Process for determining the rheological properties of materials

摘要

A process and an apparatus determine the rheological properties of medium samples. The normal forces arising in a measuring gap perpendicular to the measuring surfaces are recorded with a recording unit and the height of the measuring gap is adjusted with a positioning unit and with positioning elements actuated by the positioning unit. During the measuring procedure the initial height of the measuring gap is kept constant, by the values of the normal forces arising being linked with a calibrating function, and in that, upon detection of normal forces arising, values derived from the calibrating function are drawn upon as control signals, with which at least one sliding actuator acting on at least one of the two measuring elements is driven, which by position adjustment or height adjustment of the respective measuring element performs an immediate resetting of a height of the measuring gap, changed by the normal forces exerted by the medium sample to be examined, to the initial spacing set originally.

主权项

1. A process for determining rheological properties of medium samples disposed in a measuring gap formed by measuring surfaces facing towards one another of two measuring elements of a rotary rheometer being rotated relative to one another, which comprises the steps of:
measuring normal forces arising in the measuring gap perpendicular to the measuring surfaces with a recording unit and evaluating the normal forces via an evaluating and control unit; adjusting a height of the measuring gap with a positioning unit and with positioning elements actuated by the positioning unit, the positioning unit adjusting the positioning elements carrying the measuring elements relative to one another; and during the measuring process a value that has been set in a given case of a predetermined initial height of the measuring gap is kept constant in a substantially delay-free manner, by values of the normal forces arising being linked with values of a calibrating function ascertained previously in each case, and made available by a memory unit, the calibrating function describing a functional dependence between one of a change and enlargement of the height of the measuring gap and a normal force acting in the process in each instance on the measuring elements and, upon detection of the normal forces arising, the values derived from the calibrating function are drawn upon as control signals, with which at least one sliding actuator acting one of directly and indirectly on at least one of the two measuring elements substantially in delay-free manner or applying force to the measuring elements is driven, which by one of position adjustment and height adjustment of the respective measuring element performs an immediate resetting of the height of the measuring gap, changed by the normal forces exerted by the medium sample to be examined, to an originally set initial spacing.