TY - JOUR
T1 - Chlorinated water induced aging of pipe grade polypropylene random copolymers
AU - Fischer, Joerg
AU - Freudenthaler, Paul J.
AU - Lang, Reinhold W.
AU - Buchberger, Wolfgang
AU - Mantell, Susan C.
N1 - Publisher Copyright:
© 2019 by the authors.
PY - 2019/6/1
Y1 - 2019/6/1
N2 - Polypropylene random copolymers (PP-R) are common materials for pressurized hot water pipes. In many pipe systems, potable water is disinfected by chlorine to prevent waterborne diseases. This paper deals with hot chlorinated water induced aging of two PP-R grades with varying morphology. One material had a conventional monoclinic α crystal form (PP-Rα), whereas the other was explicitly beta-nucleated resulting in a trigonal β crystal form with a fine spherulite structure (PP-Rβ). Micro-sized specimens with a thickness of 100 μm were used for aging experiments at 60 °C in chlorinated water with 5 mg/L free chlorine, and aging indicators were monitored for exposure times of up to 2000 h. On the other hand, superimposed mechanical-environmental tests were carried out by using cracked round bar specimens with a diameter of 14 mm to determine the fatigue crack growth (FCG) resistance of both PP-R grades at 60 °C in non-chlorinated and chlorinated water. PP-Rβ was found to outperform PP-Rα with an about 30% higher time-to-embrittlement value of 2000 h. Furthermore, PP-R exhibited an enhanced FCG resistance in both non-chlorinated and chlorinated water. The effect of chlorine content on the deterioration of the FCG resistances was significantly more pronounced for PP-Rα.
AB - Polypropylene random copolymers (PP-R) are common materials for pressurized hot water pipes. In many pipe systems, potable water is disinfected by chlorine to prevent waterborne diseases. This paper deals with hot chlorinated water induced aging of two PP-R grades with varying morphology. One material had a conventional monoclinic α crystal form (PP-Rα), whereas the other was explicitly beta-nucleated resulting in a trigonal β crystal form with a fine spherulite structure (PP-Rβ). Micro-sized specimens with a thickness of 100 μm were used for aging experiments at 60 °C in chlorinated water with 5 mg/L free chlorine, and aging indicators were monitored for exposure times of up to 2000 h. On the other hand, superimposed mechanical-environmental tests were carried out by using cracked round bar specimens with a diameter of 14 mm to determine the fatigue crack growth (FCG) resistance of both PP-R grades at 60 °C in non-chlorinated and chlorinated water. PP-Rβ was found to outperform PP-Rα with an about 30% higher time-to-embrittlement value of 2000 h. Furthermore, PP-R exhibited an enhanced FCG resistance in both non-chlorinated and chlorinated water. The effect of chlorine content on the deterioration of the FCG resistances was significantly more pronounced for PP-Rα.
KW - Aging
KW - Chlorinated water
KW - Fatigue crack growth resistance
KW - Pipe grades
KW - Polypropylene
KW - Superimposed mechanical-environmental testing
UR - http://www.scopus.com/inward/record.url?scp=85067353366&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85067353366&partnerID=8YFLogxK
U2 - 10.3390/polym11060996
DO - 10.3390/polym11060996
M3 - Article
C2 - 31167458
AN - SCOPUS:85067353366
SN - 2073-4360
VL - 11
JO - Polymers
JF - Polymers
IS - 6
M1 - 996
ER -