Cellulose nanofibres and cellulose nanowhiskers based natural rubber composites: Diffusion,sorption, and permeation of aromatic organic solvents

This article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and p‐xylene in natural rubber nanocomposite membranes containing cellulose nanofibres (CNFs) and cellulose nanowhiskers (CNWs) isolated from bamboo pulp. The solvent molecules act as molecular probes to study the diffusion, sorption, and permeation through the nanocomposites, and provide information on the nanocomposite structure and matrix–filler interactions. Both the nanocelluloses were found to decrease the uptake of aromatic solvents in nanocomposite membranes, but the effect was more significant in the case on nanofibers compared to nanowhiskers. Furthermore, the uptake decreased with increased penetrant size; being the highest for benzene and the lowest for p‐xylene. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated. Comparison of the experimental values of equilibrium solvent uptake with the predicted values indicated that both the nanocelluloses have restricted the molecular mobility at the interphase and thereby decreased the transport of solvents through the materials; being more significant for nanofibers. The results showed that both the used cellulosic nanomaterials act as functional additives capable of manipulating and tailoring the transport of organic solvents through elastomeric membranes, even at concentrations as low as 2.5 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Aromatic liquid transport through filled EPDM/NBR blends

The sorption and diffusion characteristics of 70/30 ethylene propylene diene monomer rubber (EPDM)/acrylonitrile butadiene rubber (NBR) blends loaded with black fillers such as ISAF (intermediate super-abrasion furnace), HAF (high abrasion furnace) and SRF (semi-reinforcing furnace) have been investigated. The penetrants used were benzene, toluene and xylene. Filled samples have been found to show a reduced solvent uptake compared to the unfilled sample for the given blend ratio. The observations have been correlated with the morphology of the systems. Blends loaded with ISAF exhibited the lowest liquid uptake among black filled systems which has been attributed to the better filler reinforcement and enhanced crosslink density of the matrix. The extent of particulate filler reinforcement has been studied by using Kraus theory. The unfilled and filled systems have been found to exhibit non-Fickian transport behaviour. The effect of fillers on the cure and mechanical properties of the blends have also been investigated. Among the black filler loaded systems used, the ISAF mix showed the highest maximum torque value. The improvement in the cure and mechanical properties has been observed to be the highest for ISAF filled samples followed by HAF and SRF filled systems, which is in compliance with the observation from the sorption studies.     

Impact of filler geometry and surface chemistry on the degree of reinforcement and thermal stability of nitrile rubber nanocomposites

The morphological, mechanical, and thermal stability of Nitrile rubber nanocomposites reinforced with fillers such as layered silicate (LS), calcium phosphate (CP) and titanium dioxide (TO) having different particle size and chemical nature were analyzed. The results revealed that the filler geometry played an important role on the mechanical and thermal stability of the composites. Calcium phosphate and titanium dioxide filled systems showed comparatively better mechanical and thermal stability compared to neat rubber. The activation energy needed for the thermal degradation was found to be higher for layered silicate filled system. DSC (Differential Scanning Calorimetry) analysis revealed a change in the T_g values as a result of the addition of fillers. This was more prominent with the case of layered silicate filler addition in comparison with calcium phosphate and titanium dioxide. The heat capacity values of the nanocomposites were carefully evaluated. The (∆Cp) with values obtained for different nanocomposites were correlated with the degree of reinforcement. It can be assumed that more polymer chains are attached on to the surface of the filler and there exists an immobilized layer around the filler surface and the layers do not take part in the relaxation process. The FTIR spectrum of the different samples highlighted the possible filler matrix interaction. The filler dispersion and aggregation in the polymer matrix were analyzed using X-ray diffraction studies (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM).     

Mechanical,thermophysical, and diffusion properties of TiO2‐filled chlorobutyl rubber composites

The mechanical and thermophysical properties of TiO₂‐filled chlorobutyl rubber composites were investigated. These materials exhibited enhanced mechanical properties such as increased modulus, tensile strength, and hardness. The morphology of filler dispersion in the matrix was analyzed by scanning electron microscopy and atomic force microscopy. Moreover, the effect of TiO₂ content on the molecular transport of solvents was examined by means of degree of swelling, volume fraction of rubber, penetration rate of solvent, mean diffusion coefficient, etc. A periodic method was used to estimate the thermophysical behavior of samples. It was shown that the thermal conductivity and diffusivity of composites increase with increasing of TiO₂ filler content. Finally, the utilization of the material as effective chemical protective clothing against volatile organic chemicals was analyzed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Evaluation of kinetics and transport mechanism of solvents through natural rubber composites containing organically modified gadolinium oxide

The solvent transport properties of the prepared composites were analysed using solvents of varying cohesive energy density and the effect of both modified as well as unmodified filler on the sorption and diffusion behaviour of NR vulcanisates has been investigated. It is found that the equilibrium uptake decreases with increase in filler content, as anticipated owing to the restrictions offered by the filler for solvents to diffuse into the polymer matrix. The mechanism of transport in natural rubber composites was carefully tracked and it was found to exhibit an anomalous mode of solvent transport where the polymer relaxation is in par with the rate of diffusion. Theoretical modelling of the swelling parameters was done and the results were found to be in agreement with existing models. The excellent swelling resistance coupled with the simultaneous improvement in mechanical properties would definitely pave way for the utilisation of these composites as barrier membranes.     

Mechanical and swelling behavior of green nanocomposites of natural rubber latex and tubular shaped halloysite nano clay

Nanocomposites based on natural rubber latex as the matrix and naturally occurring tubular shaped nanoclay, halloysite nanotubes (HNTs) as the reinforcing phase were prepared through co‐coagulation method. XRD, morphology, mechanical, and solvent transport properties of the nanocomposites with special reference to weight percentage of nanoclay were analyzed and discussed in detail. Matrix–filler interaction was estimated from Kraus, Cunneen–Russell, and Lorentz–Park plots. Theoretical estimation of reinforcement effect revealed a better interaction between rubber and filler at lower concentration of filler. At higher loading properties decreased due to the formation of filler–filler networks than polymer–filler networks resulting in the reduction of aspect ratio of fillers. Properties of nanocomposites depend on the aspect ratio and volume fraction of reinforcing filler. Morphological analyses of the nanocomposites were done in detail from scanning electron micrographs. Theoretical modulus of nanocomposites was computed using different composite theories by varying the aspect ratio of filler and compared with experimental data. A good agreement between experimental and theoretical values was observed at lower concentration of filler. Solvent transport properties of nanocomposites were found to decrease at lower concentration of HNT because of the tortuosity of the path. POLYM. COMPOS., 37:602–611, 2016. © 2014 Society of Plastics Engineers     

Mechanochemical preparation of devulcanized ground fluoroelastomers for the enhancement of the thermal stability of nitrile–butadiene rubber vulcanizates

Mechanochemically devulcanized ground fluoroelastomer (FKM) was used as a low‐cost functional additive for the enhancement of the thermal stability of nitrile–butadiene rubber (NBR) vulcanizates. Without the use of any chemicals, the stress‐induced mechanochemical devulcanization of ground FKM was achieved through solid‐state mechanochemical milling at ambient temperature. The sol fraction of the ground FKM was increased from its original 1.4 to 19.8% after milling; this confirmed the realization of the mechanochemical devulcanization of FKM. Moreover, the oxygen‐containing polar groups on the surface of the mechanochemically milled FKM benefitted its interfacial adhesion with the polar NBR matrix. The curing characteristics and mechanical properties of the devulcanized, FKM‐filled NBR vulcanizates were investigated and compared with those of the untreated FKM‐filled NBR vulcanizates. The results show that the mechanical properties of the devulcanized FKM‐filled NBR vulcanizates were much better than those of the untreated FKM‐filled NBR vulcanizates. The presence of the reclaimed FKM significantly increased the onset degradation temperature of the NBR vulcanizates as a result of the improved polymer–filler interaction, uniform dispersion, and high thermal stability of the reclaimed FKM. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Transport studies of peanut shell powder reinforced natural rubber composites in aromatic solvents

