Soil burial test

Resistance to Microorganisms and Insects. Resistance of triacetate to microorganisms, based on soil-burial tests, is high, approaching that of polyester, acryUc, and nylon fibers. Sod-burial test results on acetate, triacetate, and cotton are shown in Figure 8. Neither acetate nor triacetate fiber is readdy attacked by moths or carpet beedes. 

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. 

Soil burial tests are popular despite the precautions that are needed. It is also important that a sufficient number of specimens are exposed so that statistical treatment of the results may be applied to compensate for some of the inevitable variations in the exposure conditions. Certain precautions originally set out in 1937 are still valid, and are as follows ... 

While these relatively simple soil burial tests are directly relevant to the underground environment, the conditions of testing have deliberately been optimised to ensure a maximum rate of degradation. The relation between this rate and the predicted rate of attack in service can only be deduced by comparison. 

EN 12225, Geotextiles and geotextile-related products. Method for determining the microbiological resistance by a soil burial test, 2000. 

Hesistance lo Microorganisms and Insects. Resistance of triacetate to microorganisms, based on soil-burial tests, is high, approaching that of polyester, acrylic, and nylon fibers. 

Fungal inoculation. This can be a Petri dish test, a tropical humidity test, or sometimes a soil burial test, which can be considered a type of superinoculation. 

Table 4.24 Soil burial tests of 5 yr duration with aluminum alloy specimensa,b...

The chemical and physical properties of nylons have been extensively described (76). Nylon will not support mildew or bacteria. Moth larvae may bite their way through nylon if imprisoned. In soil burial tests, it was found that nylon 6 retained more than 95% of its strength after six months. By contrast, wool and cotton were rotten after one month (3). Nylon may be affected by chlorine bleach, and strong oxidizing bleaches can damage it (31). 

Soil burial tests are important in the assessment of the degradation of a range of polymers by the corresponding microflora. They are performed either under field or laboratory conditions with the use of specific strains without the presence of any additional carbon source other than that supplied from the polymer (Whitney, 1996). There are certain drawbacks that should be taken into account, namely the lack of reproducibility due to the climatic conditions and the change of the microbial soil flora when in situ experiments are performed. However, in situ soil burial tests are often the most useful when the extent of biodegradability of a material is sought, especially when combined with tensile strength tests and microscopic examinations (Cain, 1992). 

Table 5 Weight Percent Gain (WPG) and Antiswelling Efficiency (ASE) of Formalized Cedar and Beech Blocks, and Their Weight Loss (WL) Due to Decay After 12 Weeks Laboratory Tests with Tyromyces palustris and Coriolus versicolor, and After 9 Months Soil Burial Test...

Table 11 Weight Loss (WL) of PF Resin-Impregnated Cedar Blocks After 12 Weeks Decay Tests, After 9 Months Soil Burial Test, and After 8 Weeks Termite Test (Group A Resins)...

Agar plate test Soil burial test Saturated atmosphere test Count test... 

Another variation on a theme includes AATCC 30 Soil Burial Test (a. 11). A temperature of 28 °C, relative humidity of 85% and water content of 20-30% for incubation over 16 weeks is the change in essential criteria. 

Typical soil burial test, here on a PVC ground sheet... 

Although soil burial testing affords a way to test samples for breakdown close to actual conditions of waste disposal, it lacks reproducibility because of the difficulties in controlling climatic factors and the populations of various biological systems that are involved. For more reproducible results, degradations by cultured fungi and bacteria as well as degradations by purified enzymes are used. 

The composted soil bed composed of variety of microbes (e.g., bacteria and fungi) can be employed in soil burial test. The microbial attack of cellulolytic microflora in a composted soil bed is considered to be the most rigorous and practical means for the evaluation of anti-deterioration treatments. The treated and untreated fabric strips are buried and exposed to the microbial... 

Seal, K.J., and Pantke, M., 1990, An interlaboratory investigation into the biodeterioration testing of plastics, with special reference to polyurethanes Part 2 Soil burial tests.. Mater. Org. 25 87-98. 

As biodegradation test we predominantly used the polyester hydrolysis with lipases. The free acids built during the ester cleavage were monitored via an automatic and improved titration system. Beside the enzyme test we also performed soil burial tests, compost simulations and tests with isolated microorganisms to check whether the results obtained with the lipase can be transferred to natural conditions. 

Figure 1. Biodegradation profiles of hot-pressed PVA based films in simulated soil burial test.

Fig. 5.11 Weight loss of starch-LDPE films during soil burial test [75]...

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