Nanostructural Evolution of Natural Rubber/Silica Nanoparticle Coagulation from Binary Colloidal Suspensions to Composites: Implications for Tire Materials

Abstract

The liquid mixing process is an advantageous production method that has recently gained industrial interest for elaborating composites based on natural rubber (NR) and filler nanoparticles (NPs). Understanding how the relevant components such as polymer, fillers, as well as proteins and lipids coming from NR organize along the fabrication process is of importance for modulating material properties. Here, we successfully employed a combination of nanoimaging techniques to unravel the structure and evolution of heteroaggregates formed by colloidal destabilization of a model NR latex−silica NPs liquid mixing process. First, field emission scanning electron microscopy (FESEM) was used to investigate the structures from the early stage of contact between the particles until the formation of a composite. Results highlight an interaction in the liquid state between NR globules contained within the latex and silica NPs, hindering coalescence among globules. The latter can be achieved by applying shear in suspension or by solvent evaporation obtaining a dried composite. Atomic force microscopy coupled to infrared spectroscopy (AFM−IR) was employed to probe the in-depth nanoscopic distribution of silica NPs revealing a restricted mobility of the NPs during evaporation. Ultimately, the spatial distribution of proteins and lipids of NR, with respect to silica NPs, was investigated using dual color fluorescence images acquired with direct stochastic optical reconstruction microscopy (d-STORM) in a correlative light electron microscopy (CLEM) approach. The presence of silica NPs is found to influence the distribution of proteins and lipids in the composite; biomolecules form clusters of ∼200 nm, which are partially colocalized with silica, highlighting an interaction between them. Our work provides comprehensive structural understanding of a model system undergoing liquid mixing, unlocking the potential of combining high-resolution imaging techniques to elucidate the structure of materials for tire applications.

Surface Heterogeneity in Amorphous Silica Nanoparticles Evidenced from Tapping AFM–IR Nanospectroscopy

“…This technique is also used to study cystine crystallites that were collected from hospital patients with cystinuria . Analyzing AFM–IR absorption spectra made it possible to investigate alkane acids in bitumen–mineral mixtures, carbonaceous inclusions in garnet porphyroblasts, , and organic matter in shale. − An AFM–IR instrument was used for the measurements of silica spheres functionalized with carboxyl groups, silica nanoparticles in natural rubber, and silicate glasses . It is also possible to detect carbon species on Fischer–Tropsch catalysts and to study zircons …”

Phosphonium Ionic Liquid‐Activated Sulfur Vulcanization: A Way Forward to Reduce Zinc Oxide Levels in Industrial Rubber Formulations

“…Cross‐linking of two‐dimensional macromolecular polymer chains into three‐dimensional network structures is an essential process by which polymer is converted into durable materials for use in various applications [1–19] . ZnO is a global activator for the sulfur vulcanization process which improves the kinetics of the curing process and promotes the short sulfidic cross‐link formation with higher densities [20–27] .…”

“…Cross-linking of two-dimensional macromolecular polymer chains into three-dimensional network structures is an essential process by which polymer is converted into durable materials for use in various applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] ZnO is a global activator for the sulfur vulcanization process which improves the kinetics of the curing process and promotes the short sulfidic cross-link formation with higher densities. [20][21][22][23][24][25][26][27] However, the low affinity of ZnO towards the non-polar rubber entails its higher consumption (3-5 parts per hundred, phr) to achieve a good distribution in the polymer matrix.…”

Green Approaches for Functionalized Silica-Based Natural Rubber Nanocomposites Using Eco-friendly Sodium Alginate Biopolymers for Superior Static and Dynamic Behaviors

“…Epoxidized natural rubber (ENR) has been extensively investigated to act as a compatibilizer and replace silane fully or partially in silica-filled rubber compounds . Cattinari et al adopted a liquid mixing process to disperse the silica nanoparticles in natural rubber. Researchers have also investigated silane with other green ingredients such as bis-epoxypropyl polysulfide (BEP) and polyoxyethylene sorbitan, coconut shell bio-oil, soyabean oil, terpene, and ENR to obtain high-performance nanocomposites.…”