Surface hydrophobicity alteration of fractionated paraffin wax, crude by-product polyolefin wax and their blend

Abstract

The surface compositions of crude by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were compared, under various conditions, by using FT-IR. Then a practical criterion was theoretically derived by back-of-the-envelope-calculation to estimate the diffusivity for the surface enrichment of hydrophilic functional groups. The hydrophobicity in terms of chemical structure and functional groups was altered by changing the environment as well as by blending wax K with wax J. The surface properties of wax J and wax M turned out more hydrophobic than that of wax K within the experimental period of water-submerged condition, even though the structure and functional groups on the surfaces of all waxes under ambient atmospheric condition are extremely similar. Thus the blend of wax M behaved unlike wax K but similarly to wax J in terms of alteration of hydrophobicity. Such values of diffusivity as 1.35×10⁻¹¹ cm²/s and 1.96×10⁻¹¹ cm²/s are established for wax J and wax M, respectively, under 1 day water-submerged condition. Furthermore, under 1 week water-submerged condition, the values of their diffusivity for wax J, wax K and wax M are estimated as 3.06×10⁻¹² cm²/s, 7.23×10⁻¹¹ cm²/s and 1.50×10⁻¹¹ cm²/s, respectively. The obtained values of diffusivity are consistent, in terms of the order of magnitude, with the value of diffusion coefficient of 5.75×10⁻¹¹ cm²/s obtained, using a very complicated empirical-formula, by Chen et al. for the investigation of surface-modifier enrichment. Thus, the suggested criterion may be very useful and practically applied to clarify the process of surface enrichment from general polymer-blends.