Date on Master's Thesis/Doctoral Dissertation

12-2013

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Committee Chair

Willing, Gerold A.

Subject

Rubber--Deterioration; Rubber chemistry; Drinking water--Purification

Abstract

Monochloramine is primarily used as a disinfectant in the drinking water distribution industry. The degradation of styrene butadiene rubber (SBR), natural rubber (NR), and ethylene propylene diene monomer-peroxide cured (EPDM-P) by monochloramine was first reported in a study published by the American Water Works Association (AWWA) in 2007. The study exposed samples of various types of rubber, including SBR, NR, and EPDM-P, to monochloramine solutions at varying concentrations and temperatures for 30 days. This study provided the basis for the present research, as at the medium temperatures and concentrations used in the study, 45 °C and 30 parts per million (ppm), the rubbers displayed standard long term degradation in a short time frame. This research was continued to better understand the impacts on the rubber during long term degradation. The experiment was set up into thirty day test periods. During these test periods, solutions containing different rubber types, temperatures, and concentrations were tested. The rubber types tested were SBR, NR, and EPDM-P. The temperatures used for the experiment were 23°C and 45°C. The lower temperature used was a control while the higher temperature characterized long term degradation. The concentrations of chloramine solution used were 1 ppm and 30 ppm. The lower concentration was the control while the higher characterized long term degradation. The experiment found the degraded rubber particle size in solution, the amount of degraded rubber particles in solution, and the particle size range over time. Results indicated that the rubber matrix was highly affected by changes in concentration of monochloramine and temperature. The chloramine solution caused the bonds in the rubber matrix to break, releasing carbon black particles into the chloramine suspension. Both concentration and temperature are large contributors to diffusion into the rubber and the degradation rate of the rubber. However, temperature has a positive exponential proportionality while concentration has a positive linear proportionality. In conclusion, both temperature and concentration play large roles in the monochloramine diffusion into the rubber and degradation rates of the elastomer bonds. Temperature and concentration similarly contributed in determining the carbon black particle sizes being released from the degraded rubber matrix.

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