ASTM D991-89 (2020) pdf free.Standard Test Method for Rubber Property-Volume Resistivity Of ElectricallyConductive and Antistatic Products.
These precision and bias statements have been pre-pared in accordance with Practice D4483.Refer to PracticeD4483 for terminology and other testing and statistical concepts.Because of the special nature of this test and its lack ofwidespread use in the industry, a limited interlaboratory Type 1test program was used to assess precision. Two materials(rubber compositions) of different volume resistivity in the form of cured sheets were prepared in one laboratory and sentto the other participating laboratory. Both laboratories wereexperienced in this testing.
In each laboratory the cured rubber sheets were mea-sured for volume resistivity on two days, on each day by twodifferent operators.The within laboratory variation, therefore,contains an “operatorR”and “day” component of variation.11.4 A test result is the median value of three measurementsof volume resistivity.  Table 1 gives the precision results. Due to the widerange of volume resistivity values that are possible (10-1000 fold variation) the analysis was conducted using the (base 10)logarithms of the (test result) volume resistivity，p.
The rather large between laboratory variation indi-cates the difficulty frequently experienced with this measure-ment by experienced laboratories and operators.In test method statistical terminology, bias isthe difference between an average test value and the referenceor true test property value. Reference values do not exist forthis test method since the value or level of the test property isexclusively defined by the test method. Bias, therefore,cannotbe determined.The electrical behavior of rubber products used inparticular applications is important for a variety of reasonssuch as safety，static changes, current transmission，etc.Thistest method is useful in predicting the behavior of such rubberproducts.
The electrode assembly (Fig. 1)shall consist of a rigid base made from an electrically insulating material having a resistivity greater than 10 T-m (forexample, hard rubber, polyethylene, polystyrene, etc.) to whicha pair of current electrodes and a pair of potential electrodes arefastened in such a manner that the four electrodes are paralleland their top surfaces are in the same horizontal plane.Anotherpair of current electrodes identical with the first pair shall befastened to a second piece of insulating material so that theycan be superimposed on the specimen directly above the firstpair.The current electrodes shall have a length at least 10 mm(0.4 in.) greater than the specimen width,a width between 5and 8 mm (0.2 and 0.3 in.), and a height uniform within 0.05mm (0.002 in.) between 10 and 15 mm (0.4 and 0.6 in.).Thepotential electrodes shall have a length and height equal to the current electrodes and shall be tapered to an edge having aradius of 0.5 mm (0.02 in.) maximum at the top surface.ASTM D991 pdf download.