The influence of Ni/Nd‐based Ziegler–Natta catalyst on microstructure configurations and properties of butadiene rubber

Neodymium (Nd)‐based Ziegler–Natta catalyst has been well known for preparing polybutadiene rubber (BR) containing high, about 98%, cis−1,4 configuration with extremely low gel content providing superior resistance to low‐temperature fatigue and abrasion. However, its cost is more expensive than a conventional nickel (Ni)‐based catalyst. The Nd‐BR has poor processability with high cold flow due to its high linearity and molecular weight. To compare with a traditional process, the BR produced by Ni‐based catalyst has higher level of branching resulting in the better processability, but it contains medium amount of gel. To balance the catalyst cost and the BR properties, this article reported the influence of a solution containing Ni‐ and Nd‐based Ziegler–Natta catalyst (Ni/Nd) using diethyl aluminum chloride and triethyl aluminum as co‐catalysts on 1,3‐butadiene (BD) conversion and physical properties of the elastomeric materials based on obtained rubber (Ni/Nd‐BR). In the presence of toluene, the increase in the Ni/Nd molar ratio from 0.0/1.0 to 0.4/0.6 yielded Ni/Nd‐BR containing cis−1,4 units of 95%–96% with significantly decreasing both levels of vinyl−1,2 and trans−1,4 configurations from 0.26% to 0.13% and 4.44% to 3.07%, respectively. When cyclohexane was applied as the reaction media, 100% BD conversion was achieved and the Ni/Nd‐BR had very low content of vinyl−1,2 unit (0.07%). The mechanical properties in terms of tensile properties and abrasion resistance of the elastomer based on Ni/Nd‐BR having high cis‐1,4 and relatively higher trans−1,4 configurations were superior to elastomers based on commercial BRs produced by using Ni‐ and Nd‐based catalyst systems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41834.     

Effect of electron donors on 1,3‐butadiene polymerization by a Ziegler–Natta catalyst based on neodymium

High‐cis polybutadiene produced by catalyst systems based on a rare earth is an elastomer used to produce green tires. This type of tire presents lower rolling resistance, which allows higher fuel economy, and thus fewer chemical compounds are discharged into the atmosphere. In this work, the influence of electron donors [tetrahydrofuran (THF) and tetramethylethylenediamine (TMEDA)] present in the polymerization solvent on the microstructure and molecular weight characteristics of the polybutadiene produced by neodymium catalysts was studied. The catalyst synthesis was carried out in glass bottles for 1 h at a temperature between 5 and 10°C. The catalyst components were diisobutylaluminum hydride, neodymium versatate, and tert‐butyl chloride. The polymerization reaction was carried out for 2 h. The reaction temperature was kept at 70± 3°C. The addition of TMEDA or THF above a determined concentration reduced the catalytic activity, molecular weight, and concentration of cis‐1,4 units (<96%), whereas the polydispersity increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2539–2543, 2005     

Kinetic modeling of polymerization of butadiene using cobalt-based Ziegler–Natta catalyst

The reaction mechanism and subsequent kinetics for polymerization of butadiene using cobalt-based Ziegler-Natta catalysts have been investigated by many researchers. Kinetic models developed from these investigations can be used to predict the monomer conversion quite accurately; however, it is difficult to develop models that accurately predict the molecular weight as a function of time or conversion. In this paper, an attempt is made to model the reaction mechanism for the polymerization of butadiene using the cobalt octoate/diethyl aluminum chloride/water catalyst system with data taken from the literature. A dual active site mechanism is proposed and incorporated in a kinetic model. In this case, all reaction steps except the formation of byproducts step have two rate constants. The simulation results predict the molecular weight as a function of conversion and time better than results from previously published models.     

Gas phase polymerization of 1,3‐butadiene with supported neodymium‐based catalyst: Investigation of molecular weight

The gas phase polymerization of 1,3‐butadiene (Bd), with supported catalyst Nd(naph)₃/Al₂Et₃Cl₃/Al(i‐Bu)₃ or/and Al(i‐Bu)₂H, was investigated. The polymerization of Bd with neodymium‐based catalysts yielded cis‐1,4 (97.2–98.9%) polybutadiene with controllable molecular weight (MW varying from 40 to 80 × 10⁴ g mol^?1). The effects of reaction temperature, reaction time, Nd(naph)₃/Al(i‐Bu)₃ molar ratio, and cocatalyst component on the catalytic activity and molecular weight of polymers were examined. It was found that there are two kinds of active sites in the catalyst system, which mainly influenced the MW and molecular weight distribution of polybutadiene. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1945–1949, 2004     

