جستجوی مقالات مرتبط با کلیدواژه « نانوخاک رس » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

In this study, the effect of adding nanoclay and carbon black to SBR on curing behavior, oil absorption and mechanical properties such as tensile strength and strain at break, hardness and abrasion resistance were investigated. At the end, we investigated the effect of carbon black (CB) and replacement a portion of CB with modified clay on tensile strength, elongation at break, hardness and abrasion resistance of SBR. Tensile strength and elongation at break were significantly improved upon addition of nanoclay and the optimum amount of nanoclay was 10 phr. The rheometric test indicated that as the nanoparticles loading increases, the scorch time and optimum cure time decrease and the cure rate increases. Adding nanoparticles to the polymer matrix improved the abrasion resistance and the abrasive volume of the samples decreased significantly with addition of nanoclay content. Adding 10 phr nanoclay to SBR containing 20 phr carbon black elongation at break and tensile strength exhibited a siginificant increase of 300% and 3 MPa respectively indicationg synergisty of carbon black and nanoclay in improving mechanical properties of SBR. Upon replacement of 10 phr CB with clay tensile strength, elongation at break and hardness improved 30%, 24% and 5% respectively and oil absorption and abrasive volume decreases 23% and 11% respectively.

Polymeric fuel tanks have considerably lighter weight in comparison to metal tanks. However, a drastic reduction in evaporation of gasoline vapor from these fuel tanks is needed. The use of nanoparticles to produce polymeric nanocomposites can be an effective way to reduce the extent of permeability and enhance mechanical and processing properties. The planar nanoclay platelets have a substantial potential in enhancement of barrier properties of polymers. It should be noted that the type of compatibilizer plays a remarkable role in the dispersion state of nanoclay.

Nanocomposite samples were prepared using melt blending method in a twin screw extruder. In order to find the optimized formulation, the effects of nanoclay content, compatibilizer type, compatibilizer content and screw speed were assessed using response surface methodology (RSM). The optimization was performed based on the lowest gas permeability, favorable impact strength and melt flow index.

In general, the increment of nanoclay content led to improvement of the barrier properties, while compatibilizer content had an optimal level. The results of optimization revealed that the sample containing 10 wt% of maleic anhydride grafted polyethylene as compatibilizer and 6 wt% of organoclay (Cloisite 20A) possesses the optimum properties. Indeed, this sample showed an optimum balance between different properties and an exfoliated morphology for nanoclay platelets was obtained. On the other hand, although the oxidized polyethylene wax with high viscosity showed the lowest gas permeability, the impact strength and melt flow index were totally undesirable. Nanocomposite samples containing low viscosity oxidized polyethylene wax exhibited the highest gas permeability.

Biopolymers are considered to be the most promising alternatives to petroleum-based polymers, because they can greatly reduce the dependence on oil and, consequently, environmental pollution. As one of the most abundant biopolymers in nature, chitosan has unique properties, including renewablility, reproducibility, biodegradability, non-toxicity and excellent flm-forming performance. These properties have made this biopolymer usable in food coatings to extend the shelf life and use in the textile, pharmaceutical, and paper industries. These types of polysaccharide flms have had limited application due to their hydrophilic nature and poor mechanical properties. Incorporating of biopolymer-based nanomaterials, known as nanocomposite flms, is one of the effective methods to improve the mechanical properties of biopolymer flms. In this regard, the purpose of this study is to investigate the effect of different concentrations of nanofller on the mechanical properties of chitosan-based flms. Nanoparticles such as graphene, carbon nanotubes, nanoclay, and nanocellulose are used as reinforcement in polymer composites. Also, the mechanical properties of chitosan based nanocomposites depend on three main factors. Also, the mechanical properties of chitosan-based nanocomposites depend on three main factors, such as the properties of polymer matrix and nano-reinforcing agent. These include the properties of the polymer matrix and the nanotechnical phase of the manufacturer, as well as interfacial interaction between fller surface and matrix polymer. In addition, for the specifc nano-reinforcement phase and polymer matrix, the properties of polymer nanocomposite are highly dependent on the dispersion and distribution of the nanoparticles at the continuous matrix phase surface.

