Polymer processing
Luisiana Morales-Zamudio; Francisco Rodriguez-Gonzalez; Minerva A.M Zamudio; Tomas Lozano; Juan Guillermo Martinez-Colunga; Saul Sanchez-Valdes; Luciano Da Silva; Erika Lopez-Martinez; Sergio Flores-Gallardo
Abstract
In this research we provide a practical guide to achieve the successful extrusion of LDPE tapes commercially used in mesh fences, with controlled dimensions, good mechanical properties and weather resistance. Here we share: 1) The die design dimensions and its specialized slotted manufacture to get the ...
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In this research we provide a practical guide to achieve the successful extrusion of LDPE tapes commercially used in mesh fences, with controlled dimensions, good mechanical properties and weather resistance. Here we share: 1) The die design dimensions and its specialized slotted manufacture to get the veins of tape, 2) Processing temperatures profile, 3) Cooling method, 4) Hot stretch ratio (HSR), and 5) The effect of colorant and ultraviolet rays’ protector, due to the outdoor use of polymer privacy tape. The formulated tape (0.8 wt. % UV protector and 5 wt. % colorant) showed the best performance under accelerated aging and reached good mechanical properties up to a time of 2000 hours compared to its initial values. The dye and the UV additive improved the mechanical properties. All these, led to obtain a LDPE tape to fulfill the expectative and characteristic of a commercial tape used for mesh fences.
Polymer processing
Sergey Chernyshov; Lyudmila R. Lyusova; Manizha B. Zharylganova; Lada A. Konyaeva
Abstract
The work examines the influence of linear low-density polyethylene on the basic technological, physical-mechanical and fatigue properties of elastomeric materials based on synthetic isoprene rubber of the SKI-3 brand. Synthetic polyisoprene rubber of SKI-3 brand manufactured by LLC “Togliattikauchuk” ...
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The work examines the influence of linear low-density polyethylene on the basic technological, physical-mechanical and fatigue properties of elastomeric materials based on synthetic isoprene rubber of the SKI-3 brand. Synthetic polyisoprene rubber of SKI-3 brand manufactured by LLC “Togliattikauchuk” was used as synthetic polyisoprene rubber, and LLDPE 218 BJ manufactured by SABIC was used as linear low-density polyethylene. Rubber blends were made in a Haake PolyLab rubber mixer for 9 minutes with further introduction of sulfur on rollers for 1.5 minutes. It was found that the introduction of linear low-density polyethylene into the rubber mixture leads to a significant increase in green strength (up to the level of natural rubber and even higher). It has also been established that LLDPE increases the Mooney viscosity of the rubber compound, the stress at 100% and 300% elongation and increases the residual elongation after rupture of the vulcanizates, but has virtually no effect on the vulcanization process of the rubber compound and has an insignificant effect on the tensile strength. The fatigue characteristics of vulcanizates containing LLDPE up to 7 wt% are at the level of the vulcanizate based on natural rubber. It has been shown that the combination of synthetic polyisoprene brand SKI-3 with linear low-density polyethylene LLDPE 218 BJ at a component ratio of 93/7 allows obtaining an elastomeric material approaching the elastomeric material based on natural rubber RRS1 in key indicators (first of all, in terms of green strength).
Polymer processing
Parthiv M. Trivedi; Sandip Patil; Virendra K. Gupta
Abstract
Ultra-high molecular weight polyolefin (UHMWPO) has enormous potential applications due to their excellent mechanical properties such as tensile strength, flexural modulus, toughness and outstanding chemical resistance. But the processing of polyolefin, in particular, UHMWPO fibers cannot be processed ...
