Scope:

The Micro Tensile test by ASTM D1708 measures the force necessary to crack a sample and how much the sample extends or elongates till the point of breakage is achieved. Comparative tensile strength and elongation properties of plastics in the form of standard microtensile test specimens are determined under defined conditions of pretreatment, temperature, humidity, and testing machine speed. The data obtained is used for material specification, components to withstand application force, and material quality control.

Test Procedure:

For the ASTM D1708 test, specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, are considered as per the guidelines given in the materials specification. Samples are put in a specific grip separation in the grips of the Universal Test Machine and pulled until failure at a slow speed. Extensometer is not used and also tensile modulus is not measured. 

Elevated or Reduced Temperature Test Procedure:

The Universal Test machine is equipped with a thermal chamber. This chamber allows traveling across the top and bottom of the chamber on the foundation and the crosshead of the Universal Tester. Inside the chamber, standard measurement devices are mounted and the thermal monitored atmosphere is tested in the same way as it is at ambient temperature. The chamber has internal electric heaters to maintain high temperatures and external carbon dioxide is used as the coolant to lower temperatures. The size of the chamber limits the maximum elongation that can be reached.

Sample Size:

Samples can be die-cut, machined, or molded. The samples are dog bone in shape, 38 mm15 mm overall in size, 5 mm x 22 mm in the gauge area.

Data:

The following calculations can be done using tensile test results:

Tensile strength (at yield and at break) 

Elongation and percent elongation at break 

Elongation and percent elongation at yield

Conclusion:

ASTM D1708 is a standard test method which determines the tensile and elongation properties of plastics in the form of standard microtensile test specimens.