Hypothesis: Among available bioplastics, polylactide exhibits superior properties, including high modulus, good processability, and compostability. However, some disadvantages, such as brittleness and low thermal resistance limit its application in some fields. In order to overcome the limitations of polylactide, it is usually modified by addition of nanoparticles or by blending with other thermoplastics. Polylactide/polyethylene (PLA/PE)-based nanocomposites were prepared using 4 phr commercially modified montmorillonite (Cloisite 30B or Cloisite 20A) and polyethylene-g-maleic anhydride compatibilizer (PE-g-MA) by melt blending technique. The structure and morphology development and also the cold crystallization kinetics of the samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC) techniques and melt linear and non-linear viscoelastic measurements. Findings: The XRD results showed that polymer intercalation into the clay galleries in PLA/PE/Cloisite 30B was higher than that in PLA/PE/Cloisite 20A. The rheological results along with the calculated data of wetting parameter showed that Cloisite 20A in blend nanocomposite could reduce the droplet size through three different mechanisms a: localization of the organoclay in the interface b: increasing the viscosity of PLA matrix and c: decreasing the extent of coalescence process. The FE-SEM micrographs showed that the nodular morphology of PLA/PE/Cloisite 30B changed to a non-nodular morphology in PLA/PE/Cloisite20A. The melt linear and non-linear viscoelastic measurements showed that a stronger 3D-network structure was formed in PLA/PE/Cloisite 20A compared to that in PLA/PE/Cloisite 30B. It was implied that the crystallization rate followed the Avrami equation with the exponent n of around 2. The results also showed that the addition of compatibilizer (PE-g-MA) into PLA/PE/Cloisite 20A or PLA/PE/Cloisite30B decreased modified crystallization rate constant (Zc), because the cold crystallization rates of compatibilized blend nanocomposites were lower than those of uncompatibilized blend nanocomposites and the role of compatibilizer in the transfer of partial organoclays from PLA matrix into the droplets.

Bitumen as a really important material road construction shows very attractive properties. Modification of bitumen by polymers increases the service life of the asphalt pavement. In order to improve the engineering properties of bitumen, both chemical and physical methods have been used which the physical methods, because of their simplicity, are more commonly employed. In physical modification, some materials such as polymers, are usually used. Polysulfide is one of the polymers that has recently attracted the interest of industries. It is interesting that this polymer which is made of heavy chlorinated petrochemical was tested to reduce the costs which are associated with bitumen modification as well as helping to alleviate the problem of waste accumulation. In this investigation, a polysulfide polymer derived from waste (waste liquid polysulfide polymer, WLPSP), in pure form and in combination with nanoclay was used to modify bitumen. The amounts of polymer added to the bitumen were 1, 3 and 5 weight percents. In the samples modified with both polymer and nanoclay, the amount of nanoclay was fixed at 2 wt%. The WLPSP polymer not only increased the softening point but also reduced the penetration of bitumen, resulting in improvement of the properties of bitumen at high temperatures. These effects could be observed for all samples of bitumen-polymer-clay and bitumen-nanoclay blends. The bitumen modified with nanoclay-polymer and nanoclay alone showed a further reduction in penetration upon WLPSP modification. The penetration index (PI) of bitumen increased, indicating a lower thermal sensitivity of modified bitumen.

