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     

Structure and properties of strain‐induced crystallization rubber–clay nanocomposites by co‐coagulating the rubber latex and clay aqueous suspension

Natural rubber (NR)–clay (clay is montmorillonite) and chloroprene rubber (CR)–clay nanocomposites were prepared by co‐coagulating the rubber latex and clay aqueous suspension. Transmission electron microscopy showed that the layers of clay were dispersed in the NR matrix at a nano level, and the aspect ratio (width/thickness) of the platelet inclusions was reduced and clay layers aligned more orderly during the compounding operation on an open mill. However, X‐ray diffraction indicated that there were some nonexfoliated clay layers in the NR matrix. Stress–strain curves showed that the moduli of NR were significantly improved with the increase of the amount of clay. At the same time, the clay layers inhibited the crystallization of NR on stretch, especially clay content of more than 10 phr. Compared with the carbon‐black‐filled NR composites, NR–clay nanocomposites exhibited high hardness, high modulus, high tear strength, and excellent antiaging and gas barrier properties. Similar to NR–clay nanocomposites, CR–clay nanocomposites also exhibited high hardness, high modulus, and high tear strength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 318–323, 2005     

Preparation,structure and properties of nitrile–butadiene rubber–organoclay nanocomposites by reactive mixing intercalation method

The nanocomposites of nitrile–butadiene rubber (NBR) and organo‐montmorillonite modified by hexadecyltrimethyl ammonium bromide (HMMT) were prepared by the reactive mixing intercalation method in the presence of the resorcinol and hexamethylenetetramine complex (RH). The structure of the NBR–RH–HMMT nanocomposites was characterized by XRD, TEM, FTIR, determination of crosslinking density, and so on. The results showed that the d‐spacing of HMMT increased substantially with RH addition and the layers of HMMT were dispersed in rubber matrix on a nanometer scale. The mechanical properties of the NBR–RH–HMMT nanocomposites were far superior to those of NBR–HMMT composites, and the glass transition temperature of NBR–RH–HMMT nanocomposite was higher than that of NBR. The reactive mixing intercalation method by introducing RH could enhance the interface combination between the rubber and the organoclay through the interactions of RH with NBR and modified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1905–1913, 2006     

Styrene–butadiene rubber/cellulose II/clay nanocomposites prepared by cocoagulation—mechanical properties

In this work, nanocomposites of styrene butadiene rubber (SBR), cellulose II, and clay were prepared by cocoagulation of SBR latex, cellulose xanthate, and clay aqueous suspension mixtures. The incorporated amount of cellulose II was 15 phr, and the clay varied from 0 to 7 phr. The influence of cellulose II and clay was investigated by rheometric, mechanical, physicochemical, and morphological properties. From the analysis of transmission electron microscopy (TEM), dispersion in nanometric scale (below 100nm) of the cellulosic and mineral components throughout the elastomeric matrix was observed. XRD analysis suggested that fully exfoliated structure could be obtained by this method when low loading of silicate layers (up to 5 phr) is used. The results from mechanical tests showed that the nanocomposites presented better mechanical properties than SBR gum vulcanizate. Furthermore, 5 phr of clay is enough to achieve the best tensile properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of acrylonitrile–butadiene copolymer hybrid nanocomposites with organoclays

Acrylonitrile–butadiene rubber (NBR) hybrid nanocomposites with organoclays were prepared by melt mixing, and their properties were compared with those of conventional rubber compounds filled with carbon black and silica. Based on X‐ray diffraction and transmission electron microscopy, the NBR nanocomposites obtained were found to form generally an intercalated structure, although they formed an exfoliated structure when the organoclay content was low enough, <2 parts per 100 rubber. The NBR nanocomposite showed a simultaneous improvement in ultimate strength and stiffness, which is generally in a trade‐off relation in rubbery materials. A characteristic fracture morphology of ‘laminated board‐type’ was observed for NBR nanocomposites instead of typical ‘cross‐hatched’ morphology in conventional rubber composites. The NBR nanocomposites also showed much higher hysteresis and tension set. Copyright © 2003 Society of Chemical Industry     

Preparation and characterization of rubber–clay nanocomposites

Rubber–clay nanocomposites were prepared by two different methods and characterized with TEM and XRD. The TEM showed clay had been dispersed to one or several layers. The XRD showed that the basal spacing in the clay was increased. It was evident that some macromolecules intercalated to the clay layer galleries. The clay layer could be uniformly dispersed in the rubber matrix on the nanometer level. The mechanical tests showed that the nanocomposites had good mechanical properties. Some properties exceeded those of rubber reinforced with carbon black, so the clay layers could be used as an important reinforcing agent as the carbon black was. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1879–1883, 2000     

