Evaluation of zeta-potential measurements for fibrous polymers
Team Leader: Martin Reischl (University of Graz, Austria)
Abstract:
The surface properties of polymers are the most important parameters regarding the interaction of these solids with other polymers, dyes, surfactants, polyelectrolytes, proteins and all other components of a surrounding phase. The knowledge of surface properties is inevitable for the control and development of technological processes utilising the interaction of the polymer with other substances.
A sensitive parameter of the polymer surfaces charge, hydrophilicity/hydrophobicity and swelling behaviour is the zeta-potential, usually facilitated via streaming potential measurements. Despite its sensitivity, zeta-potential measurements are not easy to interpret and to compare due to numerous influencing factors, from sample preparation to streaming channel geometry.
Aim of this project is the setup of standardized streaming potential measurement methods and procedures for fibrous polymer samples. The standardized procedure will allow sensitive and comparable monitoring of cellulose surfaces and the physical and chemical modifications thereof. This will provide a valuable tool for the characterisation of cellulosic polymer surfaces.
Objectives:
Selection of fibrous polymer samples, which can serve as internal standards and for calibration and verification procedures.
Preparation of procedures for sample preparation, streaming potential measurement and cleaning procedures.
Evaluation of the procedures regarding practicability.
Distribution of samples and procedures to the participating partner institutions.
Statistical assessment and comparison of the results.
Based on the results, setup of reproducible standard methods for streaming potential measurements, revision of current methods to reach best comparability.
One of the main tasks, which have to be fulfilled in the frame of the Fundamental Theme 5 is the characterisation of the surface properties of modified polysaccharide surfaces. The presented standardisation project will provide important information about the measuring and characterisation procedures of streaming potential determination for fibre samples. Measuring protocols will allow comparable monitoring as also high level of reproducibility of measuring results. This standardisation project provides the basis for the unambiguous determination and interpretation of polysaccharide surface properties.
Importance for EPNOE community and industrial partners:
The interaction properties of polysaccharide materials with the surrounding environment are determined by different surface properties like surface charge, polarity, hydrophilicity/hydrophobicity and surface morphology. These interaction properties are important parameters regarding processability of polysaccharide materials, e.g. in cleaning and bleaching procedures as well as in the use of polysaccharides in composite materials in combination with other (hydrophobic) polymers. Zeta-potential measurements offer a good possibility to determine such surface properties. The knowledge of the interaction parameters with other molecules and polymers is of inevitable interest in processing of polysaccharides and in the design of new, functional polysaccharide materials. Therefore, a standardised method for the determination of the zeta-potential will provide the basis for advanced development and production of polysaccharide materials in research and industry.
Importance for the characterisation of the polysaccharide raw materials:
The surface properties of raw materials are important factors influencing efficiency of further processing steps (cleaning, bleaching) of polysaccharide materials. Zeta-potential measurements can provide information on surface conditions, allowing efficient process control. Also for surface modifications of polysaccharides, the knowledge of the starting situation and in succession, the evaluation of the success of surface modifications can be accomplished by zeta-potential measurements.
Importance for the characterisation of polysaccharide processability:
Surface potential, molecular weight distribution and surface morphology are the key parameters in controlling the processability of polysaccharide materials. The surface potential itself cannot be assessed experimentally; therefore use is made of the measurable streaming potential and the calculation of the resulting zeta-potential. With the aid of zeta potential measurements, optimum conditions for the processing of polysaccharide materials in wet-state processes can be evaluated. Therefore, these measurements are a valuable tool in process development and control.
Applicability to the different kind of polysaccharides:
The method of streaming potential measurement can be applied in principle to all water insoluble polysaccharide materials, especially to fibres and films.
Potentiality to transform them into marketable products:
The standardised method of surface characterisation using zeta-potential measurements can in future be offered as a service to companies and research groups working in the field of processing PS materials.