Nanocomposites based on an SBR/ENR50 rubber blend with the blend ratio of 50/50 using Cloisite 15A nanoclay (5 and 10 phr)) and carbon black (20 phr) were prepared by melt mixing process. The rubber compounds were crosslinked by electron beam irradiation process at 50 and 100 kGy doses. A reference sample containing carbon black at 35 phr was prepared using a conventional sulphur curing system. The gel content of the samples was specified using gel fraction measurement. The results showed the maximum gel content for the sample having 5 phr nanoclay and 20 phr carbon black. The dynamic mechanical properties, including the storage modulus, loss modulus, and loss factor, of the nanocomposites were evaluated using dynamic mechanical analysis (DMA) tests. The results indicated that, in spite of a well dispersed nanoclay in samples containing 10 phr nanoclay and 20 phr carbon black, a minimum loss factor was observed in the sample containing 5 phr nanoclay and 20 phr carbon black at 100 kGy. On the other hand, the storage modulus of the reference sample was found to be higher than that of the sample with 5 phr nanoclay and 20 phr carbon black. The mechanical properties, including the tensile strength, stress at 100%, 200%, and 300% elongation and the percentage of elongation were measured by a tensile machine. The results showed an increase in tensile strength and the stress at different elongations for a sample with 5 phr nanoclay and 20 phr carbon black compared to the reference sample. In the corresponding SEM images of the samples having nanoclay and carbon black irradiated at 100 kGy a significantly higher surface roughness was observed.

As we have stated in our previous article, ethylene-octene copolymers are much more branched than high density polyethylene, therefore, they have lower crystallinity and melting point and better processability. In addition, due to the enhancement of the desired physical and mechanical properties of the nanocomposites such as higher thermal stability and tensile properties and lower peamability in comparison with that of the pristine polymer, there is a great tendency in using this calss of materials. The improvement in physical and mechanical properties of the nanoconmposites is mainly origined from the large aspect ratios of the organoclay platelets and the interaction between the nano-sized filler and polymers which can also make the transfer of load from the matix to the filler more efficient. Moreover, the variation of viscosity with shear rate and angular frequency can provide invaluable information on the viscoelastic property of polymer melts as well as the processability of nanocomposites. In continuation to our previous paper, our aim in this article is to give some complementary information about the mechanical properties and rheological behaviors of the above-mentioned nanocomposites by reviewing the recently published papers on this area.

Polyethylenes are among of the commodity polymers with wide-spread applications. They are being used in transportation، wire and cable، food packaging، and building industries، for instance. Ethylene-octene copolymers contain more branches in respect to that of the high density polyethylene، therefore، their crystallinities and melting points are lower and can also be processed much easier. Nowadays، there are huge interests in using polymer-clay nanocomposites because of their higher desired physical and mechanical properties such as thermal stability، tensile strength and barrier resistance in comparison with that of the unfilled polymers or the polymers which are reinforced with the same amount of micro-sized fillers. Nanoclays are modified using organic modifiers such as alkylammonium ions in order to enhance their compatibility with polymers. They can also act as a nucleating agent and change the crystallinity of polymeric materials. This nano-sized filler could also affect the thermal stability and flame retardancy but the amount of influence depends on the morphology developed. In this article، our aim is to present some information about the above-mentioned nanocomposites by reviewing the recently published papers in this area.

Controlled morphology of nanoclay layers within nanopolymer particles is a very important topic for most industries، especially in food and medical packaging. Films prepared from these nanocomposites showed improved physical and mechanical properties and high impermeability towards gases، vapors، water and even oils and hydrocarbons. One successful method to design these systems is by miniemulsion polymerization which is useful for encapsulation of all materials (solids، liquids and gases) within polymer particles، provided a suitable choice of surfactant is made with optimum HLB. Another method is «pickering» or soap free polymerization، which can also be performed in the form of miniemulsion. In this new method nanoclay is used instead of a surfactant، and therefore، final films will show honeycomb structures applicable in impermeable packaging purposes.

It is often disputed if nanoclay enhances the thermal properties of polymer nanocomposites. Scientists all over the world have reported different and some times contradictory results concerning this issue. There are papers suggested that nanoclay is a factor in improving the thermal properties، while there are other reports on its reducing effect on thermal resistance. It seems that nanoclay has two opposite actions. The barrier effect which should improve the thermal stability of a blend by char formation and the promoter effect which may encourage the degradation process and reduce the thermal stability of the system. Therefore it is important to focus on this subject in order to study the conditions affecting thermal stability of nanocomposites and the mechanism by which nanoclays improve the thermal properties of a blend.

