Volume 39, Issue 5 (September 2011)
Characterization of Carbon Black Particles Dispersion in Polymeric Matrix by Indirect Methods
Polypropylene (PP)/carbon black (CB) films were prepared via a two-step masterbatch (MB) dilution technique, by the aid of dynamic mixer following two single-screw extruders. The films were quantitatively characterized by color difference (CD), blackness and thermogravimetric analysis (TGA) methods. In the paper, the CD was numerically expressed by CD values. Furthermore, the CD values of films follow quasi-normal distribution as tested by the skewness-kurtosis method. The test of significance confirms the CD values of films are ≤1 NBS (U.S. National Bureau of Standards), which demonstrates CB particles were mixed uniformly in their polymeric matrix. The CD values (quantification) and grey card series (GS, qualification) conform to certain mathematical equation: when CD≤3.4,GS=5-CD/1.7; when CD>3.4, GS=5-lg(CD/0.85)/lg2. In addition, in order to evaluate comprehensively the mixing effect, blackness and TGA method were also employed. With the increment of CB content, the blackness of films increases, which infers that the color difference due to mixing effect of CB particles should be indirectly expressed by blackness. TGA method characterizes mixing uniformity by comparing discrepancy of ash content between films. The results indicate that the films with low CB content have a good mixing effect, while high CB content is unfavorable to decreasing the error of the TGA method.