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

Research subject:

 The binder system based on of hydroxyl-terminated polybutadiene resin (HTPB), consist of dioctyl sebacate as a plasticizer (DOS), and toluene diisocyanate as the curing agent. Reaction between the HTPB hydroxyl resin group and the curing agent isocyanate group produces a polyurethane mesh to produce a rubber with the desired properties. In this research, the rheological and mechanical properties of the binder system were investigated and Physical properties compared in the presence of three chemicals retarder polymerization Polyurethane, oxalic acid, maleic acid and tetracycline.

Research approach:

 Oxalic acid, maleic acid and tetracycline alter the properties of the binder system by specific mechanisms. Oxalic acid and maleic acid react with the isocyanate group of the curing agent to produce amides and reduce the viscosity of the binder system. Due to its chemical structure, tetracycline reacts with the curing agent and prevents the development of the main reaction between the HTPB resin and the curing agent TDI and reduces the viscosity. Infrared Fourier transform (FT-IR) test was also used to investigate the functional mechanism of these compounds. In this test, the intensities of the spectra related to each sample were compared with each other and the type of function and mechanism of each of the oxalic and maleic substances and tetracycline were determined.

The structure of the reaction product between HTPB resin and oxalic acid, maleic acid and tetracycline with curing agent was determined and confirmed by FT-IR spectrum. In-situ FT-IR study showed reduction in isocyanate peak intensity after 60/90 min. Chemorheological investigation showed best performance at 0.05% concentration for all retardants, among them tetracycline, oxalic acid and maleic acid depicted 54%, 48% and 47% reduction in viscosity build-up; respectively. Adding 0.05% of tetracycline to binder system resulted in about 20% decrease in cross link density probably due to better interaction with curing agent which emphasized the best performance of 0.05%-tetracycline as retardant.

The physical properties of electrospun nanofibrous mats have a significant effect on the behavior of electrospun mat in interaction with other surfaces, as well as on its efficiency in various applications. Therefore, determining and predicting these structural properties using controllable factors in the electrospinning process are of particular importance. On this basis, in the present research each of the structural properties of nanofibrous mat, including mat porosity, diameter and porosity of fiber, were estimated using mathematical relationships. Also, the prediction and optimization of input factors and the porosity of the mat and fibers were performed using the response surface methodology (RSM).

Poly(lactic-glycolic-acid) was used to produce nanofibrous mats. After the determination and optimization of the electrospinning process factors, which influence the structural properties of nanofibrous mats, 18 types of mats were prepared. Considering the combined effect of three electrospinning factors, including solution concentration, humidity and collector linear speed, RSM and regression methods were used to optimize and model the relationship between variables and mat properties, respectively.

Based on the mathematical relationships between the input factors and the structural characteristics of the mat, it can be revealed that the concentration is the most effective factor on the fiber diameter and mat porosity, and the collection speed is the most effective factor on the fiber porosity. According to the RSM models, the optimized values for the initial factors of concentration, humidity and collection speed based on the model designed for fiber porosity are 2% (w/v), 45% and 0.4 m/s, and based on the model designed for mat porosity are 3% (w/v), 45% and 2.4 m/s, respectively. The predicted optimized values of fiber porosity and mat porosity are 0.342% and 0.989%, respectively, which are not much different from the experimental values obtained from these points. The nanofibrous mat introduced by each of these models has created the most porosity.

Butene-1 is in excess in the polyolefin plants of Iran. Considering the properties of isotactic polybutene-1, including high creep and environmental stress cracking resistances, excellent elastic reversibility and good chemical abrasion resistance, there is a need to localize it in Iran.

Polybutene-1 was synthesized with an industrial Ziegler-Natta catalyst. To do this, polybutene-1 was synthesized by coordination polymerization of butene-1 with the help of triethylaluminium (TEAL) cocatalyst in n-hexane. By changing the monomer pressure from 1 to 1.7 bar and hydrogen amount from 0.01 to 0.13 L a wide range of polybutene-1s with different properties was obtained.