In recent years، waterborne polyurethanes as in coatings and adhesives formulations have attracted considerable attention because they are non-toxic، non-flammable and friendly to environment. Besides environmental management، the flexibility، low temperature property، high tensile strength، good adhesion and improved rheological property are specific properties of waterborne polyurethanes. Also low production cost of water borne polyurethanes over solvent-borne polyurethanes is also a reason for their applications. However، these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ionic bonds، ether groups، urethane and ester groups to hydrolysis which need to be improved. Also، low heat resistance of these materials is due to a relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different applications is the addition of inorganic fillers especially nano-sized layered silicates within polyurethane matrix. In this way water resistance، heat resistance، mechanical properties and modulus increase simultaneously. In this research، waterborne polyurethane nanocomposites with PTMG polyol، IPDI، DMPA (internal emulsifier)، TEA (neutralizer) and 1، 3 and 5weight % of Cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by contact angle test and dispersion of nano particles in the samples was characterized by X-Ray and TEM، Thermal properties and dynamic mechanical properties were measured by TGA and DMTA، respectively. The results showed that incorporation of clay into polyurethanes did reduce water absorption and increased heat resistance، modulus، particle size and contact angle. In recent years، waterborne polyurethanes including coatings and adhesives have attracted considerable attention because they are non-toxic، non-flammable and friendly to environment. Besides environmental management، flexibility، low temperature property، high tensile strength good adhesion and improved rheological property are specific evidence of waterborne polyurethanes. Also low production cost of water borne polyurethane over solvent-borne polyurethanes is also a reason for their applications. However، these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ioned bonds، ether groups، urethane groups and ester groups to hydrolysis which are needed to be improved. Also، low heat resistance of these materials is due to relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different application is the addition of inorganic fillers especially nanosized layered silicates within polyurethane matrix. In this way water resistance، heat resistance، mechanical properties and modulus increase. In this research، waterborne polyurethane nanocomposites with PTMG polyol، IPDI، DMPA (internal emulsifier)، TEA (neutralizer) and 1، 3 and 5weight % of cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by Contact angle test، dispersion of nano particles in the samples were characterized by X-Ray and TEM، Thermal properties and dynamic mechanical properties were measured by TGA and DMTA respectively. Results showed that incorporation of clay into polyurethane samples caused the reduction of water absorption، increasing of heat resistance، modulus، particle size and contact angle.

Nanocomposites based on butadiene rubber (BR)، (0، 3، 5 and 7 phr) organoclay (Cloisite 15A) and (0، 10، 20، 30، 40 phr) powder coating wastes، i. e.، epoxypolyester hybrid (EPH) were prepared using a laboratory-scale internal mixer in order to study the effect of organoclay and EPH content on the mechanical and morphological properties of the nanocomposite samples. Cure characteristics of the prepared compounds including optimum cure time (t90) and scorch time (t5) depicted a decrease in both mentioned factors with increasing nanoclay content and EPH loading. Intercalation of elastomer chains into the silicate layers was determined by d-spacing values calculated according to the results of X-ray diffraction (XRD) patterns. X-ray diffraction (XRD) results reveal the intercalation of elastomer chains into the clay galleries. This phenomenon was also confirmed according to the scanning electron microscopy (SEM) micrographs and mechanical properties of the nanocomposite samples which were observed to be improved with addition of nanoclay and EPH content.

