جستجوی مقالات مرتبط با کلیدواژه « پلی پروپیلن » در نشریات گروه « فنی و مهندسی »

Research subject: 

Polypropylene (PP) is a thermoplastic polymer that is used in a wide range of applications, including films and sheets, blow molding, injection molding, food packaging, textiles, laboratory and medical equipment, pipes, industrial and construction applications, and the manufacture of automotive components. In the applications of this polymer, improving the surface of PP has been considered. One of the usual methods for improving the surface is the cold plasma method. Plasma is a chemically highly active environment where there are many ions and radicals. In this research, atmospheric pressure gliding discharge plasma was used to increase the hydrophobicity of PP and the surface and depth changes of PP were investigated.

Research approach: 

The depth and surface changes of PP were investigated by radiating the gliding discharge plasma to the PP polymer surface at the different times. FTIR and XRD tests were performed to investigate volume changes and FESEM investigated the surface changes. The hydrophobicity of PP was investigated by contact angle (CA) test and positron lifetime spectroscopy (PALS) was used to investigate shallow depth changes.

The results show that the applied cold plasma did not cause volumetric changes in PP, but caused surface changes and roughness. In this polymer, the contact angle has increased from 30.1 ± 0.1 to 34.4 ± 0.1 and the hydrophobicity of the surface has increased. Examining the changes in holes by PALS test shows that after plasma irradiation the volume of the holes increased from 217 Å3 to 222 Å3 and their intensity decreased. This is due to the heat of the plasma and the energy of its particles.:The results show that the cold plasma caused surface and depth changes and the contact angle increased from 30.1 ± 0.1 to 34.4 ± 0.1 and the hydrophobicity of the surface increased.

The current research, the possibility of making composite from Conocarpus wood flour-based polypropylene was investigated. Conocarpus erectus is an imported species that has been cultivated in the southern provinces of the country like Khuzestan province, and as a lignocellulosic source has not yet been investigated in making wood-plastic composites. Wood flour-based polypropylene composite with different flour weight fractions (0, 10, 20. 30 and 40%) and constant 4% maleated polypropylene (MAPP) coupling agent have been fabricated using extrusion injection molding process. The effect of wood flour content has been compared with neat polypropylene specimen. Based on the results, with the increment in the proportion of wood flour, the density and mechanical properties showed a significant increase, except for the impact resistance, but no statistically significant difference was observed between the specimens containing 10 to 30% by weight of wood flour. The highest density and mechanical resistances were obtained in the products containing 40% by weight of wood flour. The impact resistance was significantly reduced with the addition of 10% wood flour, and the increase of wood flour from 10 to 40% had no significant effect. Electron microscope images of the fracture surface of the samples were also used to investigate the distribution of wood flour particles in the polymer matrix. In these images, both the overlapping of particles by polymer and the accumulation of wood flour can be seen.

The removal of carbon dioxide due to environmental problems is still of great interest to researchers. In this study, simulation of carbon dioxide removal by absorption four amine base solvents including; monoethanolamine (MEA), diethanolamine (DEA), methyl diethanolamine (MDEA) and aminomethylpropanol (AMP) in a polypropylene hollow fiber membrane reactor is investigated. A comparative study for solvents by multi-physics Comsol software based on fluid dynamics (CFD) calculations is performed. The results showed that the best adsorption rate was obtained by MEA solvent with 88% CO2 absorption rate. The absorption of carbon dioxide by each amine-based solvents in the references is investigated separately. The simulation results are validated separately for each solvent. An acceptable consistency is obtaned between the present simulation data and the results of others given refrences. Finally, as a result of this study, it is shown that the present simulation is powerfully provided suitable and alternative data for carbon dioxide removal by each four traditional amine-based solvents in compare with the available experimental data.

Twist fixation is an important part of yarn production in two methods of virtual or real twisting method. Currently, twist fixation is calculated by performing heat treatment based on a combination of stabilization of bending, strain, and torque according to common methods. This is the fact that the basis of yarn twist is simply the application of twisting force on the fibres, and as a rule, twist stabilization should be the same twisting force. In the new method, a way to evaluate the degree of stabilization of the twist, which is only caused by the torsional force applied to the fibres, is presented. With the help of Taguchi method, 25 samples were prepared under different levels of twist, temperature and time. The design is done for three factors (time, temperature, twist) and five levels for each factor. The twist, temperature and time levels are respectively (0,40,80,120,180), (23,60,90,120,150) and (0,60,90,120,150). Then heat treatment was done and the degree of twist stabilization was calculated according to the new method and predicted by regression and neural network. The results show a good correlation between the experimental and predicted results by the ANN model compared to the regression method.

