1、Resistance of Thermoplastic Piping Materials to Micro- and Macro- Biological Attack TR-11 2013 105 Decker Court Suite 825 Irving Texas 75062 Phone 469-499-1044 Fax 469-499-1063 www.plasticpipe.orgForeword RESISTANCE OF THERMOPLASTIC PIPING MATERIALS TO MICRO- AND MACRO- BIOLOGICAL ATTACK This report
2、 was developed and published with the technical help and financial support of the members of the PPI (Plastics Pipe Institute). The members have shown their interest in quality products by assisting independent standards-making and user organizations in the development of standards, and also by deve
3、loping reports on an industry-wide basis to help engineers, code officials, specifying groups, and users. The purpose of this technical report is to provide important information available to PPI on resistance of thermoplastic piping materials to micro- and macro- biological attack. This report has
4、been prepared by PPI as a service of the industry. The information in this report is offered in good faith and believed to be accurate at the time of its preparation, but is offered “as is” without any express or implied warranty, including WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
5、PURPOSE. Any reference to or testing of a particular proprietary product should not be construed as an endorsement by PPI, which does not endorse the proprietary products or processes of any manufacturer. The information in this report is offered for consideration by industry members in fulfilling t
6、heir own compliance responsibilities. PPI assumes no responsibility for compliance with applicable laws and regulations. PPI intends to revise this report from time to time, in response to comments and suggestions from users of the report. Please send suggestions of improvements to the address below
7、. Information on other publications can be obtained by contacting PPI directly or visiting the web site. Plastics Pipe Institute, Inc. www.plasticpipe.org This Technical Report was first published in February 1969, and was reviewed and republished in May 1987, January 1989, March 1999, March 2000, J
8、une 2006, and May 2013 with minor editorial changes. 105 Decker Court Suite 825 Irving Texas 75062 Phone 469-499-1044 Fax 469-499-1063 www.plasticpipe.org RESISTANCE OF THERMOPLASTIC PIPING MATERIALS TO MICRO- AND MACRO- BIOLOGICAL ATTACK 1.0 Introduction The micro- and macro-biological degradation
9、of organic materials has been of great concern the world over. Fungus was found to be a severe problem during World War II, particularly in tropical and subtropical climates where fabrics deteriorated rapidly and electrical equipment malfunctioned. Similarly, malfunction of marine communication cabl
10、es due to attack of living organisms on outer cable materials has been a continuing problem. Rodents have caused damage to underground power and communication cable. Termites have been responsible for damage to structural organic materials in most climates and soils. This report provides available i
11、nformation regarding the resistance of thermoplastic piping materials to micro- and macro- degradation. Summary information follows on resistance of thermoplastic pipe to fungi, bacteria, termites, and rodents. A considerable number of papers directly and indirectly related to plastic pipe have been
12、 screened. References that have pertinent data are presented in a list at the end of this report and are grouped according to their relative significance. 2.0 Possible Degradation Factors Fungi The term fungi refers to a family of heterotrophic plant life including molds, mildews, mushrooms, etc. Th
13、ey are completely lacking in chlorophyll, so are unable to derive energy from sunlight. Rather, they derive their energy from utilizable organic materials, such as carbohydrates, which are a particularly good nutrient for fungi. Fungi thrive in a warm humid environment and are most abundant in, but
14、by no means limited to, tropical areas. Temperatures of 25-30C and relative humidity of 85% to 100% are most favorable, although certain fungi have been found to exist at much lower temperatures. At relative humidity below 70%, fungi will show very little active growth but can survive extended perio
15、ds of exposure. As a result of extensive loss of military equipment due to fungi in tropical areas during World War II, considerable studies were made on the relations between plastics compounds and the effects of fungi (1, 2, 3, 4, 5). From the literature surveyed, it is apparent that the growth of
16、 fungi on plastics is not due to the nutrient value of the polymer or resin component but rather to lower molecular weight additives such as lubricants, stabilizers, and plasticizers. Even in the case of highly plasticized (flexible) vinyl chloride plastics, however, attack by fungi is avoided if pr
