Thermoplastic Waxy Starch Films Processed by Extrusion and Pressing: Effect of Glycerol and Water Concentration

Abstract

Thermoplastic starch properties depends of plastification process. The aim of this study was to analyze the effect of concentration of glycerol and water on plastification, glass transition temperature (T g ) and tensile properties of thermoplastic waxy starch (TPWS). Formulations were extruded in the following concentrations of starch/glycerol/water: 70/30/0 (TPWS 0%); 70/25/5 (TPWS 5%); 70/20/10 (TPWS 10%) weight percentage. Crystalline peaks in WAXS diagrams and native grains present in SEM micrographs showed that the TPWS 0% and 5% were not sufficient to promote total plastification of the waxy starch, and TPWS 10% showed the higher starch plastification. T g measurements by DMTA were 30 ºC to TPWS 0%, 23 ºC to TPWS 5% and 40 ºC to TPWS 10%. These results showed that glycerol and water had effect plasticizer in TPWS 5% and antiplasticizer in TPWS 10%. Mechanical tensile results showed that higher tensile strength was observed in the systems with more effective starch plastification.

Development of an Indicator Film Based on Cassava Starch–Chitosan Incorporated with Red Dragon Fruit Peel Anthocyanin Extract

“…Although the use of starch provides high economic value because it is inexpensive and easy to obtain, starch-based films have low elasticity and heat stability and are easily soluble in water [ 18 ]. The addition of chitosan and plasticizer in the form of glycerol is able to form a composite film that is more elastic, strong, heat-stable, and not easily penetrated by water [ 19 , 20 ]. In addition, chitosan has antioxidant and antibacterial properties [ 21 ], and is able to control the release of bioactive compounds, making its use in indicator films able to increase the responsiveness to pH [ 22 ].…”

Thermal, Morphological, and Mechanical Properties of Regular and Waxy Maize Starch Films Reinforced with Cellulose Nanofibers (CNF)

“…Features great capability to form a colorless and transparent polymer matrix, and it is also a heterogeneous material containing different concentrations of amylose and amylopectin 5 . The amylose content in waxy starch is lower than 5%, whereas ranging from regular starch 15-30% and high amylose starch 35-70% 6 .…”

“…However, it is possible to observe smooth inhomogeneous clusters in micrographs N3, W1, and W3. According to Manoel et al (2017) 6 , this fact can occur due to a possible formation of bubbles and/or partial gelatinization.…”

Advantages and Disadvantages of Bioplastics Production from Starch and Lignocellulosic Components

“…Apart from casting, other conventional methods of large-scale industrial production (e.g., extrusion and injection molding) are applied for bioplastics manufacture [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Single-screw and twin-screw extruders are the two main types used for polymer processing.…”