Effect of mechanical, barrier and adhesion properties on oxygen plasma surface modified PP

Abstract

Abstract In this work, the Polypropylene (PP) film was surface modified by Oxygen plasma treatment and the effect of mechanical, barrier and adhesion properties was studied. The PP film was plasma treated with various RF power settings of 7.2 W, 10.2 W and 29.6 W in various time intervals of 60 s, 120 s, 180 s, 240 s and 300 s. To characterize the wettability, the contact angle was measured and the surface energy values were estimated with different test liquids. The generation of oxygen functional groups on the surface of plasma modified PP and the surface change characterization were observed by attenuated total reflection-Fourier transform infrared spectroscope (ATR-FTIR) and they resulted in wettability improvement. The roughness of the PP film and the surface morphology were analyzed by Atomic Force Microscopy (AFM). It was found that the roughness value increased from 1.491 nm to 7.26 nm because of the increase of treatment time and RF power. The PP crystallinity structure of the untreated and treated PP was evaluated by X-ray diffraction analysis (XRD). The bond strength of the untreated and surface modified films were measured by T-peel test method. For the untreated and oxygen plasma treated sample, the mechanical properties like Tensile Strength and the barrier properties like oxygen transmission rate (OTR), Water vapor transmission rate (WVTR) were also calculated. From the results, the tensile strength reduced from 6 MPa to 1.350 MPa because of polypropylene etching and degradation. The OTR increased from 1851.2 to 2248.92 cc/m2/24 h and the Water vapor transmission rate increased from 9.6 to 14.24 g/m2/24 h. Industrial Relevance Plasma technology applied to packaging and printing industry is a dry, environmentally- and worker-friendly method to achieve surface alteration without modifying the bulk properties of different materials. In particular, atmospheric non-thermal plasmas are suited because most are heat sensitive polymers and applicable in continuous process. In the last years plasma technology has become a very active, high growth research field, assuming a great importance among all available material surface modifications in packaging industry.