Accession Number : ADA331109

Title :   Microbial Degradation of Polymeric Materials.

Descriptive Note : Conference Proceedings,

Corporate Author : HARVARD UNIV BOSTON MA

Personal Author(s) : Gu, Ji-Dong ; Ford, T. E. ; Thorp, K. ; Mitchell, R.

PDF Url : ADA331109

Report Date : 23 JUN 1994

Pagination or Media Count : 14

Abstract : Microorganisms and their products may be responsible for changes in physical, chemical, and electrochemical properties of polymeric materials. We investigated microbial degradation of polyimides used as :insulators in electronic packaging. Growth of microorganisms on these polymers was found to result in loss of their dielectric properties. Failure of polyimide films on stainless steel coupons caused by microbial degradation was evaluated with a fungal consortium partially identified as Aspergillus versicolor. We obtained distinctive electrochemical impedance spectroscopy (EIS) spectra showing failed polyimides in the presence of the fungal consortium. Decrease of film resistance by two orders of magnitude relative to uninoculated control systems was observed within one week of incubation. The relationship between changes of impedance spectra and microbial degradation of the coatings was further established by scanning electron microscopic (SEM) observations of fungi on the surface of the polyimides We also studied the biodeterioration of fiber reinforced composites, graphite sheets, and graphite fibers used in composite materials. One set of samples was inoculated with the fungal consortium mentioned above, and another set was kept sterile. In all inoculated treatments the fungi adhered to and grew on the composites, graphite sheets, and fiber surfaces. SEM was used to determine adhesion of fungi and subsequent etching of the samples. Fungal penetration into composite resin and graphite sheets was observed. Our data indicate that fungi may cause substantial damage to composites under conditions favorable to fungal growth.

Descriptors :   *POLYMERS, *DIELECTRIC PROPERTIES, *MICROORGANISMS, FIBERS, SYMPOSIA, CONTROL SYSTEMS, CORROSION, DAMAGE, SPECTROSCOPY, MATERIALS, COMPOSITE MATERIALS, GROWTH(GENERAL), INSULATION, RESISTANCE, ELECTRONIC SCANNERS, FIBER REINFORCED COMPOSITES, ADHESION, FILMS, ELECTRONIC EQUIPMENT, STAINLESS STEEL, ELECTROCHEMISTRY, GRAPHITE, CARBON FIBERS, ETCHING, SURFACES, COATINGS, SPECTRA, PENETRATION, SHEETS, FUNGI, PLANT GROWTH, SAMPLING, PACKAGING, INCUBATION, IMPEDANCE, CONSORTIUMS, BIODETERIORATION, POLYIMIDE RESINS.

Subject Categories : Microbiology
      Polymer Chemistry
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE