ASTM G22-76(1996)

Standard Practice for Determining Resistance of Plastics to Bacteria (Withdrawn 2002)

SCOPE
1.1 This practice covers two procedures, A and B, for determining the effect of bacteria on the properties of plastics in the form of molded and fabricated articles, tubes, rods, sheets, and film materials. Procedure B provides a more extensive contact between the test bacteria and the specimens than does Procedure A. Changes in optical, mechanical, and electrical properties may be determined by the applicable ASTM methods.  
1.2 The values stated in SI units are to be regarded as the standard.

General Information

• Status: Historical
• Publication Date: 09-Jun-1996
• ICS: 83.080.01 - Plastics in general
• Technical Committee: G03 - Weathering and Durability
• Drafting Committee: G03.04 - Biological Deterioration

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: G 22 – 76 (Reapproved 1996)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
1
Determining Resistance of Plastics to Bacteria
This standard is issued under the fixed designation G 22; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope growth of bacteria. It is generally the other components, such
as plasticizers, lubricants, stabilizers, and colorants that are
1.1 This practice covers two procedures, A and B, for
responsible for bacterial attack on plastic materials. It is
determining the effect of bacteria on the properties of plastics
important to establish the resistance of plastics to microbial
in the form of molded and fabricated articles, tubes, rods,
attack when plastics are used under conditions of high tem-
sheets, and film materials. Procedure B provides a more
perature and humidity favorable for such attack.
extensive contact between the test bacteria and the specimens
4.2 The effects to be expected are:
than does Procedure A. Changes in optical, mechanical, and
4.2.1 Surface attack, discoloration, and loss of transmission
electrical properties may be determined by the applicable
(optical).
ASTM methods.
4.2.2 Removal of susceptible plasticizers, modifiers, and
1.2 The values stated in SI units are to be regarded as the
lubricants, resulting in increased modulus (stiffness), changes
standard.
in weight, dimensions, and other physical properties, and
2. Referenced Documents
deterioration of electrical properties such as insulation resis-
tance, dielectric constant, power factor, and dielectric strength.
2.1 ASTM Standards:
4.3 Often the changes in electrical properties are due prin-
D 618 Practice for Conditioning Plastics and Electrical
2
cipally to surface growth and associated moisture, and to pH
Insulating Materials for Testing
changes caused by products of bacterial metabolism. Other
G 21 Practice for Determining Resistance of Synthetic
3
effects include preferential growths caused by nonuniform
Polymeric Materials to Fungi
dispersion of plasticizers, lubricants, and other processing
3. Summary of Practice
additives. Pronounced physical changes may be observed on
products in film form or as coatings where the ratio of surface
3.1 The procedure described herein consists of the follow-
to volume is high, and where nutrient materials such as
ing steps:
plasticizers and lubricants continue to diffuse to the surface as
3.1.1 Selection of suitable specimens for determination of
they are utilized by the organisms.
pertinent properties,
4.4 Since attack by organisms involves a large element of
3.1.2 Inoculation of specimens with suitable organisms,
change due to local accelerations and inhibitions, the order of
3.1.3 Exposure of inoculated specimens under conditions
reproducibility may be rather low. To assure that estimates of
favorable to growth,
behavior are not too optimistic, the greatest observed degree of
3.1.4 Examination and rating for visual growth, and
deterioration should be reported.
3.1.5 Removal, sterilization, and evaluation of specimens.
4.5 Conditioning of specimens such as exposure to leach-
NOTE 1—Since the procedure involves handling and working with
ing, weathering, heat treatment, etc., may have significant
bacteria that may be capable of infecting man, it is essential that personnel
effects on the resistance of plastics to bacteria. Determination
trained in microbiology perform the portion of the procedure involving
of these effects is not covered in this document.
handling of bacterial organisms and inoculated specimens.
5. Apparatus
4. Significance and Use
5.1 Glassware—Glass vessels are suitable for holding
4.1 The resin portion of plastic materials is usually resistant
specimens when laid flat. Depending on the size of the
to bacteria, in that it does not serve as a carbon source for the
specimens, the following are suggested:
5.1.1 For specimens up to 75 mm (3 in.) in diameter,
150-mm (6-in.) covered petri dishes.
1
This practice is under the jurisdiction of ASTM Committee G-3 on Durability
5.1.2 For 75-mm (3-in.) and larger specimens, such as
of Nonmetallic Materials and is the direct responsibility of Subcommittee G03.04
on Biological Deterioration.
tensile and stiffness strips, large petri dishes, trays of borosili-
Current edition approved Nov. 26, 1976. Published January 1977. Originally
cate glass; or baking dishes covered with squares of window
published as G 22 – 67 T. Last previous edition G 22 – 67 T.
2 glass
...