Catalysis
Gholam-Reza Nejabat
Abstract
Since 1999, when Takuzo Aida proposed the preparation of high density polyethylene (HDPE) crystalline nanofibers through polymerization of ethylene by a Cp2 TiCl2 /MCM-41 catalyst, many researchers have published various papers on different aspects of the idea. The published researches show that the ...
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Since 1999, when Takuzo Aida proposed the preparation of high density polyethylene (HDPE) crystalline nanofibers through polymerization of ethylene by a Cp2 TiCl2 /MCM-41 catalyst, many researchers have published various papers on different aspects of the idea. The published researches show that the endeavors to polymerize other types of alpha olefins, especially propylene, to obtain polyolefins with crystalline nanofiberous morphology have not been successful and no one has reported such morphology for them. In the present article, a possible reason behind these observations is proposed. Comparing the direction of the growth of HDPE chains and isotactic polypropylene (iPP) helices to become appropriate for making polymer crystals shows that HDPE chains are able to form crystal unit cells without concerning upward or downward chain growth direction, while the growth direction of adjacent iPP chains might be responsible for unsuccessful synthesis of crystalline iPP nanofibers in confined channels of the mesoporous catalysts. iPP helices can crystallize beside each other only in the form of anticline isochiral helices.
Catalysis
Andrea M. Rimkus; Helmut G. Alt
Abstract
Eight different zirconium phenoxyimine complexes were synthesized, characterized and tested as catalysts for ethylene polymerization. The phenoxyimine compounds were prepared by condensation of substituted salicylaldehydes with aliphatic and aromatic amines, the substituted salicylaldehydes from ortho ...
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Eight different zirconium phenoxyimine complexes were synthesized, characterized and tested as catalysts for ethylene polymerization. The phenoxyimine compounds were prepared by condensation of substituted salicylaldehydes with aliphatic and aromatic amines, the substituted salicylaldehydes from ortho substituted phenols and paraformaldehyde. The introduction of iodo substituents was achieved either by iodination of the aldehyde component followed by condensation with amines or the iodination of the aldehyde after the condensation with amines or the iodination via condensation with iodo substituted amines. Deprotonation of the hydroxy function of phenoxyimine compounds and reaction with zirconium tetrachloride gave mononuclear bis(phenoxyimine) zirconium complexes in good yields. These complexes were activated with methylaluminoxane (MAO) and applied for ethylene polymerization. The performances of the various catalysts were compared and structure-property-relationships were discussed.
Polyolefin recycling
Samira Maou; Yazid Meftah; Ahmed Meghezzi
Abstract
Thermo-mechanical recycling process is the cheapest way to recover plastic waste such as LDPE with low ecological impact. Thus, the goal of this work is to obtain high-performance microcomposites from polyvinyl chloride (PVC), recycled low-density polyethylene (r-LDPE), calcium carbonate (CaCO3), and ...
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Thermo-mechanical recycling process is the cheapest way to recover plastic waste such as LDPE with low ecological impact. Thus, the goal of this work is to obtain high-performance microcomposites from polyvinyl chloride (PVC), recycled low-density polyethylene (r-LDPE), calcium carbonate (CaCO3), and calcium/zinc stearate (CaSt2/ZnSt2). The effect of the two ratios of thermal stabilizers with different concentrations on the mechanical properties and thermal stability of PVC and PVC/r-LDPE (1:1) blend was studied. The samples were characterized using infrared spectroscopy (FTIR), mechanical tests, thermal analysis, and scanning electron microscopy (SEM). The addition of 5 phr of CaSt2:ZnSt2 (9:1) to PVC (MC4) resulted in optimal tensile strength and elongationat-break values. In addition, MC4 showed high thermal stability. Moreover, the incorporation of r-LDPE into PVC made the PVC matrix stronger and more stable than pure PVC, which yields high mechanical and thermal performances. Furthermore, an outstanding synergistic effect is obtained when a heat stabilizer rich in calcium is combined with CaCO3 and r-LDPE. This PVC/r-LDPE blend as a composite can be used in several industrial fields.