17、oper attention is paid to the selection of plasticizer and other additives (1, 2, 5). Thermoplastic materials used for the manufacture of pipe contain little (if any) non-polymeric material and have a high degree of resistance to attack by fungi because of the lack of nutrients in their compositions
18、. Despite the minimal nutritive value in most plastic pipe materials, fungi may settle and grow upon pipe surfaces, feeding upon such nutrients as fly-ash. Such growths are commonly observed on concrete and even glass which, like plastics, may serve merely as a physical support for the life cycle. S
19、uch surfaces are generally not attacked or suffer only slight surface etching. Bacteria Bacteria in general require a wetter environment than fungi for active growth. Some forms of bacteria require the presence of oxygen (aerobic) to sustain life while others are anaerobic, i.e., grow only where the
20、re is no oxygen. Others exist whether oxygen is present or not. Since bacteria of many forms are encountered in nearly all areas where water is present, it is to be expected that when pipe is installed in wet areas, it will come in contact with one or more forms of bacteria. However, laboratory test
21、s show that the situation between plastics and bacteria is the same as that with plastics and fungi, i.e., no nutrients are present in the plastic pipe compositions, and they are resistant to attack (1, 2, 3, 6, 7, 8). Termites Termites are found world-wide and are known to cause extensive damage to
22、 wood. In tests of the resistance of plastic pipe to termites and other insects, pipe samples have been buried in termite infested soil and periodically dug up and examined. In one test, the area contained decayed pine logs infested with termites. Pine strips were placed between the polyethylene pip
23、e samples to serve as bait. The soil was covered with logs which contained termites. At the end of eighteen months, the pipe was uncovered. There was no attack by termites, fungi, insects, or any other biological agent, and the pipe was in excellent condition. The pieces of pinewood that were buried
24、 with the pipe were infested with termites and heavily decayed by fungi. In another test, PVC pipe samples were exposed to termites for five years without attack on the pipe. Termite attack reported on plastic film and wire and cable insulation in Europe, Africa and Australia (9, 10) where the parti
25、cular species of termites seem especially destructive. In general, plastics used in these applications are softer and often highly plasticized, in contrast plastics used in pipe. In one report (9), it was found that termites chewed on plastic, even though they could not use it as food. It is believe
26、d that in some cases “worker“ termites burrow through soil and anything else their jaws can handle in search of food. Rodents All materials except the hardest metals, concrete, etc., are susceptible to being gnawed by rodents. Instances are generally where plastic pipe has been damaged by rodents (p
27、rimarily gophers). Most of the incidents have involved the wire and cable industry but still this is considered a minor problem. Cases with pipe are of such a random nature that it appears that rodents are neither attracted to, nor repelled by, thermoplastic pipe but simply gnaw it when it gets in t
28、heir way or when the rodents are looking for water. The period when the pipe is newly installed and the soil is loose around the pipe makes an attractive burrowing area for rodents. Pipe in sizes larger than two inch in diameter do not appear to be affected simply because it is too large for the tee
29、th to dig into the service. 3.0 Summary The inert nature of the thermoplastic materials used in pipe does not support micro-biological attack. The few isolated cases of macro-biological attack from insects and rodents appear to have occurred only because thermoplastic pipe was present, but that the
30、pipe did not attract attack. 4.0 References Primary (references that relate most directly to the subject at hand.) 1. Wessel, C.J., “Biodegradation of Plastics,“ SPE Transactions 4 (3) 193-207, July, 1964. 2. Kuhlwein, Prof. Dr. H., and Drummer, F., The Microbial Corrosion of Plastics, Translation f
31、rom 57, 183-188, March, 1967. 3. Levy, Sidney, “Designing for Environmental Resistance,“ Plastics World, 20 (5), 22-25, May, 1962. 4. Kulman, F. E., “Microbiological Deterioration of Buried Pipe and Cable Coatings, Corrosion,“ National Association of Corrosion Engineers, 14, 2136-2225, May, 1958. 5.
