Polyethylene biodegradability

Starch-Modified, Low Density Polyethylene Biodegradable thermoplastic starch-grafted low-density polyethylene. 

Compared with tar, which has a relatively short lifetime in the marine environment, the residence times of plastic, glass and non-corrodible metallic debris are indefinite. Most plastic articles are fabricated from polyethylene, polystyrene or polyvinyl chloride. With molecular weights ranging to over 500,000, the only chemical reactivity of these polymers is derived from any residual unsaturation and, therefore, they are essentially inert chemically and photochemically. Further, since indigenous microflora lack the enzyme systems necessary to degrade most of these polymers, articles manufactured from them are highly resistant or virtually immune to biodegradation. That is, the properties that render plastics so durable... 

These monomers are biodegradeable and used for the production of bioplastics. PHAs produced from the process are usually composed of 100-30,000 monomers and exist in a short chain. Naturally, the properties of PHAs are similar to thermoplastics that are obtained from petrochemical industry such as polypropylene (PP) and polyethylene (PE) as shown in Table 1 (Evan and Sikdar, 1990). 

Goma K and Gogolewski S. Biodegradable polyurethane implants U in vitro degradadon and calcification of materials from poly (e-caprolactone)-polyethylene) diols and various chain extenders. J Biomater Res, 2002, 60, 592-606. 

Schramm E, B Schink (1991) Ether-cleaving enzyme and diol dehydratase involved in anaerobic polyethylene glycol degradation by a new Acetobacterium sp. Biodegradation 2 71-79. 

Wang, P., Woodward, C.A., and Kaufman, E.N., Polyethylene glycol)-modified ligninase enhances pentachlorophenol biodegradation in water-solvent mixtures, Biotechnol. Bioeng., 64, 290-297, 1999. 

Mid-IR spectroscopy, alongside gravimetric and molecular weight determinations, has also been used to analyse the biodegradation by a thermophilic bacterium (isolated from soil) of an LDPE film [44], The mid-IR studies were undertaken using the ATR sampling technique on control samples, samples that had been UV irradiated, and samples that had been UV irradiated then incubated with bacteria. The study showed that the particular bacterial strain was capable of utilising standard and photo-oxidised polyethylene as the sole carbon source. 

Hot melt adhesives based on poly(3HB-co-3HV) have also been described [119]. Hot melts are commonly used in bookbinding, bag ending and case and carton sealing and are mostly based on synthetic materials such as polyethylene, polypropylene ethylene-vinyl acetate and styrene block copolymers [119]. Hot melts based on PHAs alleviate the dependence on petroleum based materials and allow the development of biodegradable alternatives based on natural raw materials. 

Fig. 8 Nanosystems that may function as simultaneous drug delivery and imaging agents for targeting T cells (a) liposomal systems, (b) solid biodegradable nanoparticulates, and (c) macro-molecular dendrimer complexes. PEG polyethylene glycol, Gd-DTPA gadolininum-diethylene triamine penta acetic acid. (Adapted from [48])...

The only study available on metabolites of AE was performed by Crescenzi et al. [17]. The initial biodegradation of AE occurs by cleavage at the ether bridge between the alkyl and ethoxylate chain, resulting in polyethylene glycols (PEG) and alcohols. In consecutive oxidation steps, the PEG chains are shortened and mono- and dicarboxylated metabolites (MCPEG and DCPEG, respectively) are formed. 

The second section deals with the degradability of commodity plastics and specialty potymers. Emphasis is on the biodegradation of polyethylene, its blends with starch, and constraints in the decay of such composites. Additionally, the biodegradability of different functional groups (polyethers, carbotylic adds, esters, and dioxanones) is mcamined with respect to composition and miaostructure. 

More recent work on hydrocarbon oligomers by T. Suzuki established the biodegradation of oligomers of cis-1,4-polyisoprene,(23) polybutadiene,(24) polyethylene,(25) and polystyrene(26). 

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