for promoting interfacial reaction between NR and clay. The presence of strong interfacial adhesion was found to play an important role in the crystallization process, leading to promotion of mechanical properties of the PhOH‐crosslinked NR/clay nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43214.