Study On Hydrophilicity And Lipophilicity Modification Of Polypropylene

As an important common plastic, Polypropylene's (PP) applications in industry and agriculture is very extensive because of the excellent overall performance, but, poor hydrophilicity restricted the further application of PP. In this paper, based on manufacturing coalescing-plate of separation equipment for separating oil and water, the main works focused on improving the hydrophilicity of polypropylene on the basis of improving the hydrophobicity. The critical contents and conclusions are as below:Using lipophylic surfactant, lipophobic and hydrophobic surfactant, hydrophilic surfactant to modify Polypropylene.The results show that , hydrophilic angle and lipophylic angle was 94°and 29°of pure PP。Hydrophilic angle decreased and lipophylic angle increased when cetylpyridinium bromide (CPB) was added with 3%, the minimum angle was 17°. As a excellent lipophobic and hydrophobic surfactant, modified PTFE powder (SI-130) could increase hydrophilic angle and lipophylic angle.When cetyltrimethylammonium bromide (CTAB) was added, hydrophilicty was improved, the minimum angle was 85°with 4% content of CTAB.In order to resolve the question of short empolying life of low molecular weight surfactants, we made use of strong polarity PA6 to blend polypropylene, the results reveal that, the contact angle of water was 65°with 30% PA6, but, because the contact angle of pure PA6 was 60°, therefore, the contact angle will not reduce significantly accompanied by increaseing the amount of PA6.By use of hydroxymethyl acrylamide (NHA), butyl methacrylate (BMA) monomer , we grafted polypropylene to improve the hydrophilicity. The hydrophilicity was greatly improved. The highest grafting rate was 1.6% with 3% content of NHA , the minimum contact angle was 83°; The grafting rate was the highest of 1.83% when 2.4% of BMA was added, minimum contact angle at this time, was 80°. Sulfonated by chlorosulfonic acid reaction or oxided by potassium permanganate and potassium dichromate/sulfuric acid system, polypropylene surface will exist sulfonate, carbonyl, hydroxyl and other hydrophilic groups, hydrophilicity improved because of surface roughness increasing significantly, but the method is polluting, and also, the mechanical properties of the samples severely damage bexause of strong oxidation.A certain size coalescing-plate was made of modified PP by surfactant to investigate the degreasing efficiency, the most efficient material was 4% PVDF modified polypropylene with the oil removal efficiency of 91.61%.