Polyesters degradable

As described previously, ester bonds and polyesters are used extensively in nature for temporary storage of carbon. The relative ease of making and breaking ester bonds makes them an ideal choice for degradable polymer backbones. 

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TABLE 2.3 Names, Composition, and Applications of Some Commercial Degradable Polyesters... 

Depending on dieir structure, properties, and syndietic methods, degradable polyesters can be divided into four groups poly(a-esters), poly(fi-esters), poly(lactones), and polyesters of aliphatic diols and diacids. 

Aliphatic-aromatic copoly imides, 268 Aliphatic-aromatic polyesters, 18, 19 Aliphatic degradable polyesters, 41 Aliphatic diacids, polyamide synthesis from, 183-184... 

Saad B, Hirt TD, Weld M, Uhlschmid GK, Neuenschwander P, and Suter UW. Development of degradable polyester urethanes for medical apphcations. J Biomed Mater Res, 1997, 36, 65-74. 

The next step in developing controlled degradation polyester is to understand expectations for specific product applications. Some questions to be answered include the following ... 

For recycling uses, degradable polyesters are desirable for relatively small mass applications, such as glues, thin coatings or labels, in order to facilitate the rapid cleaning of the primary structure for recycling. These applications may be rigid structures such as plastic containers or modifiers for paper products. 

Copolyesters (such as BIOMAX ) which combine aromatic esters with aliphatic esters or other polymer units (e.g. ethers and amides) provide the opportunity to adjust and control the degradation rates. These added degrees of freedom on polymer composition provide the opportunity to rebalance the polymer to more specifically match application performance in physical properties, while still maintaining the ability to adjust the copolyesters to complement the degradation of natural products for the production of methane or humic substances. Since application performance requirements and application specific environmental factors and degradation expectations vary broadly, copolyesters are, and will continue to be, an important class of degradable polyesters. 

Lastly, we show in Scheme 18.2 what would be two logical reaction products of the alkyl radical which is produced. The hydrogen abstraction was already proposed [11, 25] by others on the basis of spectroscopic evidence for an aldehyde but it has not been confirmed that the species was an aliphatic aldehyde being produced as opposed to an aromatic one and so is ambiguous. Hydrolysis of the top product of this section of the scheme would produce formic acid, which has been reported [11], However, more reasonable sources of formic acid exist in Schemes 18.3 and 18.4 (see below). The other product that one would expect to see would result in trimellitic acid being observed in the hydrolysate of the degraded polyester. This has, to our knowledge, not been reported as yet. 

Agarwal S (2010) Chemistry, chances and limitations of the radical ring-opening polymerization of cyclic ketene acetals for the synthesis of degradable polyesters. Polym Chem 1 953-954... 

The flexural modulus and heat deflection temperature of these aryl polyesters are increased by the incorporation of reinforcing fillers. PET and related aryl polyesters are resistant to nonoxidizing acids, alkalis, and salts, as well as to polar and nonpolar solvents at room temperature. (Above room temperature some alkalis and acids begin to degrade polyesters.)... 

Liquid-liquid extraction (LLE) is the traditional method to extract organic compounds from water. The low molecular weight compounds are transferred from one liquid phase to another immiscible or partially immiscible liquid by shaking them in a separation funnel. LLE is still a common method, but has several drawbacks such as low selectivity, labor intensivity, and the use of large amount, of organic solvent. LLE has been used to extract hydrolysis products of degradable polyesters such as PLA and its copolymers from the buffer solution [115]. 

Polylactide is a degradable polyester, formed by the ring-opening polymerization of lactide or the condensation polymerization of lactic acid. Lactide is produced from lactic acid, which derives from the fermentation of D-glucose, which is usually harvested from high-starch-content crops, such as com or sugar beet (Fig. 1). 

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