Science of biodegradable blends

Scalar percolation theory deals with the connectivity of a component randomly dispersed in another [7-8]. Examples of percolation are gelation during a polymerization of monomers with multifunctional linkages and the onset of conductivity in blends of conducting and non-conducting materials [9-10]. The percolation threshold p for a finite-sized object is defined as the minimum concentration (of the percolating medium) at which connectivity is established between the top and bottom surface, is different for lattices of different geometry [7]. For Id site percolation, p = 59.20%, while = 31.17% for a cubic lattice. 

Peanasky, Long and Wool applied percolation theory to analyse the degradation of starch in polymer-starch blends [11]. They found that in 3rf, the equilibrium accessible fraction of starch AJj) ), was determined by 

When p accessibility of starch on the surface of films of finite thickness occurs as follows (Fig. 7.2a). For starch particles of diameter A in a film of thickness L, the fraction of starch which can be accessed was determined by Wool and Goheen [12] as. 

The factor of two accounts for the accessibility on both sides of the film and assumes that the clusters from either side do not overlap. Equation 7.4 is therefore only valid in the range of film thickness and concentrations given by L/2 e, where the average cluster size e is determined by, 

Dynamic degradation of a polymer-starch blend is defined as the time-dependent accessibility of starch by micro-organisms A t) [13]. In this chapter, the percolation theory is extended to investigate the time dependence of starch removal in polymer-starch blends as a function of starch concentration p, the invasion mechanism, enzyme diffusion, microbial population, and starch size distribution. In this case, the time dependence of the accessibility on the fractal pathways representing the connected starch network with emphasis on both invasion and diffusion controlled mechanisms is explored. 

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AVE 02] Avella M., Errico M.E., Rimedio R., et ai, Preparation of biodegradable polyester/high-amylose-starch composites by reactive blending and their characterization , Journal of Applied Polymer Science, vol. 83, no. 7, pp. 1432-1442,2002. 

Lai, S.M., Huang, C.K. and Shen, H.F. (2005) Preparation and properties of biodegradable poly(butylene succinate)/starch blends. Journal cf Applied Ihlymer Science, 97 (1), 257-264. 

Harada, M., Ohya, T., lida, K. et al. (2007) Increased impact strength of biodegradable poly(lactic acid)/poly(butylene succinate) blend composites by using isocyanate as a reactive processing agent. Journal of Applied Polymer Science, 106 (3), 1813-1820. 

In this chapter, we have discussed polymer stmcture at the level of the repeating unit. The repeating unit not only has a specific chemical structure but also acts as the source of interaction at the molecular scale. With respect to this, now we will be introducing the concept of biodegradable polymer blends. A polymer blend is classically defined as a physical mixture of two or more polymers, which occurs on a macro scale. We are now going to also consider the science at molecular/nanometre scales, ie, taking polymer repeating unit into account rather than entire polymer chains. For the purposes of this book, the definition of a polymer blend is as follows ... 

Yang, D.Z., Hu, P., 2008. Miscibility, crystalUzation, and mechanical properties of poly (3-hydroxybutyrate) and poly(propylene carbonate) biodegradable blends. Journal of Applied Polymer Science 109, 1635—1642. 

Yang, S. Y. and Huang C. Y. Plasma treatment for enhancing mechanical and thermal properties of biodegradable PVA/starch blends. Journal of Applied Polymer Science, 109, 2452-2459 (2008). 

Jacob, J., Mani, R. and Bhattacharya, M. CompatibiUty and Properties of Biodegradable Polyester Blends. J. Polymer Science Part A Polymer Chemistry 40(12) 2003-2014 (2002). 

ARV 99] Arvanitoyannis I.S., Totally and partially biodegradable polymer blends based on natural and synthetic macromolecules preparation, physical properties, and potential as food packaging materials , Journal of Macromolecular Science - Reviews in Macromolecular Chemistry Physics, vol. C39, no. 2, pp. 205-271, 1999. 

Tsuji, H., Smith, R.,Bonfield, W. and Ikada, Y. (2000) Porous biodegradable polyesters. 1. Preparation of porous poly(L-lactide) films by extraction of poly(ethylene oxide) from their blends. Journal of Applied Polymer Science, 75, 629-631. 

Chin Han Chan, PhD, is an associate professor at the Faculty of Applied Sciences, Universiti Teknologi MARA [MARA University of Technology) in Selangor, Malaysia. She has received many research grants, has published many articles in professional journals, has published chapters in books, and has presented at many professional conferences. Her field of interest includes epoxidized natural rubber-based nanostructured blends, thermoplastic elastomer, biodegradable polyester/polyether blends, and solid polymer electrolytes. 

She has pnbhshed more than 45 papers in intematiorral and national refereed journals, more than 60 publications in conference proceedings, and more than 20 invited lectures for international conferences. She has been one of the editors of Malaysian Journal of Chemistry, Berita IKM- Chemistry in Malaysia, and books pnbhshed by Royal Society of Chemistry entitled Natural Rubber Materials, Volume 1 Blends and IPNs and Volume 2 Composites and Nanocomposites. She peer-reviews a few international journals on polymer science. Her research interest is devoted to modified natural rabber-based thermoplastic elastomers, biodegradable polyester/polyether blends, and solid polymer electrolytes... 

Tertyshnaya Yu. V. Feofanova, E. S. Popov, A. A. Biodegradation of the films poly-3-hydroxybutyrate and its blends in soil and water. Modem problems in biochemical physics. Nova Science Publ., Inc. 2012,117. 

Development of novel biodegradable polymer blends for medical use is a relatively new science. It is expected though, that new polymer blends will be developed rapidly and use as many different polymers as possible to liberate all other potential applications. One of the growing areas will be continuing to take the existing advantages of synthetic polymers to develop more desirable polymer blends. 

Averous, L., Fauconnier, N., Moro, L and Fringant, C. (2000) Blends of thermoplastic starch and polyesteramide processing and properties. Journal of Applied polymer Science, 76,1117-28. Mani, R. and Bhattacharya, M. (1998) Properties of injection moulded starch/ synthetic polymer blends. Ill Effect of amylopectin to amylose ratio in starch. European Polymer Journal, 34 (10), 1467-75. Mani, R. and Bhattacharya, M. (2001) Properties of injection moulded blends of starch and modified biodegradable polyesters. European Polymer Journal, 37, 515-26. 

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