Reinforcement of poly(dimethylsiloxane) networks by montmorillonite platelets

Abstract

A PDMS network, synthesized from a vinyl-terminated precursor, was reinforced by plate-like montmorillonite (volclay) particles with different surface cations. The optimal ratio of crosslinker-to-PDMS precursor was ascertained from the mechanical properties of networks prepared with different crosslinker concentrations. The elastic modulus of the polymer was enhanced by the montmorillonite particles. The increase in modulus was higher in the Li-than in the Na-volclay composites. The ultimate strength of the composites was also strongly enhanced by the small platelets, especially in presence of surface Li ϩ . The stronger influence of Li-volclay on the mechanical properties of the composites can be attributed to the partial formation of an intercalated structure, which leads to thinner particles with a high aspect ratio. Both composite strength and modulus were proportional to the filler-volume-fraction, but the increase in strength was limited by rising particle agglomeration at high loading. In contrast to organic-modified montmorillonite, the inorganic surface of volclay catalyzed the thermal degradation of PDMS.

Effect of natural and organically modified montmorillonite clays on the properties of polydimethylsiloxane rubber

“…38 For the MT/SR composites, the presence of MT contributed to a lower rate and broader degradation process, with an increase in T max values compared to USR, which indicated a slight stabilizing effect of this clay on PDMS chain degradation. This was in contrast to the results described by Osman et al 5 for montmorillonite/PDMS vinyl-terminated composites, where the montmorillonite enhanced the thermal degradation of PDMS. The improvement in the thermal stability of the MT/SR composites could be attributed to the increase in the crosslinking density, which restricted the mobility of the PDMS chains and hindered their intermolecular and intramolecular rearrangements.…”

“…The stress (and the resulting strain) used to determine the modulus is too small to separate agglomerated particles, and therefore, modulus enhancement is not significantly affected by particle agglomeration, as long as an uniform distribution of the filler into the matrix is ensured. 5 In addition to depending on the filler distribution (agglomerates or primary particles) in the matrix, modulus enhancement depends on the aspect ratio and volume fraction of the particles, in a similar way to that implied by the Halpin-Tsai equation. 48 The agglomerations of the MT and O-MT particles (as observed in the fracture morphologies of the composites) led to many complex shapes and sizes and, ultimately, to a distribution of aspect ratios.…”

“…4 The effects of other particulate fillers, such as mica flakes, 5 biogenic silica, and eucalyptus fibers, 6,7 in PDMS rubber have also been studied. Moreover, increasing attention has been paid to PDMS-clay composites, [8][9][10][11][12] although a few researchers 10,13 have reported that different kinds of clay have dissimilar influences on PDMS microcomposite properties.…”

The effect of inorganic particles on slot die coating of poly(vinyl alcohol) solutions

“…As mentioned by Boisvert and Persello [17], the number of attachment points is proportional to the exposed surface; an increase in stress is expected due to large effective particle size. Such behavior has also been reported elsewhere [39][40][41][42]. The increase in attachment points could lead to a higher degree of bridging flocculation, as evident from the manifestation of shearthickening and thixotropic behavior.…”

Cadmium mercury telluride and the new generation of photoelectronic devices

“…There are several approaches for the reinforcement of the PDMS [7,8], for example mixing the nano fillers such as inorganic nanoparticles, layered nanoclay, carbon nanotubes with the uncured PDMS base, followed by the curing process [9][10][11][12]; mixing the hydroxyl-terminated PDMS with a silicon alkoxide such as tetraethoxy silane (TEOS), followed by simultaneous curing of the PDMS and the sol-gel process involving hydrolysis and condensation of the TEOS [13]; copolymerization such as forming a PDMS-urethane copolymer [14], etc. Although these approaches are effective in reinforcing the PDMS, they cannot be directly applied to replicating the microstructures since the silicon mother mold will be destroyed when the rigid PDMS is peeled off from it.…”