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).
Catalysis
Mohammad Javad Sharifi; Alireza Fazlali; Seyed Hamed Mahdaviani; Davood soudbar
Abstract
The performance of the catalyst system [chromium(III)/pyrrole/co-catalyst/halide] on the trimerization of ethylene has been studied using the combined experimental and response surface method (RSM). The chromium(III) tris(2-ethylhexanoate) was synthesized and characterized by FTIR, 1HNMR and 13CNMR, ...
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The performance of the catalyst system [chromium(III)/pyrrole/co-catalyst/halide] on the trimerization of ethylene has been studied using the combined experimental and response surface method (RSM). The chromium(III) tris(2-ethylhexanoate) was synthesized and characterized by FTIR, 1HNMR and 13CNMR, to study chemical properties and identify molecular structures. The effect of four variables Al/Cr molar ratio, halide/Cr molar ratio, reaction temperature and catalyst dosage have been considered on catalyst activity, 1-hexene selectivity and polymer content. The central composite design (CCD) model with three main parameters in three response levels for each factor was applied to analyze the effects of the parameters. The comparative studies showed that carbon-tetra-chloride (CCl4) and tri-n-octyl-aluminum (TNOA) were the best candidates for this catalyst system, demonstrating high selectivity of 1-hexene formation, higher catalytic activity and lower polymer content. Based on the RSM results, the best trimerization condition for ethylene at 25 bar and 91.2°C was obtained at the catalytic system [Cr(2-EH)3/2,5-DMP/CCl4/TNOA] molar ratio of 1:6:10.8:201.5, which showed the activity of 105328 (g 1-C6/(g Cr.hr)), 99.21% selectivity for 1-hexene and no polymer was formed. The predicted process parameters were also verified by actual experiments at the optimized conditions.
Catalysis
Tatiana B. Mikenas; A. V. Sholma; Vladimir A. Zakharov; Mikhail Matsko
Abstract
The paper presents data on the effect exerted by magnesium dichloride in Ziegler-Natta catalysts on the activity and molecular weight of polyethylene (PE) produced by ethylene polymerization in the absence or presence of hydrogen. It was found that ethylene polymerization in the absence of hydrogen over ...
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The paper presents data on the effect exerted by magnesium dichloride in Ziegler-Natta catalysts on the activity and molecular weight of polyethylene (PE) produced by ethylene polymerization in the absence or presence of hydrogen. It was found that ethylene polymerization in the absence of hydrogen over titanium-magnesium catalysts (TMCs) with different ratio of titanium chloride and magnesium dichloride (Ti/Mg = 0.5 and 0.07), oxidation state of titanium (TiCl3 or TiCl4) and structural characteristics of the catalysts leads to the formation of PE with a close molecular weight. At the same time, PE obtained over a δ-TiCl3 catalyst has a much (threefold) higher molecular weight. The introduction of hydrogen during polymerization for decreasing the molecular weight of PE is accompanied by a sharp drop in activity of the δ-TiCl3 catalyst, in distinction to the highly active supported TMC containing 3 wt. % Ti. Data about the effect of hydrogen content during polymerization on the molecular weight of PE were used to calculate the ratio of rate constants for polymer chain transfer with hydrogen (KtrH) and polymer chain propagation reaction (Кр). This value was close for TMCs of different composition containing magnesium dichloride. In the case of δ-TiCl3, the KtrH/Кр value was approximately two times lower compared to TMCs.
Polymer physics
Fatima Mustafayeva; Najaf Kakhramanov; Khayala Allahverdiyeva
Abstract
The article presents the results of studies of the influence of aluminum hydroxide concentration on the crystallization process regularities of nanocomposites based on compatibilized polypropylene random copolymer and aluminum hydroxide (PP-R/PPH-g-MAH/Al(OH)3). The isothermal crystallization kinetics ...
