Effect of water and carbonyl sulfide toxins in gas propylene feed in polymerization process on physical properties of polypropylene

The effects of water and carbonyl sulfide (COS) in propylene feed of polymerization process were examined in relation to the physical and mechanical properties of synthesized polypropylene (PP). The Samples were analyzed using gel permeation chromatography, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometry (WAXS) and mechanical test. Molecular mass and isotacticity of PP were reduced by increasing poisons due to the limitation of the movement of polymer chains. The SEM images indicated that the effect of water and COS poisons on polymer morphology was insignificant. The results of DSC and optical tests revealed that an increase in water and COS poisons significantly increased the transparency of PP, which had been originated from the reduction of surface irregularities caused by escalated polymer atacticity. Nevertheless, the improvement in optical properties was very little for other properties, such as gloss and yellow index. The XRD results confirmed lower crystallinity due to escalated atacticity because of increased poisons. Furthermore, comparison of poison-contained and poison-free samples indicated that an increase in the amount of poisons led to greater tensile strength and heat distortion temperature (HDT). Since it is crucial to achieve the ultimate properties of the polymer, mechanical properties of the polymer should be considered to achieve improved transparency.