Macroscopic and Microscopic Analyses of Hydrophobic Modification of Rubbers with Silica Nanoparticles

Abstract

The wettability of rubbers with silica nanoparticle modification was investigated with theory and experiment. A simple coating technology was applied to generate the superhydrophobic styrene–butadiene rubber (SBR). Silica nanoparticles were covalently bonded with γ-methacryloxy propyl trimethoxysilane (γ-MPTMS), which was employed to improve coating durability through the thiol–ene click reaction with the SBR matrix. The contact angles of water droplets on the net and modified surfaces were then measured. The application of a three-dimensional density functional theory approach to predict the wetting contact angles showed that the chemical composition, chain conformation, and micro/nanostructure have different contributions to the hydrophobic behaviors. The theoretically predicted contact angles were partly validated by their experimental counterparts.

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

“…Lattice density functional theory has been another approach used by several groups to interrogate the validity of macroscopic models on small length scales. In these calculation, interatomic and intermolecular forces governed by Lennard‐Jones potential and the Hamaker theory are taken into account . Discrepancies between the contact angles predicted by macroscopic models and the actual contact angle measured on nanorough substrates was often attributed to significant line tension contribution .…”

Reinforcement of Natural Rubber with Bacterial Cellulose via a Latex Aqueous Microdispersion Process

“…The contact angle was used to examine the changes in hydrophilicity of the NRBC composites as shown in Table 1. The particles rich in hydroxyl groups have high hydrophilic characteristics [26]. BC is a hydrophilic substance [27]; the water contact angle of BC was around 47.5 ∘ ± 2.8.…”

Fabrication of superhydrophobic natural rubber film via grafting of methyltrichlorosilane

“…To form the roughness on the surface of rubber substrates, silica particles are generally modified using a silane coupling agent to decrease the degree of hydrophilicity of the silica and so form a hydrophobic surface on the NR surface by an ordinary coating procedure 27 . However, this technique unfortunately provides a very weak interaction between the modified silica and the surface of the substrates, which results in a low durability against scratching or washing 25,27 .…”

“…To form the roughness on the surface of rubber substrates, silica particles are generally modified using a silane coupling agent to decrease the degree of hydrophilicity of the silica and so form a hydrophobic surface on the NR surface by an ordinary coating procedure 27 . However, this technique unfortunately provides a very weak interaction between the modified silica and the surface of the substrates, which results in a low durability against scratching or washing 25,27 . Moreover, the direct incorporation of modified silica into the rubber matrix is not satisfactory for increasing the hydrophobicity, since the large amount of the modified nanoparticles (NPs) is trapped inside the polymeric phase to consequently decrease the hydrophobic performance 27 .…”

“…However, this technique unfortunately provides a very weak interaction between the modified silica and the surface of the substrates, which results in a low durability against scratching or washing 25,27 . Moreover, the direct incorporation of modified silica into the rubber matrix is not satisfactory for increasing the hydrophobicity, since the large amount of the modified nanoparticles (NPs) is trapped inside the polymeric phase to consequently decrease the hydrophobic performance 27 . To overcome these problems, methyltrichlorosilane (MTCS), a non‐fluorinated organosilicon monomer, can be applied to form the 3D polysiloxane structure onto the rubber surface via a two‐step method involving chemical coursing and sol–gel process 28,29 .…”