Powders, biodegradability testing

Figure 6-7 Biodegradation test of PLA and cellulose powders by ISO 14855-2 method using MODA instrument in controlled compost at 58°C. Reprinted with permission from [17].

Polycaprolactone (PCL) powders were prepared from PCL pellets using a rotation mechanical mixer [107]. PCL powders were separated by sieves with 60 and 120 meshes into four classes 0-125 ixm, 125-250 o,m, 0-250 jjm and 250-500 jm. Biodegradation tests of PCL powders and... 

Funabashi, M., Ninomi5ra, E, Kunioka, M. Biodegradation of polycaprolactone powders proposed as reference test materials for... 

Gas evolution tests are popular test methods because they are relatively simple, rapid (days to weeks) and sensitive. A direct measure for mineralisation is determined, and water-soluble or insoluble polymers can be tested as films, powders or objects. Furthermore, the test conditions and inoculum can be adjusted to fit the application or environment in which biodegradation should take place. Aquatic synthetic media are usually used, but also natural sea water or soil samples can be applied as biodegradation environments. A prerequisite for these media is that the backgroimd COa-evolution is limited, which excludes the application of real composting conditions. Biodegradation under composting conditions is therefore measured using an inoculum derived from matured compost with low respiration activity . ... 

Poly(lactide) (PLA) bottles were used as the test material to determine pofymer biodegradation under simulated conditions using an automatic laboratory-scale respirometrie system [23]. The results were compared with those for corn starch powder and poly(etlylene terephthalate) bottles. At 63 days of exposure at 58°C and 55% relative humidity, PLA, com starch, and PET achieved 64.2, 72.4 and 2.7% mineralization respectively. It was stated thaf based on ASTM D 6400 and ISO 14855, PLA bottles qualified as biodegradable since mineralization was greater than 60%. 

Kunioka M., Ninomiya E, Eurrabashi M. Biodegradation of poly(lactic acid) powders proposed as the reference test materials for the intematiorral standard of biodegradation evaluation methods, Polym. Deg. Stab. 91 (2006) 1919. 

The maximum test duration in principle is 6 months, while a typical minimum duration is 45 days. CO2 production is continuously measured. After subtracting the background CO2 production from the blank compost inocnlnm (withont any additional carbon source), the percentage of biodegradation is determined by the net amount of carbon of the test item that is converted to CO2. A positive reference control, cellulose, is tested in parallel to check the activity of the inocnlnm. Strict requirements are imposed on the results for cellulose in order to validate the test. The test item is preferably added in the form of a fine powder. 

Blends A and B were tested in powder form. Blend A only was photodegraded by exposing it to a commercial GE sunlamp (the equivalent of about two months of summer sunlight). Blend C was tested in film form since it is claimed that films containing starch are biodegradable (without exposure to sunlight). 

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