- Author
- Rossiter, W. J., Jr. | Nguyen, T. | Byrd, W. E. | Seiler, J. F., Jr. | Lechner, J. A.
- Title
- Cleaning of Aged EPDM Rubber Roofing Membrane Material for Patching: Laboratory Investigations and Recommendations.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Army Construction Engineering Research Lab., Champaign, IL
- Report
- NISTIR 4544, March 1991, 64 p.
- Distribution
- Not Available from National Technical Information Service
- Keywords
- aged EPDM membranes | cleaning methods | contact angle | creep rupture | FT-IR | low-sloped roofs | peel strength | roofing | scanning electron microscopy | seams | surface analysis | surface preparation methods | wettability
- Abstract
- This study assessed the relative effectiveness of different surface cleaning methods used for preparing the surface of aged EPDM membranes for patching, and recommends procedures for use in the field. The effectiveness of the methods was evaluated using tests of short-term strength and long-term creep rupture in peel, and surface analytical techniques, namely, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and contact angle measurements. A section of an aged, ballasted EPDM membrane, sampled from a roof after 10 years in service, was used in the study. The majority of the cleaning methods evaluated was selected based on a review of procedures used in the field to prepare the surface of aged EPDM rubber before patching. Cleaning the aged EPDM rubber surface removed the bulk of the contaminants and resulted in an increase of the exposed surface area of the EPDM rubber. This resulted in a decrease in the rubber's wettability by water, and a concomitant gain in the peel strengths of joints made with the cleaned rubber. All cleaning methods used in the study provided aged EPDM rubber surfaces that formed joints having peel strengths comparable to those of seams formed in the field between solvent-based adhesives and new EPDM rubber. Short-term strength and creep-rupture joints, prepared by tape-bonding the surface of heptane-cleaned aged EPDM to a surface of well-cleaned new EPDM, failed at the interface between the tape and the new rubber. But, no relationships betwen contact angle and cleaning method were found. In particular, the contact angles measured using methylene iodide varied only slightly as a function of cleaning method. The FTIR technique could distinguish the uncleaned surface of the aged EPDM from those which were well-cleaned and/or coated during cleaning. No major differences between the FTIR spectra of the specimens cleaned using the various methods were observed. SEM analysis was the only technique that distinguished particle-free surfaces from those which retained particles after cleaning. The rate of spreading of dimethyl formamide (DMF) droplets on the surface of the aged EPDM rubber was found to relate to the degree of surface cleanness. Based on the results of this laboratory study on cleaning a section of an aged EPDM rubber membrane, it was conclued that such membrane materials may be suitably cleaned for patching. It was recommended that: (1) a number of cleaning methods may be used to prepare the surface of aged EPDM rubber membrane material before patching, and (2) the change in size over time of a droplet of DMF, placed on the aged EPDM rubber after cleaning, be used for preliminary assessment of the condition of the cleaned surface.