This article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and xylene in natural rubber (NR) composite membranes containing peanut shell powder (PSP) as filler at different temperatures by conventional weight‐gain experiments. PSP used in compounding the NR was processed in two particle sizes. The solvent swelling characteristics of NR composites containing both untreated and alkali‐treated fillers were investigated. The computed sorption characteristics were discussed in terms of PSP content, particle size, nature of solvent, and temperature. All the NR‐PSP composites were found to decrease with the uptake of aromatic solvents than NR, but the effect was more significant in the case of alkali‐treated PSP composites. Furthermore, the uptake of solvent decreased with decrease in penetrant size. The estimated Arrhenius activation energies (E_D) for the processes of sorption, diffusion, and permeation showed that E_D was generally highest in xylene at the filler contents investigated. The thermodynamic parameters of the sorption process were also evaluated. The relationship between the transport behavior and the morphology of the system was examined. The mechanism of diffusion is found to be close to Fickian trend in toluene and xylene and Fickian trend in benzene. Comparison between theoretical and experimental diffusion results was made to understand the mechanism of diffusion. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Transport and solvent sensing characteristics of styrene butadiene rubber nanocomposites containing imidazolium ionic liquid modified carbon nanotubes

Obtaining strong interfacial interaction between filler and polymer matrix is very crucial for the fabrication of polymer nanocomposites with superior performance. Present study is aimed to fabricate high performance styrene butadiene rubber (SBR) nanocomposites with imidazolium type ionic liquid modified multiwalled carbon nanotube (MWCNT). Ionic liquid facilitates the dispersion of MWCNT in rubber matrix and it is obvious from transmission electron microscopy images. Diffusion of toluene through SBR nanocomposite membranes has been investigated as a function of surface modified MWCNT (f-MWCNT) content to analyze the chain dynamics and filler-polymer interactions. O₂ gas barrier effect of nanocomposites with special reference to the filler loading is explored. The substantial improvement in the barrier effect in presence of filler interpreted on the grounds of a theoretical model describing permeability of heterogeneous systems. Finally solvent sensing characteristics of prepared nanocomposites are also analyzed and it is observed that prepared nanocomposites can be used as a flexible solvent sensor.     

Property optimization in nitrile rubber composites via hybrid filler systems

Nitrile rubber–PVC composites having carbon black and mica fillers in different compositions as hybrid reinforcements were studied. The effect of the silane treatment of mica, the degree of replacement, and the molecular architecture of nitrile rubbers on static‐dynamic mechanical, swelling, and curing behavior of the resultant composites are discussed. The results showed that an increase in unsilanized and silanized mica total filler resulted in increased toughness values and decreased swelling in organic solvents together with increased vibrational damping capacity for all types of nitrile rubber composites, depending on the polyacrylonitrile content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 366–374, 2001     

Development of hydroxyapatite nanoparticles reinforced chlorinated acrylonitrile butadiene rubber/chlorinated ethylene propylene diene monomer rubber blends

Hydroxyapatite nanoparticles (HA) reinforced polymer blend based on chlorinated nitrile rubber (Cl-NBR) and chlorinated ethylene propylene diene monomer rubber (Cl-EPDM) were prepared. Resulting blend composites were analyzed with regard to their rheometric processing, crystallinity, glass transition temperature (T_g), mechanical properties, oil resistance, AC conductivity, and transport behavior. The decrease in optimum cure time with the addition of HA is more advantageous for the development of products from these blend nanocomposites. The XRD, FTIR, and SEM confirmed the attachment and uniform dispersion of HA nanoparticles in the Cl-NBR/Cl-EPDM blend. The good compatibility between polymer blend and nanoparticles was also deduced by the formation of spherically shaped HA particles in the blend matrix determined by TEM analysis. DSC analysis showed an increase in T_g of the blend with the filler loading. The addition of HA particles to the blend produced a remarkable increase in tensile and tear strength, hardness, AC conductivity, abrasion, and oil resistance. The diffusion of blend composites was decreased with an increase in penetrant size. The diffusion mechanism was found to follow an anomalous trend. Among the blend composites, the sample with 7 phr of HA not only showed good oil and solvent resistance but also a remarkable increase in AC conductivity and mechanical properties.     

