ASTM D7025 Assessing Clean Flax Fiber Fineness

Scope: 

ASTM D725 test method offers two ways to evaluate the fineness of clean loose flax fiber. First, calculation of the specific surface area by the resistance offered to airflow by a plug of flax fibers under set surroundings. And second, by the determination of the mass per unit length. Results are reported in SI units.

Test Procedure:

In ASTM D0725 test procedures consisted of two options as stated below.

Option 1- Certain mass of loose flax fibers is compressed to a fixed volume in a specimen holder. A cotton fiber instrument is used to measure the resistance to airflow. The value is converted to a specific surface index using the flax linear density.

Option 2- Mass and length measurement of a bundle of a known number of single fibers and evaluation of the average linear density of the single fibers.

There need not be any relation between the results obtained from the above-mentioned methods. Option 1 is given preference in case of vague results.

Specimen Size:

Option 1- Specific Surface Index Fineness

The test specimen is selected by random sampling from laboratory samples and then passed through a mechanical blender to open and blend fibers. The laboratory sample is conditioned to moisture equilibrium for testing which is 21 ± 1 °C and 65 ± 2% relative humidity. The amount of specimen needed is 5 g.

Option 2- Linear Density Fineness

Three specimens are selected at random from each laboratory-sampling unit. The amount of specimen needed is 0.5–7.5 mg of fibers of the specified length.

Data:

The resistance to airflow readings are converted to specific surface index fineness values using the following equation:

SSI = (J₁×R) – J₂

Where:

SSI = specific surface index

R = resistance to airflow reading

J1 = 0.899

J2 = 2.023

Conclusion:

ASTM D7025 is a standard method for measuring flax fiber fineness.