Polymers biodegradable characteristics

It is really interesting that the water vapor transmission rate is the lowest of the commonly used biodegradable polymers this characteristic is truly relevant, for example, in packaging applications. 

Savenkova L, Gercberga Z, Nikolaeva V, Dzene A, Bibers I, Kalnin M (2(XX)) Mechanical properties and biodegradation characteristics of PHB-based films. Process Biochem 35 573-579 Scott G (1999) Polymers in modem life. Polymers and the environment. Royal Society of... 

All natural polymers are considered to be biodegradable or at least not harmful to the environment. However, modification of natural polymers either by grafting synthetic polymers or by chemical conversions such as oxidation and esterification, changes their properties and biodegradation characteristics significantly. Therefore, polymers produced by any of these modifications must be evaluated for biodegradability in the same manner as purely synthetic polymers. 

There are currently biodegradable polymers with characteristics and properties very similar to those from conventional polymers derived from petroleum (Tables 1 and 2). 

Poly(lactic acid) (PLA) (Fig. 1.16) is an aliphatic polyester polymerised by lactic acid which is made by fermentation of natural raw materials, for example, com starch and sugarcanes. Due to the chiral nature of lactic acid and its effects on the polymer s characteristics, the biodegradability and mechanical properties of PLA can be tailored by varying the proportion of different forms. Meanwhile, PLA can also copolymerise with other monomers or blend with other polymers to improve some properties of the material, eg, flexibility. PLA and PLA-based copolymers are the most popular biodegradable materials for the production of absorbable sutures (Li, 1999) (Fig. 1.16). 

Natural polymers such as chitosan and alginate have received recent attention due to their desirable biodegradability characteristics [25-27]. Research in this field, to date limited in contrast to liposomes and synthetic polymers, indicates that these natural vectors have inferior transfection capabilities when... 

Summarizing, the following solutions were applied to obtain PO/natural polymer blends with useful properties and/or biodegradation characteristics— Table 5. 

Biodegradable Polymers Release Characteristics of Hydrogen-bonded Ring Containing Polymer Matrices. 15 1243-1247. 

In order to become useful dmg delivery devices, biodegradable polymers must be formable into desired shapes of appropriate size, have adequate dimensional stability and appropriate strength-loss characteristics, be completely biodegradable, and be sterilizahle (70). The polymers most often studied for biodegradable dmg delivery applications are carboxylic acid derivatives such as polyamides poly(a-hydroxy acids) such as poly(lactic acid) [26100-51-6] and poly(glycolic acid) [26124-68-5], cross-linked polyesters poly(orthoesters) poly anhydrides and poly(alkyl 2-cyanoacrylates). The relative stabiUty of hydrolytically labile linkages ia these polymers (70) is as follows ... 

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