Structure and rheological properties of silica aerogel/natural rubber latex-based slurries and composites

Abstract

This study reports on porous composites obtained from evaporating slurries based on silica aerogel (SA) and natural rubber latex (NRL) dispersed in cyclohexane and water respectively. The slurries are emulgels where droplets of NRL are entrapped in a dense suspension of SA. Confocal laser scanning microscopy reveals that the smallest silica particles organize around the latex droplets to form a steric layer consistent with a Pickering effect. Upon drying, the gel-like behavior of the slurry allows its structure maintain. The dispersive X-ray diffraction combined with scanning electronic microscopy hints that the pores are the footprint of the droplets but coated by the NRL that increasingly fills the interstices between the SA particles as the NRL concentrations increases. The elastic modulus G′ of the slurries shows a power law dependence on the SA concentration and found to be proportional to the product of the droplet size and the modulus of the SA suspension. The Young modulus of the porous composites varies as a scare route of G′ and highlights that the final mechanical features of the composite could be predicted from the viscoelastic properties and the structure of the slurry.