Catalysis
Jonas B Biagini; Joao Henrique Zimnoch dos Santos
Abstract
The determination of Ti+4 in Ziegler–Natta catalysts is highly relevant for industrial plants that use Ziegler–Natta (ZN) catalysts based on TiCl4 as a source of titanium. The catalyst preparation step requires analytical monitoring during the dilution process for the morphological effect ...
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The determination of Ti+4 in Ziegler–Natta catalysts is highly relevant for industrial plants that use Ziegler–Natta (ZN) catalysts based on TiCl4 as a source of titanium. The catalyst preparation step requires analytical monitoring during the dilution process for the morphological effect according to the relationship between the Ti+3 and Ti+4 concentrations in the polymerization process, which in turn depend on a variety of intended grades for different market applications. Spectrophotometry in the visible region was evaluated as a potential analytical technique for the quantification of Ti+4 in ZN catalysts. The present study proposes the use of an easily accessible, reliable and low-cost validated instrumental method for Ti+4 determination. Therefore, the technical details regarding sample preparation, instrumental analytical parameters and performance characteristics of the method were descriptively addressed. The quantitative evaluation of performance parameters (namely, specificity, linearity, detection and quantification limits, precision, accuracy and robustness) demonstrated successful results compared with the theoretical values of the studied reference sample. The precision of the method by visible spectrophotometry was estimated at 0.4% for the relative error, and the accuracy presented within an IC of 95% for the LOC ± 1.7 mmolTi/L for the average concentration of 339.5 mmolTi L-1 in reference to the Tyzor ® TnBT sample with a theoretical concentration of 337 mmol L-1 study solution from this work. The method was shown to be a supporting tool for quantitative Ti+4 species determination in the control of industrial processes.
Polymer chemistry
Anirban Bhar; Akshay Kumar Dey; Deepshikha Datta; Oliva Roy; Soumyadeep Routh; Arindam Mandal; Biswajit Kamila
Abstract
The global packaging industry is primarily influenced by polyolefinic materials, such as polyethylene (PE) and polypropylene (PP), which offer a combination of durability, flexibility, and cost-effectiveness. These materials have transformed modern packaging through their lightweight offerings for food, ...
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The global packaging industry is primarily influenced by polyolefinic materials, such as polyethylene (PE) and polypropylene (PP), which offer a combination of durability, flexibility, and cost-effectiveness. These materials have transformed modern packaging through their lightweight offerings for food, medical, and industrial uses. The widespread employment of non-biodegradable plastics poses substantial challenges in waste management due to their persistent presence and significant contribution to plastic pollution. This review examines the characteristics, applications, and ecological implications of polyolefins, with a particular focus on their importance in packaging. This paper examines recent advancements in biodegradable alternatives and chemical recycling methods, aiming to address the environmental challenges presented by plastic waste. Integrating natural fillers into polyolefin composites can boost biodegradability without compromising functionality. The review highlights the importance of a circular economy approach, which emphasizes sustainable practices for transforming polyolefin waste into valuable resources. This analysis explores the advantages and disadvantages of polyolefins to guide future research and sustainable packaging policy.
Composites and nanocomposites
Negin Sadat Jalili; Bahereh T. Marouf; Ali Bakhshi-Zadeh; Reza Bagheri
Abstract
The aim of the current study was to first make two compatibilizers, i.e., maleic anhydride grafted polypropylene (PP-g-MA), based on a homo-and a block copolymer. Then, these custom made compatibilizers were incorporated in PP/nanoclay composites made via direct and two-step masterbatch techniques. The ...
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The aim of the current study was to first make two compatibilizers, i.e., maleic anhydride grafted polypropylene (PP-g-MA), based on a homo-and a block copolymer. Then, these custom made compatibilizers were incorporated in PP/nanoclay composites made via direct and two-step masterbatch techniques. The influence of compatibilizer/nanoclay ratio was examined in the direct method. In the two-step processing technique, the compatibilizer content was divided to two parts such that the first part was used when making the masterbatch and the second part was incorporated in the second step when the masterbatch was diluted by the polymer matrix. The characterizations via titration test and Fourier-transform infrared (FTIR) spectroscopy revealed a higher degree of grafting reaction when homo-polymer was used for synthesizing PP-g-MA. In the next step, nanocomposites containing 3 wt.% nanoclay with three different PP-g-MA (both types)/nanoclay ratios of 1:1, 2:1, and 3:1 were made using a co-rotating twin screw extruder. X-ray diffraction (XRD) analysis was done to evaluate morphology and tensile and impact, and tests were performed to evaluate the mechanical properties of the PP samples. Based on the results, maleic anhydride grafted homo-polypropylene (HPP-g-MA) and the composition containing HPP-g-MA/nanoclay ratio of 2:1 with 7.69% improvement in Young’s modulus was reported as the recommended compatibilizer and ratio for applications. Finally, five nanocomposite samples with identical composition were made in two steps. A masterbatch containing 15 wt.% nanoclay was made first and then, it was diluted with PP to reduce the nanoclay content to 3 wt.%. All samples containing 6 wt.% PP-g-MA, but the method of addition of compatibilizer was different. In one sample, the whole compatibilizer was added into the masterbatch. In another sample, the entire PP-g-MA was added in the second stage of compounding. In the other three samples, the addition of compatibilizer was divided between the two stages of the process. The results of the study showed that the highest improvement of elastic modulus (24.26%) was obtained when the majority of the compatibilizer was added in the second step of production. This was associated with the best dispersion of nanoclay platelets in the PP matrix.