Preparation and properties of ethylene propylene rubber (EPR)–clay nanocomposites based on maleic anhydride‐modified EPR and organophilic clay

Ethylene propylene rubber–clay nanocomposites (EPR–CNs) were prepared by melt‐compounding maleic anhydride modified EPR (EPR‐MA) with organophilic clay, and their properties were examined. Silicate layers of organophilic clay were found to exfoliate and homogeneously disperse into the nanometer level in the nanocomposites by transmission electron microscopy observation. EPR–CNs exhibited higher tensile moduli compared to EPR‐MA and composites containing conventional fillers such as carbon black, talc. The storage moduli of EPR–CNs were also higher than those of EPR‐MA and the conventional composites. Creep resistances of EPR–CNs were much improved compared for EPR‐MA. Degree of swelling in hexadecane was remarkably restricted. Improvement of these properties is caused because dispersed silicate layers have much large interface with the EPR matrix and are thought to strongly restrain the EPR polymer chains. Nanocomposite technology using small amount of silicate layers is useful to improve properties of thermoplastic elastomer. Various kinds of thermoplastic elastomers are expected to be produced by loading of silicate layers with or without conventional fillers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 758–764, 2004     

Radiation induced modification of NBR and SBR montmorillonite nanocomposites

Nanocomposites of two different kinds of rubber (acrylonitrile-butadiene rubber NBR and styrene butadiene rubber SBR)/organo-montmorillonite nanocomposites modified by hexadecyltrimethyl ammonium bromide were prepared by the reactive mixing intercalation method in the presence of trimethylolpropane trimethylmethacrylate (TMPTMA). The influence of gamma irradiation on the morphology and properties of the rubber nanocomposites was investigated. Intercalated polar or unsaturated matrices (e.g., NBR and SBR)/OMMT nanocomposites can be obtained, which was confirmed by X-ray diffraction (XRD). The clay layers could be uniformly dispersed in the rubber matrix on the nanometer level. Mechanical tests showed that the nanocomposites had good mechanical properties as compared to the neat composites. The results also showed that the irradiated NBR/OMMT nanocomposites had higher thermal stabilities than irradiated SBR/OMMT nanocomposites.     

Montmorillonite clay nanocomposites based on vinyl pyridine‐styrene‐butadiene terpolymer (VPR)/acrylonitrile‐butadiene rubber (NBR) blend

This study describes a novel route to synthesize vinyl pyridine‐styrene‐butadiene terpolymer rubber (VP rubber) montmorillonite clay nanocomposites by latex blending technique. The pyridine moiety of the VP rubber was modified with methyl iodide to form the pyridinium ion during latex blending. Cation exchange reaction of the pyridinium ion of the VP rubber latex with sodium montmorillonite occurred during latex stage mixing which helped to form VP rubber‐montmorillonite clay nanocomposites. Coagulation of the latex‐clay slurry produced nanocomposites master batch. The master batch was compounded with acrylonitrile butadiene rubber (NBR). Fourier Transform Infrared Spectroscopy (FTIR) confirmed the modification of the pyridine moiety of VP rubber. Wide angle X‐ray diffraction (WAXD), scanning electron microscopy‐energy dispersive X‐ray spectrophotometry (SEM‐EDS) and transmission electron microscopy (TEM) provided the evidences of formation of nanocomposite. Remarkable improvements in the mechanical properties were found by addition of small amount of modified clay. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Mechanical properties and structures of dicyanate–clay nanocomposites

Dicyanate–clay nanocomposites comprising a dicyanate resin and a type of organically modified clay were prepared and characterized, and their thermomechanical properties were investigated. The organically modified clay had silicate layers of nanometer size intercalated with an organic modifier, which improved the compatibility between the clay and organic materials, such as dicyanate resins. Dynamic mechanical analysis was performed to investigate the thermomechanical properties of the dicyanate–clay nanocomposites containing various amounts of the clay. The storage modulus of the nanocomposites below their glass‐transition temperatures slightly increased with increasing clay content. The glass‐transition temperature of the dicyanate–clay nanocomposites increased with increasing clay content. The nanostructures of the dicyanate–clay nanocomposites were characterized by transmission electron microscopy and X‐ray diffraction analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2629–2633, 2003     