In this research, the process of surface modification, fabrication, and examination of the mechanical and electrical properties of a semi-biodegradable composite prepared from polypropylene and hemp fiber fabric has been discussed. Production of composite samples was done by dissolving polypropylene polymer in a xylene solution and then combining it with fiber fabric under pressure and temperature curing of a hot press. To improve the interface between the fibers and the matrix and to improve the mechanical properties of the produced samples, the surface of the hemp fiber fabric was modified using a 6% sodium hydroxide solution for 12 hours. To determine the mechanical properties of the produced samples, two tensile and three-point bending tests were performed. The elastic modulus, yield stress, ultimate stress, elongation, and toughness were measured from the tensile test and were analyzed and investigated. The bending of the composite was obtained from the bending test. To determine the electrical properties of the composite, the dielectric constant test was performed using a network analyzer in the x band. The maximum tensile strength and Young's modulus obtained in this research are 8 MPa and 1.6 GPa respectively. The maximum dielectric constant and loss tangent of the produced samples in the x-band is equal to 3.48 and 0.24, respectively. Finally, to validate the results obtained in this research, the results of the tests have been compared with the results of other authorities in this field.

The Spheripol process is one of the most widely used technologies in the world for the production of polypropylene (PP). The geometry of the reactor is such that the use of ideal reactors alone causes an error in the simulation results. Therefore, in this research, we have tried to combine the ideal reactors modules in Aspen Plus. v11 to get the most accurate results. In order to calculate the volume of the ideal reactor, we used the concept of «required length for fully developed flow» and considered the inlets, outlet, and pump of the reactor as a continuously stirred tank reactor (CSTR) while the other part of the reactor considered as plug flow reactor (PFR). We also used three different kinetic constants reported by three different research groups and compared the result with the production plant data. Due to the importance of the thermodynamic model for the prediction of phase behavior, we used the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state that was used by previous authors. The results are validated with the production plant data and previous articles. Also, the effect of methanol as a catalyst poison is investigated.

The goal of the current investigation was to determine how nanosilica particles affected the performance parameters of asphalt binders treated with polymers. In this investigation, nanosilica particles and polypropylene polymer were added at concentrations ranging from 0% to 4% to regulate 80/100 binder. By weight, polypropylene polymer and nanosilica particles were added to the total bitumen content. To assess the impact of nanosilica particles, asphalt performance tests such as the flexural four point beam fatigue test, indirect tensile strength, indirect tensile stiffness modulus, and draindown tests are carried out. The study's findings demonstrate that adding nanosilica particles to a modified polypropylene polymer binder increases its resistance to fatigue. This suggests that the performance characteristics of binders modified with polymers are significantly improved by nanosilica particles. The outcome also shows that bitumen modifiers made of thermoplastic polymer polypropylene and nanosilica particles enhance the functionality and longevity of asphalt mixes.

In this research, the tensile properties of polypropylene/natural rubber composite reinforced with perlite nanoparticles were studied. The mathematical modeling of analysis of variance using the surface response method was used to confirm the experimental results. The role of each materials variable and the weight percentage of natural rubber and pearlite nanoparticles on the tensile properties of the nanocomposite samples was investigated. It was observed that the values of tensile strength and elongation at break by increasing the amount of natural rubber from 20 wt.% to 40 wt.% and the constant amount of perlite nanoparticles at 3 wt.%, decreased by 14.68% (from 8.92 to 7.61 MPa) and increased by 72% (from 51.05% to 87.81%), respectively. The results obtained from the parameters optimization showed that the maximum values of tensile strength and elongation at break are 8.332 MPa and 74.38% was obtained in the sample with 3.268 wt.% of natural rubber and 4.046 wt.% of perlite nanoparticles, respectively. The scanning electron microscope images showed the positive effect of adding nanoparticles to the polypropylene/natural rubber composite due to the reduction in the size of the elastomeric phase and as a result, the increase in the tensile strength of the composite samples. Also, the proper dispersion of nanoparticles in the polymer matrix phase occurred in the sample with 5 wt.% of perlite nanoparticles and 30 wt.% of natural rubber. However, with increasing the weight percentages of nanoparticles up to 9 wt.%, some agglomerations of pearlite nanoparticles were observed in the thermoplastic phase.

