Plasticized starch polymers

After drying, the starch films with no CMSt in composition exhibited the higher value for equilibrium moisture content while the lower values were observed by addition of CMSt within plasticized starch polymer matrix due to their hydrophobic properties (Figure 7.5). 

Eilm products with good mechanical characteristics are only obtained if thermoplastic, plasticized starch has been used. If no plasticizer is used, biodegradable polymers with limited mechanical properties will be obtained. In this case, coextmsion with the base polyester or another polymer is the way to upgrade the mechanical and/or moisture barrier properties (for comparison see Table 6). 

Vacuum rotary dryers plastics, organic polymers, nylon chips, chemicals of all kinds, plastic fillers, plasticizers, organic thickeners, cellulose acetate, starch, and sulfur flakes... 

In nature, starch is based on crystalline beads of about 15-100 microns in diameter. Crystalline starch beads in plastics can be used as fillers or can be transformed into thermoplastic starch, which can either be processed alone or in combination with specific synthetic polymers. To make starch thermoplastic, its crystalline structure has to be destroyed by pressure, heat, mechanical work or use of plasticisers. Three main families of starch polymer can be used pure starch, modified starch and fermented starch polymers. 

Biotec s product portfolio includes thermoplastic starch, which can be substituted for petrochemical based plastic packaging. Stanelco s radio frequency sealing technology can be used to process starch polymers without the degradation caused by other methods such as thermal processing. The purchase of Biotec will help the company develop alternatives to petroleum-based packaging. 

In its application in biodegradable plastics, starch is either physically mixed, with the native granules kept intact, or melted and blended on a molecular level with the appropriate polymer as described in Sects. 5.7 and 5.8. In either form, the fraction of starch in the mixture which is accessible to the enzymes can be degraded by either, or both, amylases and glucosidases. 

L. Averous, Biodegradable Multiphase Systems Based on Plasticized Starch A Review. Journal of Macromolecular Science Part C-Polymer reviews 44 231-274,2004. 

If starch is modified by partially fermenting it, or esterifying or etherification, the resulting material can be extruded by adding plasticizers. Starch-based plastics are readily biodegraded. In most cases, the polymers are also water-soluble. Several suppliers now offer thermoplastic starch. Major markets include soluble films for industrial packaging, films for bags and sacks, and loose fill. 

Plasticized starch has widely been studied in a mixture with other polymers [AVE 04a, AVE 00a, AVE 00b, AVE 01a, MAR 01a, MAR 01b, SCH 04]. A large nrrmber of patents have been pubUshed on this subject [AVE 04a]. These research efforts have led to the commercialization of different biodegradable blends - some of them based on plasticized starch (Table 9.4). 

AVE Ola] Averous L., Fringant C., Association between plasticized starch and polyesters processing and performances of injected biodegradable systems . Polymer Engineering and Science, vol. 41, no. 5, pp. 727-734,2001. 

AVE 04a] Averous L., Biodegradable multiphase systems based on plasticized starch a review . Journal of Macromolecular Science Polymer Reviews, vol. 44, no. 3, pp. 231-274,2004. 

AVE 04b] Averous L., Boquillon N., Biocomposites based on plasticized starch thermal and mechanical behaviours . Carbohydrate Polymers, vol. 56, no. 2, pp. 111-122,2004. 

MAT 08] Mathew A.P., Thielemans W., Dufresne A., Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers . Journal of Applied Polymer Science, vol. 109, no. 6, pp. 4065 074,2008. 

Chitosan is obtained from the deacetylation of chitin, which is found in marine environments. Because it is insoluble in water, chitosan is dissolved in acidic solutions before being incorporated into biodegradable polymer films. It can also be plasticized with glycerol to obtain a kind of thermoplastic material like, for instance, plasticized starch (Epure, 2011]. 

Senna, M. M., Hossam, E M., El-naggar, A. W. M., Compatibilization of low-density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation. Polymer Composites 2008,29(10), 1137-1144. 

Bastioli, C., Bellotti, V, Camia, M. et al. (1994) Starch / vinyl-alcohol copolymer interactions, in Biodegradable Plastics and Polymers (eds Y. Doi and K. Fukuda), Elsevier, Amsterdam. 

BiMaris D, Prinos J, Koutsopoulos K, Vouroutzis N, Pavlidou E, Frangis N et al (1998) LDPE/ plasticized starch blends containing PE-g-MA copolymer as compatibilizer. Polym Degrad Stab 59 287-291... 

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