Thermoplastics from starch

In the next section, synthesis of thermoplastics from starch and proteins is discussed. Only these two polymers are included in the discussion as these form the majority of potential thermoplastics produced from renewable, agricultural sources. Polymers requiring chemical modification of the monomer are specifically excluded as this chapter focuses on direct utilization of natural resources. 

Starch is the major carbohydrate reserve in higher plants and has been a material of choice since the early days of human technology. Recently starch gained new importance as a raw material in the production of plastics, in particular, for the synthesis of monomers to produce polymers such as polydactic acid) and, after chemical modification (e.g. esterification) and thermomechanical processing, to produce thermoplastic starch. This chapter gives a general overview of the most recent research on the development of materials from starch, focusing on thermoplastic starch and the perspectives for future development in this field. A brief review on reactive extrusion of thermoplastic starch is also provided. 

Several companies have developed starch-based plastics. By using carefully selected starch feedstocks, and water as a plasticizer, they produce thermoplastics from nearly 100% starch, or from blends of starch with other biodegradable components. Many of these materials are water-soluble in addition to being biodegradable. The major target application has been as a replacement for polystyrene foam, including both molded cushions and loosefill. 

Shogren, R.L., Fanta, G.F. and Felker, F.C. (2006) X-Ray Drflraction study of crystal transformations in spherulitic amylose/lipid complexes from jet-cooked starch. Carbohydrate Polymers, 64,444- 51. van Soest, J.J.G., Hulleman, S.H.D.,de Wit, D. tmd Vliegenthart, J.F.G. (1999) Changes in the mechanical properties of thermoplastic potato starch in relation with changes in B-type crystallinity. Carbohydrate Polymers, 29, 225-232. 

Thermoplastic polymer foams can be prepared from starch-polyester graft copol zmers. Water is used as the plasticizer as well as the blowing agent (3). The foams have improved processability, surface properties, and an extended range of mechanical properties. 

Fig. 4. Droplet-like structure of thermoplastic com starch/EVOH blend in film from, after disagregation in boiling water (129).

Thermoplastic Elastomers from High-Density Polyethylene Natural Rubber j Thermoplastic Tapioca Starch Effects of Different Dynamic Vulcanization... 

TPEs from High-Density PolyethylenelNatural Rubberj Thermoplastic Tapioca Starch 243... 

TPEs from High-Density Polyethylene Natural Rubberj Thermoplastic Tapioca Starch 245... 

TPEs from High-Density PolyethylenejNatural Rubberj Thermoplastic Tapioca Starch 261... 

One biopolymer that is already used as a matrix for composite production is poly(lactic acid) (PLA). The PLA is a thermoplastic biopolymer with lactic acid which is derived from starch by a fermentation process as its basic monomer. High molecular weight PLA is polymerized by the lactide ring opening polymerization to PLA (Garlotta, 2001 Gupta et al., 2007 Lim et al., 2008). 

The three most common biobased biodegradable polymers are PLA, PHA, and TPS. PLA, PHA, and TPS can be made into plastic containers, packaging, bags, and bottles. All three biobased polymers can be processed with traditional plastics processing equipment. Polyhydrox-yalkanoates can be made from over 100 monomers based on P3HB, P4HB, PHB, and PHV. PHA is produced in the cells of several types of bacteria. Polylactide, or polylactic acid, is made from starch and bacteria. Thermoplastic starch is a blend of starch and other additives. 

No von Thermoplastic, blended starch Teclinology acquired from Wamer-Lamber in 1995 Novon Int. (Ecostar before — Wamer-Lamber) Plant just installed of about 3000 ton/year ... 

Special mention must be made of poly(lactic acid), a biodegradable/bio-resorbable polyester, obtained from renewable resources through fermentation of com starch sugar. This polymer can compete with conventional thermoplastics such as PET for conventional textile fibers or engineering plastics applications. Hie first Dow-Cargill PLA manufacturing facility is scheduled to produce up to 140,000 tons of Nature Works PLA per year beginning in 200245 at an estimated price close to that of other thermoplastic resins U.S. l/kg.46 Other plants are planned to be built in the near future.45... 

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