Petrochemical industry is a branch of chemical industry that uses raw materials in the form of oil and gas to produce industrial products. Various chemical or physical processes are used to produce optimal products. Among the key and strategic products in the petrochemical industry, we can mention propylene and polypropylene. Propane dehydrogenation (PDH-Propane dehydrogenation) is a highly efficient catalytic technology that is used to convert propane into propylene and finally polypropylene, and it has received wide attention today. Propylene is one of the intermediate products used in many petrochemical applications, such as the production of polypropylene resins, acrylic acids, propylene glycol, acrylonitrile, cumene/phenol and other industrial products. Usually, propylene is obtained by cracking naphtha derived from oil and is a byproduct of ethylene production, but currently, in order to produce propylene more widely, propane dehydrogenation process is used. With the increase in global demand for propylene in the automotive sector, the production of bottle caps, fabrics, packaging materials and the production of chemicals, the petrochemical industry is inevitably moving towards the targeted production of propylene. This goal will be achieved mainly through propane dehydrogenation, where propane is selectively hydrogenated (removal of hydrogen from the propane stream). The results of this research, in addition to identifying the most suitable method of producing propylene from propane (Oleflex or Catofin), indicate that the implementation of PDH projects in the country, in addition to meeting the needs of domestic industries, completing the chains It will also bring value to the country's petrochemical industry.

Despite substantial environmental and economic benefits, cold recycling of asphalt pavements is not common due to some poor field performance reports. This study investigates the effect of fiber reinforcement on the performance of cold recycled mixtures. For this purpose, cold recycled mixtures were reinforced using polypropylene fibers at two different lengths and three different contents. Indirect tensile strength, IDEAL-CT, and semicircular bending tests were carried out to find the optimum length and content of the fiber. The effect of cement on performance of fiber reinforced mixtures was also evaluated. The results show that although the use of polypropylene fibers reduces the wet strength by up to 54%, it can increase the dry strength by up to 39%. The results also indicate a significant improvement in fracture indices obtained from IDEAL-CT and SCB tests in the presence of fiber. Crack tolerance index was 3.5 times and flexibility index was 2.8 times higher at the optimum fiber content and length compared with the control mixture. It was also concluded that the addition of cement to fiber reinforced mixture can eliminate the adverse effect of fiber on moisture sensitivity, while maintaining the fracture properties similar to the control mixture. The study results show that the combined use of fibers and cement can lead to an economical cold recycled mixture with reduced emulsified asphalt content and improved mechanical properties.

The present research has studied the effect of adding perlite and natural rubber nanoparticles with various weight percentages on the tensile modulus and impact strength of polypropylene. For this purpose, different samples were produced and tested using an internal mixer based on the standards of tensile and impact tests. Also, by using of response surface methodology (RSM), the role of input parameters on the responses was investigated in order to achieve optimal mechanical properties and predict these properties with mathematical models in the form of central composite five-level design (CCD). In addition, the SEM test was used to observe the changes made in the microstructure of the samples. The results showed that the addition of 7 wt.% of pearlite nanoparticles to the matrix containing 20 wt.% of natural rubber, the value of the tensile modulus increased by 11.27% and the impact strength by 52.01% compared to the addition of 3 wt.% of pearlite nanoparticles to the same matrix. The results of multiobjective optimization proved that the optimal weight percentage of pearlite nanoparticles and natural rubber was 4.04 and 35.26% wt. respectively. Is. In this case, the highest value obtained for tensile modulus was 508.04 MPa and impact strength was determined to be 108.52 J/m. By observing the SEM images, it was concluded that the change in the size of the elastomeric phase due to the use of different weight percentages of reinforcements has caused the results of the mechanical properties of the samples to differ from each other.

Polypropylene/ ethylene–propylene-diene monomer/ Nanoclay (PP/EPDM/ Nanoclay) nanocomposite with different loadings of clay content is used in many industries because of balance on the tensile and impact strengths. Laser welding, as a fabrication method, is applied to the butt-welding of these nanocomposites. The input parameters (clay content, laser power, scan velocity, and stand-off-distance) were varied to achieve the best responses (tensile strength of welds). Response surface methodology (RSM) was utilized to relate the input parameters and the response. The effects of all input parameters on the responses were investigated. Results demonstrated that increasing the clay content from 0 to 6 wt% and increasing stand-off-distance from 5 to 8 mm decreased the tensile strength from 9.6 MPa to 6.1 MPa and 9.19 MPa to 8.36 MPa, respectively. The models showed that laser power of 100 W, traverse speed of 400–750 mm min21, and stand-off-distance of 5 – 6.5 mm, led to weld strength from 8 to 9.9 MPa.