Characterization
Mehri Dana; Gholam Hossein Zohuri; Navid Ramezanian; Saeid Asadi Shahidi; Sohail Yazdanbakhsh
Abstract
Silane cross-linking of metallocene-based polyethylene-octene elastomer (POE)/linear low density polyethylene (LLDPE) blend was carried out using two-step Sioplas process in an industrial scale twin-screw extruder. In the study, grafting and cross-linking reactions of vinyl trimethoxy silane (VTMS) were ...
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Silane cross-linking of metallocene-based polyethylene-octene elastomer (POE)/linear low density polyethylene (LLDPE) blend was carried out using two-step Sioplas process in an industrial scale twin-screw extruder. In the study, grafting and cross-linking reactions of vinyl trimethoxy silane (VTMS) were analyzed using FTIR technique. It was found that the cured compound showed absorption peaks at 1078 cm-1 and 955 cm-1 related to Si-O-Si bonds. A peak was also observed at 3405 cm-1 of hydroxyl group produced from hydrolysis of methoxyethylene group during of curing process, reflecting that curing reaction was not completed. The samples were cured at different time intervals (15 min-16 hours). The gel content values determined by solvent extraction and FTIR were in good agreement at curing times more than 4 hours. The efficiency of the silane grafting reaction was determined using the ratio of the absorption peak at 1092 cm-1 characteristic of methoxy to the transmittance peak at 1378 cm-1 characteristic of methyl group, which is considered as the internal standard. The results showed the highest efficiency of silane grafting reaction at 5 w% of VTMS with the least amount of internal standard ratio (0.029), at which the lowest MFI value, and the highest values for gel content, tear strength, compression set and hot set 200 °C were obtained.
Catalysis
Farabi Hossain; Md Enamul Hoque
Abstract
This mini-review addresses the burgeoning requirements for environmentally friendly processes in the polymer industry, focusing on recent progress in developing catalytic systems for sustainable olefin polymerization. Improvements in homogeneous and heterogeneous catalyst design have resulted in greater ...
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This mini-review addresses the burgeoning requirements for environmentally friendly processes in the polymer industry, focusing on recent progress in developing catalytic systems for sustainable olefin polymerization. Improvements in homogeneous and heterogeneous catalyst design have resulted in greater control over polymer properties (molecular weight, tacticity, comonomer incorporation). Particularly, Group 4 metallocene and post-metallocene catalysts have enjoyed high activity and a degree of control over polymer microstructure. Late transition metal catalysts (nickel and palladium complexes in particular) afford unique advantages in producing branched polyethylene and conducting polymerizations in polar solvents. Computational studies and novel support strategies have yielded improvements for heterogeneous Ziegler-Natta catalysts. Potential for reducing environmental impact through green catalysis approaches include enzyme-based systems, ionic liquids, and photoactivated catalysts. These catalytic advances have permitted previously unavailable control over polymer properties, including molecular weight distribution and functional group incorporation. Challenges remain regarding the stability of the catalysts, incorporation of comonomer, and economic feasibility. Future work focuses on new ligand design, extending the monomer scope to include renewable feeds tocks and improving the activation procedures. There is a critical need to integrate computational modeling, machine learning, and advanced characterization techniques to facilitate catalyst discovery and understanding of complex structure-property relationships. In general, this review demonstrates the ongoing development of olefin polymerization toward more sustainable practices and describes the important role of advanced catalytic systems in determining the future of the polymer industry).
Structure and property relationship
Leila Latreche; Samira Maou; Lokmane-Taha Abdi; Tahir Habila; Yazid Meftah
Abstract
Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium ...
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Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium carbonate (CaCO3) composites was examined. Three distinct heating procedures were used. First, composites were cooled from their melting phase temperature to ambient temperature. Second, composites were cooled from 130°C to a pre-determined and controlled temperature (T: 0°, 20°, 30°, 40°, 50°, 60°, 70°, 80°C). Third, composites were temperature-tested using annealing. The findings suggest that the elongation-at-break and impact strength may be improved following an initial quenching process from the melting phase to ambient temperature. On the other hand, a second quenching process at 0°C produces superior results, and a correlation between mechanical and thermal characteristics is noted; however, while these qualities are increased, others, such as flexibility, density, Vicat softening temperature (VST), and heat distortion temperature (HDT) are negatively impacted.