Morphology and activity of nanosized NdCl3 catalyst for 1,3‐butadiene polymerization

The binary lanthanide catalyst for 1,3‐butadiene was invented for 40 years ago. However, it has not been employed in commercial application due to its poor solubility and low activity. Nanosized neodymium chloride (NdCl₃) was prepared in tetrahydrofuran (THF) medium through dissolution, chelation, and colloidal formation steps. Anhydrous NdCl₃ was dissolved in THF, and ca. 1.5 THF molecules were coordinated. In the colloidal formation step, THF was slowly replaced with the addition of cyclohexane, and pale blue nuclei, nanosize below 200 nm, were formed. The structural studies for NdCl₃ · xTHF using X‐ray powder diffraction (XRD) and scanning electron microscope (SEM) indicate that high ordered crystallinity is decreased with reduced particle size from trigonal prismatic to porous sphere structure. Nano NdCl₃, obtained as colloidal state in cyclohexane, was activated with Al(iBu)₃ and Al(iBu)₂H at room temperature and employed for 1,3‐butadiene solution polymerization. The nanosized Nd catalysts showed high activity (1.0 ～ 1.3 × 10⁵ g/Nd mol · h), which is comparable to that of the ternary neodymium catalyst Nd(neodecanoate)₃/AlEt₂Cl/Al(iBu)₃. The microstructures of polybutadiene, cis, trans, and vinyl, are about 96.0, 3.5, and 0.5%, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1279–1283, 2005     

Ethylene polymerization using a novel MgCl2/SiO2‐supported Ziegler–Natta catalyst

A novel MgCl₂/SiO₂‐supported Ziegler–Natta catalyst was prepared using a new one‐pot ball milling method. Using this catalyst, polyethylenes with different molecular weight distributions were synthesized. The effects of the [Si]/[Mg] ratio, polymerization temperature and [Al]/[Ti] ratio on the catalytic activity, the kinetic behaviour and the molecular weight and the polydispersity of the resultant polymer were studied. It was found that the polydispersity index of the polymer could be adjusted over a wide range of 5–30 through regulating the [Si]/[Mg] ratio and polymerization temperature, and especially when the [Si]/[Mg] ratio was 1.70, the polydispersity index could reach over 25. This novel bi‐supported Ziegler–Natta catalyst is thus useful for preparing polyethylene with a required molecular weight distribution using current equipment and technological processes. Copyright © 2005 Society of Chemical Industry     

Polymerization of 1,3‐butadiene using neodymium chloride tripentanolate–triethyl aluminum catalyst systems

Neodymium chloride tripentanolate catalysts of the general formula NdCl₃ × nL with n = 3, L = 1‐pentanol (II), 2‐pentanol (III), and 3‐pentanol (IV) were prepared by an alcohol interchange reaction between neodymium chloride n isopropanolate (I) with pentanols. These NdCl₃ tripentanolates (II–IV) were characterized by gravimetric and elemental analysis. They were evaluated for homopolymerization of 1,3‐butadiene using triethyl aluminum as cocatalyst in cyclohexane solvent. The role of positional isomers of pentanols (1, 2, and 3) in catalytic activity on conversion, intrinsic viscosity, and microstructure was studied. The neodymium chloride tripentanolate‐2 (III) has high catalytic activity followed by (II) and (IV). The conversions were increased with increases in catalyst, cocatalyst concentrations, and temperature, and decreases in intrinsic viscosity values. The microstructure was determined by Fourier transform‐infrared spectroscopy (FTIR) and found to have a predominantly cis‐1,4 structure (>99%), which was marginally influenced by variation in cocatalyst concentration and temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 595–602, 1999     

Synthesis and mechanical properties of high impact polystyrene with in situ bulk polymerization toughened by one‐pot Nd‐based styrene–isoprene–butadiene terpolymer rubber

