Polyolefins Functionalization
Valentin Olegovich Kudyshkin; Nurad Ismatovich Bozorov; Ruslan Khaitkulovich Madiev; Bektemir Khamidovich Ruziev; Nurbek Shodievich Ashurov; Sayera Sharafovna Rashidova
Abstract
Copolymers of methyl acrylate were grafted onto low-molecular-weight polyethylene in the presence of benzoyl peroxide in o-xylene. The formation of these copolymers was confirmed by functional analysis of the ether groups and Fourier-transform infrared spectroscopy. Various synthesis patterns were demonstrated, ...
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Copolymers of methyl acrylate were grafted onto low-molecular-weight polyethylene in the presence of benzoyl peroxide in o-xylene. The formation of these copolymers was confirmed by functional analysis of the ether groups and Fourier-transform infrared spectroscopy. Various synthesis patterns were demonstrated, which furnished grafted copolymers with a wide range of compositions. X-ray diffraction analysis showed that grafting led to changes in the crystalline structure of low-molecular-weight polyethylene. The grafting sequences of the methyl acrylate units may disrupt the order of the crystalline planes in polyethylene, and with an increase in their content, the crystalline phase in polyethylene becomes less prominent. These copolymers can be used as compatibilizers for CB-filled polyethylene (CB: carbon black). The effect of the grafted copolymers on the properties of high-density polyethylene composites containing CB was evaluated. The composites of polyethylene and the grafted copolymers exhibited enhanced thermal stability, plausibly associated with a decrease in the average size of the CB particles.
Food Packaging
Ali Sefa Onsekizoglu; Ali Durmus; Ferhat Şen; Memet Vezir Kahraman; Ismail Aydin
Abstract
In this study, LDPE compounds were prepared using different types of solid and liquid natural additives by melt compounding method. Spent coffee ground (SCG) and organoclay (OCL) powders were used as bio-based and mineral-based solid additives, respectively. Carvacrol and Liquidambar orientalis ...
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In this study, LDPE compounds were prepared using different types of solid and liquid natural additives by melt compounding method. Spent coffee ground (SCG) and organoclay (OCL) powders were used as bio-based and mineral-based solid additives, respectively. Carvacrol and Liquidambar orientalis (LO) oil were used as functional liquid additives. Morphological, thermal, mechanical, viscoelastic, and antimicrobial properties of samples were characterized with various analytical methods and the effects of solid and liquid additive combinations on the physical properties of film samples were quantified. It was observed that the SCG and LO oil made the film color darker but s till transparent. Contact angle measurements indicated that the liquid additives increased the hydrophilicity of LDPE films. Based on the thermal and physical tests, it was found that the solid additives acted as reinforcing agents in LDPE matrix but liquid additives significantly modified the physical properties of LDPE composite films such as increasing the elongation and recovery rates and decreasing the creep strength as well as the improving the antimicrobial properties. The analysis of antimicrobial properties of samples using gram-positive and gram-negative bacteria exhibited that the carvacrol and LO oil significantly inhibited the bacterial growth. This study showed that transparent and antimicrobial flexible packaging films with thermal and mechanical durability could be prepared using sustainable, natural, and waste materials.
Composites and nanocomposites
Tohid Abdolahzadeh; Jalil Morshedian; Shervin Ahmadi
Abstract
Researchers have studied the possibility of various polymer composites for radiation shielding applications. Lightness and non-toxicity of these materials are their significant advantages compared to Pb base traditional and common shields. In this research, polyethylene (HDPE)-based composites for shielding ...
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Researchers have studied the possibility of various polymer composites for radiation shielding applications. Lightness and non-toxicity of these materials are their significant advantages compared to Pb base traditional and common shields. In this research, polyethylene (HDPE)-based composites for shielding against X-ray radiations were prepared by utilizing several weight fractions of the nano tungsten oxide, bismuth oxide, and barium sulfate, which were decorated on nanographene oxide (10, 15, 20, and 25 wt%). The linear and mass attenuation coefficient values of samples were investigated experimentally with an X-ray tube at radiology energy ranges and estimated theoretically by using MCNP code (Mont Carlo Nanoparticle program). Results illustrate that by increasing the nanoparticles content, the linear attenuation coefficient parameter and the absorbed dose values increased dramatically. The shielding efficiency of the prepared samples has been shown by measuring the HVL values. Furthermore, the effect of sample thicknesses on the attenuation properties of nanocomposites was studied in this research. The morphological properties of the samples were evaluated with SEM. The collected results showed that the particle size of the nanoparticles used has a uniform dispersion in the polymer matrix. The mechanical properties of nanocomposite samples were characterized by DMTA and tensile test. Nanocomposites containing 20% and 25% of tungsten oxide and bismuth oxide particles reached to 88% and 90% dose absorption, respectively.
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.
Catalysis
Alikhani Ali; Shokoufeh Hakim; Mehdi Nekoomanesh
Abstract
This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay ...