Characterization
Marzieh Alidadi-Shamsabadi; Ahmad Arefazar; Shirin Shokoohi; Mahnaz Shahzamani
Abstract
In this work, the influence of compatibilizing method on the phase morphology, mechanical properties and rheological behavior of ternary blends based on polystyrene(PS) /ethylene-propylene-diene terpolymer(EPDM)/ polyamide6 (PA6) was investigated. Two different methods (including in-situ grafted and ...
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In this work, the influence of compatibilizing method on the phase morphology, mechanical properties and rheological behavior of ternary blends based on polystyrene(PS) /ethylene-propylene-diene terpolymer(EPDM)/ polyamide6 (PA6) was investigated. Two different methods (including in-situ grafted and pre-grafted) were used to compatibilize PS/EPDM/PA6 ternary blends. In the first method, all reactive materials were mixed during mixing, but in the latter, modified EPDM was prepared first and then blended with other components. The chemical reactions occurred during blending followed by Attenuated Fourier Transform Spectroscopy (ATR-FTIR). Mechanical properties investigated by impact and tensile strength measurements. The phase microstructure was observed by Scanning electron spectroscopy (SEM) and the rheological behavior was carried out using a parallel plate rheometer in oscillatory mode. ATR-FTIR results confirmed the grafting and compatibilizing reactions. The morphology size of dispersed phase particles have dramatically changed by increasing EPDM-g-GMA content. The pre-grafted compatibilizing method has revealed finer microstructure than the other method. The modulus of all the ternary compatibilized blends has increased compared to PS/EPDM. In fact, the presence of PA6 introduces a new, more rigid phase in the blend. The pre-grafted compatibilizing method, which uses a compatibilizer content of less than 10 wt.%, is more effective than the in-situ grafted compatibilizing method. This approach results in a finer microstructure and enhanced impact strength. Additionally, it creates a more rigid interface, leading to greater elasticity, which manifests as a semi-plateau in the rheological behavior. In contrast, the in-situ grafted method produces more balanced mechanical properties overall.
Olefin synthesis
Saeed K. Amini
Abstract
Activity of 111 surface of PtGa alloy in which three atom Pt centers are covered by In atoms is investigated as single atom Pt catalyst of propane dehydrogenation (PDH) by using quantum mechanical (QM) calculations. Periodic density functional theory (DFT) is applied in these calculations, utilizing ...
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Activity of 111 surface of PtGa alloy in which three atom Pt centers are covered by In atoms is investigated as single atom Pt catalyst of propane dehydrogenation (PDH) by using quantum mechanical (QM) calculations. Periodic density functional theory (DFT) is applied in these calculations, utilizing PBE exchange-correlation functional with plane wave basis set of 680eV kinetic energy cut off. Calculated results give adsorption and conversion energies of propane to propylene including adsorption energies of intermediate states. Adsorption energies span is from -6 kJ/mole for propane up to -500 kJ/mole for CH3CH2CH2 radical. Catalyzed propane to propylene’s conversion energy is about -135 kJ/mole in comparison to about 150 kJ/mole of gas phase. Moderate adsorption energy value of about -120 kJ/mole for propylene and its higher conversion energy value of about 160 kJ/mole to CH3CH*CH2 intermediate guarantee propylene slectivity and break of conversion chain after its formation. Lower activation energy values of first and second C—H breaks show that PDH reaction on this prposed catalyst is much faster than previously reported one in which three atom Pt centers were covered by toxic Pb atoms.
Polymer processing
Mehri Dana; Mohammad Reza Nabid; Gholamhossein Zohuri; Saeid Asadi Shahidi; Sohail Yazdanbakhsh
Abstract
Styrenic thermoplastic vulcanizates (STPV) consist of polypropylene (PP) and linear low density polyethylene (LLDPE) as the continuous phases and a crosslinked hydrogenated styrene block copolymer (SEBS) as the dispersed phase were prepared in an industrial scale using a corotating twin-screw extruder. ...