The highest values of activity and isotacticity for 0.06 L hydrogen and 1.4 bar monomer pressure were 24.76 kgPB-1/gTi.barB-1 and 97%, respectively. An increase in hydrogen led to a decrease in weight average molecular weight. Using cyclohexylmethyl dimthoxysilane as external electron donor, samples with weight average molecular weight from 149500 to 913000 g/mol, polydispersity index from 2.49 to 4.29, MFR from 0.19 to higher than 100 g/10 min, density from 0.876 to 0.911 g/cm3 for crystalline form I, and isotacticity from 81% to 97% were synthesized. The highest polydispersity index was obtained for the sample synthesized under 1.4 bar monomer pressure and 0.01 L hydrogen. The lowest isotacticity index was related to the sample synthesized under 1 bar monomer pressure and 0.13 L hydrogen. This catalyst has the ability to produce polybutene-1 with a narrower molecular weight distribution compared to those reported in other works. Comparison of mechanical properties with those reported by other researchers showed an increase in elongation-at-break for the sample. With the expansion of operational conditions, variety of products and their commercialization will be possible.

Cellulose fibers such as cotton have long been used in the textile industry. The benefits of these fibers are due to good moisture absorption and body adaptability. Today, despite the advancement and development of man-made fibers, cellulose fibers are still one of the most widely used fibers in textile production. Dimensional instability and wrinkles after washing are common problems of cellulosic fabrics caused by stress in wet conditions. Research on anti-wrinkle textile finishes has been conducted since the early twentieth century, and researchers have used a variety of chemicals, including formaldehyde resins and polycarboxylic acids, for this purpose. Based on the applied chemical treatment, the finished cellulosic fabrics may find different applications. These anti-wrinkle chemical treatments increase dimensional stability and improve the texture of the treated fabric. However, these chemical treatment has some adverse effects on the treated fabrics, such as tensile strength reduction, tear-resistance decrement, and discoloration. In this study, we investigated some of these non-desirable outcomes caused by anti-wrinkle chemical treatments.

In this study, biodegradable blend based on wheat starch, gelatin and polyvinyl alcohol was prepared and ethanolic extract of propolis (5, 10 and 20 %) (EPE) as antimicrobial and antioxidant agent was incorporated. The films were prepared by solvent casting method and their microstructural, mechanical, barrier, color, antioxidant and antimicrobial properties were investigated. In the control sample, homogenous structure was not formed due to the incompatibility of the biopolymers with each other, while the addition of EPE caused to formation of uniform structure and cracks were decreased according to SEM observations. FT-IR test approved the formation of new interactions between biopolymers and components of EPE. Addition of EPE caused to decrease the tensile strength, water vapor permeability and opacity. But the elongation to break and yellowness index increased. Total phenol content and antioxidant capacity of the films increased with increasing concentrations of EPE. Different concentrations of EPE significantly affected all properties of the film, exception water absorption. The films containing EPE had more antimicrobial effects on S.aureus compared to E.coli bacteria. Generally, the film containing EPE 10% demonstrated the best physicochemical and functional characteristics. Results of this research revealed that the blend film activated with propolis extract is a good candidate for antioxidant and antimicrobial packaging and increasing the shelf life of foods.

In this research via CT scan, the relationship between physical properties of pears and storage times with bruise due to loading force was investigated. Before loading and storing, 50 pears were examined using CT scan and 27 pears with zero bruise percentage were selected. Dimensions of pears (length, width, thickness) were measured, then properties such as the equivalent diameter, geometric mean diameter, spherical coefficient, surface area and aspect ratio of calculus were calculated, then selected pears were subjected to quasi-static loading with a thin edge pressure with three forces of 15, 20 and 25 N and 5, 10 and 15 days storage was used to investigate the effect of forces on pears. Then, after loading and storing, using the CT scan in each period of storage, the rate of pear bruise was calculated. The results of the experiments showed that there is an inverse relation between geometric diameter, arithmetic and equivalent diameter, spherical coefficient and aspect ratio with the bruise percentage. Also, a direct and unreasonable relationship between the level of the surface area and the percentage of bruising was obtained. Also, according to the obtained results, during the 5-day storage period, the amount of geometric diameter, arithmetic and equivalent diameter, spherical and aspect ratio on the percentage of bruising were not significantly affected and percentage of bruising can be almost zero and with increasing storage, the above parameter's will affect the percentage of bruising.