High impact polystyrene (HIPS) resins were obtained with in situ bulk polymerization toughened by styrene–isoprene–butadiene terpolymer rubber (SIBR). SIBR prepolymer was prepared through selective polymerization of styrene (St), isoprene (Ip), and butadiene (Bd) in St with [Nd]/[Al]/[Cl] catalyst. Nd‐based catalyst exhibited more favorable activity toward conjugated diene other than St, resulting in St solution of random SIBR with high cis‐1,4 stereoregularity and low St content, which was directly exposed to the free radical polymerization of St to generate HIPS. Effect of toughened rubber and the initiators [difunctional (D2) and trifunctional (T3)] were examined to attain HIPS possessing mechanical properties as follow: impact strength, 0.9–24.8 kJ/m²; tensile strength, 16.0–27.5 MPa; and elongation at break, 7.4–107.0%. Increasing SIBR matrix in HIPS improved the impact strength and decreased tensile strength. The fracture surface morphologies of HIPS specimens were studied by notched impact tests and scanning electron microscopy (SEM), illustrating that the incremental SIBR matrix presented synergistic toughening effect of crazing to enhance the ductile fracture behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43979.     

Synthesis of polypropylene/cellulosic fiber composites using Ziegler‐Natta catalyst by in situ polymerization

Composites of polypropylene/natural fiber were obtained synthesizing polypropylene in the presence of chemically treated fibers. For this, vegetal cellulose fibers were introduced in the polymerization medium of propylene using Ziegler‐Natta catalyst. The fibers were treated to increase their compatibility with the polypropylene matrix and decrease the accessibility of functional groups to the catalyst active sites. At first, mild acid hydrolysis was performed, followed by chemical treatments with triethylaluminum and stearic alcohol. The results showed that the chemical treatments increased the crystallinity index to 73–77% in comparison with the original fiber (57.6%). The catalyst activity and its stereospecificity maintained high when fiber was treated with triethylaluminium and that with stearic alcohol. The composites contained amounts of fiber in a range of 3.1–5.8%. The fibers did not induce crystallization of PP crystallites different from the most common α‐form. Fibers were fibrillated to nanometric diameter, although micrometric length. POLYM. ENG. SCI., 56:71–78, 2016. © 2015 Society of Plastics Engineers     

In situ polymerization of polyethylene/clay nanocomposites using a novel clay‐supported Ziegler‐Natta catalyst

Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler‐Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl₄ and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nanostructure of composites was investigated by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay in these polyethylene/nanocomposites were exfoliated, intercalated, and uniformly dispersed in the polyethylene matrix even at very high concentration of the clay. Thermogravimetric analysis (TGA) shows good thermal stability of the PECNCs. Differential scanning calorimeter (DSC) results reveal considerable decrease in the crystalline phase of the PECNC samples. Results of permeability analysis show an increase in barrier properties of PECNC films. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (R_p) was found to be R_p = k[AIBN]^0.5[ 1 ]^1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol^?1. The monomer reactivity ratios in copolymerization with styrene were r ₁ = 2.65 and r_st = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Study on propene polymerization using a novel spherical Ziegler‐Natta catalyst and its kinetics

The effects of the Al/Ti ratio and external donor (ED) on the catalytic activity and kinetics of propene polymerization catalyzed by a spherical Ziegler‐Natta (Z‐N) catalyst were investigated. The preparation conditions of the catalyst play an important role in the polymerization kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3737–3740, 2003     

Dielectric properties of styrene — butadiene rubber/silica mixtures

Rice husk ash (RHA) obtained from rice mill and hydrated silica from RHA were used as a filler in vulcanized SBR 1502 and the dielectric properties were measured at a frequency of 1592 Hz at room temperature. The optimum hydrated silica content giving a good dielectric constant and conductivity was 125 parts/100 parts rubber and the dielectric loss was also high so that it could be a good insulater. There was no significant change in dielectric constant, dielectric loss and conductivity of SBR 1502 filled with RHA which could be used as high frequency dielectric due to low dielectric loss.     

Kinetics of the propylene polymerization with prepolymerization at high temperature using Ziegler‐Natta catalyst

The bulk polymerization of propylene in liquid monomers with Ziegler‐Natta catalyst at 95°C is studied, using alkyl aluminum as the cocatalyst and dicyclopentyldimethoxysilane as the external donor. The highest catalyst activity is shown at the cocatalyst/Ti molar ratio of 300, which keeps relatively constant with the molar ratio increasing from 300 to 800. Besides, the catalyst activity is up to 65 kgPP/(gCat*h) in the range of cocatalyst/donor molar ratio from 12 to 16. The polymerization reaction rate curves with and without catalyst precontacting are similar, while the activity with catalyst precontacting are higher than that without precontacting. Furthermore, the kinetics of polymerization with and without prepolymerization are investigated in the range of the polymerization temperature from 70 to 95°C. It shows that at the high temperature, the polymerization rate increases with prepolymerization. Finally, the influence of prepolymerization at 95°C on the polymerization kinetics and particle properties is also described. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41816.     

