Year-end Sale % OFF 
Abstract
The influence of chlorinated water on the global and local aging behavior of polypropylene (PP) was investigated for three differently stabilized PP grades consisting of the same PP base polymer. While one of the PP grades contained only a processing stabilizer (PP-S0), the other two were modified with a primary phenolic antioxidant (PP-S1) and a combination of a primary phenolic antioxidant and a hindered amine stabilizer (PP-S3). To study global aging effects, micro-sized specimens were pre-exposed to chlorinated water (5 mg/L free chlorine) at 60 °C for up to 750 h. Over the entire exposure period, significant material aging was detected by monitoring a continuous decrease in stabilizer content, oxidation induction temperature, mean molar mass, and mechanical strain at break. In terms of aging resistance and ultimate mechanical performance, PP-S1 was found to outperform the other two material formulations under these test conditions. Moreover, superimposed mechanical-environmental fatigue tests with cracked round bar specimens were carried out with the three PP grades in non-chlorinated (0 mg/L free chlorine) and chlorinated (5 mg/L free chlorine) water at 80 °C and 95 °C to study local crack tip aging effects. While the fatigue crack growth resistance substantially deteriorated for all three materials in chlorinated water, a significantly stronger effect was found for the higher temperature, with crack growth rates at a given stress intensity factor range in chlorinated water being ca. 30 to 50 times faster than in non-chlorinated water, depending on the material. Molar mass measurements of material samples taken from various positions of the tested CRB specimens provided clear evidence of enhanced local crack tip aging due to the chlorinated water environment.
Highlights
Polypropylene (PP) is a commonly used material for plastics pipes, for pressurized domestic hot water piping with water temperatures up to 60 ◦ C [1,2,3]
The effect of hot chlorinated water on aging and fatigue crack growth (FCG) resistance was investigated for three polypropylene (PP) grades with different stabilizer systems
For the other two PP grades, PP-S0 was stabilized with a primary phenolic antioxidant (PP-S1) and with both a primary phenolic antioxidant and a hindered amine stabilizer (PP-S3), respectively
Summary
Polypropylene (PP) is a commonly used material for plastics pipes, for pressurized domestic hot water piping with water temperatures up to 60 ◦ C [1,2,3]. Molecularly designed and stabilized PP grades have become of interest for applications in modern polymer-based solar-thermal systems. This includes both structural components exposed to only. Polymers 2019, 11, 1165 moderate stress levels (e.g., assembly components and containments) and highly stressed components such as pressurized pipes Temperatures in such solar-thermal applications can reach maximum temperatures of 80 ◦ C to 95 ◦ C [4,5,6,7]. To prevent the growth and spread of legionella, hot water temperatures of 60 ◦ C are required [11]
Sign-in/Register to view highlights & summary 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.