Polyolefin blends
Mahsa Mobini-Dehkordi; Gholam-Reza Nejabat; Mohammad-Mahdi Mortazavi
Abstract
Varying amounts of a high molecular weight poly(1-hexene) (PH, Mv=1.7×106 Da) are substituted for EPDM in an iPP/iPP-g-MA/EPDM blend (weight ratio: 76:4:20) and mechanical properties as well as phase morphology of the blends are studied and compared. The results show that by substituting the entire ...
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Varying amounts of a high molecular weight poly(1-hexene) (PH, Mv=1.7×106 Da) are substituted for EPDM in an iPP/iPP-g-MA/EPDM blend (weight ratio: 76:4:20) and mechanical properties as well as phase morphology of the blends are studied and compared. The results show that by substituting the entire EPDM with PH, the tensile strength-at-break increases from 18.7 to 21.1 MPa, elongation-at-break increases from 15.5% to 370.8%, and impact strength increases from 6.4 to 50.1 kJ.m-2. Dynamic mechanical thermal analysis (DMTA) of the blends proved their immiscibility and SEM analysis confirmed these findings by showing droplet-matrix morphologies. Studying the creep behavior of the samples shows that the blends containing PH have more creep so that by substituting all EPDM in the blends with PH, the permanent deformation increases from 0.425% to 0.505%. According to the results, PH is introduced as a candidate for improving the impact properties of iPP/iPP-g-MA/EPDM blend.
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.
Rheology
Maryam Shokrollahi; Bahereh T. Marouf; Reza Bagheri
Abstract
Dimethylbenzylidene sorbitol (DMDBS) is a common nucleating/clarifier agent used in polypropylene (PP). So many researchers have looked at different aspects of incorporating this additive on crystallization behavior of PP. The current study has focused on a rather new subject and that is the role of ...
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Dimethylbenzylidene sorbitol (DMDBS) is a common nucleating/clarifier agent used in polypropylene (PP). So many researchers have looked at different aspects of incorporating this additive on crystallization behavior of PP. The current study has focused on a rather new subject and that is the role of carrier resin of DMDBS masterbatch on the rheological behaviour of polypropylene. This goal has been achieved through studying the role of carrier resin on phase separation behavior of DMDBS upon cooling. It has been shown that a permanent bonding forms between the molecules of carrier resin and DMDBS in the masterbatch and this bonding slows down the crystallization kinetics of DMDBS in the final blend which in turn, influences its rheological behavior. Frequency sweep experiments conducted on a block co-polypropylene showed that lower values of storage shear modulus (G’), loss shear modulus (G’’), and complex shear viscosity (ɳ*) are observed if DMDBS is incorporated in the form of masterbatch. Interestingly, a different effect was observed when the masterbatch constituents were employed directly into the polypropylene, illustrating the importance of the mentioned bonding between DMDBS and the carrier resin in the masterbatch.
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.
Composites and nanocomposites
Zahra Ranjbarha; Javad Mokhtari-Aliabad; Parviz Aberoomand-Azar; Seyed Amin Mirmohammadi; Mohammad Saber-Tehrani
Abstract
In the present work, the ability of wood-plastic composite containing high density polyethylene and wood powder as a recycled material to remove methylene blue cation pigment was studied. The effect of some important parameters such as pH, adsorbent amount and contact time was investigated. Adsorption ...
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In the present work, the ability of wood-plastic composite containing high density polyethylene and wood powder as a recycled material to remove methylene blue cation pigment was studied. The effect of some important parameters such as pH, adsorbent amount and contact time was investigated. Adsorption efficiencies for methylene blue were maximized at alkaline pH. Adsorption capacity increased with increasing adsorbent amount and contact time. The value of R2 in Langmuir model was equal to 1 and the separation factor for 0.5 and 1 g of adsorbent was 0.09 and 0.1, respectively. Given that the methylene blue adsorption data were more consistent with the Langmuir isotherm model, it can be stated that the wood-plastic composite probably has uniform adsorption surfaces and the adsorption process occurred in a homogeneous system on the adsorbent surface. Based on the results of this study, it was observed that this composite is a suitable adsorbent for removing methylene blue from aqueous solutions and used as a purifying agent in the decolorization of effluents containing pigments. This adsorbent is recyclable and cost-effective for dye removal from textile industry wastewater.
