CO-DOPED POLYPYRROLE COATINGS FOR STAINLESS STEEL PROTECTION

Polypyrrole (PPy) films have been successfully electrodeposited on stainless steel substrates in aqueous solution. In this work, three systems of electrolytes were studied: oxalic acid, dodecylbenzenesulfonic acid (DBSA) and a mixture of oxalic acid and DBSA. A combination of XPS and TOF–SIMS revealed the formation of an iron oxalate layer at the interface between the oxalic acid-doped PPy (PPy(Ox)) and stainless steel and a thin layer of DBSA was observed at the interface between DBSA-doped PPy (PPy(DBSA)) and stainless steel. Similar to the PPy(Ox) system, an iron oxalate was also present at the co-doped PPy/stainless steel interface. Cyclic voltammetry indicated that an iron oxalate layer initially formed at the surface of the stainless steel when the co-doping system was used. The adhesion strength and corrosion performance of the PPy coating on stainless steel were evaluated by lap shear tests and an anodic potentiodynamic polarization technique, respectively. The co-doped PPy-coated stainless steel exhibited the best adhesion and a significant shift of corrosion potential to the positive direction. This finding opens the possibility for the co-doped PPy coating to be deployed as a strongly adherent corrosion inhibitor by using a simple one-step electropolymerization process.Polypyrrole, XPS, TOF–SIMS, cyclic voltammetry, corrosion, stainless steel

Reactive extrusion and characterization of maleic anhydride-grafted poly(lactic acid) as an interfacial compatibilizer in biopolymer composite

Good interfacial adhesion between fiber and matrix is an expected requirement for composites. The maleated poly(DL-lactic acid) (PLA) has been prepared as a compatibilizer in oil palm empty fruit bunch cellulose fiber (OPEFB) and PLA biopolymer composite. Maleic anhydride (MAH) has been grafted on the PLA structure using benzoyl peroxide (BPO) as an initiator. PLA and MAH have been mixed at different ratios by reactive twin-screw melt extrusion at 175 °C. Qualitative characterization of the maleated PLA has been done by various techniques including FT-IR, 13C NMR, XPS, DSC, TGA and SEM. The glass transition and decomposition temperatures of the maleated PLA have been influenced by MAH contents. PLA/OPEFB composite containing 10 phr of the maleated PLA has been prepared by an extrusion process. The SEM micrographs showed an improvement of interfacial adhesion between OPEFB and PLA in the composite

Controlling wettability of the each side of the PLA fabric through orientation of the working gases (O2 and CH4) during cold plasma treatment

This study aimed to obtain a bifunctional fabric from the point of view of hydrophilicity/hydrophobicity for biomedical applications. To achieve this, both sides of a fabric of polylactic acid (PLA) were subjected to a plasma treatment. While in a side the oxygen was introduced to the other side, simultaneously, was added methane. The plasma treatment was performed at 100 W, 1.8 mbar, during 30 minutes. By Scanning Electron Microscopy (SEM) morphological analysis, it became evident that the fabric side facing the oxygen inlet showed micropittings, while the reverse side had smooth surfaces. Analysis by X-Ray photoelectron spectroscopy (XPS) revealed an increase in the amount of oxygen in the surface of the PLA on both sides of the fabric. The surface function was characterized by measurements of water absorption rate, where it was determined that one fabric side was more hydrophilic than the other side. The results indicated achievement of a bifunctional fabric through orientation of working gases during a plasma treatment.The authors are acknowledging to financial support supplied by CAPES - Brasília/Brazil through of the CAPES/IGC program - CGCI n° 055/2010