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, ...
Read More
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.
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 ...
Read More
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; Farshid Ziaee
Abstract
Innovative strides in polymer synthesis have led to the successful living anionic polymerization of styrene-olefin triblock copolymers, yielding varying molecular weights and a remarkably narrow dispersity (Đ) in cyclohexane solvent at 45°C, initiated by n-butyllithium. The novel approach employs ...
Read More
Innovative strides in polymer synthesis have led to the successful living anionic polymerization of styrene-olefin triblock copolymers, yielding varying molecular weights and a remarkably narrow dispersity (Đ) in cyclohexane solvent at 45°C, initiated by n-butyllithium. The novel approach employs anionic polymerization, augmented by the aid of a coupling agent known as 1,12-dibromododecane. Unlike traditional alcohol-based methods employed in polystyrene synthesis, this coupling agent, introduced at the end of the reaction, grafts two living macro-styrene chains with the dodecane chain, effectively acting as the pivotal second component in the formation of the triblock copolymer. Extensive experimentation pinpointed 45°C as the optimal temperature for anionic copolymerization in cyclohexane solvent. The comprehensive analysis, encompassing 13C NMR, 1H NMR, FTIR spectroscopy, and GPC, confirms the successful synthesis of styrene-dodecane-styrene triblock copolymer. The NMR results illustrate successful molecular structures, while GPC attests to the precision, showing a narrow Đ of below 1.2. This pioneering approach not only underscores the efficiency of anionic polymerization in the synthesis of styrene-olefin-styrene triblock copolymer using termination strategy but also promises extensive implications in material science and industrial applications.
Olefin polymerization and copolymerization
Majedeh Mroofi; Gholamhossein Zohuri; Saeid Ahmadjo; Navid Ramezanian
Abstract
Bicenter (BCn) cobalt-bis(imine) catalysts were synthesized, used to polymerize methyl methacrylate (MMA), and 1-hexene. The effect of catalyst structure, bridging ligand, and polymerization reaction conditions were investigated. Synthesis of primary ligand of (2,6-dibenzhydryl-4-ethoxyphenyl)-N=(CH3)-C(CH3)=O ...
Read More
Bicenter (BCn) cobalt-bis(imine) catalysts were synthesized, used to polymerize methyl methacrylate (MMA), and 1-hexene. The effect of catalyst structure, bridging ligand, and polymerization reaction conditions were investigated. Synthesis of primary ligand of (2,6-dibenzhydryl-4-ethoxyphenyl)-N=(CH3)-C(CH3)=O is prepared. Following to that, the final ligands of BC1 and BC2 bicenter catalysts were prepared via reacting the primary ligand with 2,3,5,6-tetramethylbenzene-1,4-diamine and 4,4-methylenedianiline bridges, respectively. The BC1 catalyst demonstrated higher activity than the BC2 catalyst. The highest activity for the BC1 catalyst was obtained when the co-catalyst to catalyst molar ratio was [Al]/[Co]=1500:1, and the polymerization temperature was 40 °C. In comparison the BC2 catalyst demonstrated the highest activity in [Al]/[Co]=500:1 ratio, polymerization temperature of 70 °Cand showed higher thermal stability. 1HNMR analysis revealed that the highest branching density for poly(methyl methacrylates) (PMMA) produced by BC1 and BC2 catalysts was 222 and 249 branches per 1000 carbon atoms, respectively. PMMA synthesized with BC2 catalysts had the highest syndiotacticity (59%). The polymer produced with bicenter catalyst (BC1) had a relatively broad molecular weight distribution (2.9), according to GPC analysis. The synthesized catalysts demonstrated appropriate activity for the polymerization of MMA, but only moderate activity for 1-hexene monomer
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 ...
Read More
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.
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. ...
Read More
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.
Olefin polymerization and copolymerization
Evgeny E Faingol'd; Stanislav L. Saratovskikh; Andrei N. Panin; Olga N. Babkina; Igor V. Zharkov; Artur T. Kapasharov; Nikita N. Lashmanov; Gennadii V. Shilov; Natalia M. Bravaya
Abstract
Ethylene-propylene copolymerization reactions were carried out using rac-Et(2-MeInd)2ZrMe2 catalyst and (2,6-tBu2PhO-)AliBu2 as activator under varying reaction conditions. We demonstrate that reaction conditions such as monomer concentration, Al/Zr molar ratio and solvent type (toluene and heptane) ...
