Journal of Applied Research in Chemical-Polymer Engineering

Abstract Research subject: In recent years, various filament cross-sectional shapes have been employed in the production of synthetic multifilament yarns to achieve diverse applications and properties. In this study, the effect of round and rectangular cross-sectional shapes of polyethylene terephthalate (PET) multifilament yarns on the physical and crimp properties of melt-spun and draw-textured yarns was investigated.
Research approach: Partially oriented yarns (POY) were produced using an industrial melt-spinning machine, and draw-textured yarns (DTY) were prepared with an industrial frictional false-twist texturizing machine under identical conditions. All yarn samples with round and rectangular cross-sectional shapes were analyzed in terms of linear density, thermal shrinkage, degree of crystallinity, and tensile properties (strength, elongation at break, and initial modulus). For DTY yarns, additional tests were conducted to evaluate crimp properties (crimp shrinkage, crimp modulus, and crimp stability), resiliency, and the ratio of tension after the twisting zone to tension before the twisting zone (T2/T1). Furthermore, X-ray diffraction was performed on textured yarn samples to examine the fiber microstructure.
Main results: The results revealed that differences in the tensile properties and thermal shrinkage of POY yarns with both cross-sectional shapes were small, despite being statistically significant. However, greater variations were observed in DTY yarns. The DTY yarn with a rectangular cross-sectional shape exhibited higher resiliency than that with a round cross-section. Conversely, the DTY yarn with a round cross-sectional shape demonstrated superior crimp properties, which can be attributed to its higher crystallinity and, consequently, greater softness and texturability compared to the rectangular cross-sectional shape.

Abstract Research subjec: Polyethylene surfaces are often modified because of different reasons such as cleaning, etching, change in the performance of the surface, and surficial precipitation. One of the surfaces in the blow molded applications that must be treated in order to be ready for the adhesion of the labels is the surface of the bottle of the hygiene detergents, being the purpose of this research. In this paper, gliding arc plasma device is used at atmospheric pressure with air gas to modify the surface of polyethylene sheets in order to change their structure.
Methods: Various analyzes such as AFM, SEM and XPS tests have been used to investigate the changes in the chemistry and physics of polyethylene surface after plasma modification. Optical emission spectroscopy (OES) has also been used to identify plasma elements.
Findings: The contact angle between the water droplet and the polyethylene surface reached 46.96 ° after 40 s of treatment, while this contact angle was 66.53 °‌ before plasma treatment. The decrease in the contact angle size of the water droplet and the sample surface indicates the hydrophilicity of the polyethylene surface after plasma modification. The surface free energy of polyethylene was calculated before and after plasma modification using the Owens-Wendt-Rabel Kaelble method. The surface energy of polyethylene has increased from 42.20 mj.m^-2 in the control sample to 60.32 mj.m^-2 in the modified sample. The increase in surface roughness of the modified sample with gliding arc plasma was confirmed by AFM test. The surface roughness of polyethylene in the control sample was 47.18 nm, while the roughness in the modified sample increased to 59.86 nm. The XPS test confirmed the presence of oxygenated and nitrogenous functional groups on the surface of the modified sample. This test also showed the formation of C−C=O and C−O−C bonds on PE surface.

Abstract Hypothesis: Because of the widespread use of rubbers in different industries, estimating the rubber material properties and its lifetime are very important in design procedure to assure the quality and safety of the rubber components. In this study, the properties and useful lifetime prediction of EPDM rubber parts used in the production of sealing gaskets and sealants for GRP pipes were investigated and the effect of adding silica nanoparticles as well as Si69 coupling agent on these characteristics was studied.

Methods: In this work, the samples were tested under accelerated aging conditions and aged in the temperature range of 25-90 °C until 60 days. Then time-temperature superposition was carried out on tensile test and compression set results using Williams Landel Ferry (WLF) model to estimate useful lifetime of the samples. Tensile test was conducted under ISO 12244 standard and compression set test was performed according to ISO 815 standard on rubber samples. Aging effect on samples with and without silica was analyzed with FTIR. In addition, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed to observe the dispersion condition of silica nanoparticles in EPDM samples.

Findings: According to obtained results, TEM images showed no sign of nanoparticles agglomeration within the samples due to presence of Si69 and SEM graphs depicted a uniform distribution of particles in the matrix. Using time-temperature superposition principle, the lifetime was estimated about 63 and 35 years at room temperature for the rubber samples with and without silica and Si69 coupling agent, respectively. It was observed that the presence of modified silica nanoparticles improves the mechanical and thermal properties of EPDM and also increases the useful lifetime of this elastomer.

Abstract 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.
Main results: 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 ų to 222 ų 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.

