ISSN 0965-545X, Polymer Science, Ser. A, 2012, Vol. 54, No. 2, pp. 165–176. © Pleiades Publishing, Ltd., 2012. 165 1 INTRODUCTION Rising oil prices and increased activity in regards to environmental pollution prevention have pushed re- search and development of biodegradable plastics, where the development of plastics by using renewable resources which are naturally biodegradable and their possibility of combining their biodegradability with cost reduction and market needs have been the object of intensive academic and industrial researches. Starch is one of the most promising natural poly- mers to be abundant, cheap and biodegradable. Starch offers a possible alternative to the traditional non-bio- degradable polymers, especially in short life-time ap- plication and when their recycling is difficult and/or not economical. Starch consists of two major compo- nents: amylose, a mostly linear α-D(1-4)-glucan and amylopectin, an α-D-(1-4) glucan which has α-D(1-6) linkages at the branch point. The linear amylose mol- ecules of starch have a molecular weight of 0.2– 2 million, while the branched amylopectin molecules have molecular weights as high as 100–400 million. Starch is unique among carbohydrates because it oc- curs naturally as discrete granules. This is because the short branched amylopectin chains are able to form helical structures which crystallize. Starch granules exhibit hydrophilic properties and strong intermole- cular association via hydrogen bonding due to the hydroxyl groups on the granule surface. The melting point of native starch is higher than the thermal de- composition temperature: hence the poor thermal sta- bility of native starch and the need for conversion to 1 The article is published in the original. starch-based materials with a much improved property profile. Starch was used as natural filler in traditional plas- tics (PE, PP, etc.) [1–10] and particularly in polyole- fins; it helps in cost reduction and rising biodegrad- ability of resultant composite as well as in increasing the rigidity (high modulus) [3] of the material. How- ever, the starch concentration at which useful product can be obtained is therefore limited to a low range after which the materials properties suffer dramatically. The overall disintegration of these materials is achieved by the use of transition metal compounds, soluble in the thermoplastic matrix, as prooxidant additives which catalyses the photo and thermo-oxidative process. Recently, starch was used as a main component in polymer blends, it was applied in plastic rather than in the native form, where the starch granules were plasti- cized by using plasticizers under heating, giving rise to a continues phase in the form of a viscous melt which can be processed using traditional plastic processing techniques [11], such as injection molding and extru- sion. This kind of starch composites is called thermo- plastic starch (TPS). Several plasticizers have been used for plasticization process to convert starch into TPS to be used in polymer blends such as glycerol [12–21], water [21, 22], urea [23–25], formamide [22, 24–26], ethylenebisformamide [27–29], sorbitol [27, 30], citric acid [31], N-(2-hydroxyethyl)forma- mide [32] and amino acids [20, 33]. Water is more ef- fective as a plasticizer than glycerol, but the most used plasticizer in TPS preparation is glycerol due to its high boiling point, availability, and low cost. Fig- Thermoplastic Starch Blends: A Review of Recent Works 1 Mosab Kaseem, Kotiba Hamad, and Fawaz Deri Department of Chemistry, Faculty of Science, Laboratory of Materials Rheology (LMR), University of Damascus, 31513 Damascus, Syria e-mail: mosabkaseem@yahoo.com Received June 5, 2011; Revised Manuscript Received August 23, 2011 Abstract—The aim of this review is to discuss the recent developments in thermoplastic starch blends. Starch has been considered as an excellent candidate to partially substitute synthetic polymer in packaging, agricul- tural mulch and other low-cost applications. Recently, the starch granules were plasticized using different plasticizers under heating and shearing, giving rise to a continues phase in the form of a viscous melt which can be processed using traditional plastic processing techniques, such as injection molding and extrusion. This kind of starch composites is called thermoplastic starch. Unfortunately, thermoplastic starch presents some drawbacks, such as low degradation temperatures, which make it difficult to process, poor mechanical properties and high water susceptibility. Much work has been carried out to overcome these drawbacks, including the combination of thermoplastic starch with other polymers, aiming at lowering the cost and enhancing the biodegradability of the final product. DOI: 10.1134/S0965545X1202006X REVIEWS