Physical properties of natural rubber/organoclay nanocomposites compatibilized with epoxidized natural rubber

Onium ion‐modified montmorillonite (organoclay) was melt compounded with natural rubber (NR) in an internal mixer and cured by using a conventional sulfuric system. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) was used in 10 parts per hundred rubber (phr) as a compatibilizer. The effect of organoclay with different filler loading up to 10 phr was studied. Cure characteristics were determined by a Monsanto MDR2000 rheometer, whereas the tensile, compression, and tear properties of the nanocomposites were measured according to the related ASTM standards. While the torque maximum and torque minimum increased slightly, both scorch time and cure time reduced with the incorporation of organoclay. The tensile strength, elongation at break, and tear properties went through a maximum (at about 2 phr) as a function of the organoclay content. As expected, the hardness, moduli at 100% (M100) and 300% elongations (M300) increased continuously with increasing organoclay loading. The compression set decreased with incorporation of organoclay. The dispersion of the organoclay in the NR stocks was investigated by X‐ray diffraction and transmission electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1083–1092, 2006     

聚苯胺改性蒙脱土/天然橡胶纳米复合材料的制备与性能

采用原位聚合法制备了聚苯胺质量分数为20% 的聚苯胺改性蒙脱土,并以此作为增强剂利用机械混炼法制备了聚苯胺改性蒙脱土( PANI － MMT) /天然橡胶( NR) 纳米复合材料。使用X 射线衍射仪、傅里叶变换红外光谱仪及扫描电镜等对PANI － MMT 和PANI － MMT/NR 复合材料的结构进行了表征,并考察了PANI － MMT/NR 复合材料的力学性能。结果表明,PANI － MMT/NR 复合材料形成了插层型纳米结构; 与普通的有机蒙脱土/NR 复合材料相比,PANI － MMT/NR 复合材料的力学性能明显提高,PANI － MMT 添加质量为20 份时其力学性能达到最好,并超过了添加40 份炭黑N 660 的NR 的力学性能。     

Preparation and properties of natural rubber nanocomposites with solid‐state organomodified montmorillonite

A novel organomodified montmorillonite prepared by solid‐state method and its nanocomposites with natural rubber were studied. The nanocomposites were prepared by traditional rubber mixing and vulcanizing process. The properties of solid‐state organomodified montmorillonite were investigated by Fourier‐transform infrared spectroscopy (FITR) and thermogravimetric analysis (TGA). The dispersion of the layered silicate in rubber matrix was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the nanocomposites consisting of solid‐state organomodified montmorillonite and natural rubber are obtained. The solid‐state organomodified montmorillonite can not only accelerate the curing process, but also improve the mechanical and aging resistance properties of NR. The properties improvement caused by the fillers are attributed to partial intercalation of the organophilic clay by NR macromolecules. In addition, the dynamic mechanical analysis (DMA) results showed a decrease of tanδmax and increase of T_g when the organoclay is added to the rubber matrix, which is due to the confinement of the macromolecular segments into the organoclay nanolayers and the strong interaction between the filler and rubber matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

Skim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006     

On the potential of organoclay with respect to conventional fillers (carbon black,silica) for epoxidized natural rubber compatibilized natural rubber vulcanizates

Onium modified montmorillonite (organoclay) was compounded with natural rubber (NR) in an internal mixer and cured by using a conventional sulfuric system. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) in 10 parts per hundred rubber (phr) was used as a compatibilizer in this study. For comparison purposes, two commercial fillers: carbon black (grade N330) and silica (grade vulcasil‐S) were used. Cure characteristics were carried out on a Monsanto MDR2000 Rheometer. Organoclay filled vulcanizate showed the lowest values of torque maximum, torque minimum, scorch, and cure times. The kinetics of cure reaction showed organoclay could behave as a cocuring agent. The mechanical testing of the vulcanizates involved the determination of tensile and tear properties. The improvement of tensile strength, elongation at break, and tear properties in organoclay filled vulcanizate were significantly higher compared to silica and carbon black filled vulcanizates. In terms of reinforcing efficiency (RE), organoclay exhibited the highest stiffness followed by silica and carbon black filled vulcanizates. Scanning electron microscopy revealed that incorporation of various types of fillers has transformed the failure mechanism of the resulting NR vulcanizates compared to the gum vulcanizates. Dynamic mechanical thermal analysis (DMTA) revealed that the stiffness and molecular relaxation of NR vulcanizates are strongly affected by the filler–rubber interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2438–2445, 2004     

Preparation and characterization of poly(vinyl chloride)/organoclay nanocomposites by in situ intercalation

