Preparation of hydrophobic microspheres from low-temperature melting polymeric materials

A novel procedure for the preparation of hydrophobic spherical particles fr om thermoplastic materials, such as polyethylene (PE) or fossil resin (FR), is presented. These particles are particularly useful in the determination of surface forces with the atomic force microscope using the colloidal pro be technique. The preparation steps include (i) suspending powdered polymer (PE and FR) in glycerol, (ii) heating the suspension above the melting poi nt of the polymer. (iii) solidification of dispersed PE/FR droplets at a re duced temperature, (iv) filtration of the particles, and (v) washing/drying of the product. Such produced particles of PE and FR had a broad size dist ribution (2-50 mu m) and a spherical shape. The surfaces of these particles were relatively smooth, with a small number of asperities, and/or attached satellite particles or non-spherical debris. Analytical examination of the polymer surface, before and after treatment with hot glycerol, by SEM, AFM , contact angle, XPS, and FTIR measurements revealed only slight chemical c hanges on the surface caused by this treatment, which included a decrease i n the hydrophobicity of the polymer surface caused by an increased amount o f oxygen-containing polar groups. These changes were greatly diminished aft er drying, and the hydrophobicity of the PE and FR surfaces was, at least p artially. restored.