Effect of the chemical surrounding environment on the physical and mechanical properties of aged thermoplastic polymers

A complete study is presented on the response of thermoplastic and thermoplastic composite materials for bearing cages of bogie trains for rail applications to aging conditions in presence of lubricants. Glass Fiber reinforced Polyamaide 66 (GF PA66) is proposed as commercial material already used in the field while Polyether Ether Ketone (PEEK) is proposed as novel polymeric candidate material due to its chemical stability and high mechanical performance. Accelerated aging tests were performed to analyze the response of these materials to external chemical agents under different conditions. Afterwards, a complete set of mechanical and physical tests and characterization procedures were carried out, before and after ageing on suitable samples of the polymers in combination with lubricants, to evaluate the effects of the chemical environment on the mechanical and physical properties of the presented polymers. Results are highly relevant since cages are permanently soaked in lubricant during their operation life. GR PA66 presents better global mechanical properties due to the important glass fiber load (30 %). Nevertheless, the values obtained also show that PEEK remains unalterable under different aging conditions. According to the results it can be suggested that PEEK might be considered as a suitable potential alternative, when necessary, in applications with a high resistance to chemical environment requirements. The lack of published papers reporting behavior of PEEK in the analyzed circumstances highlights the novelty and importance of results obtained in this work.