Biodegradable applications

Mention should also be made here of the extensive use of poly(vinyl alcohol) in potentially biodegradable applications. At appropriate hydroxyl contents these polymers will dissolve in water (see Chapter 14) and can apparently be conveniently washed away after use as a water-soluble packaging. Biodegradation does, however, appear to be slow and first requires an oxidative step involving enzymatic attack to a ketone such as polyenolketone, which then biodegrades more rapidly. 

The CERCLA Priority List of Hazardous Substances has been annotated with information on the types of wastes and the possible biotechnological treatment methods, as shown in Table 1. The remarks on biotreatabihty of these hazardous substances are based on data from numerous papers, reviews, and books on this topic [4-8]. Databases are available on the biodegradation of hazardous substances. Eor example, the Biodegradative Strain Database [9] (bsd.cme.msu.edu) can be used to select suitable microbial strains for biodegradation applications, while the... 

Moreover, telomers of glycerol or saccharides, i.e. made from renewable materials, can be used for biodegradable applications. Owing to their skin- and eco-friendli-ness, they have potential interest as additive in the cosmetic industry. Alternatively, telomers of polysaccharides might find applications in the paper industry. 

Historically, polyanhydrides were developed in the textile industry during the first half of the 20th century as alternate fiber materials. " However, the modern polyanhydrides that are currently under investigation as drug delivery platforms represent a novel class of polymer that, unlike the polyesters, has been specifically developed for biodegradable applications. In particular, these polyanhydrides were specifically prepared in attempts to produce surface-eroding dosage forms. 

Kaabi Falahieh Asl, S., Nemeth, S., and Tan, M.J. (2014) Electrophoretic deposition of hydroxyapatite coatings on AZ31 magnesium substrate for biodegradable applications. Progr. Cryst. Growth Character Mater, 60 (3-4), 74—79. 

Blends of the commodity polymers with more specialty polymers are limited although many specific examples exist in the patent/open literature. In the design of polymer blends for specific application needs, countless opportunities can be envisioned. Examples may include PE/poly(s-caprolactone) (PCL) blends for biodegradable applications (proposed), polyolefin (PO)/poly(vinyl alcohol) (PVAL) blends for antistatic films, PO/silicone rubber blends for biomedical applications, PO/thermoplastic polyurethane TPU (or other thermoplastic elastomers) for applications similar to plasticized PVC, functionalized PO/thermoset blends. 

PROPERTIES OF SPECIAL INTEREST The a-glucopyranose linkage in starch is more susceptible to hydrolysis or enzyme attack than the / -glucopyranose linkage in cellulose, thus making starch more attractive for biodegradation applications than cellulose. 

Starch-based products are also available for applications requiring biodegradability. The starch is often blended with polymers for better properties. For example, polyethylene films containing between 5 and 10 percent cornstarch have been used in biodegradable applications. Blends of starch with vinyl alcohol are produced by Fertec (Italy) and used in... 

Polymer Blends from Renewable Resources for Biodegradable Applications... 

Polylactides (PLA) and copolymers are also of interest in biodegradable applications. This material is a thermoplastic polyester synthesized from the ring opening of lactides. Lactides are cyclic diesters of lactic acid.2 A similar material to polylactide is polyglycolide (PGA). 

Since nonbiodegradable aromatic polyesters like PET provide excellent material properties [55], with respect to easily degradable aliphatic polyesters, a number of aliphatic/aromatic copolyesters were studied and developed in order to produce materials which combined good mechanical properties and biodegradability. Major polyester producers in Europe and the USA brought aliphatic/aromatic copolyesters for biodegradable applications to the market. 

Tsakala, T. M. (1987) Formulations a liberation progressive a base de polymeres biodegradables, application a la chimiotherapie experimentale a la malaria, PhD thesis, Universite Catholique de Louvain La Neuve, Belgium. 

Because of its ease of polymerisation to high MW and its commercial availability, PCL has been the subject of a number of studies pertaining to its biodegradability [6]. Although PCL is an expensive polymer, it is used extensively in biodegradable applications typically as a starch blend. Table 6.4 provides typical properties for PCL at three degrees of polymerisation. 

In contrast to most aliphatic polyesters, aromatic polyesters like PET provide excellent material properties [50]. To combine good material properties with biodegradability, aliphatic/aromatic copolyesters have been developed. Several major polyester producers in Europe and the United States have recently begun marketing aliphatic/aromatic copolyesters for biodegradable applications. BASF markets a product, Ecoflex , which is a copolyester of butanediol, adipic acid, and dimethyl terephthalate. Eastman s Eastar Bio Copolyester 14766 is a similar aliphatic/aromatic copolyester. DuPont markets a modified PET known as Biomax . 

Recently, Lendlein et al. created a series of responsive shape memory polymers which are mechanically tough, biocompatible, and biodegradable, applicable to a number of biomedical apphcations [300,301,305]. Such shape memory polymers are achieved by copolymerizing precursors with different thermal characteristics such as the melting transition temperature. These shape memory polymers can be deformed into a temporary compressed state and they can recover the permanent shape only with the aid of an external stimulus such as temperature. This type of ape memory polymer mainly consists of two components (i) molecular switches—precmsors that can imdergo stimuh responsive deformation and can fix the formed tempo-... 

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