Biodegradable Poly ether ester s

Aromatic polyesters, such as PET, PBT or PEN, are not degradable in the presence of microorganisms, while their copolyesters with aliphatic acids show some extent of biodegradability [28,81,82]. It was reported that copolyesters based on PBT and polyfbutylene adipate) (PBA) with about 35-55 mol % of terephthalic acid residues exhibited suitable mechanical and physical properties, as well as favorable biodegradability (film approx. 100 pm degradation within 8-12 weeks in soil or compost). Beside copolymerization, the biodegradable properties of polyesters can be improved by increasing the hydrophilicity, for instance by the introduction of 

Polyfether ester)s based on polyfbutylene terephthalate) as the hard segments and polyfethylene oxide) as the soft segments, commercially available under the trade name Poly Active , demonstrated longer degradation time and formation of water-insoluble by-products rich in aromatic moieties [84,85]. 

The introduction of aliphatic add residues into polyfether ester)s chain allows the attractive combination of the advantages of aromatic polyesters, such as excellent mechanical properties and thermal stabilities and the biodegradability and solubility of aliphatic residues [86,87]. Also, the incorporation of different type of ether soft segments into aromatic polyesters could modify or enhance their degradability [88]. 

Chemical resistance of polyCether ester)s varies greatly with copolymer composition. For example, resistance to hydrocarbon solvents depends on the polymer stiffness and stiffer grades exhibited better performance. The chemical resistance of some polyfether ester)s to aliphatic hydrocarbon solvents, oils and greases is very good, even at elevated temperatures, but they are not that resistant to chlorinated solvents. They are also resistant to diluted acids, bases and to polar solvents, such as water and alcohols at room temperature, but not at temperatures above 70 °C. 

Resistance to permeation. PolyCether ester)s are rather permeable to polar molecules such as water, but are resistant to non-polar hydrocarbon and refrigerant gases. 

---