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Ultra-high molecular weight polyolefin (UHMWPO) has enormous potential applications due to their excellent mechanical properties such as tensile strength, flexural modulus, toughness and outstanding chemical resistance. But the processing of polyolefin, in particular, UHMWPO fibers cannot be processed by conventional methods due to its very high melt viscosity. In this work, we synthesized isotactic ultra-high molecular weight polypropylene (UHMWPP) resin and studied the processability of UHMWPP fibers using gel spinning and investigated physicomechanical properties. UHMWPP gel was made at various concentrations in decalin solvent at 150°C to produce consistent spinning dope solutions. The 7 wt.% concentration of UHMWPP was deemed best for fiber creation, compared to 3 wt.% and 5 wt.%. A rheological time sweep was done to ensure the gel's stability at 170°C before the spinning process. The UHMWPP's gelation and fiber formation were studied by tweaking the gel concentration and adjusting the processing temperature. The resulting UHMWPP monofilament had a measure of 220-250 denier. The hot stretched fibers were analyzed with the scanning electron microscope (SEM) to understand the surface morphology of the fibers. The crystal morphology of UHMWPP fibers was measured with wide-angle x-ray scattering (WAXS) and DSC. The X-ray measurement of hot stretched UHMWPP fibers showed crystalline peaks compared to those without stretched fibers.
Polymer processing
Shirin Shokoohi; Ghasem Naderi
Abstract
Elastomer vulcanizates based on natural rubber (NR), NR reclaim (NRR) and layered silicates were compounded in an internal mixer and cured on a two-roll mill. Cure characteristics and mechanical properties of samples based on 50NR/50NRR reinforced with Cloisite 20A, Cloisite 30B and Nanolin DK1 were ...
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Elastomer vulcanizates based on natural rubber (NR), NR reclaim (NRR) and layered silicates were compounded in an internal mixer and cured on a two-roll mill. Cure characteristics and mechanical properties of samples based on 50NR/50NRR reinforced with Cloisite 20A, Cloisite 30B and Nanolin DK1 were compared to those of conventional NR/NRR/kaolin microcomposites. Due to the light/soft nature of organoclays suppressing the friction forces, the minimum torque values decreased in the presence of organoclays, whereas the crosslink density, evidenced by the difference between the maximum and minimum torque values, increased in all samples and scorch times shortened by 37% to a minimum in the presence of Nanolin alkaline/catalytic role in the cure reaction. Fatigue resistance improved by about 10% benefiting the crack tips blunting/energy consuming hysteresis mechanisms motivated by the organoclays among which Nanolin DK1 provides the most efficient dispersion/distribution of nanolayers by faster intragallery crosslinking reactions that pushes the stacks apart. Higher states of dispersion in this sample would also promote strain-induced crystallization under deformation responsible for the improvements seen in the modulus and elongation-at-break. Two-step mixing sequence further improved the compound performance due to the dispersion state progress confirmed by X-ray diffraction and transmission electron microscopy (20% in fatigue resistance and 53% in tensile modulus). In-situ compatibilization through bis(triethoxysilylpropyl)tetrasulfide bi-functional silane coupling agent also promoted modulus and fatigue resistance. However, a prolonged scorch time was observed due tothe blinded NR cure-reactive sites as well as steric hindrance of large functional groups in the presence of this coupling agent.
Characterization
Reza Poorghasemi; Yousef Jahani
Abstract
In this work, the compatibility and crystallinity of low density polyethylene (LDPE) and polybutene-1 (PB-1) blends were studied. Various blends of LDPE/PB-1 containing 5, 10 and 20 wt.% PB-1 were prepared in a corotating twin-screw extruder and characterized by scanning electron microscopy (SEM), shear ...