The fabrication of polypropylene composites using various types of reinforcements to improve the mechanical properties has received much attention in recent years. In this paper, enhancing the mechanical properties of polypropylene composites by adding different classes of natural and synthetic particle and fiber reinforcements were reviewed. Accordingly, it was found that the fabrication of polypropylene composites leads to an increase either in the strength of samples and corresponding mechanical properties. Moreover, surface modification and processing reinforcements, especially natural fibers via chemical and physical methods were studied. The results show an increase in the adhesion of reinforcements surface inside the polypropylene, which results in strength enhancement and improving the mechanical properties of polypropylene composites. The evidence from this study points towards the idea that the increased use of modified natural fibers in polylropylene composites and those natural or synthetic reinforcements which form hybrid composites provide promising research topics in the future.

One of the most important weakness points of concrete is its drawback in tension and cracking. The use of fibers in concrete greatly reduces this disadvantage. Fiber reinforced cementitious composite (FRCC) is a type of fiber reinforced concrete (FRC) that does not contain coarse aggregate and has only fine aggregate. In fact, the high level of cement in FRCC is a problem for the environment. This problem can be solved with using different cement replacement materials as a part of cement. In this study, the effect of copper slag on the mechanical properties and fracture energy of fiber reinforced cementitious composite (FRCC) containing polypropylene fiber is investigated. Silica fume and copper slag were replaced as a part of cement. For this purpose, a control mix without silica fume and copper slag, 4 mixes containing 5%, 7%, 10% and 15 % silica fume, and 4 mixtures with 5%, 10%, 20% and 30 % copper slag were casted. In specimens containing silica fume, the ones with 15% of it had the highest quantity of fracture energy, compressive, tensile, and flexural strengths. Among the samples having copper slag, the ones containing 10% and 20% of it had the highest values above. It is worth noting that some binary mixtures containing both copper slag and silica fume were prepared too. Comparing the results of all the mentioned mixtures, it is concluded that the best results belong to the binary mixture containing both 15 % copper slag and 15 % of silica fume.

The purpose of this study is to investigate the effects of adding nanosilica and microsilica on the mechanical properties of cementitious composites containing polypropylene fibers. For this purpose, 13 composite mixes with the water to cement ratio of 0.28 were considered. One mix without microsilica and nanosilica, 4 mixtures with 0.5%, 1%, 3% and 5% nanosilica replacement levels, 4 mixes with 5%, 7%, 10%, 15% of microsilica, and 4 mixtures with the combination of microsilica and nanosilica were investigated. According to the results of the experiments, the composite samples containing microsilica and nanosilica had better results than the samples containing only one of these particles. In fact, the results of 28-day tests showed that the combination of 10% microsilica and 1% nanosilica produced the best cementitious composite according to compressive, tensile and flexural tests.The compressive strength was 61.32 MPa, which was 44.69 percent higher than the control mix, the tensile strength was 4.319 MPa with 34.88 percent improvement, and the flexural strength was 6.971 MPa with 30.37 percent improvement from the control mix. Using more than 3 percent of microsilica had negative effects in all circumstances comparing to the control mix. For example, the ones containing 5 percent of nanosilica and without microsilica had the compressive strength of 37.41 MPa, which was 11.72 percent lower than the control mix.

P olyolefins (POs) are one of the most widely used classes of polymeric materials withlow flammability. Today, the use of halogen-free retardants (HFFRs) for polyolefinsis important due to the environmental problems of halogen additives. Halogen-free flameretardants are divided into several categories, which the most important include phosphorusbasedtypes, minerals, nitrogen, silicon, boron, and intumescent systems. In this article,the operation mechanism and performance of these additives as the flame retardants forPOs-based systems are reviewed. The results show that in order to achieve the desiredflame resistance properties for polyolefins, due to the relatively low efficiency of mosthalogen-free flame retardant compounds, large amounts are used in the formulation,resulting in a significant decrease of thier mechanical properties. To overcome this problem,combinations of halogen-free flame retardants with synergistic effect should be used forPOs. Based on the studies, it has been found that intumescent systems are the most effectiveadditives, along with most of the halogen-free additives to achieve the synergistic effectin creating flame resistance for polyolefins. This synergistic effect is created by the solidphase mechanism and the strengthening of the protective coating in this phase due to thepresence of a intumescent systems.

