Polyethylene/Clay Nanocomposites Made with Metallocenes Supported on Different Organoclays

Abstract

The success of in situ polymerizations, measured by means of high polymerization activity, uniform exfoliation and clay dispersion in the polymer matrix, and good powder morphology, depends on how well the catalyst is supported onto the clay surface. A novel catalyst supporting method that does not require the addition of methylaluminoxane was applied to different organically modified clays and sodium montmorillonite. The supported catalysts were used to polymerize ethylene. We found out that only the clay modified with tertiary ammonium salts was an effective support for ethylene polymerization, generating a supported catalyst that has high polymerization activity, and produces nanocomposites with good powder morphology and excellent clay exfoliation. magnified image

An Efficient In Situ Polymerization Method for the Production of Polyethylene/Clay Nanocomposites: Effect of Polymerization Conditions on Particle Morphology

“…Table 1 compares the zirconium loadings on B10 and B20 catalysts measured with ICP‐AES. Supporting efficiencies were calculated using the pure clay weight, excluding the weight of organic modifiers and supported catalyst, as explained in a previous publication 19. According to Table 1, when the number of catalyst moles added per gram of Cloisite 93A changes from 10 to 20 µmol, the Zr loading on the clay surface approximately doubles.…”

“…A large number of articles have been published on the in situ polymerization of olefins for the production of polyolefin/clay nanocomposites 1–20. Despite significant recent progress, this technique still faces some drawbacks, such as low activity, the need to use methylaluminoxane (MAO) during the polymerization, and poor clay exfoliation.…”

“…In a previous publication,19 we proposed an in situ polymerization technique in which organic modified clays (organoclays) were modified with trimethylaluminum (TMA) before the catalyst impregnation step, and used for ethylene polymerization in the absence of MAO, making polyethylene/clay nanocomposites; for this technique, only organoclays modified with tertiary ammonium (Cloisite 93A) led to supported catalysts that were effective for the production of nanocomposites with good clay dispersion at relatively high polymerization rates. During the initial evaluation of this system, it became apparent that the polymerization temperature, triisobutylaluminum (TIBA) concentration, and zirconium loading on clay influenced in situ polymerization behavior.…”

Polymer/ Clay Nanocomposites: Concepts, Researches, Applications and Trends for The Future

“…The organophilic clays (Cloisite 20A, 20B, 30B and 93A) were used as a support to the Cp 2 ZrCl 2 catalyzer. The higher polymerization rate was obtained with Cloisite 93A and the clay layers were dispersed and exfoliated in the PE matrix [30].…”

Control of molecular weight and polydispersity in polyethylene/needle-like shaped clay nanocomposites obtained by in situ polymerization with metallocene catalysts

“…The level of dispersion can be correlated to the solubility parameters of the solvent and organically modified organoclay. Therefore, treating the bentonite with tertiary or quaternary ammonium salts can improve its swellability in the polymerization medium [37,38]. However, a prior modification is necessary for this type of clay.…”