Polysaccharides
Starch is a polymer of D-glucose organised in two major constituents of huge molecular weights amylose and amylopectin. Amylose contains amorphous and crystalline regions. It forms a linear structure constituted by repeating units of 1-4a-glucose Fig. 1.1 . Amylopectin is branched on amylose in starch Fig. 1.2 Moore and Saunders, 1997 Flieger et al., 2003 . The natural crystalline structure of starch must be dismantled in order to produce a thermoplastic material. It is achieved by the...
References Uvf
Babanalbandi A, Hill D J T, Hunter D S, Kettle L 1999 , 'Thermal stability of poly lactic acid before and after y-radiolysis', Polym. Int., 48 10 , 980-984. Baiardo M, Frisoni G, Scandola M, Rimelen M, Lips D, Ruffieux K, Wintermantal E 2003 , 'Thermal and mechanical properties of plasticized poly L-lactic acid ', J. Appl. Polym. Sei., 90, 1731-1738. Berl M, Scharngal N 1988 , 'Poly lactones 9. Polymerization mechanism of metal alkoxide initiated polymerizations of lactide and various...
Polyorthoesters
These polymers appear to be particularly useful for controlled drug release. Initially poly orthoesters were prepared by condensation of 2,2-diethoxytetrahydrofuran and a dialcohol47 B ecause the tetrahydrofuran component of the polymers does not provide the necessary rigidity Tg varies from body temperature or lower , this material had limited utility as a solid implant designed for drug delivery. An alternative route uses 5,5 undecane and a dialcohol.48 Mechanical properties of the polymer...
Biodegradation of chemically synthesized aliphatic polyesters
The biodegradability of the chemically synthesized polyesters is significantly influenced by the chemical structure and physicochemical properties, such as melting temperature and crystallinity of the polymer. Tokiwa et al., 1988 Tokiwa and Jarerat, 2004 Albertsson and Ljungqvist, 1988a,b Mathisen and Albertsson, 1990 . The rate of degradation decreases with the increasing melting temperature. Tokiwa and Suzuki, 1981 . Also, orientation of the polymer molecules reduces the rate of degradation....
Polyaspartic acid
Poly aspartic acid PAsp has been extensively studied as one of the candidates for the replacement of polycarboxylate compounds, because PAsp has some beneficial characteristics, such as calcium sequestration capacities and dispersing capacities. PAsp is industrially produced only by a chemical method. The produced PAsp is composed of the L- and D-enantiomers of aspartic acid and also having a- and -linkages Fig. 14.20 . Poly a-L-aspartate is prepared by the enzyme-catalyzed polymerization of...
References
Arnaud, R., Dabin, P. and Lemaire, J. 1994 'Photooxydation and biodegradation of commercial photodegradable polyethylenes', Polymer Degradation and Stability, 46, 211-224. Bastioli, C. 2002 'Starch-polymer composites' in Geralds Scott, Degradable Polymers Principles and Applications 2nd edn, Kluwer Academic Publishers, 133-161. Bastioli, C. and Facco, S. 2001 Biodegradable Plastics, 2001 Conference, Frankfurt, Germany, November 26-27. Beckwith, S.W. 2003 'Natural Fiber - Reinforcement...
Natural fibres in combination with synthetic biodegradable polymers
There are a number of reports in the literature concerning research on reinforcement of synthetic biodegradable polymers. These polymers include polyester amides, poly butylene succinate-co-butylene adipate PBSA and polycaprolactone PCL . For example, Tserki et al. 2003 examined the performance of composites in which cotton fibre wastes were combined with a commercial polyester of the PBSA type. A maleated derivative of the polyester was produced by mixing and heating together appropriate...
Polyester amides synthesis
Poly ester amide s are conveniently synthesized by polycondensation techniques as applied in the synthesis of polyesters and polyamides. One can choose either to use methods where preformed monomers are condensed, use ring-opening polymerization or combine both methods. The preformed monomers may contain either ester or amide functional groups and all the possible combinations lead to architectural variations of poly ester amide s. The placement of amide and ester groups along the polymer chain...
Processing of aliphatic polyesters in supercritical carbon dioxide
The use of supercritical carbon dioxide has the unique advantage of combining synthesis of aliphatic polyesters and pocessing. For instance, the polyester formed in the high-pressure reactor can be in situ loaded by guest molecules, or collected as microparticles and porous material. Synthesis of micro- and nanoparticles Microparticles can be produced by a simple technique that consists of spraying a polymer, e.g., PLLA, solution in dichloromethane or dimethylsulfoxide , through a nozzle into a...
Polyacrylate and polycyanoacrylate
Poly sodium acrylate s are widely used as dispersing agents, chelating agents, scale inhibitors, flocculating agents, and detergent builders. It is generally believed that their biodegradation rate is very slow in the environment. However, sodium acrylate oligomers with molecular weights lower than approximately 500 to 700 are subject to biodegradation in the environment Matsumura et al., 1988a Larson et al., 1997 . Hayashi et al. isolated the acrylate oligomer-degrading strain, Arthrobacter...
Ringopening polymerisation of lactones and lactides in supercritical carbon
Ring-opening polymerisation in supercritical carbon dioxide has been investigated in the presence of both organometallics and enzymes, as mentioned in section 4.2. In 2001, Kobayashi and co-workers reported on ring-opening polymerisation of eCL, undecanolide and dodecanolide promoted by Candida Antarctica lipase in supercritical carbon dioxide Takamoto, 2001 . Control of ring-opening polymerisation is rather poor as testified by high polydispersity gt 3 and low molecular weight 1,000 . More...