Studies were carried out on the effect of adding different percentages of montmorillonite (3، 5، 7 and 9% of starch weight) on the physical properties of potato starch-MMT nanocomposites. Heat resistance and mechanical properties of films were measured by differential scanning calorimetry (DSC) and tensile test. Nanoparticles distribution in polymer matrix was investigated using X-ray diffraction test (XRD). For investigation of water vapor resistance of film samples، moisture sorption and water vapor permeability (WVP) were measured. The results showed that the distribution of nanoparticles in the polymer matrix was exfoliated. WVP in pure starch films was 2. 62×10-7 g/mhPa and with the addition of 9% MMT it was reduced to 1. 43×10-7 g/mhPa. With the addition of nanoclay from zero to 9%، the ultimate tensile strength of nanocomposite samples was increased from 5. 9 to 6. 63 MPa and strain-to-break was decreased from 34. 82 to 26. 83%. But the rising trend was not significant for nanocomposite samples containing low concentrations of nanoclay (0-7%). The main reasons for the enhancement of mechanical properties due to the addition of nanoclay were to establish hydrogen bonding between polymer chains and clay layers، filling the empty spaces and increase the crystalline domains. Investigation of thermal resistance of nanocomposite samples showed that they have higher thermal resistance and melting point in comparison with pure starch films. With the addition of nanoclay from zero to 9%، the melting point of film samples was increased from 218 to 232. 1°C. With the addition of nanoclay، probably the mobility of amylopectin chains decreased and crystalline domains increased. Also، with increasing nanoclay content، the glass transition temperature of nanocomposite samples was increased. This result corresponded to shrinkage in free volume and thus reduction in the polymer chains mobility in amorphous regions.

Recently، using nanoparticles in polymeric blend have been considered by many researchers a new epoch for generation of materials to meet different requirements in various industries such as car، sport، military، structure and electronic. The transesterification reaction in polyester blends during melt mixing plays an important role in the components compatibility، and the ultimate properties of the blend affected by this reaction. In this study the transesterification reaction in the blend of poly (butylene terephthalate) (PBT) /polycarbonate (PC) was studied at the presence of three commercial organic modified montmorillonite namely Cloisite 30B، Cloisite 20A and Cloisite 15A. The main difference among these nanoparticles is their surface chemical structures and initial gallery heights. Fourier transform infrared spectroscopy (FTIR) and small angel X-ray scattering (SAXS) analysis showed that tranesterification reaction was improved at the presence of Cloisite 20A and Cloisite 15A and an intercalation morphology was obtained. While in the samples containing Cloisite 30B a thermal degradation occurred and initial gallery of the nanoparticles was increased. Dynamical mechanical thermal analysis results revealed that by addition of nanoclay to polymer blend، the glass transition of polymers draw on to each other which means more compatibility has been obtained and transestrification reaction has been improved at presence of the nanoparticles. Scanning electron microscope (SEM) micrographs showed droplet-matrix morphology for PC/PBT: 70/30 ratio and co-continuous for PC/PBT: 50/50. By incorporation of nanoparticles the finer morphology was obtained in PC/PBT: 70/30 and co- continuous morphology changed to micro co-continuous in PC/PBT: 50/50.

Natural rubber and styrene butadiene rubber (NR/SBR) reinforced with short nylon fibers along with nanoclay (Cloisite 15A) hybrid composites were prepared in an internal and a two roll-mill mixer by a three-step mixing process. The effects of fiber content at a constant loading of 3 wt% nanoclay were studied on the microstructure, mechanical and morphological properties of the prepared nanocomposites. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol, hexamethylene tetramine and hydrated silica (HRH). The curing characteristics of the composites were determined and subsequently vulcanized at 150°C using a hot press. It was observed that the cure time and swelling index of the composites decreased while maximum torque, and cure rate increased with increasing of short fiber and nanoclay contents. The structure and fracture surface morphology of the nanocomposites were characterized using X-ray diffraction, scanning electron microscopy. X-ray diffraction results of nanocomposites indicated that the interlayer distance of silicate layers increased. The mechanical properties (tensile, tear strength, elongation-at-break and hardness) ofnanocomposites containing virgin and waste fibers in the longitudinal direction are compared.

