Rheology thermoplastic starch

Addition of starch has a nucleating effect, which increases the rate of crystallisation. The rheology of starch/PCL blends depends on the extent of starch granule destruction and the formation of thermoplastic starch during extrusion. Increasing the heat and shear intensities can reduce the melt viscosity, but enhance the extrudate-swell properties of the polymer. 

A review of initial research on processing, rheology and properties of thermoplastic starch is provided by Lai [3] and concentrates on effects of starch... 

WiUett, J.L., Jasberg, B.K. and Swanson, C.L. (1995) Rheology of thermoplastic starch effects of temperature, moisture content, and additives on melt viscosity. Polymer Engineering and Science, 35, 202-210. 

M. Kaseem, K. Hamad, F. Deri, Rheological and mechanical properties of polypropylene/ thermoplastic starch blend. Polymer Bulletin 68 (4) (2012) 1079-1091. 

Aichholzer W, Fritz H.-G. Rheological characterization of thermoplastic starch materials. Starch 50(1998)77. 

Rodriguez-Gonzalez F. J., Ramsay B.A., Favis B.D. Rheological and thermal properties of thermoplastic starch with high glycerol content, Carbohydr. Polym. 58 (2004) 139. 

Shin BY, Lee SI, Shin YS, Balakrishnan S, Narayan R. Rheological, mechanical and biodegradation studies of blends of thermoplastic starch and polycaprolactone. Polym Eng Sci 2004 44 1429-38. 

Willett JL, Jasberg BK, Swanson CL, (1995a) Rheology of thermoplastic starch - effects of temperature moisture content and additives on melt viscosity . Poly. Eng. Sci., v35, n2 202-210. 

Yu, L, Christov, V., Christie, G., Gray, J., Dutt, U., Harvey, T., Halley, P., Coombs, S., Jayasekara, R. and Lonegan, G. (1999) Effect of additives on gelatinization, rheological properties and biodegradability of thermoplastic starch. Macromolecular Symposia, 144, 371. 

Rheological measnrements in time sweep mode for thermoplastic wheat starch (TPS) with 40% glycerol content demonstrate that TPS has excellent thermal stability at 150°C, but becomes unstable at temperatures above 180°C [25], However, it was found that TPS stability is maintained for short time periods at temperatnres up to 200°C. 

The materials that degrade into small stable particles are blends often starches are blended with non-degradable thermoplastics such as PE. The same considerations noted in this section on multiphase polymers hold true for these blends. For instance, the interfacial energy and rheology play a role in the size of the dispersed phases. These blends can often be processed by standard melt forming polymer techniques, by compounding and extrusion into films and fibers and injection or blow molded to form polymer... 

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