Polymers degradable, test methods

Other simple tests include the soil burial test used to demonstrate the biodegradabiUty of polycaprolactone (25), following its disappearance as a function of time, and the clear 2one method which indicates biodegradation by the formation of a clear 2one in an agar medium of the test polymer or plastic as it is consumed (26). The burial test is still used as a confirmatory test method in the real-world environment after quantitative laboratory methods indicate bio degradation. 

Polymers degrade before they vaporize, so indirect methods must be used to determine their solubility parameters. The simplest of these methods is a two-valued bar graph, as is illustrated in Figure 2.24. A series of solvents of known solubility parameter are used. Each is tested to determine if it is a solvent for the polymer. The yes or no answers are then plotted at different heights along the <5, abscissa. The value of corresponding to the midpoint of the yes bar is taken to be the solubility parameter S2 of the polymer. This is a reverse application of equation (24). The argument is now that solvents that are found to dissolve the polymer must have solubility parameters close to the unknown solubility parameter of the polymer. 

Handbook of Polymer Testing provides in one volume that comprehensive coverage of physical test methods for polymers. The properties considered cover the whole range of physical parameters, including mechanical, optical, electrical, and thermal as well as resistance to degradation, nondestructive testing, and tests for processability. All the main polymer classes are included rubbers, plastics, foams, textiles, coated fabrics, and composites. For each property, the fundamental principles and approaches arc discussed and particular requirements and the relevant international and national standards for the different polymer classes considered, together with the most-up-to-date techniques. 

Of interest in studies of polymer degradation are two standard tests, the ASTM D 3850 (1994) test method for rapid thermal degradation of solid electrical insulating materials by thermogravimetric method, and the ASTM D 6370 (1999) standard test method for rubber compositional analysis by thermogravimetry. 

It will be evident from The Green Report (page 94) that the development of reproducible test methods for degradable polymers is an essential prerequisite to the manufacture and use of these materials. Standard test methods can be categorised under three headings which differ... 

Bioassimilation of polymers is primarily controlled by the rate of abiotic peroxidation or hydrolysis. Information is available in the published literature which could form the basis of biodegradation tests but has so far not been incorporated in standard test methods. However, in the long-term it is important that science-based test methods should be developed to permit users of degradable materials in agriculture, shipping and packaging to take advantage of these new materials. 

Degradable polymer a polymer designed to undergo a significant change in its chemical structure under specific environmental conditions, resulting in a loss of properties that may vary as measured by standard test methods appropriate to the pol)rmer and the application in a p eriod of time that determines its classification. 

Tilstra, L., and Johnsonbaugh, D., 1993a, A test method to determine r idly if polymers are biodegradable. J. Environ. Polym. Degrad. 1 247-255. 

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