Contribution of physico-chemical properties of interfaces on dispersibility, adhesion and flocculation of filler particles in rubber

Reinforcing fillers are added to elastomeric compounds to improve and adjust several mechanical, dynamical, tribological, etc. properties with respect to different applications, i.e. for automotive tires, or technical rubber goods. Carbon black and precipitated silica are widely used as rubber reinforcing fillers; however, some new classes of nanosized substances like organophilic modified clay or carbon nanotubes are presently intensive studied as possible future filler systems in combination with carbon black or silica.An important parameter for the dispersibility and compatibility of the filler in the polymer matrix of rubber compounds is the surface energy and surface polarity of the solid filler particles. Therefore, we systematically measured and compared the dynamic contact angles of a collection of different filler types (carbon blacks, silica, carbon nanotubes and organoclays) using the Wilhelmy method, whereby the particles were fixed as a thin layer at a double-sided adhesive tape. From the contact angle values the polar and disperse part of the surface energies of the filler particles were calculated by fitting Fowkes formula. For an estimation of the compatibility of the fillers with different types of rubber polymers we additionally analyzed the surface energy and polarity of the gum (unfilled) elastomers. From the evaluated surface energies and polarities, thermodynamic predictors for the dispersibility (enthalpy of immersion), the adhesion between filler particles and polymer matrix in the nanocomposite, and for the flocculation behaviour of the particles in a rubber matrix (difference in the works of adhesion) were derived. These thermodynamic predictors improve considerably the compounding process of novel rubber nanocomposites with respect to target-oriented adjustment of rubber properties.     

聚氯乙烯/丁腈胶粉共混型热塑性弹性体

将聚氯乙烯与废丁腈胶粉经高温机械共混，制备了动态交联的共混型热塑性弹性体。讨论了共混比，硫化体系及其用量，废胶粉品种（丁腈胶粉，轮胎胶粉）等因素对热塑性弹性体性能的影响，同时将聚氯乙烯／丁腈胶粉与聚氯乙烯／轮胎胶粉制备的共混型热塑性弹性体的性能进行了比较。结果表明，以聚氯乙烯100份（质量份，下同），邻苯二甲酸二辛酯50份，丁腈胶粉80份，丁腈橡胶20份，过氧化二异丙苯0．5份，氧化锌5份及适量其他助剂可制得综合性能较好的共混型热塑性弹性体。扫描电镜结果显示该共混型热塑性弹性体具有较好的相容性。     

Properties of silica‐filled styrene‐butadiene rubber compounds containing acrylonitrile‐butadiene rubber: The influence of the acrylonitrile‐butadiene rubber type

Because silica has strong filler‐filler interactions and adsorbs polar materials, a silica‐filled rubber compound exhibits poor dispersion of the filler and poor cure characteristics in comparison with those of a carbon black‐filled rubber compound. Acrylonitrile‐butadiene rubber (NBR) improves filler dispersion in silica‐filled styrene‐butadiene rubber (SBR) compounds. The influence of the NBR type on the properties of silica‐filled SBR compounds containing NBR was studied with NBRs of various acrylonitrile contents. The composition of the bound rubber was different from that of the compounded rubber. The NBR content of the bound rubber was higher than that of the compounded rubber; this became clearer for NBR with a higher acrylonitrile content. The Mooney scorch time and cure rate became faster as the acrylonitrile content in NBR increased. The modulus increased with an increase in the acrylonitrile content of NBR because the crosslink density increased. The experimental results could be explained by interactions of the nitrile group of NBR with silica. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 385–393, 2002     