Polymer physics
Buncha Suksut; Chonticha Seesong; Nutchalida Phueaksri; Chantarawan Chuephlob
Abstract
The effect of calcium lactate (CL) and epoxidized soil bean (ESO) on the crystallization kinetics of polypropylene (PP) was investigated by using polarized optical microscope (POM) and differential scanning calorimetry (DSC). The experiments were performed under both non-isothermal and isothermal conditions. ...
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The effect of calcium lactate (CL) and epoxidized soil bean (ESO) on the crystallization kinetics of polypropylene (PP) was investigated by using polarized optical microscope (POM) and differential scanning calorimetry (DSC). The experiments were performed under both non-isothermal and isothermal conditions. The development of spherulitic microstructure and crystallization kinetics were influenced by both CL and ESO. CL was an efficient nucleating agent for the crystallization of PP. The addition of CL facilitated faster spherulite growth and crystallization rate, while reduced the spherulite size. An opposite performance was discovered with the incorporation of ESO. Nucleation effect of CL on the PP crystallization was less effective with the presence of ESO. Compared with PP/CL, PP/CL/ESO provided a large spherulite size, slow spherulite growth, and a low crystallization rate. This is attributed to the ESO inhibited the nucleation site of CL. However, the degree of crystallinity and the Avrami exponents remained unchanged with the inclusion of both CL and ESO.
Membrane
Ahmed Fadhil Jumaah; Reza Abedini
Abstract
Propylene is a widely used compound in various industrial applications, but its separation from propane, which is often associated with it, remains a significant challenge. Among the separation methods, membrane technology, particularly polymeric membranes, offers an attractive solution due to its relatively ...
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Propylene is a widely used compound in various industrial applications, but its separation from propane, which is often associated with it, remains a significant challenge. Among the separation methods, membrane technology, particularly polymeric membranes, offers an attractive solution due to its relatively low cos t and simplicity. In this study, hydroxyl-functionalized graphene (G─OH) nanosheets were used as an additive in a Pebax 1657 matrix. The results from Fourier Transform Infrared Spectroscopy (FTIR) revealed that the interaction between Pebax and G─OH is physical, characterized by a shift in some peaks due to hydrogen bonding. The proper dispersion of G─OH in the Pebax matrix was confirmed by Differential Scanning Calorimetry (DSC), which also showed an increase in the glass transition temperature (Tg), indicating the rigidity of Pebax chains in the presence of G─OH. Thermogravimetric Analysis (TGA) results demonstrated that the degradation temperatures (Td) of Pebax/ G─OH 1 wt.% and Pebax/G─OH 2 wt.% membranes were 335°C and 330°C, respectively. A comprehensive gas permeation study, including pure and mixed gas tests at feed pressures of 2, 6, and 10 bar, as well as a long-term stability test, was conducted on the membranes. Among all the MMMs, Pebax/G─OH 1.5 wt.% demonstrated the best gas separation performance, achieving a propylene permeability of 89.8 barrer and a C3H6/C3H8 selectivity of 9.8. Additionally, under mixed gas permeation tests (50:50 v/v of C3H6 and C3H8), this membrane exhibited a propylene permeability of 76.3 barrer and a C3H6/C3H8 selectivity of 8.8. Finally, the performance of the MMMs in C3H6/C3H8 separation was benchmarked against the Robeson upper bound curve.
Catalysis
Kefeng Xie; Wei Hao; Shengyuan Xu; Jie Wang; Xiong Wang; Zhengang Han
Abstract
The substituents on cyclopentadienyl (Cp) can regulate the electronic effect and hindrance of the active center in the metallocene catalyst. This modification can greatly change the catalytic activity of the catalyst and affect some features of the polymer. In order to study the effect of alkyl substituents ...
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The substituents on cyclopentadienyl (Cp) can regulate the electronic effect and hindrance of the active center in the metallocene catalyst. This modification can greatly change the catalytic activity of the catalyst and affect some features of the polymer. In order to study the effect of alkyl substituents on Cp in the performance of a typical metallocene catalyst Cp2TiCl2 for ethylene polymerization, two types of catalyst active centers were designed, including non-bridge Cp2(R)TiCH3]+ and bridge [NCP2 (R)TiCH3]+ (R = H, Me, iPr). The effects of alkyl substituent steric hindrance were explored by density functional theory on the complex of catalyst active center with ethylene and the formation of transition state. The results showed that the increase of substituent steric hindrance was unfavorable to complex between ethylene monomer with catalyst active center. Moreover, the bigger alkyl substituent, the greater the activation energy of ethylene insertion into catalyst active center and the more difficult is ethylene polymerization. Therefore, the performance of metallocene catalysts could be regulated by the substituent on Cp.
