Study On Hydrophilicity Modification Of Polypropylene

Polypropylene (PP) is one of the most commonly used plastics because of its versatile properties, wild applicability, and low cost. However, PP is limited in its further application due to its non-polarity and crystallizability, poor compatibility with synthetic polar polymers, inorganic fillers and enhanced materials, poor dyeability, adhesivity, antistatic property, and hydrophilicity. In this paper, PP was hydrophilic modified by three means: solid phase grafting with acrylic acid (AA), blending with ethylene-acrylic acid copolymer (EAA), and impregnating into surfactant, separately.Graft copolymerization to introduce appropriate polar group or chain onto PP backbone is a simple and effective approach of hydrophilic modification. Compared with other grafting methods, solid phase grafting is such a high efficient and energy conserving method that it is studied and applied wildly at the present time. In this study, solid phase grafting technology for AA onto PP was investigated in details, and the effects of factors, including reaction time, reaction temperature, as well as concentration of monomer and initiator, on grafting reaction were also studied. It was proved by Fourier transform infrared spectroscopy (FTIR) that AA was actually grafted onto the PP backbone. Contact angle of water was measured to characterize the hydrophilicity of grafted PP. The results showed that the maximum graft degree was achieved as 1.31% when the reaction was operated under 120℃, for 90min with PP:AA:BPO=100:10:0.4(mass ratio). The contact angle of the grafted PP decreased from 90°(original PP) to 81.3°, indicating the improvement of hydrophilicity. It was found by differential scanning calorimeter (DSC) that, PP solid phase grafting AA copolymer (PP-g-AA) possessed lower melting and crystallization temperatures, higher melting and crystallization enthalpy, larger crystallization rate as well as crystallinity than the original PP. The results of thermogravimetric analyses (TGA) indicated that graft modification could enhance the thermal stability of the material.