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In this work, the compatibility and crystallinity of low density polyethylene (LDPE) and polybutene-1 (PB-1) blends were studied. Various blends of LDPE/PB-1 containing 5, 10 and 20 wt.% PB-1 were prepared in a corotating twin-screw extruder and characterized by scanning electron microscopy (SEM), shear oscillation rheology and wide-angle X-ray diffractometry (WAXD). A matrix-droplet morphology was observed in SEM images, indicating incompatibility of the two polymers in the solid state. Compared to neat LDPE, the relaxation spectra of the blends were broadened, and a slight increase in their relaxation times was observed. The relaxation time of the blends was enhanced by increasing PB-1 content, which was further proved by fitting rheological data in the Carreau-Yasuda model. Deviation of Cole-Cole diagrams from circular shape means that the blend samples were not miscible and the positive-deviation behavior of the complex viscosity and storage modulus from the mixing rule revealed the formation of strong interfacial interactions. The crystallinity of both LLDPE and PB-1 was decreased as a result of blending. The peaks attributed to the form II of PB-1 crystals were eliminated and the peaks related to LDPE were obviously weakened, suggesting to prevent crystallinity of polymers which is associated with a reduction in the total crystallinity percentage for the blend. The reduction of crystallinity was more pronounced in PB-1 phase.
Polymer processing
Milad Moradian; Taher Azdast; Ali Doniavi
Abstract
Polyolefins have been widely used in the electrical insulation and cable industry in recent years. One of the main usages of these materials is dielectric insulation in coaxial cables. Low attenuation and high signal transmission speed are among the desired features in coaxial cables. The role of polyethylene ...
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Polyolefins have been widely used in the electrical insulation and cable industry in recent years. One of the main usages of these materials is dielectric insulation in coaxial cables. Low attenuation and high signal transmission speed are among the desired features in coaxial cables. The role of polyethylene foam on signal transmission speed in the coaxial cables is the main focus of this study. In the present study, the velocity factor of coaxial samples with different dielectric structures is investigated in both theoretical and experimental approaches. In theoretical formulation, only the void fraction of foam is taken into consideration and other foam properties such as cell density, cell size, and foam structure are neglected. This is the reason for the difference observed between theoretical and experimental results. In theoretical results, a linear increase in the velocity factor is witnessed with the increase of the void fraction while in experimental results there are some exceptions. The foaming degree of the samples was reached 63% causing a 37.7% decrease in theoretical relative permittivity and consequently a 26.8% increase in theoretical velocity factor. On the other hand, up to 36% increase is observed in the experimentally measured velocity factor of foamed dielectric samples compared to the samples with solid polyethylene dielectric.
Polymer processing
Moammadreza Nakhaei; Ali Ahmadi; Ghasem Naderi
Abstract
Polyamide 6 / nitrile butadiene rubber / nanoclay (PA6/NBR/clay) nanocomposite has gathered wide acceptance in industry. Laser welding, as a fabrication method, is applied to welding of polymer nanocomposites. In this study, the input parameters (clay (Closite 30B) content, laser power, scan velocity ...
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Polyamide 6 / nitrile butadiene rubber / nanoclay (PA6/NBR/clay) nanocomposite has gathered wide acceptance in industry. Laser welding, as a fabrication method, is applied to welding of polymer nanocomposites. In this study, the input parameters (clay (Closite 30B) content, laser power, scan velocity and stand-off-distance) are varied to achieve the best responses (tensile strength of welds). Response surface methodology (RSM) is utilized to investigate the effect of input parameters on mechanical properties. Morphology and tensile properties of nanocomposites were observed with scan electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test. The results demonstrated that increasing the clay content from 1 to 5%wt and stand-off-distance from 4 to 8 mm decreased tensile strength of welds about 15% and 5%, respectively. The tensile strength of PA6/NBR composite is 25.6, whereas the prediction models showed that under optimal conditions of laser power of 105 W, scan velocity of 300 mm/min and stand-off-distance of 4 mm, the maximum tensile strength of PA6/NBR nanocomposite with 1, 3 and 5 % nanoclay are 27.2 MPa, 27.6 MPa and 24.7 MPa, respectively. These tensile strengths are about 99, 89 and 73% of the strength of these nanocomposites before welding.
