Comparative characterization of selected additives by high resolution thermogravimetry and nitrogen adsorption

Abstract

Silicas and carbon blacks are often used as additives in the production of rubber, plastics, paint, ink, etc. Physicochemical properties of the materials depend not only on the properties of principal component, its chemical nature, degree of cross-linking, polarity, but also on the structural and surface properties of additives (fillers), i.e., their surface area, porous structure, hydrophobicity, etc. In the present work selected additives have been characterized by low temperature adsorption and high-resolution thermogravimetry (TGA). Nitrogen adsorption isotherms measured over a wide pressure range were used to evaluate the specific surface area and total pore volume. In addition, the pore volume and adsorption energy distributions were evaluated from the adsorption data in order to characterize the surface and structural properties of the samples studied. High-resolution TGA has been used to study the weight-loss as a function of temperature for both samples immersed in organic liquids such as n-butanol and n-heptane, and those exposed to their vapors. The characteristic features of the weight-loss curves were analyzed in order to assess the total porosity and the specific surface area of the additives studied as well as to obtain additional information about microstructural and surface heterogeneities of these samples. Thermogravimetric values of the total porosity and the specific surface area were compared with those obtained by nitrogen adsorption measurements for selected rubber additives.