Cel
The overall aims of the research are to look at the basic relationships between structure and properties in thermoplastic starches. On the basis of increased knowledge, it is hoped to develop new technology and improve existing technology concerned with melting processes and mechanisms plasticisation, as well as characterise the molten phase and its time dependent properties. In addition, the project will generate and test predictions of the properties of starch based thermoplastics (TS) and their relationship to raw material sources and processing conditions, as well as to evaluate to what extent the addition of other polymers lead to improved characteristics. A further objective is to identify new outlets for thermoplastic starches, determine areas of application and to identify the best raw materials for such applications.
The objectives of the present project are to develop a scientific and technical expertise on thermoplastic starches (TS) and exploit this knowledge to create new market outlets for starches and starchy fractions. This is a low cost material suitable for production of biodegradable films, coatings and articles which could be used to replace petrochemical thermoplastics in short duration applications eg. coatings, packaging (food and non-food), materials for encapsulation and slow release of active agents such as agrochemicals. Development of applications for starch in non-food areas would considerably enlarge the quantitative demand for starch, and other feedstocks to be used as plasticizers or additives, and will greatly diversify the quantitative demand of these primary products. To achieve these purposes a collaborative research has been organized that integrates pre-industrial, industrial and scientific skills and expertise of the partners.
On a scientific point of view, this programme concerns phase transitions and the time-dependence of the properties of the processed materials, including biodegradability: relationships with raw material composition, structure and the mechanical and thermal history during manufacturing will be investigated. Production of TS from starches and flours from different origins will be scaled up to obtain appreciable amounts of TS. The processability and end-uses properties of such TS will be investigated up to the pilot plant scale, for industrial testing. The backbone of this proposal is to use modern concepts of polymer science in order to establish process-structure-property relationships and enable development of new processes for obtaining optimal material properties. Also the project aims at developing a number of new applications for a range of TS.
Opportunities exist to increase greatly the extent and uses of TS through an integrated approach.
Thermoplastics based on petrochemical resources are widely used for production of films, coatings and food packaging. There are opportunities to replace these with biodegradable products based on starch. However, there is a need to match quality and performance of such novel products with those of the established plastics, at a competitive price. The objectives of this project are to obtain more background information concerning factors of relevance to production and use of thermoplastic starches. In particular, the project focuses on phase transitions and time-dependent changes in properties in relation to biodegradability, raw material composition and chemical structure, as well as mechanical and thermal history during manufacture. The participants are also making various products using starches and flours of varying origin and investigating novel applications.
In the first year the work focused on the following aspects:
- availability, isolation and characterisation of raw materials
- development of preparative and experimental methods
- standardisation of analytical and production methods
- inventory of available equipment
Wet and dry separation technology has resulted in starches and starchy fractions of wheat, smooth and wrinkled pea, maize and rye, providing well characterised materials to the participants. Extruded and compression moulded thermoplastics based on these raw materials are also available.
The melting of starch has been studied using the Flory Huggins model and various parameters derived from studies of the melting and dissolution behaviour of wholly crystalline materials. The effects of low molecular weight solutes have been investigated showing differences between diols and traditional starch solvents. An improved FT IR method for measuring changes in short range order such as helicity has been developed.
Two methods for quantitative analysis of starch crystallinity have been developed. The relation between amylose and amylopectin ratio and the mechanical properties has been studied. Processing studies have established the relation between rheological properties of the melt and molecular degradation during extrusion. Models have been applied to describe and understand this relation and a method for physical depolymerisation has been studied.
Initial experiments investigating the changes in starch structure during extrusion have been performed, showing that during extrusion crystallinity and helicity decrease steadily but other structures appear to be formed that have a significant effect on the mechanical properties. A test device has been developed for compression moulding of starch below and above plasticisation temperature. The glass transition has been studied in detail, showing two transitions at high glycerol content indicating phase separation. Methods for dynamic mechanical analysis and a method for dielectric thermal analysis has been developed.
It was demonstrated that the amount of water present during processing influences the mechanical properties of thermoplastic starch, while various chemical modifications of starch have been carried out to increase hydrophobicity, with both high and low degrees of substitution.
The potential for controlling enzymatic activity in extruders was identified in a two stage extruder. Main variables and operating conditions have been analysed. Twin screw extruders were shown to be useful in continuous starch extrusion with thermo-labile enzymes for controlled chain degradation. A model was developed which showed good correlation with experimental data. A process for production of bleached cellulose from wheat bran and beet pulp has been developed in order to make composites.
Kinetic analysis of retrogradation processes have been carried out and a model for this process was developed. Influence of the composition (amylose/amylopectin ratio, plasticiser content) has been studied. Glycerol was demonstrated to slow down retrogradation.
A method for determination of water sorption isotherms has been set up. This is one of a number of standardised testing methods which have been devised.
Within the project, cooperations and exchanges were set up and an extensive amounts of round robin tests and inventories were made with exchange of knowledge and skills based on comparison of standard samples using common technology and analysis methods, resulting in cooperations between the various groups detailed below.
Dziedzina nauki
- engineering and technologymaterials engineeringcrystals
- engineering and technologymaterials engineeringcomposites
- engineering and technologychemical engineeringseparation technologies
- engineering and technologymaterials engineeringcoating and films
- engineering and technologyother engineering and technologiesfood technologyfood packaging
Zaproszenie do składania wniosków
Data not availableSystem finansowania
CSC - Cost-sharing contractsKoordynator
6700 AA WAGENINGEN
Niderlandy