Polymer processing
Ali Mahmoudi Yayshahri; Seyed Jamaleddin Peighambardoust; Abolfazl Shenavar
Abstract
High impact polystyrene (HIPS)/corn starch blends were prepared in presence of glycerol as a plasticizer via melt extrusion process by a twin-screw extruder. The novelty of this work is first, because of the use of pre-gelatinized corn starch as modified one and second, the procedure of making blends ...
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High impact polystyrene (HIPS)/corn starch blends were prepared in presence of glycerol as a plasticizer via melt extrusion process by a twin-screw extruder. The novelty of this work is first, because of the use of pre-gelatinized corn starch as modified one and second, the procedure of making blends by extruder which makes it ease of access and also industrially possible. The blends were then characterized by scanning electron microscopy (SEM) to visualize morphology of blends and dispersion of starch in HIPS matrix, soil burial test (SBT) to investigate of blend biodegradability by measuring weight loss of samples, Izod impact strength test to evaluate of impact properties, melt flow index (MFI), thermo-gravimetric analysis (TGA) and Vicat softening point (VSP) tests to evaluate their thermal properties of prepared blend samples. Results indicated that these properties were affected by the amount of starch and glycerol used for preparation of blends in a way that addition of starch and glycerol led to a faster degradation rate especially in first two weeks, more decomposition stages through TGA, decrease in values of Izod impact strength and VSP. Measurements also showed that higher amount of starch led to decrease in the value of melt flow rate (MFR), although it was increased by addition of glycerol.
Polymer processing
Ali Foroozan; Tahereh Behboodi; Yousef Jahani
Abstract
In this study, the compatibility of the blends of polypropylene (PP) and polybutene-1(PB-1) homopolymer before and after long chain branching process were studied. The blends were prepared and long-chain branched directly via reactive extrusion process in presence of free radical initiator and trimethylolpropane ...
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In this study, the compatibility of the blends of polypropylene (PP) and polybutene-1(PB-1) homopolymer before and after long chain branching process were studied. The blends were prepared and long-chain branched directly via reactive extrusion process in presence of free radical initiator and trimethylolpropane tri methacrylate (TMPTMA) poly functional monomer. The optimum percentage of TMPTMA and PB-1 resin have determined by measuring the grafting efficiency and by studying the rheological behavior in shear steady state and transient extensional mode and the morphology of samples were investigated by scanning electron microscopy (SEM). Referring to the blends’ morphologies observed in SEM images which were approved by rheological data, it was found an enhanced compatibility in the blend by branching with 1.5wt% for TMPTMA and 10wt% for PB-1 resin. In this composition, the highest grafting efficiency of 37% and branch index of 5.2 achieved. The zero shear viscosity (η0) of PP is increased from 4500 Pa.s to 6800 Pa.s after branching process and enhanced more to 2400 Pa.s by using 10 wt% PB-1 resin. The Long-chain branched structure showed prominent higher zero-shear viscosity, longer relaxation time and pronounced strain-hardening behaviors. The branching behavior of samples were quantified by using extensional viscosity data and the branch index of samples were determined.
Polymer processing
Fatemeh Hassan; Mehdi Entezam
Abstract
Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was ...
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Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was carried out at different doses (0-80 kGy) under atmosphere air and at ambient temperature. Melt flow index (MFI) measurements showed PP samples irradiated in the range of 10 to 40 kGy are suitable to use in injection molding. Electron beam irradiation decreased the viscosity and the shear thinning rheological behavior of PP. The differential scanning calorimetry (DSC) analysis revealed that electron beam irradiation increased the crystallinity percentage and temperature of PP, but decreased the melting temperature. Among all treated samples, the PP20, irradiated at the dose of 20 kGy, showed the highest impact resistance. It had higher Young’s modulus and tensile strength, but lower elongation-at-break in comparison with untreated PP.
Polymer processing
Shahab Hoseinpour; Yoones Jafarzadeh; Reza Yegani; Sepideh Masoumi
Abstract
The aim of the present work is to enhance the antifouling properties of polypropylene (PP) membrane based on hydrophilicity improvement. Different contents of neat and modified nanodiamond (0.25, 0.50, 0.75 and 1.00 wt.%) were embedded into PP membranes. Nanodiamond nanoparticles were carboxylated by ...
