Effect of Particle Aggregation on the Mechanical Properties of a Reinforced Organic−Inorganic Hybrid Sol−Gel Composite

Abstract

Sol-gel materials are often reinforced through the addition of particulate fillers to improve their mechanical properties, such as toughness or stiffness. Related studies of filled polymeric materials suggest that the effectiveness of added reinforcements may depend sensitively on the state of particulate aggregation in the composites. In some systems and situations, aggregates are found to enhance properties, while in others they are deleterious. The objective of the present study was to determine the effect of state of aggregation of alumina nanoparticle fillers on the mechanical properties of a GPS sol-gel hybrid composite. Aggregates of different sizes were produced at loadings of 3.6, 7.5, and 16.8 volume percent in the GPS sol-gel monoliths by inducing aggregation through the addition of varying amounts of tetrasodium pyrophospate (TSPP). The small amounts of TSPP required to induce varying states of aggregation did not affect the properties of the gel in the absence of the particles. Unaggregated particles or small aggregates were found to impart significant improvements in the mechanical properties of the gel, but at a particular critical aggregate size and beyond, the cured material cracked and crumbled. The critical size was found to correspond roughly to an effective aggregate volume fraction of 0.64 in the final composite, suggestive of a randomly close-packed aggregate structure.

Graphene/poly(3,4-ethylenedioxythiophene) hydrogel with excellent mechanical performance and high conductivity

“…Thus the fracture press of the EGP hydrogels raised as the mass of EDOT increased. For EGP3 hydrogel, the large amount of PEDOT clusters filled in hydrogel materials could absorb the stresses through deformation and irreversible breakdown under an external force [40,41], endowing the hydrogel with additional mechanical strength.…”

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

“…If the stiffness of hybrid structures would stem from interparticle interactions, it would mean that highly aggregated structures would exhibit supreme properties and no dispersion techniques would be necessary upon mixing of NPs into the polymer. However, experiments show rather the opposite effect when the aggregates reach a critical size and polymer‐NP interactions are mandatory . For example, modulus of NPs network was experimentally measured in the order of a couple of MPa .…”

A rheological method for selecting nano-kaolin powder as filler in SBR rubber

“…Relationships between the stiffness of polymer reinforced with inorganic powders and the viscosity of a dispersion of the inorganic powders in a liquid phase have been studied in a dilute range (Ferrari, Stefani, & Beruto, 2006;Poovarodom, Hosseinpour, & Berg, 2008 not be used for reinforced rubber because the concentration of the dispersed phase is too high. Thus the anticipated relationship should call for comparison of the yield stress of concentrated liquid dispersions with the stiffness of reinforced rubbers.…”