Influence of nanoclay‐carbon black hybrid fillers on cure and properties of natural rubber compounds

The influence of organically modified nanoclay‐carbon black (CB) hybrid filler on the curing behavior of natural rubber (NR) was explored in this investigation. Here an effort was paid to understand the curing kinetics of organomodified nanoclay filled rubber compounds. On the basis of two different types of modified clay, NR nanocomposites were prepared and cured by a conventional vulcanization system. A faster curing rate and lower torque values were found when the modification was done by quaternary ammonium compounds. The activation energy of the rubber curing process decreased with the incorporation of nanoclay. In addition, it was revealed that the quaternary ammonium compounds used as modifier in the clay show a plasticization effect. Additionally, X‐ray diffraction studies indicated, that the basal spacing of the clay minerals was increased in both cases after incorporation in the rubber matrix. The dynamic mechanical analysis using a strain sweep mode showed that the Payne effect decreases because of an improved dispersion of CB induced by the presence of nanoclay. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Safe amine based zinc dithiocarbamates for the vulcanization of carbon black reinforced natural rubber

Binary combination of three safe amine based synthesized zinc dithiocarbamates (ZDC), namely zinc (N‐benzyl piperazino) dithiocarbamate (ZBPDC), zinc (N‐ethyl piperazino) dithiocarbamate (ZEPDC), and zinc (N‐phenyl piperazino) dithiocarbamate (ZPPDC) with mercapto benzothiazole disulfide (MBTS) as an effective accelerator system for the vulcanization of carbon black (N330, N550, and N774) filled natural rubber (NR) composites are studied. A comparison between the safe amine based zinc dithiocarbamates with the unsafe zinc dimethyl dithiocarbamate (ZDMC) in the light of mechanical and aging resistance behavior, introduces the non carcinogenic rubber additives in the filled vulcanization of rubber. Both accelerator and filler have the major importance for improving the mechanical as well as aging resistance behavior of the resultant vulcanizate. Variation in the filler and also filler to oil ratio are done to optimize the mechanical properties. SEM studies of different types of filler with different amounts show that N330 at 30 phr loading composites forms more homogeneity and less aggregated structures. Natural rubber systems with N330 carbon black show the best results with respect to tensile strength, but after the aging N774 carbon black filled system indicates better retention in the tensile strength. ZPPDC‐MBTS accelerated vulcanizate shows the better age resistance behavior than ZDMC‐MBTS accelerated vulcanizate. From both the points of age resistance and mechanical properties, ZBPDC‐MBTS accelerator system is the suitable substitute for ZDMC‐MBTS accelerated system in the filled vulcanization of natural rubber composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39988.     

Role of in situ generated silica for rubber science and technology

Filled rubbers have a long history in rubber technology. Filler morphology in the rubber matrix significantly influences the performance of filled rubber products. Therefore, we have to achieve a certain morphology of filler in the rubbery matrix in order to enjoy good reinforcement. However, it has not been sufficiently known what kind of morphology is necessary for the reinforcement, because preparations of adequate models for the characterization of filler morphology have been difficult. The in situ silica filling of the rubber matrix can be modeled for the preparations. In this paper, the characteristic features of in situ silica generated in diene rubbers are reviewed, citing recent reports. Two important models are presented. One is a homogeneous silica filling in situ, producing soft rubber nanocomposites. The other is the formation of an in situ silica filler network, creating stiff rubber nanocomposites. The controlled in situ silica filling is useful to evaluate the reinforcement effect of filler in a rubber matrix. © 2016 Society of Chemical Industry     

Effect of polymer–clay interaction on solvent transport behavior of fluoroelastomer–clay nanocomposites and prediction of aspect ratio of nanoclay

