Ageing properties and polymer/fuel interactions of polyamide 12 exposed to (bio)diesel at high temperature

• Published in: Npj Materials degradation 2019-01, Vol.3 (1), Article 1
• Main Authors: Wei, Xin-Feng, De Vico, Loris, Larroche, Pierre, Kallio, Kai J., Bruder, Stefan, Bellander, Martin, Gedde, Ulf W., Hedenqvist, Mikael S.
• Format: Article
• Language: English
• Subjects: 639/301/923/1028; 639/638/298/303; Aging; Animal fat; Annealing; Automobiles; Automotive fuels; Biodiesel fuels; Biomass; Carbon; Chemistry and Materials Science; Corrosion and Coatings; Crops; Degradation; Diesel fuels; Electrochemistry; Exposure; Fats; Fuel systems; Glass transition temperature; High temperature; In vehicle; Materials Science; Mechanical properties; Oligomers; Oxidation; Polyamide resins; Polymers; Refuse as fuel; Structural Materials; Transportation industry; Tribology
• ISSN: 2397-2106; 2397-2106
• DOI: 10.1038/s41529-018-0065-y

Biodiesel derived from oil crops and animal fats has been developed as a promising carbon-neutral alternative to petroleum fuels in the transport sector, but the compatibility between biodiesel/petroleum diesel and polymer components in the automotive fuel system has not been free from controversy. In this present study, the degradation of polyamide 12 (PA12), one of the most common polymers used in vehicle fuel systems, has been investigated after exposure to petroleum diesel, biodiesel and a mixture of these (20 vol.% of biodiesel/80 vol.% petroleum diesel). Fuel sorption kinetics, glass transition temperature data and mechanical properties all showed that the fuels plasticized the PA12. In addition, monomers and oligomers were extracted from PA12 by the fuels. The long-term exposure led to oxidation and an annealing-induced increase in crystallinity of the polymer. The plasticization, oxidation and annealing effects were combined with the tensile mechanical properties to assess the overall degree of ageing and degradation of the PA12 material. The fuel-polymer interactions and ageing mechanisms, demonstrated here at high temperature for PA12, are 'generic' in the sense that they are also expected to occur, to various degrees, with many other polymers and they indicate that care should be taken when choosing polymers in applications where they will be exposed to fuels at high temperature. Biofuels: perishing polymers The degradation of a polymer commonly used in vehicle fuel systems has been tested on exposure to petroleum diesel and biodiesel. As part of the drive to develop carbon-neutral alternatives to petroleum, biofuels generated from oil crops and animal fats have been developed and their implementation is on the rise. However, there are molecular differences between bio- and petroleum fuels and how they affect the performance of polymer vehicle components is not entirely clear. Now a team lead by Mikael Hedenqvist from KTH Royal Institute of Technology in Stockholm and Kai Kallio from Volvo Car Corporation in Göteborg have investigated the degradation of the commonly used ‘polyamide 12’ under operational high-temperature conditions on exposure to petroleum diesel, biodiesel and a mixture of the two. They saw that the polymer experienced essentially the same type of ageing mechanisms, although to different degrees.