Abstract Research subject: In recent years, several studies have been performed for improving the adhesion properties of polyurethane and acrylic pressure-sensitive adhesives (PSAs). Generally, polyurethane PSAs are of higher shear strength, while acrylic PSAs have higher tack. This research is a feasibility study of exploiting the properties of both of these adhesives through a simple blending method, and the adhesion properties were evaluated.
Research approach: First, acrylic copolymer (Ac) consisting of 82 vol. % butyl acrylate and 18 vol. % methyl methacrylate was solution polymerized. On the other hand, a thermoplastic polyurethane (TPU) containing 17.5 wt. % hard segment was prepared by bulk polymerization. Blending of these two polymers was performed by solution mixing. Solutions of the pure polymers and their blends at different contents were cast on polyethylene terephthalate backing and dried at room temperature. Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry were used to identify TPU and Ac. Loop tack, static shear strength, dynamic mechanical behavior, contact angle of sessile drop, morphology, and haze of the PSAs were evaluated.
Main results: Tack of the acrylic PSA was higher than TPU PSA. Tack of the blend PSAs containing 20, 40, and 60 wt. % TPU was higher than the pure components and that of the blend containing 40 wt. % TPU was maximum. This blend demonstrated the lowest water contact angle compared to the other blends and the shortest relaxation time compared to the pure polymers, which resulted in better wetting and higher tack. The shear strength of the PSAs increased with increase in the content of TPU to higher than 40 wt. % in the blends compared to the acrylic PSA; so that the pure TPU showed the highest modulus at various frequencies and hence exhibited high-shear PSA characteristics in the Chang’s viscoelastic window and the highest adhesion strength. The immiscibility of the blends was confirmed by measuring the haze and calculating the Hansen solubility parameter.

Abstract Abstract
Research subject: Due to the drought and lack of water resources, many efforts have been made to store water properly recently. Using of multilayer polyethylene tanks is an efficient measure in order to solve this problem and it has received considerable attention. Proper manufacturing conditions will greatly improve the strength of these tanks and their applications.
Research approach: In this study, the effect of cooling process on the final properties of polyethylene tanks prepared by rotational molding method is investigated. Three different cooling methods comprised of cooling with water, cooling by air, and quiescent cooling is selected and their mechanical and thermal properties were investigated.
Main results: The results of the tensile test show that as the tank is cooled faster, the elongation at break will be higher. It is also demonstrated that the air cooling method results in the lower elongation at break. The results of the thermal properties show that higher cooling rate creates thicker crystals in the fragment which requires higher energy to overcome these thick crystals. According to the results of the thermal properties and using the softening temperature test it is found that by increasing the cooling rate, the softening temperature will be increased as well which will improve the application of the tank in high temperature conditions. Melt flow rate and density tests are also performed to confirm the results of mechanical and thermal properties, respectively. Charpy impact test is performed at ambient temperature to confirm mechanical behavior induced by crystal structure. All in all, cooling by water performs better than other methods in terms of mechanical and thermal properties.

Abstract Research Subject: Polymer melts show complex response under the act of deformation. This response has direct relation to their molecular structure. The purpose of this study was to investigate the rheological behavior of branched polymers and the effect of branching on linear and nonlinear viscoelastic flow for usage in various industrial applications.
Research Approach: For this purpose, the tests such as frequency sweep and extensional for two polyethylene (LDPE) with long branches have been used. From these tests we obtained storage and loss moduli, complex viscosity and extensional viscosity. Molecular models in nonlinear regions can also be used in this regard. Main Results: Linear tests can partly show the presence of branch in LDPE, while nonlinear tests show strain hardening behavior for branched sample. One of the models for branched polymers is the Multimode Pom-Pom (MPP) model which can be used to predict the strain hardening phenomenon in extensional flows. In this study, the average number of lateral branches was also calculated using this model.

Abstract Abstract
Research subject: The need to increase agricultural production in proportion to population growth and water crisis management requires initiatives that can increase the quantity and quality of crops by using soil moisture storage methods while preserving the environment. In this study, the effect of different wt. % of Thermoplastic starch (TPS) with maleic anhydride (MA) as compatibilizer and nanoclay (15A) on gel content and mechanical properties of Polylactic acid (PLA) and blends of Linear low-density polyethylene/ Low-density polyethylene (LLDPE / LDPE) was evaluated.
Research approach: Here, 0, 10, 20 and 30 wt. % TPS were added to the blends of LLDPE/LDPE (20/80) and also PLA. Independent parameters in the experimental design were wt. % of TPS, basic polymer type that was PLA or TPS and aging test. For dependent parameters were considered gel content, tensile strength, elongation at break and elastic modulus. Experiments were designed in General Full Factorial Design and performed in three replications.
Main results: Gel content in LLDPE/LDPE blends increased with the addition of TPS and decreased for PLA blends. The gel content change range for experimental samples before and after the aging test was between 10 to 21 and 2 to 5 percent, respectively. Tensile strength and elongation at break were reduced by adding TPS in both series of compounds before aging test. But this reducing rate was less in the 20 wt. % of TPS. The values ​​of tensile strength and elongation at break were: 12 to 19 MPa and 50 to 350 percent, respectively. These values changed after the aging test between 7 and 11 MPa and from zero to 5 percent, respectively.
Keywords: biodegradability, low density polyethylene, poly lactic acid, thermoplastic starch.

Abstract The porosity of electrospun nanofibers web is a significant parameter affecting various areas of nanofibers applications. Thus, at first, the effect of most effective parameters, the concentration of polymer solution and flow rate, on the diameter of polyvinyl alcohol nanofibers, as a dissolving component, were investigated. Afterward, the hybrid web of polyamide 6/polyvinyl alcohol (PA/P) was prepared via a two-sided dual-nozzles electrospinning method. The morphology, diameter, pore size of nanofibers web and the effect of dissolving constituent were studied based on images of the scanning electron microscope. To measuring the porosity of nanofibrous webs, three practical and straightforward methods that have been proposed in the literature were utilized. It was observed that when one component was dissolved, the diameter of the resultant web was decreased, and the porosity has been reduced to about 70% based on the best selected method of porosity. Additionally, the average pore size of electrospun PA6 webs has been decreased about 30-58% relative to the original hybrid webs.