Recent Advances in Reactive Extrusion Processing of Biodegradable Polymer‐Based Compositions

Abstract

This review reports on recent advances in the design of biodegradable polymers built from petroleum and renewable resources using reactive extrusion processing. Reactive extrusion represents a unique tool to manufacture biodegradable polymers upon different types of reactive modification in a cost‐effective way. Partially based on our ongoing research, ring‐opening polymerization of biodegradable polyesters will be approached as well as the chemical modification of biodegradable polymers, particularly natural polymers. The development of environmentally friendly polymer blends as well as (nano)composites from natural polymers, including natural fibers and nanoclays, through reactive extrusion, as an efficient way to improve the interfacial adhesion between these components, will be also discussed.magnified image

Sheets of branched poly(lactic acid) obtained by one step reactive extrusion calendering process: Melt rheology analysis

“…Pyrolysis mechanisms should also be considered but at high temperatures (>300ºC) where cis-elimination ( Figure 1e) gives rise to the formation of carboxylic acid groups and a polymer chain containing acryloyl groups [9]. The extrusion process can take advantage of these degradation reaction products when combined with reactive agents, promotes polymerization (chain extension), grafting, branching and functionalization [10]. On one side, reactive extrusion is an attractive way to minimize the degradation effects during processing and to enlarge its processing window.…”

Preparation and properties of biodegradable starch–clay nanocomposites

“…The main challenge for preparing nanocomposites is the nanoscale dispersion of clay in the biopolymer matrix. Montmorillonite is the most commonly used natural clay and has been successfully applied in numerous nanocomposite systems (Giannelis, 1996;Paul & Robeson, 2008;Pavlidou & Papaspyrides, 2008;Raquez, Narayan, & Dubois, 2008;Ray & Okamoto, 2003). However, most of the reported starch-clay nanocomposites suffer from poor dispersion, which is required for obtaining high performance materials (Bagdi, Muller, & Pukanszky, 2006;Chiou et al, 2006;Pandey & Singh, 2005;Park, Lee, Park, Cho, & Ha, 2003;Park et al, 2002;Wilhelm, Sierakowski, Souza, & Wypych, 2003a, 2003b.…”

Water Susceptibility and Mechanical Properties of Thermoplastic Starch–Pectin Blends Reactively Extruded with Edible Citric Acid

“…Reactive extrusion has been successfully applied to TPS polymers 1 and has resulted in more flexible and less brittle TPS materials 5,[26][27][28][29] when compared to similar TPS materials obtained by conventional extrusion. However, few studies have investigated reative extrusion under edible acids and fewer have examined the use of reactive extrusion on cationic starch bio-based polymers 15 and even less have studied high methoxyl pectin polymers or pectin-starch composites and neither are information about such polymers mechanical or barrier performance.…”

“…Cationic and in natura starches were added to pectin in order to evaluate both starches polymers water susceptibility and mechanical properties, when blended by reactive extrusion with pectin in presence of citric acid. Besides of the edible and nontoxic characteristics of citric acid, its utilization is justified also due to pectin ability in forming gel at low pH (normally using citric acid), in presence of high temperature [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] . …”