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The aim of the present work is to enhance the antifouling properties of polypropylene (PP) membrane based on hydrophilicity improvement. Different contents of neat and modified nanodiamond (0.25, 0.50, 0.75 and 1.00 wt.%) were embedded into PP membranes. Nanodiamond nanoparticles were carboxylated by heat treatment method and the presence of carboxyl functional groups on the surface of nanoparticles was confirmed by FTIR analysis. Membranes were then characterized by FESEM, contact angle and tensile strength tests. At the same content of nanoparticles, hydrophilicity, pure water flux and tensile strength of PP/ND-COOH membranes were more than those of PP/ND membranes. Membranes embedded with 0.75 wt. % of neat and modified nanoparticles were used in a submerged membrane bioreactor (SMBR) system along with neat PP membrane. The results showed that critical flux values for neat PP, PP/ND and PP/ND-COOH membranes were 7, 18 and 22 L/(m2.h), respectively. Analysis of fouling mechanisms revealed that antifouling properties of 0.75 wt. % PP/ND-COOH membrane were higher than those of other two ones so that irreversible fouling ratio decreased from 88.9% for neat PP to 47.8% for PP/ND-COOH membrane.
Polymer processing
Jun Huang; Guanghua Tian; Huayi Li; Lei Li; Qian Li; He Huang; Shuirong Zheng; Youliang Hu
Abstract
In this work, a series of polypropylene/polyvinyl butyral (PP/PVB) blends were prepared by melt-blending process, at PVB loadings 3 wt%, 10 wt%, and 30 wt%. The effects of PVB on crystallization behavior of PP were investigated by differential scanning calorimetry (DSC), and polarized optical ...
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In this work, a series of polypropylene/polyvinyl butyral (PP/PVB) blends were prepared by melt-blending process, at PVB loadings 3 wt%, 10 wt%, and 30 wt%. The effects of PVB on crystallization behavior of PP were investigated by differential scanning calorimetry (DSC), and polarized optical microscopy (POM). The isothermal crystallization kinetics were analyzed by Avrami equations. It was found that the addition of PVB strikingly reduced the overall crystallization rate of PP. The POM results further indicated that the crystallization rate of PP/PVB was significantly reduced by reducing the nucleation density of PP with the addition of PVB. The fractured surface morphology of PP/PVB blends was characterized by scanning electron microscopy (SEM), and the results showed that the PVB was uniformly dispersed in the PP matrix as small spherical particles, with a good dispersion and dimensional stability.
Polymer processing
Mehdi Hajiabdolrasouli; Amir Babaei
Abstract
The effects of three different mixers, two different feeding orders and nanoclay content on the structure development and rheological properties of PE/nanoclay nanocomposite samples were investigated. Fractional Zener and Carreau–Yasuda models were applied to discuss the melt linear viscoelastic ...
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The effects of three different mixers, two different feeding orders and nanoclay content on the structure development and rheological properties of PE/nanoclay nanocomposite samples were investigated. Fractional Zener and Carreau–Yasuda models were applied to discuss the melt linear viscoelastic properties of the samples. Moreover, scaling law for fractal networks was used to quantify clay dispersion depended on the PE matrix structure. The simultaneous feeding resulted in better dispersion and melt intercalation for the nanoclay as compared to the compatibilizer/nanoclay masterbatch feeding. The twin screw extruder (Brabender DSE 25 model) showed greater potential for melt intercalation of PE/nanoclay as compared to the internal mixers (Brabender W50 and Haake Rheomix 3000 batch mixer) . Comparing the thermal Analysis of PE, PE/PE-g-MA and PE/nanoclay samples by DSC technique showed the opposite effect of the compatibilizer and the nanoclay to crystallization behavior of PE. PE/nanoclay cast film samples were produced with three different draw ratios. X-ray diffraction structural analysis in conjunction with the melt linear viscoelastic measurements confirmed that the PE/nanoclay cast film produced at higher draw ratio showed the more effective melt intercalation. Tensile test showed the machine direction modulus and yield strength of both PE and PE/nanoclay cast film samples reduced with increase of draw ratio
Polymer processing
Amir Mostafapour; Ghasem Naderi; Mohammad Reza Nakhaei
Abstract
In this study, thermoplastic polyolefin elastomeric (TPO) nanocomposites were fabricated by friction stir processing. The effect of different pin geometries on clay dispersion and mechanical properties of the TPO nanocomposite reinforced with 3% wt nanoclay has been first investigated. The optimum pin ...
