Unzipped Multiwalled Carbon Nanotube Oxide/Multiwalled Carbon Nanotube Hybrids for Polymer Reinforcement

Multiwalled carbon nanotubes (MWNTs) have been widely used as nanofillers for polymer reinforcement. However, it has been restricted by the limited available interface area of MWNTs in the polymer matrices. Oxidation unzipping of MWNTs is an effective way to solve this problem. The unzipped multiwalled carbon nanotube oxides (UMCNOs) exhibit excellent enhancement effect with low weight fractions, but agglomeration of UMCNOs at a relatively higher loading still hampered the mechanical reinforcement of polymer composites. In this paper, we interestingly found that the dispersion of UMCNOs in polymer matrices can be significantly improved with the combination of pristine MWNTs. The hybrids of MWNTs and UMCNOs (U/Ms) can be easily obtained by adding the pristine MWNTs into the UMCNOs aqueous dispersion, followed by sonication. With a π-stacking interaction, the UMCNOs were attached onto the outwalls of MWNTs. The morphologies and structure of the U/Ms were characterized by several measurements. The mechanical testing of the resultant poly­(vinyl alcohol) (PVA)-based composites demonstrated that the U/Ms can be used as ideal reinforcing fillers. Compared to PVA, the yield strength and Young’s modulus of U/M–PVA composites with a loading of 0.7 wt % of the U/Ms approached ∼145.8 MPa and 6.9 GPa, respectively, which are increases of ∼107.4% and ∼122.5%, respectively. The results of tensile tests demonstrated that the reinforcement effect of U/Ms is superior to the individual UMCNOs and MWNTs, because of the synergistic interaction of UMCNOs and MWNTs

Typical numerical model and the parallel bond contact in PFC2D.

Typical numerical model and the parallel bond contact in PFC2D.</p

Verification of the experimental and numerical results.

(a) Failure morphology, (b) Stress-strain curve.</p

Flow of the RCTs selection.

<p>Flow of the RCTs selection.</p

Microscopic parameters of rock.

Microscopic parameters of rock.</p

Peak stress and elastic modulus under different random seeds.

Peak stress and elastic modulus under different random seeds.</p

Crack initiation stress and crack initiation strain in each model.

Crack initiation stress and crack initiation strain in each model.</p

Variation curves of the total number of cracks and the number of shear cracks for each model.

Variation curves of the total number of cracks and the number of shear cracks for each model.</p

Contact force chain and crack evolution characteristics of the models with two and three circular holes.

(a) Two horizontally arranged circular holes, (b) Two vertically arranged circular holes, (c) Two horizontally arranged circular holes, (d) Two vertically arranged circular holes.</p

Stress-strain curves, peak stress, and elastic modulus changes of the models with two and three circular holes.

(a) Stress-strain curves of each comparative model, (b) Peak stress and elastic modulus.</p