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Styrenic thermoplastic vulcanizates (STPV) consist of polypropylene (PP) and linear low density polyethylene (LLDPE) as the continuous phases and a crosslinked hydrogenated styrene block copolymer (SEBS) as the dispersed phase were prepared in an industrial scale using a corotating twin-screw extruder. Morphological study of the TPVs was carried out using a scanning electron microscope (SEM). Rheological study of the SEBS compounds carried with different content of 2,5-Dimethyl-2,5-di(tert-butylperoxy) hexane peroxide (0.5, 1, 2 and 4 wt. %). T90 appeared with 4 w% peroxide shows that curing has been completed. Effect of peroxide content (0.5 to 1.2 wt.%) on properties of the TPVs was led to an increase in tensile strength (from 5.6 to 7.4 MPa) and hardness to a certain extent (74 shore A). On the other hand, mechanical properties such as the elongation at break (from 592% to 284%), the melt flow index (MFI) (from 29.6 to 3.14 g/10 min at 190 °C, 10 kg) and tear strength (from 35 to 30 kg f/cm) are decreased. The compression set at low temperature (70 °C) is not changed so much, at high temperature (120 °C), while, is reduced due to higher curing (from 69% to 46%). Heat aging was carried out (at 85 °C for 168 h) on the TPVs which were prepared via the different content of peroxide (0.5 wt. % to 1.2 wt. %). It was found that the results of elongation and the hardness after aging have the lowest amount using 0.9 wt.% peroxide. However, the tensile strength after aging decreased with increasing the content of peroxide. As a result of increasing curing with increasing content of peroxide, the melting point of the prepared TPVs was disappears. The results of using triallylcyanurate (TAC) and bismaleimide (BMI) as a co-curing agent in peroxide curing indicate that all of the tensile strength, hardness and elongation at break (from 897 to 1082%) of the STPV were increased with BMI. Heat ageing study and compression set on the STPV with TAC was slightly raised compared to BMI. Also, the results of dynamic vulcanization on the properties of TPV based on SEBS/LLDPE/PP indicate that Crosslink density and gel content of TPV are close to that of EPDM rubber (fully crosslinked) and higher than that of TPE (without crosslinking). The results show that the tensile strength and density of the dynamically crosslinked blend have not changed significantly under peroxide curing.
Polyolefins Industry
Derradji Dadache; Farid Rouabah; Zahir Rahem
Abstract
This study demonstrates that quenching and annealing significantly influence the mechanical and thermophysical behavior of low density polyethylene (LDPE). Rapid quenching at temperature of –25 °C enhances ductility by increasing elongation at break, despite reducing thermophysical properties, ...
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This study demonstrates that quenching and annealing significantly influence the mechanical and thermophysical behavior of low density polyethylene (LDPE). Rapid quenching at temperature of –25 °C enhances ductility by increasing elongation at break, despite reducing thermophysical properties, likely due to microstructural refinement. In contrast, post-quenching annealing especially at 100 °C improves thermal conductivity and crystallinity but reduces ductility. The results underscore a tunable balance between thermal and mechanical performance, governed by the interplay of beta (β-) and alpha (α-) relaxation modes during heat treatment. Post-quenching annealing of low density polyethylene LDPE, particularly at 100 °C, significantly enhanced thermal conductivity, diffusivity, and crystallinity, albeit with a trade-off in ductility and increased brittleness. Quenching within the beta (β-) relaxation range promoted maximum ductility, while annealing in the alpha (α-) relaxation range improved thermophysical properties. These findings reveal that precise control of heat treatment conditions enables a tunable balance between mechanical flexibility and thermophysical performance in LDPE
Polyolefin degradation
Abdelhay Smaida; Yacine Mecheri; Larbi Boukezzi; Slimane Bouazabia
Abstract
This study focuses on the study of long-term electrical aging effects on dielectric behavior of cross-linked polyethylene (XLPE) used as insulation in high voltage cables. For this reason, we have performed long-term electrical aging tests on full size of HV 36/60 kV XLPE cable samples at three voltage ...
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This study focuses on the study of long-term electrical aging effects on dielectric behavior of cross-linked polyethylene (XLPE) used as insulation in high voltage cables. For this reason, we have performed long-term electrical aging tests on full size of HV 36/60 kV XLPE cable samples at three voltage levels (U0 = 36 kV, 2U0 = 72 kV and 3U0 = 108 kV) during 680 hours. The studied properties are partial discharge threshold, dielectric loss factor, relative permittivity and transverse resistivity. Besides, physico-chemical changes were assessed using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD). In the end of paper, the evolution of mechanical properties and hot set test with aging time and voltage levels have been presented and analyzed as additional diagnostic precursors. The obtained results illustrate that examined properties are widely affected by long-term electrical aging. The increase in partial discharges and dissipation factor depending to the voltage level and the aging time and the decrease in partial discharge threshold voltage and transverse resistivity are the mostly marked degradation precursors. These degradation precursors are supported by the increase of carbonyl groups and reduction in the crystallinity degree of the polymer under long-term electrical aging. These parameters are useful parameters for evaluating the quality of underground XLPE cable insulator.
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