Self‐heating properties of styrene‐butadiene rubber

Rubbers, including styrene‐butadiene rubber (SBR), are well known to be susceptible to self‐heating. SBR is used in a wide range of applications and is often produced in the form of a crumb which is then used to form the final product. The crumb may be transported and stored in large quantities. Self‐heating properties of a SBR crumb have been determined using standard oven methods. The results indicate that self‐heating is a real hazard for SBR crumb. The results are generally consistent with recent measurements by Clothier and Prichard (Combust. Flame 2003; 133 :207–210) for rubber tyre crumb. Copyright © 2005 John Wiley & Sons, Ltd.     

Three‐site mechanism and molecular weight: Time dependency in liquid propylene batch polymerization using a MgCl2‐supported Ziegler‐Natta catalyst

This article demonstrates that the molecular weight of propylene homopolymer decreases with time, and that the molecular weight distribution (MWD) narrows when a highly active MgCl₂‐supported catalyst is used in a liquid pool polymerization at constant H₂ concentration and temperature. To track the change in molecular weight and its distribution during polymerization, small portions of homo polymer samples were taken during the reaction. These samples were analyzed by Cross Fractionation Chromatograph (CFC), and the resulting data were treated with a three‐site model. These analyses clearly showed that the high molecular weight fraction of the distribution decreases as a function of time. At the same time, the MWD narrows because the weight‐average molecular weight decreases faster than the number‐average molecular weight. A probable mechanism based on the reaction of an external donor with AlEt₃ is proposed to explain these phenomena. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1035–1047, 2001     

Modeling of butadiene polymerization using cobalt octoate/DEAC/water catalyst

Two-level fractional factorial designs were employed to study the solution polymerization of butadiene in a batch reactor using cobalt octoate/DEAC/water as catalyst. Conversion and molecular weight data obtained as functions of time were used to develop a kinetic model, and the estimated kinetic parameters were correlated empirically with four operating variables: temperature and concentrations of cobalt octoate, DEAC, and water. The experimental data indicate that at high water concentration a significant amount of oligomers is formed during early stages of polymerization, and the molecular weight of polymer increases with time. Analysis of the data suggests instantaneous initiation, first order propagation with cobalt and monomer, and transfer to monomer. Models which do not take account of the branching are shown to be incapable of fitting data for both M _n and M _w. The catalyst decay seems to follow a first-order mechanism, but the evidence is somewhat inconclusive.     

Morphology and mechanical properties of clay/styrene‐butadiene rubber nanocomposites

Based on the character of a clay that could be separated into many 1‐nm thickness monolayers, clay styrene‐butadiene rubber (SBR) nanocomposites were acquired by mixing the SBR latex with a clay/water dispersion and coagulating the mixture. The structure of the dispersion of clay in the SBR was studied through TEM. The mechanical properties of clay/SBR nanocomposites with different filling amounts of clay were studied. The results showed that the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4–10 nm and its aggregation formed by several or many layer bundles. Compared with the other filler, some mechanical properties of clay/SBR nanocomposites exceeded those of carbon black/SBR composites and they were higher than those of clay/SBR composites produced by directly mixing clay with SBR through regular rubber processing means. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1873–1878, 2000     

MgCl2‐supported Ziegler–Natta catalyst containing dibenzoyl sulfide donor for propylene polymerization

Polypropylene (PP) was synthesized in the presence of Ziegler–Natta catalysts composed of MgCl₂‐TiCl₄‐internal donor/AlR₃‐external donor. Diisobutyl phthalate is a well‐known internal donor in current PP production. Nevertheless, phthalates are often blamed as endocrine disruptors. The objective is to find an ecofriendly internal donor producing PP with maintaining its physical properties. When using dibenzoyl sulfide, synthesized PP shows the superiority to diisobutyl phthalate in the activity of catalyst (40 vs. 22 kg PP/g catalyst), the isotacticity of polymer (99.5 vs. 98.0 wt % of heptane insolubles), and the molecular weight distribution of PP product (M_w/M_n = 4.8 vs. 4). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40743.