Polyolefin blends
Aravind Raj; Pachipala Rithik; Prathipati Sai Sudheer; Kedarisetty Sampath Vachan; Murugasamy Kannan
Abstract
In this study, polypropylene (PP) was blended with polylactic acid (PLA) to enhance PP's mechanical properties, such as tensile strength and modulus, and to encourage the adoption of eco-friendly, renewable resource based material in polymer production. Even though PLA's biodegradability cannot be fully ...
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In this study, polypropylene (PP) was blended with polylactic acid (PLA) to enhance PP's mechanical properties, such as tensile strength and modulus, and to encourage the adoption of eco-friendly, renewable resource based material in polymer production. Even though PLA's biodegradability cannot be fully utilized in PP/PLA blends, but PLA can still improve PP's mechanical properties and provide an alternative resource for biobased raw materials. To meet the requirement, PP and PLA were blended in a 70:30 ratios with a compatibilizer and nanosilica at different loading levels by melt-blending. Blends of PP and PLA materials were processed without any problems, since both materials have melting points in the range of 170°C. Despite this, the properties of polymer blends are limited by the immiscibility between these neat polymers. To solve this problem, compatibilizers like polypropylene-grafted-maleic anhydride (PP-g-MA) were added to blends to improve their compatibility. Nanosilica was also added to this compatibilizer to study the system's compatibility and modify the hydrophobicity of PLA. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), tensile strength, and field emission scanning electron microscopy (FESEM) were used to analyze the polymer blend. Results indicate that compatibilizers play a significant role in improving tensile properties, thermal stability, and blend dispersion in the system, mainly in 5 parts compatibilizer-based systems. Composition with 5 parts compatibilizer increases tensile strength of 70/30 blend from 19.7 to 27 MPa, while elongation increases from 2.2 to 3.6 %. Additionally, a composition with 0.7 parts of nanosilica increases the modulus from 1488 to 1732 MPa when compared to the 70/30 blend.
Composites and nanocomposites
Hamed NazarpourFard
Abstract
Polyvinylpyrrolidone (PVP) composites based on rice husk (RH), rice husk carbon (RHC, i.e., black rice husk ash (BRHA)) and rice husk ash (RHA, i.e., white rice husk ash (WRHA)) were prepared separately through solution casting method. Similar composites were made using polystyrene (PS) through the same ...
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Polyvinylpyrrolidone (PVP) composites based on rice husk (RH), rice husk carbon (RHC, i.e., black rice husk ash (BRHA)) and rice husk ash (RHA, i.e., white rice husk ash (WRHA)) were prepared separately through solution casting method. Similar composites were made using polystyrene (PS) through the same protocol. The carbon and ash obtained from this type of rice husk were obtained via pyrolysis at 300 and 600 °C, respectively, for 1 hour. The effects of these additives on the spectroscopic characteristics of polymers were verified by examining the infrared (FT-IR) and X-ray diffraction (XRD) spectra of the prepared composites. The resulting showed a remarkable difference between the spectra of parent polymers and the corresponding composites. Changes in peak width and 2θ parameters (observed in XRD patterns) revealed that PVP possesses better interactions with RHC, while PS has better interactions with RHA. Due to the high hydrophilicity of PVP, some investigations were accomplished on the hydrophilic properties of PVP samples. Polystyrene did not reveal detectable water vapor absorption (WVA), thus this experiment was not carried out for PS samples. Eventually, it was disclosed that there are significant discrepancies between the hydrophilic properties of PVP and its composites. In the other word, the WVA decreased from 290% for parent PVP to 210% for PVP-RHC composite.
Polyolefin degradation
Marzieh Alidadi-Shamsabadi; Shirin Shokoohi; Mahnaz Shahzamani; Homa Abbasian-Peykani
Abstract
In this work, the photo-aging behavior of high impact polystyrene (HIPS), polystyrene/ethylene propylene diene monomer (PS/EPDM) binary blends, and compatibilized polystyrene/ethylene propylene diene monomer/ polyamide 6 (PS/EPDM/PA6) ternary blends was studied and compared together. Photo-degradation ...
