The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Abstract

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

Influence of Nanoclay on the Thermo-Mechanical Properties of Silicone Pressure-Sensitive Adhesives

“…X-ray diffraction was used to confirm the nanoclay (montmorillonite) characteristics’ patterns (green and blue curves) and modificated dellite by ammonium salt fillers. The modification was observed in Figure 2 —on the graph, an increase in d-spacing is visible for modified dellite (red and black curves) and the shift is much more evident, which might suggest the use of more modifying compound [ 38 , 39 ].…”

“…The Dellite 67 G and Dellite CW9 spectra are characterized by a significant decrease in the relative intensity of the bands at around 3500 and 1650 cm −1 compared with Dellite HPS and Dellite LVF, which indicated that the surface of modified dellite changed from a hydrophilic to a hydrophobic character and the content of water decreased [ 35 , 37 ]. Moreover, for Delite CW9, absorption bonds were observed, which is typical for ammonium salt modification and proves the high hydrophobicity of the material [ 38 ].…”

“…It increased from 150 to 220 °C or 225 °C (the maximum of the study), i.e., it increased by 70–75 degrees. With an increase in the filler content on dellite-modified ammonium salt, a decrease in thermal resistance was noted and, at 3 wt., a drastic decrease (below the thermal resistance of unmodified glue felts), which may result from the modification of ammonium salt, which increases the tendency of the filler to agglomerate, and thus causes uneven distribution in the adhesive tape [ 15 , 16 , 18 , 38 ]. However, for unmodified fillers, no significant changes were noted depending on the degree of filling.…”

“…Moreover, it turned out that the addition of a filler not modified with ammonium salts has a more beneficial effect on the peel of the adhesive film. This is most likely because of the fact that the introduced modifying material influences the content of silicon material in measured samples (it significantly reduces it); therefore, compared with samples modified with unmodified material, they showed lower shrinkage [ 18 , 38 ]. When comparing the results of unmodified fillers, no significant changes in shrinkage were noted; the same was true when comparing the influence of modified fillers.…”

New Organophilic Montmorillonites with Lactic Acid Oligomers and Other Environmentally Friendly Compounds and Their Effect on Mechanical Properties of Polylactide (PLA)

“…However, this leads to a significant increase in the cost of modified Mt. Organically modified aluminosilicates have been extensively tested and are used as components of composites [ 16 , 17 , 18 , 19 ], as organic molecules adsorbents in several water-soil or air treatment technologies, as well, as rheology modifiers in paints, cosmetics, lubricants, and oil-based drilling fluids [ 20 , 21 , 22 , 23 , 24 ].…”