Biodegradable edible bioplarmers are the best alternatives to synthetic plastics. In this study, sodium caseinate edible films containing different levels of hemp seed oil (10, 20 and 30% w/w) was produced and their physical, barrier and antimicrobial properties were investigated. By adding hemp seed oil up to 30% (w/w), the thickness, transparency, and solubility of films decreased, and the contact angle increased. The permeability to water vapor was reduced from 76.4×10-11 to 5.1×10-11 g m-1s-1 Pa-1, and oxygen permeation was increased from 11 to 28.3 cm3μm cm-2 day-1 Kpa-1 by addition of hemp seed oil. The disk diffusion method was used to investigate the antimicrobial effect of sodium caseinate film containing hemp seed oil on three pathogenic bacterial strains including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The largest inhibitory diameter for S. aureus, E. coli, and P. aeruginosa was 31.28, 19.05 and 15.40 mm, respectively. As a result, sodium caseinate films containing hemp seed oil has the most effect on gram-positive bacteria. The results revealed that that adding hemp seed oil improves the physical, barrier and antimicrobial properties of sodium caseinate-based films and coatings.

Hypothesis: A two-component methylmethacrylate (MMA) traffic paint, used in cold plastic road marking, is considered as a vital part of the safety infrastructure of the road networks and a tool for delineation and traffic control. This system must be well-maintained during its service life. The aim of this study was to evaluate the effect of benzoyl peroxide (BPO) curing agent content on the physical and mechanical properties of MMA traffic paints.
In order to optimize the amount of BPO, samples of two-component traffic paint were prepared and cured with 0.4, 0.8, 1.0, 1.2, 1.4, 1.6 and 2.0 wt% BPO. Different physical and mechanical properties of the samples, such as traffic no pick-up time, hardness, resistance against accelerated weathering conditions were evaluated and their mechanical properties were assessed using stress-strain analysis (SSA) and dynamic mechanical thermal analysis (DMTA).
Findings: The results showed that the amount of BPO was a critical parameter in physical mechanical performance of the paints, in such a way that the low and high levels of curing agent (0.4 wt% and 2.0 wt%, respectively) led to loss of paint properties. This could be related to insufficient curing agent (0.4 wt%) and its overdose (2.0 wt%) in the polymerization of methylmethacrylate. Increasing the curing agent to its optimal amount did not increase the polymer network density, and in some cases impaired the mechanical properties of the samples. The results also showed that the increase in peroxide content reduced the drying time (no pick-up time). Within the optimal range of BPO content level at 1.2 and 1.6 wt%, we achieved traffic paints of two-component formulations with optimum physical and mechanical properties.

In this review paper, Epoxy-based nanocomposite coatings are focused that are produced by hyperbranched polymer-modified nanofillers. At first, keywords like epoxy, nanocomposite, hyperbranched polymer are defined and then fabrication methods and modification of nanocomposite coatings, various categorizations, advantages and disadvantages are investigated. Consequently, the effect of modification and addition of different nanoparticles on the characteristics of the coating such as physical-mechanical properties, anticorrosion and dispersion level are reviewed. Considering the discussions it can be concluded that using hyperbranched polymers as modifier for nanoparticles in order to improve the dispersion and its stability and increasing the various properties of the nanocomposite coatings, is useful and promising.