32、 Stahl, William H., and Pessen, Helmut, “Funginertness of Internally Plasticized Polymers,“ Modern Plastics, 111-112, July, 1954. 6. Connolly, R. A., “Effect of Seven-Year Marine Exposure on Organic Materials,“ Materials Research & Standards, 193-201, March, 1963, 7. Snoke, Lloyd R., “Resistance of
33、Organic Materials and Cable Structures to Marine Biological Attack,“ The Bell Technical Journal, 1095-1126, September, 1957. 8. Steinberg, Priscilla L., “Resistance of Organic Materials to Marine Bacterial Attack,“ Developments of Industrial Microbiology, 2, 271-81, 1961, Plenum Press. 9. Harris, W.
34、 Victor, “Termites in Europe,“ New Scientist, 614-17, March, 1962. 10. Gay, F. J., and Wetherly, A. H., “Laboratory Studies of Termite Resistance of Plastics. The Termite Resistance of Plastics,“ Australia Commonwealth Scientific Industrial Research Organization, Division of Etomology, Technical Pap
35、er No. 5, 1962. 11. Greathouse and Wessel, Deterioration of Materials, Causes and Preventive Techniques, Reinhold Publishing Corp., 1954. Test Methods (references that do not specifically refer to pipe materials, but where significant information is given regarding test methods.) 12. Adams, Edward,
36、“Microbiological Deterioration of Organic Materials: Its Prevention and Methods of Test,“ Miscellaneous Publications 188 of the National Bureau of Standards, July 1, 1947. 13. Steffens, H. G, “Quick Test for Fungus Resistance,“ Modern Packaging, 168-169, July, 1949. 14. Harvey, James V., Testing the
37、 Fungal Resistance of Plastic Coated Fabrics & Plastic Films, Research Report from the Quartermaster General Laboratories, Micro-Biological Series No. 13, April 22, 1949. Miscellaneous 15. Ross, Sidney H., Rosenwasser, Eugene S., and Teitell, Leonard, “Effects of Fungus on Barriers,“ Modern Packagin
38、g, 180-184, 237-241, June, 1956. 16. Welch, Jack F., and Duggan, E.W., “Rodent-Resistant Vinyl Films,“ Modern Packaging, 130-131, 182-183, February, 1952. 17. Tomashot, R. C., and Hamilton, E. L., The Effects of Fungus Growth and Moisture Upon the Strength Properties of Reinforced Plastics, WADC Tec
39、hnical Report 56 18. ASTIA Document No. AD97183, Wright Air Development Center, August, 1956, p. 9. 19. Harvey, James V., and Meloro, Francis A., Studies of Degradation of Plastic Films by Fungi and Bacteria, Research Report, Microbiology Series Report No. 16, Quartermaster General Laboratories, Aug
40、ust 15, 1949. 20. Daoust, Dorothy Beck, Meloro, Francis A., and Boor, Ladislav, Studies of Deterioration of Plastic Films by Fungi and Bacteria, II, Research Service Test Report C & P-259-F, Office of the Quartermaster General, Chemical and Plastics Laboratories, October 3, 1951. 21. Manowitz, Milto
41、n, Daoust, Dorothy Beck, and Meloro, Francis A., Micro-Biological Evaluation of Vinyl Coated Fabrics by Inoculations and Soil Burial Procedures, Research Service Test Report C & P-320-F, Quartermaster Research and Development Laboratories, January 26, 1953. 22. Berk, Sigmund, Effect of Fungus Growth on Tensile Strength of Polyvinyl Chloride Films Plasticized with Three Plasticizers, ASTM Bulletin (TP 181) 53-55, September, 1950.
