New Insights in Polymer-Biofuels Interaction

This paper deals with polymer-fuel interaction focusing on specific effects of biofuels on polyethylene (PE) in automotive applications. The practical objective is to develop a predictable approach for durability of polyethylene tanks in contact of ethanol based or biofuel based fuels. In the case of ethanol, the main consequence on PE durability is a reduction of the rate of stabilizer extraction; this latter phenomenon can be modeled by first order kinetics with a rate constant that obeys the Arrhenius equation. Concerning biodiesels, the study was focused on soy and rapeseed methyl ester which were compared to methyl oleate and methyl linoleate used as model compounds. Here, PE-fuel interactions can be described as well as physical interaction, linked to the oil penetration into the polymer, as chemical interaction linked to an eventual co-oxidation of PE and oil. Both aspects were investigated. Concerning biofuel transport in PE, it appeared that the oil diffusivity depends only of temperature and oil molar mass. Some aspects of the temperature dependence of the oil solubility in PE are discussed. About chemical interaction between oil and PE, it was put in evidence that unsaturated fatty esters promote and accelerate PE oxidation. A co-oxidation kinetic model was proposed to describe this process.