References Oiy
1. Scott G, Atmospheric Oxidation, Amsterdam, Elsevier, 1965. 2. Billingham N C and Calvert P D in Allen N S, Degradation and Stabilization of Polyolefins, London, Applied Science, 1-28, 1983. 3. Carlsson D J and Wiles D M, Encyclopedia of Polymer Science and Engineering, 2nd edn, New York, Wiley, 4, 631-696, 1986. 4. Wiles D M, 'The photodegradation of fiber-forming polymers' in Geuskens G, Degradation and Stabilization of Polymers, London, Applied Science, 137-155, 1975. 5. Wiles D M,...
Plasticization of PLAbased bioplastics
The brittleness and stiffness of PLA are major drawbacks in many fields of application. Plasticizers are widely used in the plastics industry to improve processability, flexibility, and ductility of glassy polymers Sears et al., 1982 . In semicrystalline polymers like PLA, an efficient plasticizer is expected to reduce the glass transition of the amorphous domains if the Tg is near or lower than ambient temperature, flexibility is achieved. Meanwhile, it depresses the melting point of the...
Conclusion 1
In this research protein-based nanocomposites have been successfully produced via a novel melt blending technique. In the blends, the unmodified sodium montmorillonite clay was initially treated with a high-powered sonifier in a solution of glycerol and distilled water. This solution was then added to a soy protein isolate and processed through an extruder. The ultrasonically treated nanocomposite material that was produced exhibited an exfoliated type structure as observed by WAXS and TEM and...
Bibliography
Due to the ever-increasing number of publications dealing with ring-opening polymersation of lactones, lactides, and related materials, there is a need continuously to review and up-date the available information. Several review articles are now available and have been mentioned within the manuscript and may be found in the following list of publications. During the last few years, several research groups have actively contributed to progress in the field and the reader is advised to trace...
Blends with starch
In disposable applications, PLA competes with cheap mass polymers like polyethylene, polypropylene, or polystyrene. Therefore, reducing the price of PLA without sacrificing its excellent biodegradability while maintaining certain mechanical and thermal properties is an effective approach. Starch, a degradable carbohydrate biopolymer from natural resources, consists of polysaccharides amylose and amylopectin. Native starch usually exists in granular form, in which the polymer molecules are...
Polymer structure and biodgradation
The polymer structures of PVA, such as the saponification degree, polymerization degree, tacticity, and 1,2-glycol content, are responsible for its biodegradability Hatanaka et al., 1995a,b Matsumura et al., 1994 . It is reported that the 1,3-diols of PVA were dehydrogenated at a greater rate than the 1,2-diols which is produced by the head-to-head reaction of the monomer Hatanaka et al., 1995a,b . The unreacted acetyl moiety of PVA was hydrolyzed by esterase, which was isolated from the...
Polyalkene succinate
A series of biodegradable polyesters using 1,4 butane diol and succinic acid has been produced using polycondensation reaction. The method yields pre-polymers of molecular mass of approximately 10,000, which is then coupled to increase the molecular mass by chain extenders, such as di-isocyanate or di-amines. Chain extenders are bifunctional low molecular weight chemicals that react with end groups in the polymers. In polyesters, the end groups are hydroxyl and carboxyl. Polybutylene succinate,...
Physical and chemical properties of PHA polymers
Physical and chemical properties of the P 3HB-co-3HV copolymer can be controlled by varying the mol percentage of 3HV, with greater elasticity conferred by an increased HV content. The industrially important monomeric composition of PHA copolyester can be regulated through a judicious choice of microorganism, substrate to cosubstrate ratios, and general fermentation conditions. The physical and mechanical properties of P 3HB , similar to those of polypropylene, are those of a thermoplastic,...
Biodegradation of PHA
One of the most important properties of PHA is their biodegradability. To assess the polyhydroxyalkanoate PHA -biodegrading capacity of soil, numbers of aerobic PHBV-degrading microorganisms degraders were estimated by Song et al40 The numbers of PHBV degraders were estimated to be 4.3 x 105 per gram of dry garden soil, 5.06 x 105 per gram of dry paddy-field soil, and 3.87 x 105 per gram of dry river-bank soil. It was found that the PHBV-biodegrading capacity of the soil increased as the number...
Lignocellulosic biomass as a renewable and valueadded feedstock for
This chapter describes the major components of forest biomass and relates the associated value-added and biodegradable polymeric products that can be generated from each component. The chapter begins with a description of the major lignocellulosic resources available in forest ecosystems, with a focus on the two largest fractions, namely cellulose and hemicellulose, and how these renewable resources will be refined and processed in the near future. The history and rationale behind development...
References Txx
Ali R, Iannace S and Nicolais L 2003 , 'Effect of processing conditions on mechanical and viscoelastic properties of biocomposites', J Appl Polym Sci, 88, 1637-1642. Alvarez V A, Ruscekaite R A and V zquez A 2003 , 'Mechanical properties and water absorption behaviour of composites made from a biodegradable matrix and alkaline-treated sisal fibres', J Comp Mat, 37 17 , 1575-1588. Andersen T L 1997 , 'Development of a rapid press consolidation technique for continuous fibre reinforced...