In-line determination of plasticized wheat starch viscoelastic behavior: impact of processing

Advanced Nano-biocomposites Based on Starch

“…By using conventional polymer processing techniques such as extrusion, native starch (also known as raw starch) in the form of granules can be transformed into a molten state with the presence of low content of "plasticizers" such as water and glycerol. This converted form of starch is known as "plasticized starch," "thermoplastic starch" (although its behavior is not totally thermoplastic but more thermo-mechano-plastic (Martin et al 2003)), or abbreviated as "TPS," which can be produced into different end-use forms such as extruded, molded, thermoformed, or blown articles ). Despite of the advantages mentioned above, starch-based plastic materials are known to have limitations such as poor processability and limited properties (e.g., weak mechanical properties, large evolution of properties during aging, and high water sensitivity).…”

Rheological properties of thermoplastic starch studied by multipass rheometer

“…Since TPS is a non-Newtonian fluid (Della Valle et al, 1996;Lai & Kokini, 1990;Martin et al, 2003;Xie et al, 2009), Rabinowitsch correction was applied when calculating the shear rate (Klyosov, 2007):…”

“…In some studies (Lai & Kokini, 1990;Xie et al, 2009), raw starch was first plasticised using a twin-screw extruder; then, a single-screw extruder equipped with a slit/capillary die was used to evaluate the rheological properties of plasticised starch during the second run. Other studies (Della Valle, Colonna, Patria, & Vergnes, 1996;Martin, Averous, & Della Valle, 2003) involved using a slit/capillary die which directly installed at the head of the twin-screw extruder to carry out online rheological measurement of starch for a single run. From the past reports (Cervone & Harper, 1978;Fletcher, McMaster, Richmond, & Smith, 1985;Padmanabhan & Bhattacharya, 1991;Senouci & Smith, 1988;Vergnes & Villemaire, 1987;Willett, Jasberg, & Swanson, 1995), it has been found that thermoplastic behaviour of low-hydrated molten starch normally depends on various processing factors such as temperature, moisture (and plasticiser) content, specific mechanical energy (SME), screw speed, and even extruder barrel pressure; based on the basic shear-thinning model (Á = K˙ n−1 ), various modified rheological models relating to these effects have been proposed to describe the rheological properties of TPS.…”

“…Though some past studies of rheological properties of TPS considered the effect of starch transformation or molecular degradation during extrusion processing (Della Valle, Boché, Colonna, & Vergnes, 1995;Della Valle, Colonna, Patria, & Vergnes, 1996;Lai & Kokini, 1990;Martin et al, 2003;Willett, Millard, & Jasberg, 1997), a very recent finding (Liu, Halley, & Gilbert, 2010) revealed that extrusion degradation process only cause the size distribution of starch molecules to narrow and converge toward a maximum stable size due to both the selective scission and the maximum stable size concept. This means starch melt may achieve a stable structural (and thus rheological) state under processing with shear and heat treatments.…”

Properties and Biodegradation Nature of Thermoplastic Starch

“…This mechanical treatment reduces the crystallinity of starch granules. Figure 1 shows that the viscosity of plasticized starch is of the same order and magnitude as those of synthetic thermoplastics at lower temperatures [Martin et al, 2003]. …”