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In this work, the photo-aging behavior of high impact polystyrene (HIPS), polystyrene/ethylene propylene diene monomer (PS/EPDM) binary blends, and compatibilized polystyrene/ethylene propylene diene monomer/ polyamide 6 (PS/EPDM/PA6) ternary blends was studied and compared together. Photo-degradation of polymer blends faces considerable challenges, because a polymer blend is a compound of multiple components with particular interactions and its components may function as degrading or stabilizing agents. Photo-aging generally can cause changes in the color and mechanical properties of polymer compounds. Attenuated total reflection Fourier transform spectroscopy (ATR-FTIR) was conducted to study the chemical interactions between components in the prepared samples. The morphological structure of blends was studied by using scanning electron microscopy (SEM). The impact and tensile strength of the samples were measured and compared after exposure to UV radiation. To study the changes in the appearance, the yellowness index values of the samples were followed at different periods of exposure to UV irradiation. The post-radiation results showed similar mechanical performance of ternary and binary blends with the retention of mechanical properties close to each other. The impact strength and elongation-at-break for the HIPS sample were greatly reduced compared to the blends, showing their retention by 8.46 and 7.86%, respectively. The ultimate tensile strength retention in each sample is between 70 and 82% and there is no significant difference between them. The final yellowness index of HIPS was measured to be 1.6 and 1.2 times higher than that of the binary and ternary blends, respectively.
Composites and nanocomposites
Ali Yakoub Alkhair; Emiru Yidnekachew Melesse; Irina Anatol'evna Kirsh; Yulia Aleksandrovna Filinskaya; Izabella Sergeevna Tveritnikova; Oleg Igorevich Mihryachev
Abstract
Bio-composite from linear low-density polyethylene (LLDPE) with lysozyme, mixed lysosome and glucose oxidase enzymes was synthesized through the melt extrusion system, respectively. The aim of this work was evaluation and characterization of the effect of lysosome, mixed lysosome and glucose oxidase ...
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Bio-composite from linear low-density polyethylene (LLDPE) with lysozyme, mixed lysosome and glucose oxidase enzymes was synthesized through the melt extrusion system, respectively. The aim of this work was evaluation and characterization of the effect of lysosome, mixed lysosome and glucose oxidase enzymes on the mechanical, water vapor transfer rate, and structural appearance of the Bio based LLDPE composite films. Along this line, 50 g of LLDPE pellets incorporated with 1%, 5%, and 10% (w/w) of lysozyme alone, mixed lysosome and glucose oxidase were examined, apparently. Pure LLDPE was used as a control. Over all, biocomposite with 5 and 10%(w/w) of mixed lysosome and glucose oxidase enzymes did not result in good outcome and not even enough for characterization. The surface structure of biocomposites was examined through the digital microscopy for identify dispersion of enzymes inside the LLDPE matrix and at higher concentration (10w/w%) dense and large surface are formed. However, good dispersion and reinforcing activity of enzymes in the LLDPE matrix was noticed with small concentration of lysosome (1, and 5w/w%) enzymes. The mechanical strength and elongation at break of biocomposite composite films were found to increase with small concentration (1 and 5 w/w%), but decrease with increasing of enzyme concentration. Averagely, the WVTR showed increase as the enzyme concentration increased. Besides, the Fourier-transform infrared spectroscopy (FTIR) was used to determine structural configuration of the enzymes in LDPE matrix; single sharp stretching breaks at 570 cm-1 with 1, 5 and 10 wt.% was corresponded to the existence of enzyme bands. All in one, the addition of lysozomes and glucose oxidase in small concentration has high potential in development of biocomposite relative to the traditional plastic composites.
Olefin polymerization and copolymerization
Hiren Bhajiwala; Virendrakumar Gupta
Abstract
Ultra-high molecular weight polyethylene (UHMWPE) was synthesized using Bi-supported SiO2/MgCl2/TiCl4 (Si-Mg-Ti) Ziegler-Natta catalyst in conjugation with triethyl aluminum (TEA). The impact of temperature and the presence of a chain-terminating agent were examined in the context of ethylene polymerization. ...
