REACTIVE EXTRUSION FOR FORMING STARCH-BASED BIOPACKAGING

TOMY J. GUTIERREZ; GUARÁS, MARÍA PAULA; ALVAREZ, VERA ALEJANDRA

Biopackaging

CRC Press

Lugar: San Luis; Año: 2017; p. 288 - 316

Reactive extrusion (REx) combines mass and heat transport operations, which together with simultaneous chemical reactions taking place inside the extruder, modify the properties of existing polymers or generate new ones. This process is increasingly becoming recognized as a powerful technique to develop and manufacture a variety of novel polymeric materials in a highly efficient and flexible way. The combination of chemical reactions and transport phenomena in an extruder provides an invaluable window of opportunity for the compatibilization of synthetic resins and biopolymers such as starch, or the compatibilization of synthetic resins and natural fillers.REx was developed in the 1980´s primarily for the modification of synthetic polymers. Since then, however, the technology has been rapidly developed and applied in various areas such as viscosity-breaking, polymerization, grafting, cross-linking and coupling reactions, amongst others.The use of extruders as chemical reactors enables high viscosity polymers to be processed in the absence of solvents giving large operational flexibility due to the broad range of processing conditions available, for example,pressure (0-500 atm) and temperature (70-500 oC), the viability of multiple feed systems, and the capacity to control both residence time (distribution) and the degree of mixing (van Duin et al. 2001).Examples of this process in the literature emphasize the fact that the use of extruders has changed in recent decades from the preparation and modification of polymers for the plastics industry, to the creation of thermoplastic materials, new and unusual resins and other synthetic polymers for industry using REx (Xie et al. 2006).The most widely used reactive extruders are still single-screw and twin-screw extruders. Single-screw extruders generally have three basic zones: a primary feed zone, a melt zone and a pump zone (Fig. 1). The most common types of twin-screw extruders are co-rotating ones with intermeshing screws. These are suitable for many reactive processes as they give excellent control of residence times, superior mixing intensity, good heat transfer and are self-wiping (White et al. 1987).