Effect of the organic groups of difunctional silanes on the preparation of coated clays for olefin polymer modification

Abstract

Sodium montmorillonite (MMT) was organically modified with hexadecyltrimethyl-ammonium ions and subsequently treated with dichlorosilanes and water, aimed at in situ silane condensation polymerization and modification of clay platelets by polysiloxane coatings. Dimethyldichlorosilane, methylphenyldichlorosilane, and diphenyldichlorosilane were used to produce three siloxane-modified organoclays. The structure and morphology of the clay materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric studies (TG) and scanning electron microscopy (SEM). XRD results showed that the silanes were effectively polymerized in the clay galleries, forming a nanocomposite of intercalated particles. A fraction of the siloxane formed is bonded to the clay surface by covalent siloxane bonds. Strong structural differences in both morphology and thermal stability of the materials may occur when changing methyl or phenyl groups in the siloxane structure. The formation mechanism of these intercalated nanocomposite particles is considered. Finally, these modified clays were incorporated in an olefin polymer and morphological analyses using transmission electron microscope (TEM) images were carried out.

Morphological Study of HDPE/Clay Hybrids Synthesized by an Alternative Compatibilization Path

“…This can be the result of higher clay dispersion caused by the in situ generation of oligomers into the organophilic clay. These results are in agreement with previous scanning electron microscopy studies of these additives (Monasterio et al, 2010).…”

“…These results are in agreement with the GPC results (Monasterio et al, 2010 (Table 2) and they explain the above mentioned viscosity decrease ( Figure 5). Interestingly in group II, dimers were synthesized and the chemical nature of the interaction was similar.…”

“…Subsequently, they were mixed with HDPE by melting process thus each composite contained ~3%wt clay. The preparation conditions and the results from X-ray diffraction, Fourier transform infrared spectroscopy and non-oxidative thermal degradation of the clays and the polymeric materials can be found in Monasterio et al (2010 and .…”

Edge Structure of Montmorillonite from Atomistic Simulations

“…When a solvent accessible Mg is substituted at the edge, the average number of H-bonds between the water and the bridging oxygen was inverted Si and non-octahedral Al structures were stabilized by water bridging H-bonds reported for the pyrophyllite edge surface [37,38]. Although experiments have not y direct evidence of an inverted Si in 2:1 dioctahedral phyllosilicates, the alternative EF st in principle, explain some inconsistencies in smectite reactivity [63][64][65]. A rec thermodynamics study based on DFT has suggested that these inverted Si at t pyrophyllite are possible defect structures at the AC edge of 2:1 phyllosilicates [61].…”

Modification of Montmorillonite with Alkyl Silanes and Fluorosurfactant for Clay/fluoroelastomer (FKM) Nanocomposites

“…The size of large clay particles and the low affinity of natural clays to most organic polymers diminish their reinforcing ability in CPN (Bergaya et al, 2011). It is important to make the particles compatible via organophylization to facilitate their intercalation with the hydrophobic polymer macromolecules (He et al, 2005), in order to improve the clay dispersion in the matrix and enhance efficiency in modifying the final properties (Akelah and Moet, 1996;Zhu and Xanthos, 2004;Park et al, 2004;He et al, 2005;Joo et al, 2008;Qian et al, 2009;Daniel et al, 2008;Monasterio, 2010;Das et al, 2011;Bergaya et al, 2011). While both the basal spacing and the chemical affinity of silicate layers are important for their dispersion, two approaches are used for clay modification: interlayer ion exchange with surfactant, and treatment of functional groups on the clay surface and edges by organic compounds such as silane (Hussain et al, 2006;Shen et al, 2007;Joo et al, 2008;Daniel et al, 2008;Qian et al, 2009;Monasterio, 2010;Bergaya et al, 2011).…”