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Ultra-high molecular weight polyethylene (UHMWPE) was synthesized using Bi-supported SiO2/MgCl2/TiCl4 (Si-Mg-Ti) Ziegler-Natta catalyst in conjugation with triethyl aluminum (TEA). The impact of temperature and the presence of a chain-terminating agent were examined in the context of ethylene polymerization. The findings showed that as temperature decreases, the activity of the polymerization decreases, and the molecular weight of the polymer increases. Conversely, in the presence of a chain-terminating agent, the molecular weight of the polymer decreases. The introduction of Triethyl borate (TEB) and Tetraethoxy silane (TEOS) as an external donor has a pronounced effect on the catalyst activity, causing a significant decrease, while simultaneously leading to a substantial increase in the viscosity average molecular weight (Mv). Additionally, when a chain-terminating agent is added along with Triethyl borate (TEB) in the system, it results in a significant decrease in molecular weight, albeit with a slight increase in activity compared to a system without a donor. The crystallinity, particle size and bulk density of the polymer synthesized with and without external donor also investigated.
Composites and nanocomposites
Reza Naghdi; Tahereh Nejat
Abstract
The ever-increasing environmental constraints over waste disposal led us to study the feasibility of valorizing bagasse/ polypropylene composites via nanosilica and mercerization treatments. Water absorption and thickness swelling of the nanocomposites improved due to the barrier properties of nanosilica ...
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The ever-increasing environmental constraints over waste disposal led us to study the feasibility of valorizing bagasse/ polypropylene composites via nanosilica and mercerization treatments. Water absorption and thickness swelling of the nanocomposites improved due to the barrier properties of nanosilica particles. FTIR spectra revealed decreased hydroxyl groups as well as carbonyl groups disappearance after alkali treatment. Except for impact strength, the combined nanosilica-mercerization treatment could enhance the mechanical performance of the biocomposites. Thermogravimetric analysis showed higher degradation temperatures and residual char yields after the combined nanosilica-mercerization treatment. Furthermore, differential scanning calorimetry indicated that the individual mercerization and nanosilica treatments had no distinct effect on the thermal performance of the composites, whereas the combined treatment brought about marked improvements in the given properties, e.g; melting and crystallization temperatures and crystallinity rate. The present study introduces a novel technique to valorize a totally waste-based bagasse/ polypropylene composite material holding a promising potential for various industrial applications.
Simulation & Modeling
Yogeshwar N Thakare; Ajay V Kothari; Saurabh Shinde; Pooja Kadam; Natarajan Venkateswaran; Virendrakumar Gupta
Abstract
MgCl2 supported Ti catalyst is used in commercial propylene polymerization process. Morphology is a key performance determination parameter for polymer resins produced by commercial olefin polymerization process. Higher resin flowability and bulk density (greater than 0.38g/cc) are demonstrated by ‘good’ ...
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MgCl2 supported Ti catalyst is used in commercial propylene polymerization process. Morphology is a key performance determination parameter for polymer resins produced by commercial olefin polymerization process. Higher resin flowability and bulk density (greater than 0.38g/cc) are demonstrated by ‘good’ morphological resins (sphericity close to ‘1’). Polymer resin morphology is controlled by morphology of the catalyst used as well as polymerization conditions. The industrially accepted approaches to control polymer resin morphology are by controlling catalyst morphology through various approaches like pre-polymerization of the catalysts. Morphology of the catalyst is dependent on precursor (support) morphology and process parameters for making the catalyst. In this work, we have developed magnesium alkoxide precursor, a Ziegler-Natta catalyst using the precursor and studied its performance in gas phase propylene polymerization process. Further, morphology of different precursor and catalyst samples is evaluated and correlated it using a “computer vision” based approach. The approach involves modeling the circularity (as an analog of sphericity) of a catalyst and precursor particle. It is observed that the circularity of catalyst particles is lower than that of precursor, due to attrition in the process. It is also reflected in increase in particle size distribution span from 0.83 to 1.32 while synthesis of catalyst from precursor. This approach provides a tool to evaluate and screen the catalysts for using in polymerization.
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.