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This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay nanocomposites. The results revealed that by increasing MAO exposure time productivity decreased. Modification of nanoclay by NH3/MAO led to formation of exfoliated structures. In treatment with NH3/DDA, the change in reflux time resulted in different structures. SEM demonstrated that the morphology of the nanocomposites strongly depended on the modification method and treatment time. Dynamic mechanical analysis indicated that the elastic modulus of the nanocomposites increased by increasing MAO exposure time. The nanocomposites treated with different MAO exposure times showed similar thermal degradation behavior. The nanocomposite modified under the condition of 24 h DDA reflux time indicated the lowest thermal decomposition temperature due to poor dispersion of nanoclay in the synthesized nanocomposite. The nanocomposites modified by NH3/MAO had higher degree of crystallinity compared to those modified by NH3/DDA, which could be attributed to the difference in dispersion level of the modified clays. A relationship between the rheological properties, weight fraction and dispersion of modified nanoclay was observed. The findings showed that the modification condition had a significant influence on the morphology and properties of the synthesized nanocomposites.
Catalysis
Liang Zhu; Xuelian He; Ruihua Cheng; Zhen Liu; Ning Zhao; Boping Liu
Abstract
SiO2/MgCl2 (ethoxide type)/TiCl4 Ziegler-Natta catalysts for use in ethylene polymerization and ethylene/1-hexene copolymerization have been prepared using silica with a supported layer of magnesium ethoxide (Mg(OEt)2) as a catalyst precursor, followed by treating with TiCl4 at different Ti/Mg ...
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SiO2/MgCl2 (ethoxide type)/TiCl4 Ziegler-Natta catalysts for use in ethylene polymerization and ethylene/1-hexene copolymerization have been prepared using silica with a supported layer of magnesium ethoxide (Mg(OEt)2) as a catalyst precursor, followed by treating with TiCl4 at different Ti/Mg molar ratios, which showed significant effects on the active centers and pore structures of the catalysts. The formation amount of β-MgCl2 carrier increased to a maximum with increasing the Ti/Mg molar ratio from 1.50 to 2.25, and then decreased with the further increasing of Ti/Mg molar to 2.50. When the Ti/Mg molar ratio reached 2.25, the catalyst showed the best performance of polymerization, which could be attributed to the most active centers, high surface area and loose surface structure, mainly owing to the high conversion of Mg(OEt)2 to β-MgCl2. The polymers obtained showed medium and high molecular weight (Mw) with medium molecular weight distribution (MWD). In contrast to the conventional Mg(OEt)2-based ZN catalysts, the sphericity of particles was easy to control in this bi-supported catalyst. Furthermore, the prepared catalysts exhibited rather high activity, good copolymerization ability and hydrogen response.
Catalysis
Ting Fu; Ruihua Cheng; Xuelian He; Zhen Liu; Zhou Tian; Boping Liu
Abstract
Vanadium-modified (SiO2/MgO/MgCl2)•TiClx Ziegler-Natta catalysts were prepared through co-impregnation of water-soluble magnesium and vanadium salts under different pH values. Several key factors such as pH value of co-impregnation solution during catalyst preparation, catalyst performances including ...
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Vanadium-modified (SiO2/MgO/MgCl2)•TiClx Ziegler-Natta catalysts were prepared through co-impregnation of water-soluble magnesium and vanadium salts under different pH values. Several key factors such as pH value of co-impregnation solution during catalyst preparation, catalyst performances including catalytic activity, ethylene/1-hexene copolymerization and hydrogen response were investigated. It is found that the components, structures and performance of the catalysts are obviously affected by changing the pH value (pH=5, 7 and 9) of co-impregnation solution. An appropriate pH value (pH=7) can maximize catalytic activity and hydrogen response, while lower pH value (pH=5) is beneficial to the 1-hexene incorporation. The GPC results show that the polymers obtained have high average molecular weight.
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
Catalysis
Feng He; Peiyuan Li; Anyang Wu; Tao Xu; Zhisheng Fu; Liang Zhu; Zhiqiang Fan
Abstract
In this paper, a series of well-defined polyethylene-b-polytetrafluoroethylene diblock copolymers (PE–b– PTFEs) were prepared by a coupling reaction of hydroxyl-terminated polyethylene (PE–OH) and isocyanateterminated 1H,1H-perfluoro-1-tetradecanol (PFDO–NCO). PE–OH was ...
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In this paper, a series of well-defined polyethylene-b-polytetrafluoroethylene diblock copolymers (PE–b– PTFEs) were prepared by a coupling reaction of hydroxyl-terminated polyethylene (PE–OH) and isocyanateterminated 1H,1H-perfluoro-1-tetradecanol (PFDO–NCO). PE–OH was prepared by the coordination chain transfer polymerization using 2,6-bis[1-(2,6-diisopropylphenyl)imino ethyl] pyridine iron (II) dichloride /dry ethylaluminoxane/ZnEt2 as catalyst and subsequent in situ oxidation with oxygen. PFDO–NCO was synthesized through the condensation reaction of 1H,1H- perfluoro-1-tetradecanol (PFDO) with isophoronediisocyanate (IPDI). Subsequently, the thermal characterization and the application of these diblock copolymers were investigated. The relationship between the molecular structure and the properties was disclosed. The results indicated that the diblock copolymers were effective surface modification agents for linear low density polyethylene (LLDPE). After that the PE–b–PTFE being spin-coated onto the surface of LLDPE film, the film was dramatically turned into a superhydrophobic film with a water contact angle as high as 151.4º. This kind of film is potential to be used as selfcleaning, anti-icing and anticorrosion material.