The utilization of concrete Incorporating with fibers is one of the proper issues of construction industry in last years. The main focus of this research to design a high performance self-compacted fiber reinforced concrete (SCFRC) by using an evolutionary algorithm, which is implemented in MATLAB. Crow Search Algorithm (CSA) and Genetic Algorithm (GA) are statistical ways which are developed by optimization based meta-heuristic solutions. A total of 67 concrete mixtures were considered by varying the levels of key factors affecting concrete strength of concrete, namely, water content (137.2-195 kg/m3), cement content (325.5-520 kg/m3), coarse aggregate content (722-920 kg/m3), fine aggregate content (804.9-960 kg/m3), nano silica content (0-49.6 kg/m3),percentage of volumetric of fibers (0-0.9 %), lime stone powder content (0-288.9 kg/m3) and superplasticizer content (1.75-10.5 kg/m3) were developed to design optimized mixture proportions. The objective function called maximizing concrete strength was formulated as an optimization problem on the basis of Multiple Linear Regression (MLR) method. The constrains including ratio of mixture proportions and absolute volume of mixture design were utilized to obtain an optimal-strength and cost-effective design. The concrete technological constraints were identified as the factors of experimental design for concrete production. The evolutionary implementation of results reached incorporating mixture proportions having strengths in range of 30 - 88.7 MPa. Five numerical examples for optimum mixture design of SCFRC were considered to evaluate the capability and efficiency of CSA and GA algorithm. These results were compared and concluded that CSA (3.38-14.49 % of mean error) performed better than GA (7.95-15.52 % of mean error) for this application. Also, the proposed evolutionary CSA and GA algorithms are found to be reliable and robustness tools to solve and optimize engineering and concrete technological problem.

Sugarcane bagasse is one of the most abundant types of natural fibers which can be utilized to fabricate natural composite materials. Since bagasse is one of the wastes of Khuzestan province sugarcane factories, recycling might be an opportunity to enjoy its economic and environmental benefits. In the present study, the mechanical and microstructural properties of Bagasse/Polypropylene natural composite fabricated by the injection molding method were investigated. Bagasse fibers after drying process were mixed up to polypropylene with 10, 30, 40 and 50% weight fraction of bagasse. In order to investigate the mechanical properties, experimental tests consist of tensile test and Charpy impact tests were carried out. The results showed that the maximum material strength was obtained from the sample made of 40% weight fraction of bagasse. The strength of 40% bagasse was found about 10%more than 50% bagasse the microstructural analysis was indicated that the failure mechanism of 40% bagasse was mainly affected by fiber breakage. However, the main failure mechanism of 50% bagasse was changed to fiber pull out. Additionally, impact absorbed energy was significantly decreased by increasing the bagasse weight fraction.

Piezoelectricity can be described as a capability of some particular materials which convert mechanical energy to electrical and vice versa. In addition to ceramics (such as PZT) and polar polymers (PVDF and its copolymers), non-polar cellular polymers have received much attention in the last two decades due to their reasonable price, light weight, flexibility, and piezoelectric coefficient (d33). These polymers are used for a variety of applications, such as energy absorbers, sensors, and the medical sciences. PP, PET, PEN, PE and COP are thermoplastic materials which show high piezoelectric coefficient. By placing these cellular films in a strong electric field (corona discharge or between two electrodes) and in the vicinity of ionizing gas, the gas is ionized by electric field and remains inside the cells, indicating a bipolar moment. Due to the quasi-piezoelectric behavior of these materials, they are called ‘piezoelectrets’ and their properties are called ‘ferroelectricity’. Important factors such as cell structure (morphology, size and density), ionizing gas type, and Young's modulus have direct effect on the piezoelectric coefficient. Furthermore, some post-processing treatments such as chemical and stretching processes improve the piezoelectric properties. Polypropylene is one of the most widely used cellular polymers in the field of piezoelectrics due to features such as reasonable price, good fatigue resistance, and good charge trapping in cells, which has provided a study platform for other polymers. In this review article, we discuss on recent developments in improving piezoelectric coefficient and the work process. The effects of different parameters like electrical breakdown strength of various gases, additives, servicing temperature of polymers and Young's modulus on piezoelectricity in cellular polymers are investigated.

Friction stir welding is one of the new methods of solid state welding. This welding method has many advantages over traditional methods of fusion welding due to low input temperature and non-melting and freezing of materials. In this study, the tensile strength variations of the welded specimens were investigated based on two parameters of the geometry of the tool and the angle of the device for the welding of polypropylene sheets. In order to obtain the optimal value of these parameters, other variables such as rotational speed and linear velocity of tools are assumed constant. After welding the samples, a standard tensile test was performed on the samples. The results show that the tool geometry has a great influence on the tensile strength and the appearance of the weld and the pieces welded by the tools with a welder's helmet have a higher strength. Also under the same conditions, the highest tensile strength is when the angle of the machine is 2°.