Biodegradable polyamides

Biodegradable polyamides have also been prepared from amino acids. For example, aspartic acid can be converted to polyaspartate, abbreviated as TPA (thermal polyaspartate). TRA is commonly used as an alternative to poly(acrylic acid), which is used to line the pumps and boilers of wastewater treatment facilities. 

Nonionic water-soluble biodegradable polyamides are reported by Bailey [115], Chiellini et al. [116], and Ahmed for disposable fibers and webs [117]. 

Biodegradable polyamides have been reported together with the formation of ladder polymers by 1,3-dipolar cyclo-addition of a cyclic dinitrone. 

As well as natural threads (silk, flax, cotton), nylon (the general name of polyamides) is also biodegradable. Polyamide 6,6, polyamide 6, and their mixtures with other polyamides are used for thread production. Nylon sutures are water-absorbable and they cause moderate tissue reaction. After implantation they undergo slow biodegradation and fragmentation. After two years they have lost about 25% of their mechanic resistance. 

Heteroatom Chain Backbone Polymers. This class of polymers includes polyesters, which have been widely studied from the initial period of research on biodegradable polymers, polyamides, polyethers, polyacetals, and other condensation polymers. Their linkages are quite frequendy found in nature and these polymers are more likely to biodegrade than hydrocarbon-based polymers. 

Over 250,000 metric tons of microcrystaUine cellulose have been sold siace its commercialisation ia 1962 and demand continues to iacrease. Its utihty has led to development of other coUoidal polymer microcrystals (see Colloids). For example, polyamides and polyesters from recycled materials can be biodegraded to give microcrystals having a size of 30 nm (37). 

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 ... 

Whereas polyetheylene, polypropylene, and polystyrene are virtually non-biodegradable, only specially modified, not widely employed, polyamides and polyurethanes are susceptible to biodegradation [2]. Consequently, the use... 

The ester class also comprises natural oils, such as vegetable oil [75] spent sunflower oil [940,941,992,993] and natural fats, for example, sulfonated flsh fat [161]. In water-based mud systems no harmful foams are formed from partially hydrolyzed glycerides of predominantly unsaturated Ci6 to C24 fatty acids. The partial glycerides can be used at low temperatures and are biodegradable and nontoxic [1280]. A composition for high-temperature applications is available [1818]. It is a mixture of long chain polyesters and polyamides. 

Oppermann FB, Fickaitz S, Steinbiichel A (1998) Biodegradation of polyamides. Polym Degrad Stab 59 337-344... 

In dentistry, silicones are primarily used as dental-impression materials where chemical- and bioinertness are critical, and, thus, thoroughly evaluated.546 The development of a method for the detection of antibodies to silicones has been reviewed,547 as the search for novel silicone biomaterials continues. Thus, aromatic polyamide-silicone resins have been reviewed as a new class of biomaterials.548 In a short review, the comparison of silicones with their major competitor in biomaterials, polyurethanes, has been conducted.549 But silicones are also used in the modification of polyurethanes and other polymers via co-polymerization, formation of IPNs, blending, or functionalization by grafting, affecting both bulk and surface characteristics of the materials, as discussed in the recent reviews.550-552 A number of papers deal specifically with surface modification of silicones for medical applications, as described in a recent reference.555 The role of silicones in biodegradable polyurethane co-polymers,554 and in other hydrolytically degradable co-polymers,555 was recently studied. 

Recently the biodegradability of polymers has become very important to the chemical industry and society in general. Chapter 19 describes studies on the biodegradability of polyamides by a number of bacteria. 

Of the polymers studied the methylated polyamides B and C are both biodegradable and photodegradable. Their use in agriculture are being studied. 

It is an alternating polyamide copolymer of glycine (H N-CH -COOH) and amino caproic acid [H2N (0112)5 COOH] and is biodegradable. Can you write the structure of this copolymer ... 

Polyesters and polyamides are the most prevalent of this type of polymer. Poly(ethylene terephthalate) is used in bottle manufacture and along with other packaging plastics is not biodegradable. Potts(54) established very early that only low melting and low molecular weight aliphatic polyesters were biodegradable. 

The susceptibility of CPAEs to hydrolysis by R. delemar lipase decreased with the shortening of the polyamide blocks and with increasing polyamide content (Figure 10). The simple blends of nylon and PCL at 270 °C for 10 min retained high biodegradability of PCL. 

Polycondensation reactions in oriented monolayers and bilayers proceed without catalysis, and simply occur due to the high packing density of the reactive groups and their orientation in these layers. Bulk condensation of the a-amino acid esters at higher temperatures does not lead to polypeptides but to 2,5-diketopiperazines. No diketopiperazines are found in polycondensed monolayers or liposomes. Polycondensation in monolayers and liposomes leading to oriented polyamides represents a new route for stabilizing model membranes under mild conditions. In addition, polypeptide vesicles may be cleavable by enzymes in the blood vessels. In this case, they would represent the first example of stable but biodegradable polymeric liposomes. 

Synthetic fibers have been characterized by a resistance to degradation over forensically relevant timescales (Table 7.4). Nylon (polyamide), polyester, and acrylic fibers show considerable resistance to soil burial. Regenerated cellulose fibers (rayon viscose), however, share the vulnerability of natural cellulose to decomposition (Rowe 1997). However, they do show a higher degree of resistance to biodegradation compared with natural fibers or regenerated cellulose, with the exception of triacetate. 

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