Effect of rubber polarity on selective wetting of carbon nanotubes in ternary blends

Abstract

Carbon nanotubes (CNTs) with special nanoscale structure combined with the high strength of the carbon-carbon bondings and a large aspect ratio opens up a wide range of new applications [1]. However, the physical properties of the CNT-polymer composites are often below expectations, because a sufficiently effective force transfer between the polymer matrix and CNTs has not yet been reached. In order to exploit the exceptional mechanical and electrical properties of CNTs in polymer composites, the filler wetting and dispersion as well as the filler-polymer interaction must be increased [2][3][4]. It is generally known, that the smaller the contact angle ! between polymer and filler, the better the wettability of the filler and the stronger the polymer-filler interaction. Although the contact angle ! can be calculated from the surface tension of the individual components of the mixture, it is not sufficient for the description of the complex wetting behavior of the filler in rubber compounding [5]. The reason is that the filler wetting is not only thermodynamically determined, but it is also a kinetic process. Due to the agglomerate structure of filler polymer chains need a certain time Abstract. Based on atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) analysis of the rubber-filler gel (wetting concept) the kinetics of selective wetting of carbon nanotubes (CNTs) in ternary styrene butadiene rubber (SBR)/butadiene rubber (BR)/natural rubber (NR) blends was qualitatively and quantitatively characterized. Almost all CNTs are found to be wetted by the non-polar NR but not by the other non-polar rubber like BR or weakly polar SBR. It was proposed that phospholipids, which are linked to the "-terminal of NR can interact with the CNT surface through cation-# interactions forming strong bonding between NR and CNTs. Using the corrected surface tension value of NR, which involves the effect of phospholipids found in our previous work the selective wetting of CNTs in ternary rubber blends can be well predicted using the Z-model for a thermodynamic equilibrium state. By replacing the non-polar BR by a polar rubber like nitrile butadiene rubber (NBR) as a blend component CNTs are wetted by NBR slightly more than by NR thanks to the strong interaction between CNTs and nitrile groups of NBR. SBR remains unbound to CNTs in both blends.

Evaluation of mechanical, thermal, electrical, and transport properties of MWCNT‐filled NR/NBR blend composites

“…Le et al reported that there is a cation‐ pi interaction between the phospholipids in NR and the CNT surfaces. From literature, it can be seen that polymers can wrap around CNTs, forming supramolecular complexes . This can be explained by the wrapping mechanism that attributed to certain specific interactions between the polymer and the CNT.…”

“…MWCNT can act as a compatibilizer in NR/NBR blends. Le et al developed a ternary blend of NR/NBR/SBR using CNT as the filler. They reported that CNT mainly reside in the polar NBR and non‐polar NR than in weak polar SBR.…”

Combination of Self-Healing Butyl Rubber and Natural Rubber Composites for Improving the Stability

“…Particularly, in the case of electric vehicle (EV) technology, the tire with low thickness, high durability and electrically conducting are essential. Nowadays, many types of natural rubber (NR) [ 1 ] and synthetic rubber (SR) have been investigated such as styrene-butadiene rubber (SBR) [ 2 ], butadiene rubber (BR) [ 3 ] and their blends including NR/SBR, SBR/BR and NR/BR/SBR [ 4 , 5 , 6 ]. This is attributed to the superior elasticity and flexibility of NR and BR [ 7 , 8 ] along with the SBR which has well rolling properties and wet fraction due to π–π interaction of existing benzene ring in the molecular structure [ 9 ].…”

Influence of Treated Distillate Aromatic Extract (TDAE) Content and Addition Time on Rubber-Filler Interactions in Silica Filled SBR/BR Blends

“…Increase in bound rubber content with the presence of silane, increasing filler content and mixing time was observed [ 21 , 22 ], when it decreased at high extraction temperatures [ 20 ]. In binary and ternary rubber blend systems, the wetting concept was widely used to identify filler localization and rubber–filler interactions [ 23 , 24 , 25 , 26 ]. The bounded rubber principle lies under the wetting concept as well; however, the calculations are carried out differently from the bound rubber concept.…”