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The article presents the results of studies of the influence of aluminum hydroxide concentration on the crystallization process regularities of nanocomposites based on compatibilized polypropylene random copolymer and aluminum hydroxide (PP-R/PPH-g-MAH/Al(OH)3). The isothermal crystallization kinetics of compatibilized polypropylene random copolymer composites containing 1, 3, 5, 10, 20, 30 and 50 wt. % of aluminum hydroxide was determined by the stepwise dilatometry method using the Kolmogorov-Avrami equation. The crystallization behaviors of composites were investigated on an IIRT-1 device converted into a dilatometer, in the process of stepwise cooling of samples under a load of 5.3 kg. In this study, maleic anhydride functionalized homopolypropylene (PPH-g-MAH) was employed as a compatibilizer to enhance the compatibility between the PP-R and Al(OH)3. Considering the dependence of specific volume and free specific volume on temperature, the first-order phase transition was established and the glass transition temperature values of the composites were determined. The mechanism of formation and development of crystallization centers in the region of the first-order phase transition was investigated. The obtained values of “n” prove that the mechanism or nature of the growth of crystallization centers changes into three-dimensional spherulitic - two-dimensional disc-shaped - one-dimensional rod-shaped with an increase in the amount of aluminum hydroxide in composite. The study of the temperature dependence of the specific volume for the studied samples showed that the first order phase transition occurs at a temperature of 125°C. It was determined that the second order phase transition temperature (the glass transition temperature determined by the dilatometric method) increases with the increase in the amount of filler.
Olefin polymerization and copolymerization
Nona Ghasemi Hamedani; Fatemeh Poorsank; Hassan Arabi; Seyed Mehdi Ghafelehbashi
Abstract
Insights have been developed into the influence of different structures, including bismethoxymethylfluorene (B) and 2,2-diisopropyl succinate (I), on both internal donor (ID) and external donor (ED) roles on the performance of MgCl2/ID/TiCl4. Catalyst performance including activity, hydrogen response, ...
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Insights have been developed into the influence of different structures, including bismethoxymethylfluorene (B) and 2,2-diisopropyl succinate (I), on both internal donor (ID) and external donor (ED) roles on the performance of MgCl2/ID/TiCl4. Catalyst performance including activity, hydrogen response, molecular weight distribution and thermal properties is explained through the coordination nature of external donors and its correlation with the internal donor. Replacement of the typical alkoxysilane ED with B and I leads to an overall decrease in activity, which is more pronounced (average 1.4 times) in systems with similar structures as ID and ED. However, these compounds significantly enhance hydrogen response. The use of B as ED leads to an average 1.5-fold increase in MFI and usage of I as ED results in an average 1.1 times increase in MFI. Changing the ED influenced the thermal properties so that in the catalyst with the succinate structure as ID, altering the ED from alkoxysilane to I, leads to an increase in crystallinity from 43.86% to 48.12%. These findings suggest that the choice of package of internal and external donor can significantly influence the resulting polymer characteristics.
Structure and property relationship
Buncha Suksut; Pathamanat Poonkasem; Sirirat Prasittinawa; Patcharapon Somdee
Abstract
Composites of polypropylene (PP) and calcium lactate (CL) with a constant weight percentage of 60% and 40%, respectively, were compounded with 3, 5 and 7 phr of epoxidized soybean oil (ESO) plasticizer using an internal mixer. The testing samples were prepared using an injection molding technique. The ...
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Composites of polypropylene (PP) and calcium lactate (CL) with a constant weight percentage of 60% and 40%, respectively, were compounded with 3, 5 and 7 phr of epoxidized soybean oil (ESO) plasticizer using an internal mixer. The testing samples were prepared using an injection molding technique. The effects of the mold temperature and annealing treatment on the morphological and mechanical properties of PP-based composites using polarized optical microscopy (POM), differential scanning calorimetry (DSC), universal testing machines (UTM), and impact tester were performed. The results showed a remarkable increase in the elongation-at-break and impact strength, but a noticeable decrease in tensile strength and stiffness with increasing ESO contents. The experimental results also indicated that the higher mold temperature significantly improved the tensile strength and stiffness of samples due to an increase in spherulite size for neat PP, PP/CL composite and PP/CL composite with 3 phr of ESO. Additionally, annealing treatment enhanced the tensile and impact strengths of both neat PP and PP/CL composite, which was attributed to the increase in the crystal perfection and degree of crystallinity. These findings suggested that mechanical improvements using high mold temperature and annealing treatment were confined to the incorporation of an ESO plasticizer. The resulting performance of the plasticized PP composites after thermal treatment was described by two possibilities: the loss in the adhesion between the components and the migration of plasticizer.
