Biodegradable thermoplastic

Poly-P-hydroxybutyrate (PHB) is a biodegradable thermoplastic that is produced by several microorganism. The PHB synthesis has been characterized eutrophus and the operon iavolved ia PHB productioa has beea cloaed. Recombiaant E. coli straias that can produce high levels of... 

With the renewed interest in environmentally friendly products, ceUulose esters are being re-evaluated as a natural source of biodegradable thermoplastics. CeUulose acetates are potentiaUy biodegradable (152). Films prepared from a ceUulose acetate with a DS of 2.5 were shown to require only a 10—12 day incubation period for extensive degradation in an in vitro enrichment assay. Similarly, films prepared from a ceUulose acetate with a DS of 1.7 saw 70% degradation in 27 days in a wastewater treatment facUity, whereas films prepared from a ceUulose acetate with a DS of 2.5 required approximately 10 weeks for similar degradation to occur. The results of this work demonstrate that ceUulose acetate fibers and films are potentiaUy environmentally nonpersistant. 

Bayer AG (1995) Biodegradable thermoplastic BAK1095. KU-marketing, Informations-systeme, KU 48.872... 

POIRIER, Y., DENNIS, D.E., KLOMPARENS, K., SOMMERVILLE, C., Polyhydroxybutyrate, a biodegradable thermoplastic, produced in transgenic plants, Science, 1992, 256, 520-523. 

Simmons S, Thomas EL (1995) Structural characteristics of biodegradable thermoplastic starch/poly(ethylene-vinyl alcohol) blends. J Appl Polym Sci 58 2259-2285... 

The copolymer poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-PHV) produced by A eutrophus has generated more interest than poly-(R)-3-hydroxybutyrate (PHB) homopolymer. Since these bacterial polyesters are biodegradable thermoplastics, their mechanical and physical properties have received much attention. PHB is a relatively stiff and brittle material because of its high crystallinity. However, the physiochemi-cal and mechanical properties of [P(HB-HV)] vary widely and depend on the molar percentage of 3-hydroxyvalerate (HV) in the copolymer (4,5) as shown inTable 1. Propionic acid is converted by a synthetase to propionyl-CoA, and the biosynthetic P-ketothiolase catalyzes the condensation of propionyl-CoA with acetyl-CoA to 3-ketovaleryl-CoA by the acetoacetyl-CoA reductase. The hydroxyvaleryl moiety is finally covalently linked to the polyester by the PHA synthase (6). 

Biodegradable thermoplastics, like PHB and PLA, can be processed by conventional thermoplastic processing technologies, such as extrusion, injection molding, melt spinning, blowing film, and melt blown, for a wide range of application as enviromnentally friendly materials and for medical applications. 

A biodegradable thermoplastic composition comprising polyvinyl alcohols, polyurethanes or polyacrylates, cellulose fibers, and chitosan is disclosed in U.S. Pat. No. 5,306,550 [125]. 

Biodegradable thermoplastic composites, comprising aliphatic polyester urethanes or polyester amides and wood flour as a reinforcing material, are described in U.S. Pat. No. 5,827,905 [126]. 

Poly(butylene succinate) (PBS) is an important member of biodegradable aliphatic polyester family. PBS and related copolymers have shown considerable promise for uses as environmentally biodegradable thermoplastics, as well as bioabsorbable/biocompatible medical materials (/). In both cases, practical applications require that the polymer possess a high molecular weight (M >20,000) so that it can have useful mechanical properties. 

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

Starch-Modified Polypropylene Biodegradable thermoplastic starch-grafted polypropylene. 

Starch-Modified Polyurethane Biodegradable thermoplastic starch-grafted polyurethane. 

With the increase in the recent environmental awareness, there is an improved interest from the food industry to replace the existing non-biodegradable thermoplastics with PLA for certain beverage products. PLA bottles are predominantly used for beverage containers, which are not sensitive to oxygen. While barrier properties of PLA bottles may be improved by various technologies, their implementation is currently limited due to higher production costs. 

Botana et al. [50] have prepared polymer nanocomposites, based on a bacterial biodegradable thermoplastic polyester, PHB and two commercial montmorillonites [MMT], unmodified and modified by melt-blending technique at 165°C. PHB/Na and PHB/ C30B were characterized by differential scanning calorimetry [DSC], polarized optical microscopy [POM], X-ray diffraction [XRD], transmission electron microscopy [TEM], mechanical properties, and burning behavior. Intercalation/exfoliation observed by TEM and XRD was more pronounced for PHB30B than PHB/Na,... 

One of the most studied blends has been the one composed of P(3HB) and polylactide, both commercially available polymers with superior thermal and mechanical properties than other commercial polymers. Polylactide is a chemically synthesized, biodegradable thermoplastic and derived from renewable resources. It has been shown that this blend exhibited greater flexibility and hydrolytic biodegradation than the Polylactide or P(3HB) alone [75]. 

Du, G., Yu, J. Green technology for conversion of food scraps to biodegradable thermoplastic polyhydroxyalkanoates. Environ. Sci. Technol. 36, 5511-5516 (2002)... 

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