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In this study, thermoplastic polyolefin elastomeric (TPO) nanocomposites were fabricated by friction stir processing. The effect of different pin geometries on clay dispersion and mechanical properties of the TPO nanocomposite reinforced with 3% wt nanoclay has been first investigated. The optimum pin geometry namely threaded cylindrical pin was then used to fabricate the nanocomposites containing 3, 5 and 7 wt% nanoclay. The results showed that increase in the clay content increased the tensile strength and tensile modulus of the nanocomposite from 15.8 to 22.76 MPa and 568 to 751 MPa, respectively. The experimental stress – strain curves of nanocomposites were compared with eight constitutive models including Mooney – Rivlin, the second-order polynomial, Neo – Hookean, Yeoh, Arruda – Boyce, Van der Waals and the third- and sixth-order Ogden. The comparisons showed that there was an agreement between the experimental data and the sixth-order Ogden model. Three micromechanical models Halpin – Tsai, inverse rule of mixture and linear rule of mixture were applied to investigate the Young’s modulus of nanocomposites. Because of the significant difference between the Young’s modulus obtained from these models and the ones obtained from experimental data, a modifying factor was used to improve the theoretical predictions obtained from the models.
Polymer processing
Mohammadreza Rahnama; Abdulrasoul Oromiehie; Shervin Ahmadi; Ismaeil Ghasemi
Abstract
In this research, high oxygen-barrier films were organized based on low-density polyethylene (LDPE)/ ethylene vinyl alcohol (EVOH)/ polyethylene-grafted maleic anhydride (LDPE-g-MA) compatibilizer. The effects of 10–30 wt. % EVOH and 0–10 wt. % LDPE-g-MA loadings on the properties of final ...
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In this research, high oxygen-barrier films were organized based on low-density polyethylene (LDPE)/ ethylene vinyl alcohol (EVOH)/ polyethylene-grafted maleic anhydride (LDPE-g-MA) compatibilizer. The effects of 10–30 wt. % EVOH and 0–10 wt. % LDPE-g-MA loadings on the properties of final films were evaluated. The morphology of specimens was observed by using scanning electron microscopy (SEM). Oxygen transfer rate (OTR) results revealed that the addition of EVOH up to 30 wt. % to neat LDPE could significantly decrease oxygen permeability. The LDPE-g-MA which increased the permeability needed to be fine-tuned its amount based on the EVOH loading in different samples. The experimental results revealed that the addition of 30 wt. % EVOH to the LDPE matrix without adding LDPE-g-MA gave the best oxygen barrier properties. Elastic modulus and tensile strength increased with incorporation of EVOH and LDPE-g-MA into the polyethylene matrix. On the other hand, elongation-at-break decreased with the addition of EVOH and increased with the introduction of compatibilizer to the samples. Incorporation of EVOH and LDPE-g-MA into the LDPE matrix and increasing their amounts led to higher storage modulus and zero shear rate viscosity, but lowered the frequency value at the intersection point of storage modulus (G') and loss modulus (G''). The only exception was that in the samples without compatibilizer, the increase in the EVOH content resulted in a lower zero shear rate viscosity and a higher frequency value at the intersection point of G' and G''.