Preparation and properties of styrene–ethylene–butylene–styrene block copolymer/clay nanocomposites: I. Effect of clay content and compatibilizer types

BACKGROUND: Polymer/clay (silicate) systems exhibit great promise for industrial applications due to their ability to display synergistically advanced properties with relatively small amounts of clay loads. The effects of various compatibilizers on styrene–ethylene–butylene–styrene block copolymer (SEBS)/clay nanocomposites with various amounts of clay using a melt mixing process are investigated. RESULTS: SEBS/clay nanocomposites were prepared via melt mixing. Two types of maleated compatibilizers, styrene–ethylene–butylene–styrene block copolymer grafted maleic anhydride (SEBS‐g‐MA) and polypropylene grafted maleic anhydride (PP‐g‐MA), were incorporated to improve the dispersion of various amounts of commercial organoclay (denoted as 20A). Experimental samples were analyzed using X‐ray diffraction and transmission electron microscopy. Thermal stability was enhanced through the addition of clay with or without compatibilizers. The dynamic mechanical properties and rheological properties indicated enhanced interaction for the compatibilized nanocomposites. In particular, the PP‐g‐MA compatibilized system conferred higher tensile strength or Young's modulus than the SEBS‐g‐MA compatibilized system, although SEBS‐g‐MA seemed to further expand the interlayer spacing of the clay compared with PP‐g‐MA. CONCLUSION: These unusual results suggest that the matrix properties and compatibilizer types are crucial factors in attaining the best mechanical property performance at a specific clay content. Copyright © 2007 Society of Chemical Industry     

Rubber–clay nanocomposite by solution blending

Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA‐45) and organomodified clay (12Me‐MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (?100 to +100°C) showed that the storage moduli of these rubber–clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA‐45. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2216–2220, 2003     

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     

The role of rubber characteristics in preparing rubber/clay nanocomposites by melt compounding

Rubber/organic clay (OC) nanocomposites were produced by melt blending. Polar or unsaturated matrices (e.g., NBR and SBR) could easily enter into OC layers, whereas using nonpolar unsaturated rubber (EPDM), without other additives' help, intercalation structure could not be directly obtained. For the EPDM system, an intercalated structure was observed in presence of stearic acid (SA) for composites composed of SA and OC. Transmission electron microscopy observation showed that the dispersion of clay in nonpolar saturated rubber matrix was much poorer than that in polar or unsaturated matrix. The same effect of polar matrix was confirmed by comparison between IIR/OC and BIIR/OC systems. Moreover, using OC pretreated by SA (S‐OC), the dispersion of clay was obviously improved in the investigated nanocomposites, due to the intercalation of SA into OC interlayers. Especially in the nonpolar saturated EPDM system, the intercalation structure could be easily observed. Relative to the corresponding nanocomposites using OC, tensile strengths and the stresses at low strain of NBR and SBR based nanocomposites with S‐OC were significantly improved; while with EPDM nanocomposite, using S‐OC, only tensile strengths were improved but the stresses at low strain were almost the same, which should be related to the different interfacial force between OC and different rubber matrices. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of interfacial attraction on intercalation in polymer/clay nanocomposites

In order to examine the adhesive behavior of a polar polymer between hydrophilic clay layers, the so‐called glue effect, a clay intercalation by an ethylene–vinyl alcohol (EVOH) copolymer, which was capable of strong hydrogen bonding with the silicate surface of clay, was prepared by the melt intercalation technique and compared with a clay nanocomposite containing styrene–acrylonitrile (SAN) copolymer of less polar interaction energy in terms of the morphology and mechanical properties. Although initial penetration of the guest polymer into the gallery of the host clay occurred more rapidly for EVOH because of its strong hydrophilic nature, the dissociation of clay nanoplatelets was better developed for SAN with less polar interaction with clay, well evidencing the fact that the glue effect effectively affects the intercalation behavior of polymer/clay nanocomposites. However, the mechanical properties of the EVOH/clay nanocomposite were superior to those of SAN/clay nanocomposites. Although dissociation of respective silicate layers was poor for EVOH/clay nanocomposites, strong attractive energy stabilizes the interface between inorganic nanoparticles and the polymer matrix much more effectively, resulting in higher mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2749–2753, 2006     

Polyamide 6/clay nanocomposites using a cointercalation organophilic clay via melt compounding

