The Expanding Role of Semi-Conductive Polyurethane in Electro-Photographic Systems

Abstract

This paper explores the increasing use of semi-conductive polyurethane materials in dry toner Developer, Charging, Cleaning, Intermediate Transfer and Transfer functions, and Developer, Intermediate Transfer and Squeegee functions in liquid toner systems. If you design or specify semiconductive polymer materials for these functions, this paper will provide information on the important design characteristics to communicate to the polyurethane manufacturer. Also discussed is a common language for those specifications and for identifying testing and measurement methods for those characteristics. Testing and measuring methods of Volume Resistivity and Electrical characteristics are explored in detail. A common formula for specifying resistivity is explained and the effect of time, temperature and humidity on this measurement are discussed. Basic molding and machining processes used are reviewed briefly at the beginning of this paper, as are application descriptions. The major functional and quality characteristics to be determined and considered for these applications are:a) Electrical Properties; Volume Resistivity, Change in Volume Resistivity over time (and/or over total energy transmitted), Change in Volume Resistivity under differing temperature and humidity conditions, Other electrical properties such as R/C charge-decay time and Refresh rate and relation to nip residence time.b) Physical Properties: Compression Modulus and Durometer [JIS or Shore] (relation to nip width), Tensile, Tear, Shear and Cut Strength, Resilience, Compression Set, Wear and Abrasion Resistance, Surface Energy and release characteristics and COF. Chemical and ozone resistance, Surface roughness, Load and Dynamic properties (tan-δ, Hysteresis and balancing issues)c) Base Chemistry: Material class or base polymer group (i.e. Polyester or Polyether Polyurethane and how this relates to Chemical Resistance and Hydrolytic Stability.), and the use of differing conductive agents in these systems.d) Attribute Defect Criteria and Dimensional tolerance issues.