In this article, poly(vinyl chloride) (PVC)–organoclay nanocomposites were prepared via in situ polymerization intercalation and melt blending intercalation, respectively. Their nanostructures were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Differences in the morphologies of the PVC hybrids prepared by in situ intercalation and melt intercalation were investigated. In addition, three kinds of organoclay were used, in order to consider the effect of the interlayer environment on intercalation. The results show that ammonium cations have a great influence on the hybrids prepared by melt intercalation, while they have no obvious effect on the nanostructures of the composites produced via in situ intercalation due to its distinctive process and its mechanism. Copyright © 2004 Society of Chemical Industry     

黏土/天然橡胶纳米复合材料的制备及性能

利用乳液插层法制备了黏土／天然橡胶纳米复合材料,研究了该复合材料的力学性能、应力应变行为、耐磨性、气体阻隔性和耐老化性能。结果表明,黏土／天然橡胶纳米复合材料与高耐磨炭黑(N330)、白炭黑增强橡胶相比,邵尔A型硬度、定伸应力和撕裂强度较高,拉伸强度相当。黏土、N330以及白炭黑对天然橡胶的拉伸结晶有影响,填料用量对材料拉伸强度的影响存在最佳值。黏土／天然橡胶纳米复合材料具有良好的耐磨性、气体阻隔性和耐老化性能。     

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     

Preparation and characterization of poly(styrene‐co‐butadiene) and polybutadiene rubber/clay nanocomposites

Poly(styrene‐co‐butadiene) rubber (SBR) and polybutadiene rubber (BR)/clay nanocomposites have been prepared. The effects of the incorporation of inorganically and organically modified clays on the vulcanization reactions of SBR and BR were analysed by rheometry and differential scanning calorimetry. A reduction in scorch time (t_s1) and optimum time (t₉₅) was observed for both the rubbers when organoclay was added and this was attributed to the amine groups of the organic modifier. However, t_s1 and t₉₅ were further increased as the clay content was increased. A reduction in torque value was obtained for the organoclay nanocomposites, indicating a lower number of crosslinks formed. The organoclays favoured the vulcanization process although the vulcanizing effect was reduced with increasing clay content. The tensile strength and elongation of SBR were improved significantly with organoclay. The improvement of the tensile properties of BR with organoclay was less noticeable than inorganic‐modified clay. Nevertheless, these mechanical properties were enhanced with addition of clay. The mechanical properties of the nanocomposites were dependent on filler size and dispersion, and also compatibility between fillers and the rubber matrix. Copyright © 2004 Society of Chemical Industry     

Preparation and characterization of low density polyethylene/ethylene methyl acrylate glycidyl methacrylate/organoclay nanocomposites

The effects of organoclay type, compatibilizer, and the addition order of components during melt‐blending process on the morphology and thermal, mechanical, and flow properties of ternary nanocomposites based on low‐density polyethylene (LDPE) were investigated. As a compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA), as organoclays Cloisites® 15A, 25A, and 30B were used. All samples were prepared by a corotating twin screw extruder, followed by injection molding. The highest increase of the basal spacing for ternary nanocomposites was obtained in LDPE/E‐MA‐GMA/Cloisite® 30B nanocomposites with interlayer spacing of 59.2 Å. Organoclay and compatibilizer addition did not influence the melting/crystallization behavior of the compositions, and both compatibilizer and organoclays had no significant nucleation activity in LDPE. Among the ternary nanocomposites, the maximum increase in tensile strength and tensile modulus values was observed for nanocomposites containing organoclay Cloisite® 15A. The improvement with respect to neat LDPE was 43% for tensile strength and 44% for tensile modulus. According to the mechanical analysis, the best sequence of component addition was the one in which LDPE, organoclay, and compatibilizer were simultaneously fed to the extruder in the first run, and the product of the first run was extruded once more. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of surface modification of silicon carbide nanoparticles on the properties of nanocomposites based on epoxidized natural rubber/natural rubber blends

Improvement of the properties of rubber nanocomposites is a challenge for the rubber industry because of the need for higher performance materials. Addition of a nanometer‐sized filler such as silicon carbide (SiC) to enhance the mechanical properties of rubber nanocomposites has rarely been attempted. The main problem associated with using SiC nanoparticles as a reinforcing natural rubber (NR) filler compound is poor dispersion of SiC in the NR matrix because of their incompatibility. To solve this problem, rubber nanocomposites were prepared with SiC that had undergone surface modification with azobisisobutyronitrile (AIBN) and used as a filler in blends of epoxidized natural rubber (ENR) and natural rubber. The effect of surface modification and ENR content on the curing characteristics, dynamic mechanical properties, morphology and heat buildup of the blends were investigated. The results showed that modification of SiC with AIBN resulted in successful bonding to the surface of SiC. It was found that modified SiC nanoparticles were well dispersed in the ENR/NR matrix, leading to good filler‐rubber interaction and improved compatibility between the rubber and filler in comparison with unmodified SiC. The mechanical properties and heat buildup when modified SiC was used as filled in ENR/NR blends were improved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45289.     

