A series of waterborne polyurethane (WBPU)/multiwalled carbon nanotube (CNT) and WBPU/nitric acid treated multiwalled carbon nanotube (A‐CNT) composites were prepared by in situ polymerization in an aqueous medium. The optimum nitric acid treatment time was about 0.5 h. The effects of the CNT and A‐CNT contents on the dynamic mechanical thermal properties, mechanical properties, hardness, electrical conductivity, and antistatic properties of the two kinds of composites were compared. The tensile strength and modulus, the glass‐transition temperatures of the soft and hard segments (Tgs and Tgh, respectively), and ΔTg (Tgh − Tgs) of WBPU for both composites increased with increasing CNT and A‐CNT contents. However, these properties of the WBPU/A‐CNT composites were higher than those of the WBPU/CNT composites with the same CNT content. The electrical conductivities of the WBPU/CNT1.5 and WBPU/A‐CNT1.5 composites containing 1.5 wt % CNTs (8.0 × 10−4 and 1.1 × 10−3 S/cm) were nearly 8 and 9 orders of magnitude higher than that of WBPU (2.5 × 10−12 S/cm), respectively. The half‐life of the electrostatic charge (τ1/2) values of the WBPU/CNT0.1 and WBPU/A‐CNT0.1 composites containing 0.1 wt % CNTs were below 10 s, and the composites had good antistatic properties. From these results, A‐CNT was found to be a better reinforcer than CNT. These results suggest that WBPU/A‐CNT composites prepared by in situ polymerization have high potential as new materials for waterborne coatings with good physical, antistatic, and conductive properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3973–3985, 2005

Nitric acid treated multiwalled carbon nanotubes (A-CNTs) were dispersed in a waterborne polyurethane (WBPU) matrix to obtain WBPU/A-CNT nanocomposite films (99.99/0.01-98.5/1.5) with enhanced thermal, mechanical, and electrical properties. By X-ray photoelectron spectroscopy (XPS), the oxygen content of the carbon nanotube (CNT) surface was found to increase with increasing acid treatment time. With increasing acid treatment time, the contact angle of the CNT surface was significantly decreased from 15 to 0°. The mean particle sizes of the raw CNT and A-CNT aqueous solutions were 404.2 and 17.2 nm, respectively, indicating that the acid treatment led to a reduced agglomeration of CNTs. The electrical conductivity of raw CNT was 23 S/cm, and that of A-CNT significantly increased with increasing acid treatment time up to 30 min and then decreased a little. By dynamic mechanical thermal analysis, the storage modulus and loss tangent peak temperature (the glass-transition temperature) of the WBPU/A-CNT nanocomposites were found to increase with increasing A-CNT content. The initial tensile moduli and tensile strengths of the nanocomposite film with 1.5 wt % loading of A-CNT were enhanced by about 19 and 12%, respectively, compared to the corresponding values for the original WBPU film. The WBPU/A-CNT1.5 nanocomposite film containing 1.5 wt % of A-CNT exhibited a conductivity of 1.2 ϫ 10 Ϫ4 S/cm, which was nearly eight orders of magnitude higher that of the WBPU film (2.5 ϫ 10 Ϫ12 S/cm). The antistatic half-life ( 1/2 ) of the WBPU film was about 110 s, indicating that pure the WBPU film was a typical electrostatic material. However, those of the WBPU/A-CNT nanocomposites decreased exponentially with increasing A-CNT content. The WBPU/A-CNT1.5 sample, containing 1.5 wt % of A-CNT and with a 1/2 of 1 s, had good antistatic properties.

A conductive poly(aniline codoped with dodecyl benzene sulfonic acid and hydrochloric acid) [PANI-D/H, yield: 32.2%, intrinsic viscosity ([]): 1.39 dL/g, electrical conductivity: 7.3 S/cm] was synthesized by chemical oxidative polymerization from aniline-dodecylbenzene sulfonic acid salt (A-DS)/aniline-hydrochloric acid salt (A-HS) (6/4M ratio) in an aqueous system. Waterborne polyurethane (WBPU) dispersion obtained from isophorone diisocyanate/poly(tetramethylene oxide)glycol/dimethylol propionic acid/ethylene diamine/triethylene amine/water was used as a matrix polymer. The blend films of WBPU/PANI-D/H with various weight ratios (99.9/0.1-25/75) were prepared by solution blending/casting. Effect of PANI-D/H content on the mechanical property, dynamic mechanical property, hardness, electrical conductivity, and antistaticity of WBPU/PANI-D/H blend films was investigated. The dynamic storage modulus and initial tensile modulus increased with increasing PANI-D/H content up to 1 wt %, and then it was significantly decreased about the content. With increasing PANI-D/H content, the glass transition temperature of soft segment (T gs ) and hard segment (T gh ) of WBPU/PANI-D/H blend films were shifted a bit to lower the temperature. The tensile strength and hardness of WBPU/PANI-D/H blend films increased a little with increasing PANI-D/H content up to 0.5 wt %, and then it was dramatically decreased over the content. The elongation at break of WBPU/PANI-D/H decreased with an increase in PANI-D/H content. From these results, it was concluded that 0.5-1 wt % of PANI-D/H was the critical concentration to reinforce those various properties of WBPU/PANI-D/H blend films prepared in this study. The electrical conductivity of WBPU/ultrasonic treated PANI-D/H (particle size: 0.7 m) blend films prepared here increased from 4.0 ϫ 10 Ϫ7 to 0.33 S/cm with increasing PANI-D/H content from 0.1 to 75 wt %. The antistatic half-life time ( 1/2 ) of pure WBPU film was about 110 s. However, those of WBPU/ultrasonic treated PANI-D/H blend films ( 1/2 : 8.2-0.1 s, and almost 0 s) were found to decrease exponentially with increasing PANI-D/H content (0.1-9 wt %, and above 9 wt %).

No abstract

No abstract