Read More
Ethylene-propylene copolymerization reactions were carried out using rac-Et(2-MeInd)2ZrMe2 catalyst and (2,6-tBu2PhO-)AliBu2 as activator under varying reaction conditions. We demonstrate that reaction conditions such as monomer concentration, Al/Zr molar ratio and solvent type (toluene and heptane) all have significant effect on activity of the system and copolymers composition. The decrease in reaction pressure from 11 to 3 atm leads to: a) 1.6-fold increase in specific activity (from 3030 to 4840 kg copolymer/(mol Zr•h•atm)), b) increase of Mn value from 38 to 89 kg/mol, and c) increase of ethylene content in copolymer from 87 to 92 mol %. The increase of ethylene/propylene molar ratio from 0.7 to 2 does not significantly affect activity but leads to the rise in the ethylene content in copolymer from 92 to 97 mol % and, correspondingly, to the increase of copolymer crystallinity from 43 to 48%. As a result, thermal and mechanical properties of the obtained polymers also change, according to the shifts in copolymers composition. The change in Al/Zr molar ratio is confirmed to have great effect on the catalytic activity of our systems. In a row of Al/Zr= 100, 150, 200, 300 mol/mol, the lowest activity of 80 and the highest one of 8550 kg copolymer/(mol Zr•h•atm) are observed at 100 and 150 molar ratios correspondingly. We have also demonstrated the ability of catalytic systems with isobutylaluminum aryloxide activators to operate in aliphatic medium (heptane). On another note, during the reaction quenching, aryloxide activator hydrolyzes the polymer infused with 2,6-di-tert-butylphenol antioxidant. This results in the increased resistance of copolymers to the thermal-oxidative degradation. The presence of 4 wt.% phenol in the copolymer leads to an increase in the 5% mass loss temperature by 67°C. Moreover, increasing the residual phenol content from 2 to 4 wt.% affects the mechanical properties of the copolymers: the elongation-at-break increases from 500 to 600%, and the tensile strength decreases from 10 to 8 MPa.
Olefin polymerization and copolymerization
Virendrakumar. Gupta; Hiren Manojkumar Bhajiwala
Abstract
The copolymerization of methyl acrylate (MA) and glycidyl methacrylate (GMA) with 1-hexene was carried out using activator regenerator by electron transfer atom transfer radical polymerization (ARGET ATRP) employing Cu(0)/CuBr2 as a catalyst, pentamethyl diethylenetriamine (PMDETA) as a ligand, and ethyl ...
Read More
The copolymerization of methyl acrylate (MA) and glycidyl methacrylate (GMA) with 1-hexene was carried out using activator regenerator by electron transfer atom transfer radical polymerization (ARGET ATRP) employing Cu(0)/CuBr2 as a catalyst, pentamethyl diethylenetriamine (PMDETA) as a ligand, and ethyl 2-bromoisopropionate (EBriP) as the initiator, all at a reaction temperature of 70°C. This process resulted in the production of viscous and transparent copolymers, namely poly (methyl acrylate-co-1-hexene) or PMH and poly (glycidyl methacrylate-co- 1-hexene) or PGMH. For the MA/1-Hex copolymer, conversion rates ranged from a maximum of 31 wt.% to a minimum of 12 wt.%, while the GMA/1-hexene copolymer exhibited conversion rates ranging from a maximum of 42 wt.% to a minimum of 12 wt.%. It was observed that increasing the amount of 1-hexene during the synthesis led to a higher incorporation of 1-hexene content in both the MA and GMA polymer backbones, with a maximum of 15 wt.% and 18 wt.% of 1-hexene being incorporated into PMH and PGMH, respectively. The incorporation of 1-hexene was confirmed through Nuclear Magnetic Resonance (NMR) studies, including 1H, 13C, and DEPT 135 studies. Additionally, the copolymer PMH and PGMH exhibited monomodal molecular weight distribution curves when evaluated using the size exclusion chromatography (SEC) high-performance liquid chromatography (HPLC) technique, with polydispersity values in the range of 1.19-1.37 and 1.07-1.11, respectively. These findings indicate that the copolymerization process was well-controlled and followed a radical polymerization mechanism.
Olefin polymerization and copolymerization
Mohsen Javaheri; Mehdi Nekoomanesh; Yousef Jahani
Abstract
The concentration of ethylene and 1-butene in n-hexane as polymerization media was calculated at five different pressure levels (4, 6, 8, 10, and 12 bar) and four different 1-butene concentrations (0.13, 0.26, 0.39, and 0.52 mol/L) in n-hexane at T= 80°C using the Peng-Robinson thermodynamic equation ...
