Composting, degradable polyester

The company claims easy processing results from the high compatibility of the blend components. The formulation consists of more than 10% PLA (purchased from NatureWorks LLC) plus a biodegradable co-polyester and special additives. FKuR says a special combination of compatibilisers permits coupling between the PLA and the co-polyester. The compound is homogeneous, which allows the film to be drawn down to 8 microns. Film up to 110 microns thick is 90% degraded after twelve weeks in composting conditions. 

The solution is a combination of aliphatic polyesters and aromatic polyesters. This involves modifying the crystalline structure of PBT by incorporating aliphatic monomer (adipic acid) in the polymer chain in such a way that the material properties of the polymer would remain acceptable (e.g., melting point of the crystalline range still around 100 °C), but the polymer would also be readily compostable/biodegradable. In this way it was possible to combine the degradability of aliphatic polyesters with the outstanding properties of aromatic polyesters. 

Starch, cellulose and sugars quickly biodegrade (several days or weeks). (Co)polyesters (PBAT, PBAT-stareh, PHA, PBS, PBSA) biodegrade less easily (several months). However, some materials almost do not biodegrade this is the case for PET, polyolefins (PE, PP) and PVC which take several hundred years to biodegrade. PLA degrades very quickly in compost (several weeks) but a lot longer at room temperature (several years). 

Aliphatic polyesters, described above, are relatively expensive. In the same way as starch, they rely on microbial activity in compost or soil to degrade. Both these products degrade by a process of hydrodegradation. 

Buchanan, C.M., Boggs, C.N., Dorschel, D., Gardner, R.M., Komarek, R.J., Watterson, T.L., and White, A.W., 1995, Composting of miscible cellulose acetate propionate-aliphatic polyester blends, y. Environ. Polym. Degrad, 1-11. 

PBS and its copolymers can be degraded in various environments, such as natural water, soil burial, activated sludge, and compost. The environmental biodegradation rate is sensitive to both the properties of the polyester and the environment, e.g., the microorganisms, nutrient, temperature, and humidity. Eor instance, Bionolle has different biodegradation rates in various enviromnents, as presented in Table 7 (Fujimaki 1998). Table 8 shows biodegradation properties of several aliphatic polyesters in different waters (Kasuya et al. 1998). It has been demonstrated that... 

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