ASTM D1505 Density Gradient Tube Testing for Plastics & Polymers

Scope:

The ASTM D 1505 standard test method says that a solid’s density is an easily measurable property that can help with identifying it, keeping track of physical changes in a sample, and showing that samples are consistent with each other. This testing procedure is intended to produce findings that are more accurate than 0.05%.

Test Procedure:

The first procedure is to wet three representative test specimens with the less dense of the two liquids used in the tube and then carefully place them within the tube. The next step, which normally takes 10 minutes or more, is to wait for the tube and specimens to reach equilibrium. It is advised to recheck a few hours after settling for thin films with a thickness of 1 to 2 mils, which typically takes about 112 hours.

 Reading the height of each float and specimen is crucial. To do this, a line is drawn through each center of the volume, and the three values that result are averaged. The height of the floats and specimens should be measured using a cathetometer from an arbitrary level, using

by drawing a line through each object’s volume center. If the balance cannot be reached, the specimen might be soaking up the liquid.

A wire screen basket attached to a long wire must be progressively withdrawn in order to remove outdated samples without messing up the gradient. The use of a clock motor makes this convenient. After cleaning, the basket should be properly reinserted into the tube by being gently dragged out from the base. Importantly, this process must be carried out slowly (approximately 30 minutes per 300-mm length of the column), in order to preserve the density gradient.

Video 01: Density-gradient centrifugation

Test Specimen:

A component of the item being tested must be the test specimen. The piece must have dimensions that allow for the most precise measurement of the center of volume of the suspended specimen, but it can be cut into any shape that makes identification simple. When cutting, exercise caution. sample to prevent density changes brought on by compressive stress.

Data:

In this ASTM D 1505 standard test method, use interpolation to calculate the density as follows:

               x = a +x-yb-az-y

 Where,

The two standard floats’ densities are a and b;

The distances between the two standards, a and b, used to measure the unknown from a specific level are y and z; 

x is the height of the unknown above the same degree of arbitrariness.

Conclusion:

For precisely determining the density of plastics using a density-gradient method, the ASTM D 1505 Standard Test Method for Density of Plastics by Density-Gradient Technique is an essential technique.