Diffusion and sorption of methyl ethyl ketone and tetrahydrofuran through fluoroelastomer‐clay nanocomposites were investigated in the temperature range of 30–60°C by swelling experiments. Slightly non‐Fickian transport behavior was found for these nanocomposites, having variation of type of nanoclay and loading. Different transport parameters depend on the size and shape of the penetrant molecules. The results were used to study the effect of nanoclay on the solvent transport‐properties of nanocomposites and their interactions with solvents. The diffusion coefficient of methyl ethyl ketone at 30°C for neat rubber was 1.43 × 10^?8 cm² s^?1, while those of the unmodified and the modified clay filled samples at 4 phr loading were 0.24 × 10^?8 and 0.50 × 10^?8 cm² s^?1, respectively. At 8 and 16 phr loading of the unmodified clay, it was found to be 0.44 × 10^?8 and 0.64 × 10^?8 cm² s^?1, respectively. The samples were also reswelled after deswelling. Surprisingly, transport behavior became Fickian on reswelling. Interestingly, ratio of diffusion coefficients of the filled system to the neat system was found to be almost same for the first time swelling and reswelling experiments. The results showed that better polymer‐clay interaction in the case of the unmodified‐clay filled nanocomposites is responsible for enhanced solvent‐resistance property. From the permeation data, for the first time, aspect ratio of nanoclays in different composites was calculated and found to have good correlation with the morphology data obtained from transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermo-mechanical characterization of fumed silica-epoxy nanocomposites

DGEBA-based epoxy nanocomposites filled with various amounts of fumed silica nanopowders (10, 20 and 30 phr corresponding to 3.3, 6.4 and 9.2% by volume) were prepared by a solvent assisted dispersion procedure. The obtained nanocomposites were analyzed by means of differential scanning calorimetry, dynamic-mechanical thermal analysis, uniaxial tensile tests on un-notched samples and three-point bending tests on notched samples.

All the thermal and mechanical properties showed non-monotonic trends with relative minima as the silica content increased. A trend inversion in the physical properties was detected at the highest filler level tested, which was not previously observed for epoxy systems filled with comparable amounts of unmodified silica. The behavior could be explained by considering a reduction of cross-linking degree of the epoxy matrix due to the huge viscosity increase induced by the silica nanoparticles during composites preparation. On the other hand, the physical immobilization of the cross-linked matrix can be supposed to be responsible for the inversion of the properties trend at the highest filler level, which is presumably very close to the percolation threshold.     

溶剂对丁腈橡胶溶解、尺寸、结构和催化加氢的影响研究

丁腈橡胶（NBR）是由丁二烯和丙烯腈共聚而制得的一种重要的合成橡胶,而由NBR选择性加氢制得的氢化丁腈橡胶（HNBR）,不仅保持了NBR原有的耐油和耐磨性,其耐侯性、耐臭氧性等均得到极大改善,被广泛用于武器部件、航天用密封件等领域,是不饱和聚合物化学改性领域的一个重要研究课题。本文采用纳米粒度仪、乌氏黏度计、傅里叶变换红外等表征手段,结合密度泛函理论计算（DFT）,系统研究了溶剂性质对NBR在溶剂中的溶解行为、尺寸分布、分子结构及催化加氢性能等的影响。实验结果表明强亲电子溶剂不能溶解NBR,给电子溶剂及部分弱亲电子溶剂能较好地溶解NBR,特别是在酮类溶剂中,NBR粒径小且分布集中。DFT结果表明相比于气相氛围,在所有溶剂氛围中NBR链段里双键的键长均有所增长,且随着溶剂的极性增加而呈增长的趋势,NBR的偶极矩也随着溶剂极性增加而增加。特别是在酮类溶剂中,受溶剂效应的影响NBR分子的HOMO轨道由分子边缘向分子内部移动,表明对链段内部CC双键可能产生积极的影响。加氢结果表明在给电子溶剂中的加氢效果均优于弱亲电子溶剂,但无论选择何种溶剂,对NBR中CC双键的加氢选择性均为100%。该研究为NBR非均相溶液加氢体系中溶剂的筛选提供了理论依据。