Synthesis and characterization of polyaniline–organoclay nanocomposites

Polyaniline (PANI)–organoclay nanocomposites were prepared. Intercalation of aniline monomer into montmorillonite (MMT) modified by polyoxyalkylene was followed by subsequent oxidative polymerization of the aniline in the interlayer spacing. The organoclay was prepared by cation exchange process between sodium cation in MMT and onium ion in four different types of polyoxyalkylene diamine and triamine with different molecular weight. Infrared spectra confirm the electrostatic interaction between the positively charged onium group (NH₃⁺) and the negatively charged surface of MMT. X‐ray diffraction analysis provides a structural information. The absence of d₀₀₁ diffraction band in the nanocomposites was observed at certain types and contents of organoclay. Scanning electron microscopy and transmission electron microscopy were employed to determine the dispersion of the clay into PANI. The thermal degradation behavior of PANI in the nanocomposites has been investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites are more thermally stable than pristine PANI. This improvement is attributed to the presence of nanolayers with high aspect ratio acting as barriers, thus shielding the diffusion of degraded PANI from the nanocomposites. The electrical conductivity of the nanocomposites was increased 30 times more than that of pure MMT at a certain concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface modification of MWCNT to improve the mechanical and thermal properties of natural rubber nanocomposites

In this study, we focused on the synergistic effect between carbon black (CB) and multiwall carbon nanotube (MWCNT) hybrid fillers. In particular, the surface modification of pristine MWCNT (P-MWCNT) via an acid (oxidation) treatment was used to improve their dispersion, as well as the mechanical and thermal properties of their corresponding natural rubber (NR)-based nanocomposites. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were carried out to determine the presence of functional groups on the oxidized MWCNT (O-MWCNT). After vulcanization, dynamic mechanical analysis (DMA), tensile properties, hardness, thermal conductivity, swelling behaviour in toluene and SEM characterizations were performed on both NR/CB/P-MWCNT- and NR/CB/O-MWCNT-based nanocomposites. The results showed the positive effect of MWCNT surface oxidation on the fillers' dispersion and nanocomposites' properties.     

机械共混法制备剥离型天然橡胶蒙脱土纳米复合材料及其微观结构与力学性能

采用常规的双辊混炼法制备出了剥离型的天然橡胶/蒙脱土纳米复合材料。利用透射电子显微镜观察复合材料的亚微观形态,测试了材料的物理性能,研究了材料的应力-应变变化曲线,表征了材料的加工流动性变化,测试结果表明制备出了剥离型纳米复合材料,低填充量(小于3份)时力学性能大大提高,应力-应变明显变化,加工流动性略有不同。     

Melt‐compounded natural rubber nanocomposites with pristine and organophilic layered silicates of natural and synthetic origin

Composites based on natural rubber (NR) and containing organophilic and pristine layered silicates of natural and synthetic origin were produced by melt compounding and sulfur curing. The curing, thermomechanical, and mechanical properties of the mixes, which contained 10 phr (parts per hundred parts of rubber) silicates, were determined. The dispersion of the silicates was studied by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Organophilic clays accelerated the sulfur curing of NR, which was believed to occur because of a complexation reaction in which the amine groups of the clay intercalants participated. The property improvements caused by the fillers were ranked as follows: organophilic clays > pristine synthetic layered silicate (sodium fluorohectorite) > pristine natural clay (purified sodium bentonite) > precipitated nonlayered silica (used as a reference). This was attributed to partial intercalation of the organophilic clay by NR on the basis of XRD and TEM results and to the high aspect ratio of the fluorohectorite. Apart from intercalation, severe confinement (i.e., the collapse of the interlayer distance) of the organoclays was observed. This peculiar feature was traced to the formation of a zinc coordination complex, which extracted the amine intercalant of the organoclays, thus causing the collapse of the layers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 813–819, 2004     

Morphology and properties of polymer/organoclay nanocomposites based on poly(ethylene terephthalate) and sulfopolyester blends

Poly(ethylene terephthalate) (PET) nanocomposite films containing two different organoclays, Cloisite 30B^® (C30B) and Nanomer I.28E^® (N28E), were prepared by melt blending. In order to increase the gallery spacing of the clay particles, a sulfopolyester (PET ionomer or PETi) was added to the nanocomposites via a master‐batch approach. The morphological, thermal and gas barrier characteristics of the nanocomposite films were studied using several characterization techniques such as scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, rheometry and oxygen permeability. PET and PETi were found to form immiscible polymer blends and the nanoparticles were preferentially located in the PETi dispersed phase. A better dispersion of clay was obtained for nanocomposites containing N28E with PETi. On the contrary, for nanocomposites containing C30B and PETi, the number of tactoids increased and the clay distribution and dispersion became worse than for C30B alone. Overall, the best properties were obtained for the PET/C30B nanocomposite without PETi. Higher crystallinity was found for all nanocomposite films in comparison to that of neat PET. © 2012 Society of Chemical Industry     