The effect of microwave thermal treatment on mechanical properties of composites made from MDF dust-polypropylene was investigated. In this regard، nanoclay (Cloisite 15A) was added in three different (2، 4 and 6 %wt) levels into the composites. Furthermore، polypropylene (PP) was used as a matrix material and maleic anhydride-grafted polypropylene (MAPP) was used as coupling agent at 4%wt. The medium density fibreboard (MDF) dust was used as lignocellulosic material in the present study. Test samples were made، using extrusion process (twin screw)، as granules. Then، samples with dimensions 30×20×1 cm were prepared with 1 g/cm3 nominal density for the polymer composites using hot pressing method. The bending strength and impact strength were measured according to the technical specifications CEN/TS15534:2007 and D-4495 regulation of ASTM standard، respectively. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) techniques were employed to evaluate the extent of intercalation and exfoliation of silicate layers in the nanocomposites. Finally، the mechanical tests of flexural strength، flexural modulus and impact strength were performed on the samples. The results showed that the highest flexural strength، flexural modulus and impact strength were obtained at level 2 wt% nanoclay particles. The mechanical strength of the samples that were treated by microwave radiation was the highest. Also، X-ray diffraction studies showed increases in the interlayer spacing of silicate layers and intercalation of polymer chains between the clay layers. Scanning electron microscopy results showed that in the nanocomposites treated by microwave radiation، MDF dust was desirably compounded with thermoplastic materials.

The effect of nanocaly on crystalline structure of poly(vinylidene fluoride),PVDF, and the morphology of the resulting nano-composite were investigatedusing different characterization techniques. The presence of 3wt% Cloisite 30B in PVDF matrix results in 11 fold increase in the percentage of beta crystalline content of the polymer. This was found to be attributed to the epitaxial effect of the clay surface. The beta crystalline content of the pure polymer (6%) was raised to 68% in the composite. Addition of 5wt% polyamide 6 (PA6) improved dispersion of nanoclay which led to augmentation of the viscosity and displacement of the crossover frequency of the compatibilized composite towards lower frequencies. However, due to stronger affinity of the PA6 towards organically modified clay the epitaxial effect of the clay on crystalline structure of PVDF was totally eliminated. The reduction of viscosity in incompatibilized nanocomposite was attributed to reduced number of PVDF chain entanglements in the presence of nanoclay. Meanwhile, increase in viscosity and displacement of crossover frequency towards lower frequencies were attributed to formation of clay-PA nanoparticles and PVDF-polyamide 6 interactions.It is expected that the presence of polyamide 6 promotes the formation of oriented-beta crystals in PVDF, which in turn improves the piezoelectric properties of the polymer.

Although there are many works published on shape memory polyurethanes,but no report is found on PCL-based polyurethane composite using PCLwith molecular weight of 2000 g/mol and nanoclay particles via in-situ polymerization. In this work, we try to approach some problems concerning the chemical structure, dispersion of nanoparticles in the matrix and interaction between nanoparticles and polymer in shape memory of PCL (Mn= 2000 g/mol)-based polyurethane/nanoclay composites. While PCL (Mn= 2000 g/mol) polyurethane constituted the soft segments, MDI/BD formed the hard segments. The weight ratio of soft to hard segments was found to be 65/35. Composites were synthesized in presence 1 and 3 wt% of nanoclay (Cloisite®30B) via in-situ polymerization by a twostep method. Effect of nano particles on their interactions with polyurethane chains,crystallinity, mechanical properties and shape memory have been investigated using FTIR, DSC, tensile test and shape memory analysis, respectively. Phase mixing and hydrogen bonding intensified with 1 wt% nanoclay particles, whereas 3 wt% nanoclay led to phase separation. XRD, MTDSC, AFM analyses showed exfoliation of samples with 1 wt% nanoclay in the matrix and better tensile strength in comparison with pure sample and higher shape recovery compared to all other samples. Crystallinity of soft segments resulted in higher modulus and improvement of shape memory. TGA results showed a three-step degradation mechanism for PCL, MDI and BDO-based polyurethane.