ESTIMATION OF SURFACE FREE-ENERGY OF OXIDIZED CARBON-BLACK

The interfacial free energy is one of the main factor controlling the dispersion of the filler in polymer matrices. It is necessary to know the accurate value of the surface free energy of the filler for analysis of the dispersal properties of particles in polymer composites. The measurements of surface free energy of CB particles are very difficult for these powder-like shapes. The purpose of the present study is to measure the surface free energy of oxidized CB. Carbon black, Seast 300, 27 nm indiameter, was used as original CB, and two kinds of oxidized CB were prepared by oxidation for 3 h in 25% and 50% boiled nitric acid. IGC (inverse gas chromatography) measurements were performed with a Shimadzu gas chromatograph GC-7 A with a TCD detector. The glass columns (2.1 m long, 3 mm in diameter) were used and a column temperature was 90-degrees-C. Helium was used as a carrier gas. ESCA (electron spectroscopy for chemical analysis) measurements were performed with a JEOL photo electron spectrometer JSP-80 under a vacuum of 10(-6) Pa. MgK-alpha (10 kV, 10 mA) was used as X-ray source. The dispersive components of surface free energies of oxidized CB particles could be estimated by IGC and they were slightly increased by oxidation. The polar components of them estimated by ESCA as the atomic ratios [O]/[C] on the CB surfaces were greatly increased by oxidation. The values of the surface free energy of CB which are defined as the sum of the dispersive and polar components measured in this work agreed with the generally reported values.