Ali Behboudi; Yoones Jafarzadeh; Reza Yegani; Ali Akbari
Abstract
Grinded glass fiber (GGF) embedded high density polyethylene (HDPE) membranes were prepared via thermally induced phase separation method. FESEM images showed that all the membranes had leafy structure, indicating a solid-liquid mechanism during phase separation. The results of EDX and TGA analyses confirmed ...
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Grinded glass fiber (GGF) embedded high density polyethylene (HDPE) membranes were prepared via thermally induced phase separation method. FESEM images showed that all the membranes had leafy structure, indicating a solid-liquid mechanism during phase separation. The results of EDX and TGA analyses confirmed that the fibers were dispersed in the HDPE matrix uniformly. Normalized water flux of the membranes increased from 1 for the neat HDPE membrane to more than 4 for 10 wt% GGF/HDPE membrane. Moreover, the contact angle decreased from 129° to 94° as the GGF content increased in the membranes, showing an improvement in the surface hydrophilicity of the membranes. The AFM results revealed that the surface roughness of the membranes was increased with increasing the GGF content. The results of abrasion test revealed that the GGF/HDPE membranes had a more abrasion resistance than the neat HDPE membrane. Finally, the fouling behavior of the membranes was investigated by the filtration of BSA protein solution and the results showed that with increasing the glass fiber content, total fouling ratio decreased from 90% for the neat HDPE membrane to 62% for 10 wt% GGF/HDPE membrane, indicating that the antifouling properties of the membranes were improved due to the presence of glass fiber.
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''.
Polymeric foams
Christophe Daniel; Simona Longo; Gaetano Guerra
Abstract
Monolithic aerogels of high molecular weight polyethylene (Mw= 3x106- 6x106 g/mol) have been prepared by solvent extraction with supercritical carbon dioxide from thermoreversible gels prepared in decalin. These low density and highly porous aerogels present an apparent porosity up to 90%. The aerogel ...
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Monolithic aerogels of high molecular weight polyethylene (Mw= 3x106- 6x106 g/mol) have been prepared by solvent extraction with supercritical carbon dioxide from thermoreversible gels prepared in decalin. These low density and highly porous aerogels present an apparent porosity up to 90%. The aerogel morphology observed by scanning electron microscopy (SEM) is characterized by spherulitic structures being interconnected by fibers. X-ray diffraction experiments show that PE aerogels are highly crystalline with a degree of crystallinity of c.a. 80% and PE chains being packed into the typical orthorombic unit cell. Combined SEM and N2 sorption investigations show that PE aerogels are essentially macroporous with a small amount of mesopores. The oil-sorption performance of polyethylene aerogels has been also evaluated in this study in order to assess a possible use of these materials for oil spillage recovery and results show that aerogel macropores allow a very fast sorption kinetics with a 100% oil weight uptake obtained in less than 1 minute.
Catalysis
G. Hossein Zohuri; Saman Damavandi; Saeid Ahmadjo; Reza sandaroos; Mohammad A. Shamekhi
Abstract
A FI Zr-based catalyst of bis[N-(3,5-dicumylsalicylidene)-2′,6′diisopropylanilinato]zirconium(IV) dichloride was prepared and used for polymerization of ethylene. The effects of reaction conditions on the polymerization were examined in detail. The increase in ethylene pressure and rise ...
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A FI Zr-based catalyst of bis[N-(3,5-dicumylsalicylidene)-2′,6′diisopropylanilinato]zirconium(IV) dichloride was prepared and used for polymerization of ethylene. The effects of reaction conditions on the polymerization were examined in detail. The increase in ethylene pressure and rise in polymerization temperature up to 35 oC were favorable for catalyst/MAO to raise the catalytic activity as well as the viscosity-average molecular weight (Mv) of polyethylene. The activity of the catalyst was linearly increased with increasing MAO concentration and no optimum activity was observed in the range studied. Although introduction of the bulky cumyl and 2′,6′-diisopropyl alkyl substitution groups on ortho positions to the phenoxy-oxygen and on phenyl ring on the N, respectively enhanced the viscosity average molecular weight (Mv) of the obtained polymer strongly, diminished the activity of the catalyst. Neither the activity of the catalyst nor the (Mv) of the obtained polymer were sensitive to hydrogen concentration. However, higher amount of hydrogen could slightly increase the activity of the catalyst. The (Mv) of polyethylene ranged from 2.14×106 to 2.77×106 at the monomer pressure of 3 and 5 bar respectively which are much higher than that of the reported FI Zr-based catalysts.
