ASTM D7836 Measurement of Yield Stress of Paints, Inks, and Related Liquid Materials

Scope:

ASTM D7836 method for stress measurements has been useful in establishing root causes of flow problems such as extreme orange peel and sagging etc. The stress ramp applied to the material exceeds the yield stress of the material. Torque increases the rotation of the spindle and the value of the torque is converted into a yield stress value. The yield stress value may be measured by discrete temperature, and in this way, the material can be tested within its packaging.

Procedure:

As per ASTM D7836 testing, the yield stress can be measured in three ways. Test Method A uses a viscometer with coaxial shear stress versus shear rate which determines the dynamic yield stress. “Dynamic” indicates that the material has been allowed to flow and that the yield stress value is mathematically calculated. Test Method B uses a stress rheometer to determine the yield stress value. As torque is applied to the spindle, the yield stress in the material increases. The stress reading at the onset of spindle rotation is the yield stress value for the material. Test Method C uses a rotational viscometer. The vane spindle is rotated slowly at a fixed speed. The yield stress value is determined when the torque value reaches a maximum.

Video 01: Overview of viscosity and yield stress

Result:

Through the above-mentioned methods, the yield stress of paints, inks, and related liquid materials can easily be determined.

Conclusion:

ASTM D7836 method for stress measurements has been useful in establishing root causes of flow problems such as extreme orange peel and sagging etc.