Microbial degradation of plastics

Plastic materials generally are considered non-degradable, yet many materials do suffer from microbial degradation while in service. Signs of degradation include discoloration, odor, or loss of physical properties. The most widely preserved polymer is flexible polyvinyl chloride (PVC), used in swimming pool, pond and ditch liners, as well as shower curtains, upholstery, outdoor patio furniture, roofing (single ply), marine tops, refrigerator gaskets and automotive side molding. Polyolefins and polyurethanes also require preservation in certain applications. The key end-uses requiring preservatives for polyethylene, polypropylene and their associated alloys include mop buckets, roofing, carpet fibers, cutting boards, and the like. Polyurethane (PU) requires preservation when used in shoe soles, shoe uppers, as well as in expanded foam for carpet underlay and padding for furniture cushions and mattresses.

1 5.13.1 History of plastics and biocides for plastics

The development of synthetic...

Appendices

Appendix A

1.1 Bacterial Resistance (Qualitative) Kirby Bauer

The samples are placed on nutrient agar inoculated with:

Table 6

After 24 hours of incubation at 37°C, antibacterial activity is evaluated by measuring (in mm) the size of a clear zone of no growth (Zone of Inhibition) around each sample, and visually determining growth in the contact area.

Bacterial growth is rated by the following scale:

1.1.1 No Growth Contact Area (NGCA)

This is a designation frequently used in bacterial tests. Bacterial organisms are difficult to determine on the sample itself, so the area immediately under the sample is examined for growth. This is usually a passing designation and indicates that no bacterial colonies were found under the sample.

1.1.2 Growth Contact Area (GCA)

This indicates failure of the sample since colonies of bacteria are detected immediately under the sample in contact with the same.

Appendix B

2.1 Mildew Resistance Pink Stain ASTM E-1428-96

The samples are placed on nutrient agar inoculated with the pink staining organism, Stv. reticulum ATCC 25607. After 14 days of incubation at 28°C, antifungal activity is evaluated by visually rating the degree of stain.

Surface stain is rated by the following scale.

No Stain	(NS)
Trace of Stain	(TS)
Light Stain	(LS)
Moderate Stain	(MS)
Heavy Stain	(HS)

Appendix C

3.1 ASTM G-21-96 Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi

The samples are placed on (non-nutrient) mineral salts agar and inoculated with a mixed fungal spore suspension of:

Aspergillus niger	ATCC 9642
Penicillium pinophilium	ATCC 9644
Chaetomium globosum	ATCC 6205
Aureobasidium pullulans	ATCC 9348
Gliocladium virens	ATCC 9645

After 21–28 days incubation at 28°C, antifungal activity is evaluated by visually rating the degree of fungal growth on the samples.

Surface fungal growth is rated by the following scale:

No Growth	(NG)
Traces of Growth (less than 10% coverage)	(TG)
Light Growth (10 to 30% coverage)	(LG)
Medium Growth (30 to 60% coverage)	(MG)
Heavy Growth (60% to complete coverage)	(HG)

ASTM Rating

• 0 = No Growth

• 1 = Traces of Growth

• 2 = Light Growth

• 3 = Medium Growth

• 4 = Heavy Growth

Appendix D

4.1 New York State Spec. #63 (1992) Mattress Covering Material

The samples are quantitatively evaluated for bacteriostatic activity by placing 0.2 ml of diluted culture of the test bacteria (10⁵ organisms) in direct contact with the sample. After 24 hours incubation at 37°C and 100% relative humidity, the samples are diluted with sterile letheen broth and the number of surviving organisms determined by the standard plate count method. The percent survival is calculated by comparison to an untreated control film.

Maximum N.Y. State Spec. Requirements:

• Staphylococcus aureus — 2% survival

• Klebsiella pneumoniae — 17% survival

Appendix E

5.1 Quantitative Assessment of Antibacterial Activity on Carpets AATCC Test Method 174-1991 Part II

The samples are quantitatively evaluated for bacteriostatic activity by placing 0.1 to 0.5 ml of diluted culture of the test bacteria (10⁵ organisms) in direct contact with the sample. After 24 hours incubation at 37°C and 100% relative humidity, the samples are diluted with sterile letheen broth and the number of surviving organisms determined by the standard plate count. The percent reduction is calculated by comparison to the number of organisms recovered at zero contact time.

Appendix F

6.1 Antibacterial Finishes on Textile Materials: Assessment of AATCC Method 100-1993

The samples are quantitatively evaluated for bacteriostatic activity by placing 1.0 ml of a diluted culture of the test bacteria (10⁵ organisms) in direct contact with the sterilized sample. After 24 hours incubation at 37°C and 100% relative humidity, the samples are diluted with sterile letheen broth and the number of surviving organisms determined by the standard plate count. The percent reduction is calculated by comparison to the number of organisms recovered at zero contact time.

Appendix G

7.1 Soil Burial Procedure

The samples are placed horizontally on a four-inch bed of soil and covered with a one-inch layer of loosely packed soil. After incubation in a chamber maintained at 85°F and a relative humidity of 85 to 95%, the samples are recovered and the microbial stain is determined.

Stain is rated as follows:

No Stain	(NS)
Trace Stain	(TS)
Light Stain	(LS)
Moderate Stain	(MS)
Heavy Stain	(HS)

Appendix H

8.1 ASTM G-29-96 Standard Practice for Determining Algal Resistance of Plastic Films

The samples are suspended in jars and inoculated with a suspension of the alga: Oscillatoria sp. The jars are filled with a diluted salts solution and illuminated by four 20-watt “cool light” fluorescent bulbs for 12 hours each day. At three-day intervals, a fresh inoculum of algae is added to each sample jar. After 14 days at room temperature, the samples are removed and examined for adherent algal growth.

Appendix I MIL. STD. 810E Method 508.4

The samples are placed in a humidity chamber.

The samples are then inoculated with a mixed fungal spore suspension of:

Aspergillus niger	ATCC 9642
Aspergillus flavus	ATCC 9643
Aspergillus versicolor	ATCC 11730
Penicillium funiculosum	ATCC 11797
Chaetomium globosum	ATCC 6205

Incubation takes place under a daily cycle of temperature and humidity conditions consisting of 20 hours at a relative humidity of 95±5% and an air temperature of 30°±1°C (86°±2°F) followed by a four-hour period in which a condition of 95% (±5%) relative humidity at 25°±1°C (77°±2°F) is maintained for at least two hours. Up to a total of two hours of the four-hour period is used for the transitions of temperature and relative humidity. Temperature and humidity conditions during the transition period are as follows:

• Temperature 24° to 31°C (75° to 88°F) and relative humidity of >90%.

• After 28–84 days incubation, the samples are examined by visually rating the degree of surface fungal growth.

No Growth	(NG)
Traces of Growth (less than 10% coverage)	(TG)
Light Growth (10 to 30% coverage)	(LG)
Moderate Growth (30 to 60% coverage)	(MG)
Heavy Growth (60% to complete coverage)	(HG)