Abstract
In this study, the relationship between structure and mechanical properties of aged PBT composite was investigated. Short glass fiber reinforced PBT composites were subjected to aging tests in environments typically found in hermetic compressors. Diffusion kinetics were addressed by a periodic control of samples weight, and samples aged in oil presented mass variation of 1.2-1.6%, depending on test temperature. Most diffusion curves followed Fickian behavior, and the diffusion coefficient for each condition was obtained. Aging effect was investigated by 3-point bending tests, where samples aged at 180°C presented a significant reduction in all evaluated properties. Control environment induced minor variations, supposedly related to physical aging and increase in crystallinity. Imaging analyses through scanning electronic microscopy (SEM) technique allowed observation of the predominant fracture mechanism. Aged samples presented few or no localized plastic deformation at all, which is in accordance with the lower strain observed in mechanical tests. Differential scanning calorimetry (DSC) analyses proved degree of crystallinity increase for all aged samples, depending mainly on temperature of exposure. Infrared (FTIR) analysis proved the presence of oil absorbed in PBT chemical structure, and it was proposed a method for comparing degree of crystallinity, based on the absorbance bands ratio A0(1458 cm-1)/A0(956 cm-1).
Highlights
Polymeric materials are already widely used in the production of disposable and short-life-cycle products
There was no evidence of any important structural change that could indicate the occurrence of some. It was proved the interaction between polybutylene terephthalate (PBT) composite and the ester oil/tetrafluoroethane mixture
A phenomenon that is not predicted by Fickian behavior, is the solubilization and extraction of oligomers, which is likely to occur in high temperatures
Summary
Polymeric materials are already widely used in the production of disposable and short-life-cycle products. Most polymers present high damping properties, are good thermal and electrical insulators and less susceptible to corrosion. They allow more freedom of design and ease of processability, usually accompanied with reduction of production costs. The exposure of polymers to chemicaland thermally aggressive environments may lead to a gradual alteration of molecular conformation, chain size distribution and chemical composition, among others[1,2]. In other words, it occurs a time-dependent properties degradation, known as aging. The engineer will select a grade of polymer that does not react, or that have minimum interaction with the work environment; one example is the fabrication of fuel tanks made of high density polyethylene (HDPE), a polymer that presents high chemical resistance against oil, diesel, alcohol and gasoline
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