Polyamide 6/clay nanocomposites (PA6CN) were prepared via the melt compounding method by using a new kind of organophilic clay, which was obtained through cointercalation of epoxy resin and quaternary ammonium into Na‐montmorillonite. The dispersion effect of this kind of organophilic clay in the matrix was studied by means of X‐ray diffraction (XRD) and transmission electron microscopy (TEM); the silicate layers were dispersed homogeneously and nearly exfoliated in the matrix. This was probably the result of the strong interaction between epoxy groups and amide end groups of PA6. The mechanical properties and heat distortion temperature (HDT) of PA6CN increased dramatically. The notched Izod impact strength of PA6CN was 80% higher than that of PA6 when the clay loading was 5 wt %. Even at 10 wt % clay content, the impact strength was still higher than that of PA6. The finely dispersed silicate layers and the strong interaction between silicate layers and matrix decreased the water absorption. At 10 wt % clay content, PA6CN only absorbs half the amount of water compared with PA6. The dynamic mechanical properties of PA6CN were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 953–958, 2003     

Effect of the clay size on the dispersion morphology and emulsion stability of ABS/layered silicate nanocomposites

ABS/layered silicate nanocomposites were synthesized through an emulsion polymerization with different sizes of silicates. The particle sizes of Laponite, Cloisite‐Na and Kunipia‐F are about 20–30, 70–150, and 300–500 nm, respectively. When ABS was synthesized by the emulsion polymerization in the presence of Laponite and Cloisite‐Na, ABS/layered silicate nanocomposite emulsion showed a stable suspension without the precipitation of solid particle. On the other hand, ABS/layered silicate nanocomposite synthesized with Kunipia‐F showed the precipitation of large aggregated particles and the phase separation. Smaller sizes of silicates like Laponite and Cloisite‐Na than polymerized particle worked as resided barrier preventing the emulsion particle from coagulation. Larger size of silicate like Kunipia‐F than emulsion particle was not able to enclose the emulsion particle delicately because of its stiffness and large aspect ratio. The monomers inserted into the intercalated Kunipia‐F connected the ABS particles and clay particles. The Kunipia‐F particles anchored ABS particles around them inducing the aggregation and precipitation of ABS particles. ABS copolymer emulsion and aqueous silicate dispersion were mixed to compare with synthesized ABS/layered silicate nanocomposites and showed a stable suspension. With small amount of Laponite or Cloisite‐Na, nanocomposite emulsion of Kunipia‐F was also stabilized. Laponite and Cloisite‐Na worked as a steric stabilizer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comparing styrene butadiene rubber–clay nanocomposites prepared by melt intercalation and latex‐coagulation methods

Among different methods for preparation of rubber–clay nanocomposites, melt intercalation and latex‐coagulation methods are more practiced. In this study, dispersion of pristine nanoclay by the latex‐coagulation method and organically modified nanoclay by the melt‐intercalation method in styrene butadiene rubber were compared, based on the same amount of mineral clay in the composites. Dispersion of nanoclay was examined by X‐ray diffraction before and after vulcanization, and by atomic force microscopy after vulcanization. It was shown that final structure of nanoclay in the composites was intercalated by both methods, with better dispersion resulting from coagulation of latex over mixing in the melt state. Dynamic–mechanical–thermal analysis and tension tests were used to further assess dispersion and polymer–filler interactions. These tests confirmed better dispersion and larger interfacial area for pristine nanoclay in the latex‐coagulated rubber through observing lower peak loss factor, higher growth of stress in stretching, and lower elongation at break when compared with those for the nanocomposite prepared by the melt mixing. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

三元乙丙橡胶/黏土纳米复合材料

利用熔融插层和双羟基甲基十二烷基氯化铵插层剂改性黏土的方法，制备了三元乙丙橡胶／黏土纳米复合材料。X射线衍射(XRD)和透射电镜(TEM)的测试结果表明，形成的纳米复合材料为剥离型。探索了制作该纳米复合材料的最佳工艺方法。研究了这种材料的力学性能及老化性能，分析了该有机黏土增强橡胶的机理。结果表明，在对黏土进行有机改性时，插层剂中的双羟基与黏土中的氧原子形成了氢键，而使黏土层间的相互作用减弱，层间距增大，使三元乙丙橡胶(EPDM)分子链插入黏土层间而导致黏土剥离是该纳米材料形成的主要原因。有机黏土用量为15份时，试样的拉伸强度高迭24．9MPa，扯断伸长率为666％；前者比纯EPDM提高了3～4倍，后者上升了140％。试样的撕裂强度也有明显的改善，而邵尔A型硬度却随有机黏土用量的增加没有明显的变化。同时，试样的耐热老化性能也有了明显的改善．