Overview
ISO/TS 11888:2017 - "Nanotechnologies - Characterization of multiwall carbon nanotubes - Mesoscopic shape factors" - defines methods to quantify the mesoscopic shape of multiwall carbon nanotubes (MWCNTs). The technical specification focuses on measuring the static bending persistence length (SBPL) and related mesoscopic descriptors using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), viscometry, and light scattering (DLS / DDLS). SBPL typically ranges from several tens of nanometres to several hundred micrometres and is key to understanding MWCNT behavior in materials and dispersions.
Key topics and requirements
- Primary measurement objectives
- Determine SBPL, contour length (L), end-to-end distance (R), bending ratio (Db) and intrinsic viscosity.
- Imaging and analysis
- High-resolution SEM imaging (typical recommended magnifications: 10 000× and 20 000×) and TEM for internal diameter measurements.
- Procedures for extracting contour lengths and end-to-end distances from images and calculating mean-squared values and bending ratios.
- Defined measurement methods for SBPL
- Method 1: Statistical approach using ≥100 individual MWCNTs across contour-length bins to plot bending ratio vs. reciprocal contour length (most accurate).
- Method 2: Mean radius of curvature from ≥100 tubes as an approximate SBPL.
- Method 3: Focused sampling of ~10 tubes at ~2 µm contour length to estimate SBPL.
- Sample preparation
- Ball-milling, dispersion (e.g., DMF + ultrasonication), centrifugation and filtration procedures are provided to produce representative samples for SEM/TEM.
- Complementary techniques
- Viscometry and (de)polarized dynamic light scattering (DLS/DDLS) are described in annexes as supporting measurements for mesoscopic shape and dispersion quality.
- Reporting
- Prescribed test-report content and formulae (Annex A) for reproducibility.
Applications and users
Who benefits:
- Materials scientists and nanomaterials researchers characterizing MWCNT morphology.
- Quality control and manufacturing labs validating MWCNT batches.
- Polymer composite developers optimizing electrical percolation, mechanical reinforcement and rheology.
- Toxicologists and EHS professionals assessing shape-dependent exposure and hazard metrics (see ISO/TR 12885 for safety handling).
Practical uses:
- Predicting MWCNT contribution to composite conductivity, mechanical models and dispersion behavior.
- Establishing batch-to-batch reproducibility and acceptance criteria for CVD-produced MWCNTs.
- Informing formulation and loading strategies to achieve target performance (e.g., percolation thresholds).
Related standards
Keywords: ISO/TS 11888:2017, MWCNT, mesoscopic shape factors, SBPL, SEM, TEM, viscometry, DLS, DDLS, carbon nanotube characterization.