Irradiation is a modern method of food preservation. In this research were evaluated irradiation dose effect, shelf-life and storage time of on some qualitative and rheological properties of potatoes tuber. The samples were purchased from the store's Atomic Energy Organization and were stored for a week in the cold (4°C) in order to prevent chemical changes in the tissues. In order to samples irradiation was used cobalt-60 source (Gamma-cell 220). The samples were irradiated with 0 (control), 2, 5 and 8 kGy and then were storage for 150 days at a temperature of 6°C and at ambient temperature (18°C). Samples dry matter and starch content was higher for doses of 2 kGy and stored at a temperature of 6°C to 22.01 and 12.09 %, respectively. Geometric mean diameter and sphericity values ​​decreased with increasing radiation dose to 23.27 and 8.39 % and the dose of 8 kGy irradiated samples had the lowest values to 40.12 and 76.41 %, respectively. Also, a *, b *, color changes and BI increased by increasing the radiation dose to 2.9T 3.2T 5.13, 4.97 % and L* decreased to 2.14%, too. Moreover, three component model was calculated using by Maxwell Model and results show that with increasing dose of irradiation and temperature, relaxation stress decreased and relaxation time increased to 39.96 and 27%, respectively.

Rapeseed oil-filled ethyl cellulose microcapsules were prepared using a two-step solvent evaporation method. The prepared oil-filled microcapsules were characterized by; optical microscopy, scanning electron microscopy and particle size analyzer. The mechanical properties of carboxylated styrene/butadiene copolymer latex films containing various levels of microcapsules were studied using DMTA and tensile strength measurements. The characterization test results showed that rapeseed oil-contained microcapsules with a regular spherical shape, diameter range of 10-45 μm, and a relatively rough porous shell were successfully prepared. The results also revealed that the overall mechanical properties of the latex films containing oil-filled microcapsules improved, due to reinforcing effect of capsules within the latex films; with the best results using 1-2 wt% of oil-filled microcapsules. The improved results were obtained in reinforcing the samples before tests such as tensile tension, capsule rupturing and the oil release within the polymeric network by maintaining the integrity of the films by plasticization of the surrounding polymeric network, increased elongation-at-break, and enhanced resistance against tear or break. With further increasing of microcapsules content up to 3 wt%, there was a drop in overall mechanical properties of latex films, due to possible aggregation of microcapsules, presence of free rapeseed oil within the latex film and weak polymer/microcapsules interface. A proper distribution and dispersion of oil-filled microcapsules within the latex film, and rupture of sufficiently large microcapsules under stress, oil release within the polymeric network and easy movement of the chains were the main requirements for achieving latex film with good mechanical properties.

To investigate the effect of epoxy-polyester resin on mechanical and physical properties of wood-plastic composite, polypropylene, wood flour and epoxy-polyester resin were mixed by an internal mixer and molded. The epoxy-polyester resin can be cured and made cross links between chains at the mixing temperature; so it can affect the properties of the composite. The result of tensile and flexural tests revealed that introduction of epoxy-polyester resin increased tensile and flexural modulus but reduced mechanical strength as well as elongation at break. Also such a material decreased impact strength. On the other hand, epoxy-polyester resin reduced water absorption of the samples and consequently decline thickness swelling. Therefore, it reduced stresses which were produced by swelling as a result of water absorption in the sample and shrinkage after drying.

In this research، the effect of some drawing parameters on the physical properties of polyester filament yarn was investigated. Heating operations were carried out with two simultaneous (heating with drawing) and sequential (heating after drawing). The results showed that the tenacity and initial modulus of PET yarns increased with increasing the draw ratio at a selected optimum heating operation. The simultaneous method gives rise to the resultant drawn yarn with superior tensile properties and low shrinkage.

In different industries, protective oils are applied temporarily on the metal substrates to prevent corrosion damages. This layer should be removed before applying organic coatings. Alkali solution and solvent wash are the most frequently methods to remove oil from surface. Aforesaid methods can not remove this layer perfectly. As a result, always some residual protective oil remains on the metal surface. In this work the effect of this layer on properties of automotive phosphate layer was investigated using scanning electron microscope (SEM) and weight of phosphate layer. It was seen that oil pollution reduced the homogeneity of phosphate layer, changed the crystal shape of phosphate layer and decreased the weight of phosphate layer. In addition, the effect of residual oil on the different physical-mechanical properties of coating systems was investigated. It was seen that residual oil improved bending, cupping and impact properties of coating due to diffusion of the residual oil in coating layer. In the other hand, corrosion resistance decreased because of adhesion failure.