Plasticized starch-based multilayers

In spite of the number and diversity of studies on multilayer flows and stability, only a few articles [MAR 01b, MAR 02, WAN 00] and patents [AVE04a] have reported on the use of plasticized starch in co-extmsion. Various different stratified stractures have been obtained by co-extrusion with different polyesters such as PQ., PBSA, PLA, PBAT or PHAs [AVE 04a, MAR 02, MAR 01b, WAN 00], 

In comparison to a conventional blend, the biodegradation of a multilayer is modified because of the stratification of its phases. The polyester-based skin first needs to be pierced for the micro-organisms to reach the core of the material, which will then biodegrade rapidly. The kinetics of biodegradation is therefore very specific, and depends, in this case, on the polyester which is used. Thus, it can also be modulated [GAT 02]. 

---

Multilayer coextrusion has been widely used, studied and understood in the domain of synthetic polymers for its effect on the viscosity of polymers, die geometry, layer distribution, encapsulation, and interfacial instabilities, influencing the quality and functionality of the multilayer products. Despite the number and diversity of studies on multilayer flow and stability, only some articles report the use of biopolyester in coextrusion processes. Different stratified structures were processed by coextrusion and studied. But very few studies have been carried out with PHA. Most of these are based on the association between PHA e.g. PHBV, and plasticized starch. Applications of such PHA-based multilayers as commodities are primarily limited by PHA cost and have been until now by PHA availability, and thus attention is being focused on products with plastics constituting only a minor part, such as paper coatings like the plastic film moisture barrier in food and drink cartons and in sanitary napkins. 

MAR 01b] Martin O., Schwach E., Averous L., et al, Properties of biodegradable multilayer films based on plasticized wheat starch , Starch/Staerke, vol. 53, no. 8, pp. 372-... 

Martin, O., Schwach, E., Av6rous, L., and Couturier, Y., 2001, Properties of Biodegradable Multilayer Films Based on Plasticized Wheat Starch. Starch/Starke 53 372-380. 

---