Rubber materials from elastomers and nanocellulose powders: filler dispersion and mechanical reinforcement

Abstract

Rubber materials with well-dispersed fillers and large mechanical reinforcement have been obtained by melt-processing a diene elastomer matrix and tailored nanocellulose powders having both a high specific surface area and a modified interface. Such filler powders with a specific surface area of 180 m2 g-1 and 100 m2 g-1 have been obtained by freeze-drying suspensions of short needle-like cellulose nanocrystals (CNCs) and entangled networks of microfibrillated cellulose (MFC) in tert-butanol/water, respectively. A quantitative and toposelective filler surface esterification was performed using a gas-phase protocol either with palmitoyl chloride (PCl) to obtain a hydrophobic but non-reactive nanocellulose interface, or with 3,3'-dithiopropionic acid chloride (DTACl) to introduce reactive groups that can covalently bind the nanocellulose interface to the dienic matrix in a subsequent vulcanization process. A set of filled materials was prepared varying the filler morphology, interface and volume fraction. Transmission electron microscopy images of ultrathin cryo-sections showed that modified nanocellulose fillers presented a relatively homogeneous distribution up to a volume fraction of 20%. The materials also exhibited a significant modulus increase, while keeping an extensibility in the same range as that of the neat matrix. Strikingly, in the case of the reactive interface, a strong stress-stiffening behavior was evidenced from the upward curvature of the tensile curve, leading to a large increase of the ultimate stress (up to 7 times that of the neat matrix). Taken together, these properties, which have never been previously reported for nanocellulose-filled elastomers, match well the mechanical characteristics of industrial carbon black or silica-loaded elastomers.

Synthesis and chemical modification of crystalline nanocellulose to reinforce natural rubber composites

“…While in most of the reported works, hand layup method, melt mixing, and solution casting are followed for CNC loading. [21][22][23][24][25] Therefore, the effect of surface modification on CNC dispersion through two roll mixing is presumed to be validated in the present investigation. Surface modification of CNC is done following a reported method where isocyanatepropyltriethoxysilane is employed.…”

“…21 Fumagalli's group reported melt-processing of a diene elastomer with 3,3 0 -dithiopropionic acid chloride and palmitoyl chloride tuned nanocellulose powders which showed a high specific surface area with a modified interface. 22 Thomas et al used zinc-modified CNCs to achieve better dispersion in the NR matrix and very good tensile strength thereby. 23 There are also some reports on CNC based NR composites where achieving adequate reinforcement remains an issue.…”

Cellulose Nanofibers Isolated from the Cuscuta Reflexa Plant as a Green Reinforcement of Natural Rubber

“…It was observed that 3,3'-dithiopropionic acid chloride (DTACl) modified cellulosic nanocrystals (CNC) can covalently bound to styrene-butadiene rubber (SBR) effectively [15]. The homogeneous dispersion of DTACl modified cellulose nanocrystals provides an additional strain stiffening effect which was similar to the behavior exhibited by silica and carbon black in elastomers.…”

Recent Developments in Nanocellulose-Reinforced Rubber Matrix Composites: A Review

“…Fumagalli et al [26] researched the potential of surface-modified CNCs and CNFs with 3,3′-dithiodipropionic acid chloride (DTACl) in SBR. They reported the occurrence of a reactive interface and strong stiffening behavior with the addition of the modified nanofillers.…”

“…The search for substitutes and alternatives of conventional fillers for rubber applications is the driving force in research and development sectors in rubberbased research groups and large-scale industries. Recent advances show the prowess of nanocellulose in achieving or surpassing the current reinforcing performance of conventional fillers [25,26].…”