Physical properties and cure characteristics of natural rubber/nanoclay composites with two different compatibilizers

The effects of epoxidized natural rubber (ENR) and maleic anhydride‐grafted polybutadiene (PB‐g‐MA) as compatibilizers to rubber formulations with and without organo‐modified layered silicates are investigated. The physical properties and curing characteristics of composites are studied by moving die rheometer, rubber process analyzer, tensile, tear, and hardness testing. The state of organoclay intercalation was determined by X‐ray diffraction method. The addition of compatibilizers, especially ENR 50, results in further intercalation or exfoliation of the organoclay that increased the clay dispersion in the rubber matrix. ENR 50 with organo‐modified clay improves the physical properties and changes the curing profile. The addition of PB‐g‐MA without organoclay increases the tensile strength (σ_max) by increasing the stock viscosity of the rubber compound. Interestingly, simultaneous increase in hardness and σ_max is achieved in the presence of both compatibilizers, a characteristic that is difficult to achieve and sometimes required in rubber processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterisation of polyamide–polyimide organoclay nanocomposites

BACKGROUND: Ternary nanocomposites containing an organomodified layered silicate polyimide additive within a polyamide matrix have been investigated to gain greater insight into structure–property relationships and potential high‐temperature automotive applications. RESULTS: Polyamide nanocomposite blends, containing 3 wt% of organoclay, were prepared and compared with organoclay‐reinforced polyamide and neat polyamide. Nanoclay addition significantly increased heat distortion temperature, as well as both the tensile and flexural moduli and strength. The addition of polyimide demonstrated further increases in heat distortion temperature, glass transition temperature and the flexural and tensile moduli by about 17, 21 and 40%, respectively. The tensile and flexural strengths were either unaffected or decreased modestly, although the strain‐to‐failure decreased substantially. Morphological studies using transmission electron microscopy (TEM) and X‐ray diffraction showed that the nanoclay was dispersed within the ternary blends forming highly intercalated nanocomposites, regardless of the presence and level of polyimide. However, TEM revealed clay agglomeration at the polyamide–polyimide interface which degraded the mechanical properties. CONCLUSIONS: A range of improvements in mechanical properties have been achieved through the addition of a polyimide additive to a polyamide nanocomposite. The decrease in ductility, arising from the poor polyamide–polyimide interface and nanoclay clustering, clearly requires improving for this deficiency to be overcome. Copyright © 2008 Society of Chemical Industry     

高性能橡胶/黏土纳米复合材料的制备与结构

研究了硬脂酸(SA)处理有机黏土(OC)制备橡胶/黏土纳米复合材料的结构与性能,并与未处理的OC制备的纳米复合材料进行了对比。结果表明,SA上的—COOH与OC片层表面的—OH发生了酯化反应,促使SA插层进入OC层间,使层间距扩大。采用SA处理OC制备出分散相态细致均匀、力学性能优异的丁腈橡胶/黏土(NBR/SA-OC)纳米复合材料;当OC与SA的质量比为10∶6时,纳米复合材料的性能最优。用带有极性和反应官能团的橡胶制备橡胶/黏土纳米复合材料,OC的分散性更好,与未处理的OC制备的纳米复合材料相比力学性能更优。     

The effect of organoclay on the mechanical properties and morphology of injection‐molded polyamide 6/polypropylene nanocomposites

Nanocomposites containing a thermoplastic blend and organophilic layered clay (organoclay) were produced by melt compounding. The blend composition was kept constant [polyamide 6 (PA6) 70 wt % + polypropylene (PP) 30 wt %], whereas the organoclay content was varied between 0 and 10 wt %. The mechanical properties of the nanocomposites were determined on injection‐molded specimens in both tensile and flexural loading. Highest strength values were observed at an organoclay content of 4 wt % for the blends. The flexural strength was superior to the tensile one, which was traced to the effect of the molding‐induced skin‐core structure. Increasing organoclay amount resulted in severe material embrittlement reflected in a drop of both strength and strain values. The morphology of the nanocomposites was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersion X‐ray analysis (EDX), and X‐ray diffraction (XRD). It was established that the organoclay is well dispersed (exfoliated) and preferentially embedded in the PA6 phase. Further, the exfoliation degree of the organoclay decreased with increasing organoclay content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 175–189, 2004