Read More
The concentration of ethylene and 1-butene in n-hexane as polymerization media was calculated at five different pressure levels (4, 6, 8, 10, and 12 bar) and four different 1-butene concentrations (0.13, 0.26, 0.39, and 0.52 mol/L) in n-hexane at T= 80°C using the Peng-Robinson thermodynamic equation of state. Some combinations of conditions were selected to perform the copolymerization reaction in the presence of an industrial TiCl4/MgCl2 Ziegler-Natta catalyst. The forms of the synthesized products were visually and qualitatively classified as either powder or sticky. The percentage of incorporated 1-butene comonomer into the polyethylene chains was analyzed using calibrated FTIR tests. It was shown that for ethylene/1-butene concentration ratios (β) in n-hexane above approximately 1.80, the product forms as a powder. For values below 1.30 threshold, the product was sticky. Thus, this ratio could be used as a criterion for selecting the proper combination of copolymerization pressure and 1-butene concentration when aiming to achieve a powdered form of the product. It was shown that β has a strong correlation with the weight percentage of 1-butene in the final LLDPE polymer. Therefore it can be used as an accurate prediction for wt.% of incorporated 1-butene into the LLDPE chain within the studied concentration ranges with the specific catalyst system utilized.
Catalysis
Kotohiro Nomura
Abstract
Certain cyclic olefin copolymers (COCs) are known as promising amorphous materials with high transparency in the UV-vis region, thermal and humidity resistance, low dielectric constant, low water absorption, and dimensional stability. This short review focuses on the synthesis of (new) cyclic olefin ...
Read More
Certain cyclic olefin copolymers (COCs) are known as promising amorphous materials with high transparency in the UV-vis region, thermal and humidity resistance, low dielectric constant, low water absorption, and dimensional stability. This short review focuses on the synthesis of (new) cyclic olefin copolymers by designed (nonbridged) half-titanocene catalysts, which enabled to proceed synthesis of the amorphous polymers by ethylene/ propylene copolymerization not only with norbornene (NBE), and tetracyclododecene (TCD), but also with so called low strained cyclic olefins (cyclopentene, cyclohexene, cycloheptene, and cyclooctene). Their thermal properties (glass transition temperature, Tg values) are affected by structure of the cyclic olefin employed and the contents, whereas linear relationships between Tg values and the contents were observed in all cases.
Catalysis
Hongfan Hu; Rongqing Ma; Chenxi Cui; Guoliang Mao; Shixuan Xin
Abstract
Due to the large ionic radius and high electro-positivity nature, rare earth metal complexes are difficult to stabilize and undergo pathways like ligand redistribution and intramolecular C-H activation. To solve such problems and retain reactive versatility, rare earth complexes supported by a variety ...
Read More
Due to the large ionic radius and high electro-positivity nature, rare earth metal complexes are difficult to stabilize and undergo pathways like ligand redistribution and intramolecular C-H activation. To solve such problems and retain reactive versatility, rare earth complexes supported by a variety of tridentate PNP pincer ligands have been explored. Such complexes can serve as perfect precursors for preparing ultra-active rare earth species containing two metal-carbon bands, let alone Ln=N and Ln=P multiple bonds. In addition, the combined stability and activity of the cation rare earth mediates made them the best catalysts for the polymerization of olefins and other non-polar hydrocarbon monomers, especially conjugated dienes. The practical utilization of rare earth metal catalysts for new materials production have also extensively explored by experts from the academic and industries.
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 ...
Read More
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.
Catalysis
Nina V. Semikolenova; Valentina N. Panchenko; Mikhail A. Matsko; Vladimir A. Zakharov
Abstract
For preparation of highly active supported catalyst with bis(imino)pyridyl Fe(II) complexes (Fe1, Fe2) and N,N-α-diimine complex of Ni (Ni3), silica modified with alumina (SiO2 (Al)) was used as a support. Data on the possibility to regulate molecular weight (MW) and molecular weight distribution ...
Read More
For preparation of highly active supported catalyst with bis(imino)pyridyl Fe(II) complexes (Fe1, Fe2) and N,N-α-diimine complex of Ni (Ni3), silica modified with alumina (SiO2 (Al)) was used as a support. Data on the possibility to regulate molecular weight (MW) and molecular weight distribution (MWD) of polyethylene (PE), produced over the supported catalyst Fe1/SiO2 (Al)+TIBA by variation of polymerization temperature and the addition of hydrogen and hexene-1, are obtained. The prepared PE samples were characterized by Mw values varied from 80 to 350 kg/mol and various MMD (Mw/Mn=4.6-11.7).By grafting on SiO2(Al) of two different iron bis(imino)pyridyl complexes, producing PE with diverse MW, bi-component catalyst was prepared. This catalyst generates linear PE with broad and bimodal MWD (Mw/Mn=33). Fixation on SiO2(Al) of α-diimine Ni(II) pre-catalyst (Ni3), yielding high molecular weight branched PE at the ethylene homopolymerization, and bis(imino)pyridyl Fe(II) complex (Fe2) that forms lower molecular weight linear PE, affords formation of a new bi-component catalyst. The catalyst produces PE with broad MWD and high content of branches concentrated in high molecular weight PE fraction.
