Investigation of Polypropylene Sulfurized with Thiourea Solution by AFM and SEM

Layers of sulfur and sulfur compounds were prepared on surface of polypropylene (PP) by sorbtion-difussion method at 90 °C in acidic 3 mol/l thiourea solution with 0.005 mol/l additive (NH4)2S2O8. Duration of sulfurization varied from 1 to 7 h. The surface of PP was investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), turbidimetric and gravimetric methods. Amount of sorbed sulfur varied from 0.055 mg/cm2 to 0.094 mg/cm2. Analysis by AFM method revealed that layers on PP were not continuous. Sulfur particles like islands grew with increased duration of sulfuring. Width of particles varied from 0.6 nm to 1.1 nm, average height varied from 288 nm to 715 nm, roughness of PP surface increased from 27 nm to 88 nm. Sulfurized PP surface was investigated by SEM. Cross-sectional microphotograph of PP showed that thickness of sulfurized layers was about 3 µm – 13 µm and depended on sulfuring duration. Sulfur diffused to PP, forming sulfur particles which seemed like separate islands on the surface