© WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001 0038-9056/2001/0808-0368 $17.50+.50/0 368 Starch/Stärke 53 (2001) 368–371 Research Paper 1 Introduction Starch has been considered for many years as a polymer with a high potential [1–3] for packaging applications be- cause of low cost, renewability and biodegradability. The feasibility of starch processing using plastic processing equipments has long been demonstrated [4]. During the extrusion of starch, the combination of shear, temperature and plasticisers allows to produce a molten thermoplastic material by disruption of the native crystalline granular structure and plasticisation. This plasticised starch could be suitable for injection moulding or thermoforming. How- ever, only a small number of industrial applications can be presently observed. In fact, different weaknesses limit the utilisation of plasticised starch in packaging applications. Major drawbacks are water sensitivity [5], change of me- chanical properties with time [6] (crystallisation due to ageing and plasticisation by water adsorption) and low impact strength resistance. For thermoforming applica- tions, these weaknesses are especially important due to low wall thickness of the produced objects. In previous publications, we have investigated the behav- iour of blends between plasticised wheat starch (PWS) and polyesters [7– 9]. Mechanical properties of such ma- terials are in good agreement with classical rules of mix- ture. Among the different commercial polyesters tested [9], BAK (Bayer, Germany) and Eastar Bio (Eastman, USA) seem to offer a significant degree of compatibility with the starchy phase. For the different polyesters test- ed, an important decrease in water sensitivity has been measured, whatever the PWS and polyester type and content. Unfortunately, for thermoforming applications, such blends cannot provide sufficient stiffness due to in- trinsic softness of the polyesters tested. Several studies demonstrated the general interest in cel- lulose fibres used as reinforcement for thermoplastic ma- terials [10– 12]. We have investigated the behaviour of PWS/cellulose fibres composites by means of (Dynamic Mechanical Thermoanalysis) (DMTA), tensile and impact strength measurements. Applications of such materials for thermoforming purposes are reported. Packaging stor- age conditions are also tested. 2 Materials and Methods Wheat starch was obtained from Chamtor (France). Cel- lulose fibres (Arbocel) were provided by Rettenmaier (Germany). The characteristics of the fibres are given in Tab. 1. Glycerol was a 99% purity grade according the supplier (Chamtor). This plasticiser was used without fur- ther purification. Luc Avérous a , Christophe Fringant b , Laurence Moro a a UMR INRA/URCA (FARE), CERME: Materials and Packaging Research Centre, ESIEC , BP1029, 51686 Reims Cedex 2, France b ARD – Agro-industry Research and Develop- ment, Rte de Bazancourt, 51110 Pomacle, France Starch-Based Biodegradable Materials Suitable for Thermoforming Packaging* In previous works, we had shown that blending plasticised wheat starch (PWS) with biodegradable polyesters improves properties such as the water resistance. The pres- ent study was more specifically based on PWS/cellulose fibres composites. In addition, these multiphase systems (blends and composites) have been tested with respect to thermoforming applications. The composites shown an increase in modulus and strength, improved temperature stability and glass transition shifts. After sheet extru- sion, each type of materials (blends and composites) was thermoformed. The ageing of the resulting thermoformed trays was tested in storage conditions from 4 °C to am- bient temperature, composites based-materials show reduced ageing compared to PWS. Keywords: Plasticised wheat starch; Packaging; Thermoforming; Cellulose fibres Correspondence: Luc Avérous, UMR INRA/URCA (FARE), CERME: Materials and Packaging Research Centre, ESIEC, BP1029, 51686 Reims Cedex 2, France. Phone: (+) 33-326 913399, Fax: (+) 33-326 913803, e-mail: luc.averous@univ. reims.fr. Tab. 1. Cellulose fibres characteristics (99.5% leafwood cellulose). Fibre type Fibre length (L) Diameter (d) L/d Ratio B600 60 μm 20 μm 3 BC200 300 μm 20 μm 15 B400 900 μm 20 μm 45 * based on a lecture presented at the Food Biopack Conference, Copenhagen, August 27–29, 2000.