Olefin polymerization and copolymerization
Yingying Mi; Zaixing Yang; Fei Zhou; Xuelian He
Abstract
A copolymerization reaction was carried out by adding different contents of 5-ethylidene-2-norbomene or cyclopentene to dicyclopentadiene (DCPD) using an optimized polymerization process. The effects of different amounts of the comonomers on the conversion, mechanical properties and thermal stability ...
Read More
A copolymerization reaction was carried out by adding different contents of 5-ethylidene-2-norbomene or cyclopentene to dicyclopentadiene (DCPD) using an optimized polymerization process. The effects of different amounts of the comonomers on the conversion, mechanical properties and thermal stability of the polymer products were investigated and compared. The results showed that the addition of 5-ethylidene-2-norbomene accelerated the reaction rate and had little effect on the overall conversion rate of the reaction, while the addition of cyclopentene decreased the reaction rate and conversion rate. The tensile modulus, tensile strength, flexural modulus and flexural strength of the copolymer showed a trend of increasing and then decreasing with the increase of the comonomers content, reaching a peak at 5wt% of 5-ethylidene-2-norbomene or 3wt% of cyclopentene. At this peak condition, its impact strength could be improved by 50% compared to DCPD homopolymer. Below this peak condition, the Tg and thermal stability of the copolymer did not change significantly.
Olefin polymerization and copolymerization
Saber Ghasemi Karaj-Abad; Lily Sadr; Mojtaba Abbasian; Mehdi Hosseinzadeh; Solmaz Esmaeily Shoja; Mehdi Jaymand
Abstract
In this study, for the first time, a novel strategy for the synthesis of graft copolymers using polystyrene (PSt) monomer from surface modification of poly(ethylene terephthalate) PET through surface-initiated nitroxide-mediated radical polymerization was performed. For this purpose, the PET surface ...
Read More
In this study, for the first time, a novel strategy for the synthesis of graft copolymers using polystyrene (PSt) monomer from surface modification of poly(ethylene terephthalate) PET through surface-initiated nitroxide-mediated radical polymerization was performed. For this purpose, the PET surface was first aminated by 1,3-diamino propane, which was used as an amination agent. Second, phenyl chloro acetylation of PET was prepared by coupling amino and hydroxyl groups with α-phenyl chloro acetyl chloride. Afterward, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was synthesized, then 1-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPO–OH) was obtained by reduction of TEMPO with sodium ascorbate and coupled with chloroacetylated PET to obtain PET-TEMPO macroinitiator. Furthermore, the (St) monomer was grafted onto the PET surfaces through the “grafting from” technique. The obtained macroinitiator for living radical polymerization was heated in the adjacency of (St) monomer to obtain the graft copolymer (PET-g-PSt) onto the PET surfaces. Finally, PET-g-PSt/MMt nanocomposite was synthesized by the solution intercalation method. The surface combination, morphology, and thermal properties of the modified PET films were proved using various characterization methods such as transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), differential scanning calorimetry (DSC), thermogravimetric analysis, X-ray photoelectron spectroscopy, and termination electron microscopy (TEM).
Olefin polymerization and copolymerization
Ahmad-Ali Shokri; Saeid Talebi; Mehdi Salami-Kalajahi
Abstract
Laboratory runs can be minimized via experimental design which yields the optimum and best data regarding the independent parameters. In this research work, response surface methodology (RSM) based on a threelevel central composite design (CCD) was utilized to optimize and evaluate the interactive effects ...
