Biodegradable composites

The chemical composition of particles can be just as varied as their shape. Commercial particles can consist of polymers or copolymers, inorganic constructs, metals and semiconductors, superparamagnetic composites, biodegradable constructs, and synthetic dendrimers and dendrons. Often, both the composition of a particle and its shape govern its suitability for a particular purpose. For instance, composite particles containing superparamagnetic iron oxide typically are used for small-scale affinity separations, especially for cell separations followed by flow cytometry analysis or fluorescence-activated cell sorting (FACS). Core-shell semiconductor particles, by... 

The Bolivar Coastal Fields (BCF) of eastern Lake Maracaibo, Venezuela, contain five classes of oil as reflected by their API gravities, C15+ saturates-and-aromatics contents as well as their total nitrogen, sulfur, and oxygen (NSO) compositions. Biodegradation appears to have had a major role in controlling the... 

Wang, L., Auty, M.A.E., Kerry, J.P. Physical assessment of composite biodegradable films manufactured using whey protein isolate, gelatin and sodium alginate. J. Food Eng. 96, 199-207 (2010)... 

The fundamental elements used in our approach consist of applying the composite theory in order to design composite biodegradable scaffolds based on the structural organisation and performance of the living tissue. 

Sample Preservation Without preservation, many solid samples are subject to changes in chemical composition due to the loss of volatile material, biodegradation, and chemical reactivity (particularly redox reactions). Samples stored at reduced temperatures are less prone to biodegradation and the loss of volatile material, but fracturing and phase separations may present problems. The loss of volatile material is minimized by ensuring that the sample completely fills its container without leaving a headspace where gases can collect. Samples collected from materials that have not been exposed to O2 are particularly susceptible to oxidation reactions. For example, the contact of air with anaerobic sediments must be prevented. 

It is evident that the area of water-soluble polymer covets a multitude of appHcations and encompasses a broad spectmm of compositions. Proteins (qv) and other biological materials ate coveted elsewhere in the Eniyclopedia. One of the products of this type, poly(aspartic acid), may be developed into interesting biodegradable commercial appHcations (70,71). 

Polyesters are known to be produced by many bacteria as intracellular reserve materials for use as a food source during periods of environmental stress. They have received a great deal of attention since the 1970s because they are biodegradable, can be processed as plastic materials, are produced from renewable resources, and can be produced by many bacteria in a range of compositions. The thermoplastic polymers have properties that vary from soft elastomers to rigid brittie plastics in accordance with the stmcture of the pendent side-chain of the polyester. The general stmcture of this class of compounds is shown by (3), where R = CH3, n = >100, and m = 0-8. 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aUphatic polyesters with inorganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibiUty of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and biodegradabihty is attempted. Starch and additives have been evaluated ia detail from the perspective of stmcture and compatibiUty with starch (214). 

Biodegradable film (148), foam-molding compositions, eg, sponges (149), tobacco substitutes (150), and microencapsulated dmg-deHvery systems (151) are potentially new and usefiil appHcations for ceUulose acetate esters. 

As AOS is a mixture of different chemical species, determination of its composition by modern analytical techniques is perhaps even more important than for most other surfactants this chapter therefore also describes the state of the art of the analysis of AOS. The chapter also contains a brief review of the biodegradability and the toxicity of AOS. 

In a continuous model river test system it can be shown that after passage through a sewage treatment plant ester sulfonates have no significant influence on the qualitative and quantitative composition of the biocenosis of a receiving water [113]. All the investigations into the environmental fate of a-sulfo fatty acid esters demonstrate that aquatic toxicity is alleviated by their fast ultimate biodegradability, which allows them to be classified as environmentally compatible. 

Of interest is the relative composition of the LABs, particularly the different amount of 2-phenyl isomer and of nonlinear alkylates, given in Table 8. Branched alkylbenzene (BAB) formed by the AlCl3-catalyzed reaction between propylene, condensed to its tetramer, and benzene are less biodegradable and are termed biologically hard. LABs have to a large extent replaced BABs in the domestic markets because of their improved biodegradability. 

Such studies have shown that it is the chemical structure and composition that determine whether or not synthetic polymers are biodegradable. On the other hand, the precise rate at which a synthetic polymer will degrade is determined by the specific morphology of the article into which the polymer has been fabricated. 

Polymer layered-silicate day nano-composites (PLCN) attracted lately major interests into the industry and academic fields, since they usually show improved properties with comparison by virgin polymers or their conventional micro and macro-composites. Improvements induded increase in strength, heat resistance (Giannelis, 1998), flammability (Gilman, 2000) and a decrease in gas permeability (Xu et ah, 2001) as well as an increase in biodegradability (Sinha et al., 2002). 

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