Verifying Polyethylene Hydrostatic Balance Test Calibration for Entry
Polyethylene hydrostatic testing requires degassed, temperature-corrected fluid baths and void-free plaques to prevent false 0.002 g/cm³ receiving rejections.
Deionized Water Degasification
Meaning
High-precision density measurement of polymer samples via hydrostatic weighing requires an immersion medium that is free of dissolved gases. Deionized water degasification is the process of removing dissolved air and carbon dioxide from pure water before using it as the liquid medium for displacement measurements. This step governs the reliability of the buoyant force calculation by preventing micro-bubbles from forming on the suspended polymer specimen.
The boundary of this process is reached when the dissolved gas concentration falls below the threshold where nucleation occurs at the test temperature.
Fluid Preparation
Standard water absorbs ambient air until it reaches thermal and chemical equilibrium with the surrounding environment. Laboratory procedures perform deionized water degasification using vacuum exposure, boiling, or ultrasonic agitation. This pre-treatment ensures that the water density matches standard reference tables with high precision.
Measurement Error
Small air bubbles adhering to the sample can skew density readings.
Experimental Procedure
The test specimen is lowered into the treated water on a thin suspension wire to measure its submerged weight. If deionized water degasification is incomplete, microscopic bubbles will cling to the textured surface of a moulded polymer sample, artificially increasing its buoyancy and leading to an underestimation of its density and crystalline fraction. Maintaining a degassed state is therefore critical throughout the testing cycle.