Read More
Laboratory runs can be minimized via experimental design which yields the optimum and best data regarding the independent parameters. In this research work, response surface methodology (RSM) based on a threelevel central composite design (CCD) was utilized to optimize and evaluate the interactive effects of processing conditions for polymerization of 1,3-butadiene (Bd) diene monomer using Ziegler-Natta catalyst. The polybutadiene rubber (PBR) having different cis content and molecular weight was obtained. The catalyst components included neodymium versatate (NdV3) as catalyst, triethyl aluminum (TEAL) as cocatalyst or activator, and ethylaluminum sesquichloride (EASC) as chloride donor. For the modeling, three independent variables, namely monomer concentration (8-28 wt%), reaction time (1.5-2.5 h), and reaction temperature (45-75ºC) at three levels were selected to optimize the dependent variables or responses including monomer conversion, viscosity-average molecular weight and the cis isomer content of the obtained polymer. The interaction between three crucial parameters was studied and modeled. Quadratic models were obtained to relate process conditions to dependent variables. It was observed that the optimal conditions predicted by RSM were consistent with the experimental data. Statistical analysis demonstrated that concentration of the monomer and the time of reaction significantly affected cis content. Moreover, processing conditions to achieve the desired response variables were predicted and experimentally approved. The optimal reaction conditions derived from RSM are monomer concentration = 19 wt%, polymerization time = 2 hours, and polymerization temperature = 50ºC. Polymerization was carried out at optimum conditions. The appropriate level of dependent variables including 94.2% monomer conversion, 151812 g/mol viscosity-average molecular weight and 98.8% cis content was acquired.
Olefin polymerization and copolymerization
Wei Wang; Taoyi Zhang; Liping Hou
Abstract
The present paper systematically studies the homo- and copolymerization of ethylene or propylene using metallocene as catalyst and diethyl zinc as chain transfer agent to obtain the polyolefin waxes with narrow molecular weight distribution and with a high activity. The molecular weight of the resultant ...
Read More
The present paper systematically studies the homo- and copolymerization of ethylene or propylene using metallocene as catalyst and diethyl zinc as chain transfer agent to obtain the polyolefin waxes with narrow molecular weight distribution and with a high activity. The molecular weight of the resultant polymer could be controllable by the concentration of diethyl zinc quantitatively. The introduction of a-olefin into the ethylene polymerization system would shield the chain transfer action, and the shielding effect in propylene (co) polymerization is more serious, due to the mass transfer resistance of the substituents on the monomers. Branched comonomer and long chain comonomer provide stronger shielding effect. The regression results show that the order of the chain transfer reaction of propylene polymerization is smaller than that of ethylene polymerization, and the order of the chain transfer reaction of copolymerization is less than that of homopolymerization. It indicates that the substituent on the monomer would result in the deviation of the regression data from the ideal primary reaction order.
Olefin polymerization and copolymerization
Aliasghar Mahdavi Akerdi; Mehdi Nekoomanesh
Abstract
The condition of oligo-micelle formation of sodium di-isodecyl sulfosuccinate (SDIDS) emulsifier in hydroalcoholic solutions is used to study particle formation of vinyl chloride emulsion polymerization in a batch reactor. The change on micellization behavior was investigated by critical micelle concentration ...
Read More
The condition of oligo-micelle formation of sodium di-isodecyl sulfosuccinate (SDIDS) emulsifier in hydroalcoholic solutions is used to study particle formation of vinyl chloride emulsion polymerization in a batch reactor. The change on micellization behavior was investigated by critical micelle concentration (CMC) and zeta potential parameters. To detect the occurrence of secondary nucleation or particle aggregation, or both the particle size and number of particles were investigated as a criterion for the particle nucleation and growth process. The results showed that the alcohol (co-solvent) content had a strong effect on the oligo-micelles formation and emulsion polymerization performance. Namely, decreasing the alcohol content and increasing the anion content in the SDIDS samples increased the overall reaction rate and latex stability. This also decreased the chain growth rate, the particle size, and the coarse particle formation. Also, the results showed that different condition of oligo-micelle formation would lead to different particle growth history
Olefin polymerization and copolymerization
Mojtaba Farrokhi; Mahdi Abdollahi
Abstract
Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important in the laboratories and industries. In this study, using various simple and inexpensive ...
Read More
Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important in the laboratories and industries. In this study, using various simple and inexpensive techniques with only free radical mechanism, it was tried to synthesize PSt with different low (< 2×104 g mol-1) to high (> 105 g mol-1) molecular weights. PSts with high and moderate molecular weights (2×104-105 g mol-1) were synthesized using thermal and conventional free radical polymerizations, respectively. Reverse iodine transfer radical polymerization (RITP) was utilized to synthesize PSt with a low and controlled molecular weight. Conversion, molecular weight distribution and PSt structure were analyzed using 1H-NMR spectroscopy and size exclusion chromatography (SEC), respectively. Moreover, ω-iodo poly(dimethylsiloxane), i.e. PDMS-I, was also used as a macrotransfer agent for ITP of styrene. Diblock copolymer of PDMS-b-PSt was characterized by 1H-NMR and SEC analyses.
