JEC COMPOSITES MAGAZINE - Issue #39 - March/April 2008 - 43

Biodegradability and standard tests to measure the biodegradability of polymers in terms of degradation rates in compost and biological oxygen demand (BOD). A specific enzymatic test has also been developed to screen biodegradation kinetics before conducting long-term standard tests. temperature by plasticization. Due to the hydrophilic nature of many amino acids, polyols (such as glycerol or sorbitol) are commonly used to plasticize proteins. We investigated the influence of a number of parameters, including plasticizer type and content, storage conditions, presence of cottonseed shells, presence of lipids, and processing conditions. The results showed that the presence of plasticizers tends to reduce Young’s modulus and tensile strength and to increase elongation at break. This effect is stronger when the plasticizer content and the number of hydroxyl groups from the plasticizer are increased. Storage conditions also have a strong influence on mechanical properties, water being a good plasticizer for proteins. The presence of shells tends to reduce the mechanical performance of films. At very low contents (<2 wt%), shells can promote a positive effect by increasing tensile strength and rigidity. Above 2 wt%, shells reduce mechanical strength, because they act as crack initiators due to their morphology and their poor adhesion to the protein matrix. The presence of lipids reduces the rigidity of materials. A poor cohesion is obtained. This has been attributed to a phase separation between lipids and proteins. Finally, as regards the influence of processing conditions, the best results are obtained when films are subjected to pressure at 120°C. At lower temperatures, film cohesion is poor (low Young’s modulus). At higher temperatures, elongation at break decreases due to potential cross-linking or degradation reactions. The tensile strength/elongation at break curve (Figure 2) shows that the best results are obtained when films containing a low amount of shell Fig.2: Tensile strength as a function of elongation at break for various films prepared in different matter are conditions : plasticized by glycerol and plasticized with processed at 90°C, 120°C, 140°C, 120°C containing shells plasticized by glycerol and triethanolamine and processed at 120°C processed at 120°C. Case study projects COTONBIOMAT – FP5 – Development of biodegradable protein-based materials from cotton seed derivatives using dry technologies Agricultural items like mulching films, silage films, bags and plant pots can be considered as interesting applications in which biosourced and biodegradable polymers could replace oil-based polymers (mainly polyolefins), which generate a huge amount of hard-to-recycle waste. Biodegradable protein-based engineering polymers are challenging alternatives. With a worldwide production of about 33 million metric tons, cotton-seed cakes are currently the most abundant source of plant proteins after soybeans. These products seem to be very attractive for non-food applications such as biodegradable polymers. In most cases, wet processes such as casting are used for these materials; the objective is to be able to use the dry processing technologies (such as extrusion and thermo-moulding) that are currently used for synthetic polymers (Figure 1). Fig.1: Details of a cottonseed – Films obtained after thermo-moulding cotton flour and cakes Cotonbiomat was a research project in the E.U. Commission’s Fifth Framework Programme (FP5) that focused on developing this protein-based biopolymer through dry processes. The Materials Research Centre of the Ales School of Mines became involved in this project, which was managed by the International Agronomy Research Centre CIRAD (Montpellier, France) and implemented in co-operation with South American companies and institutions from Brazil and Argentina. Dry technologies require proteins with a thermoplastic behaviour, i.e. viscous flow at high temperature. In many cases, the glass transition temperature of proteins is very close to their thermal degradation temperature. To widen the processing window, proteins are mixed with small molecules likely to lower their glass transition BIOCOMPOSITES – ADEME/AGRICE – Development of a multilayered starch-based biocomposite for packaging applications Current packaging materials consist of a variety of oil-derived polymers (mainly polyolefins such as polyethylene, polypropylene and polystyrene), metals, glass, paper, or various combinations thereof. Food-grade packaging has to meet specific optimum requirements, especially for storage and interaction with food. Hence, the development of new bio-based food packaging materials can be considered as a tremendous challenge, both for academia and No39 March - April 2008 / JEC Composites Magazine

JEC COMPOSITES MAGAZINE - Issue #39 - March/April 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #39 - March/April 2008