Development of a methodology based on plasma treatments for production of superhydrophobic polyamide

• Grant number: 11/20464-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2012
• End date: January 31, 2013
• Field of knowledge: Physical Sciences and Mathematics - Physics - Physics of Fluids, Plasma Physics and Electrical Discharge
• Principal Investigator: Elidiane Cipriano Rangel da Cruz
• Grantee: Adriana de Oliveira Delgado Silva
• Host Institution: Universidade Estadual Paulista (UNESP). Campus Experimental de Sorocaba. Sorocaba , SP, Brazil

Abstract

The application of polymeric composites in aerospacial and automobilistic industries is in progressive rise due to their suitable properties, as lightness and mechanical resistance, associated to low cost. In particular, the polyamides PA, known as nylon, are used for a large number of applications, especially in the automotive industry. However, the high affinity of the polyamide towards water promotes absorption of this compound from atmosphere resulting in swelling and in changes of the component final dimensions, which limits their useful life-time. One way to try to overcome such drawbacks is to develop a superhydrophobic layer on the nylon surface in order to avoid the contact of vapors and liquids with the interior of the material. The plasma treatment has revealed to be a powerful tool for changing the properties of solid surfaces. In this context, the project aims to develop a superhydrophobic layer on the polyamide PA66, keeping its mechanical properties. For this, two types of treatment are proposed: 1) plasma ablation combined with plasma immersion ion implantation, in order to obtain a micro- and nano-structured surface; and 2) surface coating with an organometalic film from plasma of hexamethyldisiloxane, HMDSO. The experimental parameters used in each type of treatment will be varied in order to find an optimized condition, which reduces the wettability of the polyamide, preserves its mechanical properties and could be scaled to industrial applications. In the treatments based on plasma ablation and ion implantation, Ar and Ar/O$_2$ plasmas will be employed, varying the gas proportion, the plasma power and pressure, exposure time as well as the magnitude and frequency of the applied pulses. In the treatments based on coating, the layers will be produced from plasmas of HMDSO, diluted in Ar and O$_2$, and the effects of plasma chemical composition, pressure and power on the wettability of the polyamide will be investigated. The treated and as-received material will be analised through different techniques. The wettability will be analyzed by contact angle experiments, while the roughness will be determined by topographical images from AFM (Atomic Force Microscopy) and also by topographic profiles from profilometry. The surface morphology will be evaluated through scanning electron microscopy and the chemical composition profile by RBS (Rutherford Backscattering Spectroscopy). Infrared spectroscopy and profilometry will be applied to determine the chemical structure and thickness of the deposited layers, respectively. The effect of the treatments on the mechanical properties of the samples will be investigated by nanoindentation. At the end of the research, we hope to develop a methodology based on plasma treatment, which is able to produce superhydrophobic nylon without loss in mechanical resistance, and could be applicable to industrial production lines. Certainly, this result will represent a great progress in scientific and technological knowledge concerning the processing of engineering materials. (AU)