Simulation & Modeling
Parisa Mohammadzadeh Pakdel; Reza Yegani; Mahdi Salami Hosseini; Elham Shokri
Abstract
In the current study, the flow field and morphology development of a polyethylene (PE) and ethylene vinyl acetate (EVA) blend were investigated numerically during extrusion through a spinneret using Fluent 6.3.26 software. The interface of the two phases was tracked using the volume of fluid (VOF) method. ...
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In the current study, the flow field and morphology development of a polyethylene (PE) and ethylene vinyl acetate (EVA) blend were investigated numerically during extrusion through a spinneret using Fluent 6.3.26 software. The interface of the two phases was tracked using the volume of fluid (VOF) method. In a conventional spinneret, EVA droplets near the walls break up due to the high shear rate, while the central droplet deforms without breaking up. To enhance the breakup of EVA droplets, the effects of device geometry, including the spinneret angle and the presence of one or two lamps, were investigated in detail. The numerical results indicated that a decrease in the spinneret angle from 60° to 45° causes the central droplet to become more elongated in the flow direction. Additionally, the results showed that the presence of one or two lamps in the conical zone of the spinneret causes a portion of the central droplet to break up.
Olefin polymerization and copolymerization
Tingting Yang; Ao Li; Yawei Qin; Jin-Yong Dong
Abstract
Polypropylene is one of the most widely used synthetic resins, which is mainly synthesized with Ziegler-Natta catalysts. In this paper, the functionalized Ziegler-Natta catalyst is applied to prepare high-performance polypropylene. A new way to synthesize functionalized Ziegler-Natta catalysts is to ...
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Polypropylene is one of the most widely used synthetic resins, which is mainly synthesized with Ziegler-Natta catalysts. In this paper, the functionalized Ziegler-Natta catalyst is applied to prepare high-performance polypropylene. A new way to synthesize functionalized Ziegler-Natta catalysts is to dope with inorganic nanoparticles. The MgCl2/TiCl4/BMMF catalysts doped with halloysite nanotubes were prepared and applied to synthesize polypropylene containing less than 200ppm halloysite nanotubes. It is found that doping nanotubes in Ziegler-Natta catalyst has little impact on the structure, composition and activity of the catalyst, and polypropylene with high isotactic degree and molecular weight was synthesized with the functionalized Ziegler-Natta catalyst. Halloysite nanotubes are found to be dispersed in polypropylene in the form of individual nanotube, forming percolated network in the polymer melt effectively. Moreover, the polypropylene containing halloysite nanotubes exhibited better mechanical and thermal resistance properties as compared with conventional polypropylene, and the thermo-oxidative properties of which do not deteriorate as the introduction of nanotubes. This research provides a facile way to relieve the contradiction between the high activity of catalyst and high content of nanoparticles during the preparation of polyolefin nanocomposites by in-situ polymerization, and a new idea to prepare polyolefin nanocomposites by in-situ polymerization.
Olefin polymerization and copolymerization
Mohammad Reza Jozaghkar; Seyed Mehrdad Jalilian; Farshid Ziaee
Abstract
This study was designed to investigate the effect of molar ratio of 1-octene and type as well as concentration of Lewis acids on the free radical copolymerization of butyl methacrylate (BMA) with 1-octene. The synthesized copolymers have been substantially described by FTIR, 1H NMR, GPC and DSC. The ...
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This study was designed to investigate the effect of molar ratio of 1-octene and type as well as concentration of Lewis acids on the free radical copolymerization of butyl methacrylate (BMA) with 1-octene. The synthesized copolymers have been substantially described by FTIR, 1H NMR, GPC and DSC. The quantitative 1H NMR and GPC demonstrated that by increase in the molar ratio of 1-octene and Lewis acids to BMA, the incorporation of 1-octene in the copolymer backbone enhanced, Mn reduced and polydispersity became narrower. The maximum incorporation of 1-octene (13.7%) was observed for sample CSC7 having [1-octene/BMA] of 3 mol% and [AlCl3/BMA] of 1.5 mol%. The DSC results confirmed the NMR and GPC outcomes, suggesting a decrease in Tg by increasing 1-octene in the copolymer backbone. Moreover, it is found that temperature has a remarkable influence on the copolymerization behavior. The results also showed that by substituting the acrylate monomer from butyl methacrylate to butyl acrylate, the incorporation of 1-octene increased.
