ASTM D3632 Accelerated Aging of Adhesive Joints by Oxygen-Pressure Test

Scope:

ASTM D3632 describes the test to compare the relative abilities of adhesive films and adhesive-bonded joints to resist deterioration in a high-pressure oxygen environment. While it is significant for elastomer-based construction adhesives, which are exposed to the risk of oxygen degradation, it can also be used for other adhesives which may be similarly susceptible. ASTM D3632 applies to wood-to-wood and wood-to-metal joints, as well as free adhesive films. Adherends treated with chemicals can also be evaluated by this test method. The test provides only comparative information and must be evaluated with reference to the known performance of similar bonded joints under natural and accelerated aging environments. The data provided by the test is useful for research and development or in manufacturing quality control.

Procedure:

The ASTM D3632 test method involves exposing specimens with known physical properties to a controlled aging environment for varying durations and noting the changes in their physical properties. Three types of specimens are offered: a wood-to-wood lap joint termed Type A, a wood-to-metal joint named type B, and Type C which is an unsupported film. Types A and B are tested for shear strength of the lap-joint, whereas Type C is tested for flexibility. 

The ASTM D3632 test offers three options for possible exposure durations and property testing frequency. These include constant exposure for either 500 hours or 1000 hours with a single property test at the end and exposure upto 1000 hours, with tests every 200 hours. The aging test apparatus comprises an oxygen pressure vessel with a suitable non-hazardous heating mechanism and temperature controls. 

The specimens must be fabricated as detailed in section 9.0 of ASTM D3632 and then conditioned by oven drying for three days at about 60°C (140°F) under ambient relative humidity and atmospheric pressure before being placed in the oxygen vessel. The aging is done using oxygen at 2.07 Mpa (300 psi) at an elevated temperature of 70° C (158°F). Lap shear testing is done by usual ASTM tensile testing methods, in a testing machine.

Video 01: Oxygen bomb (Air bomb) aging test chamber

Specimen size:

The specimens for the lap shear test must be made from the same adherends and adhesive materials that will be used in service. Several rectangular pieces are cut out from larger pieces to fabricate the specimens. Typically, for ASTM D3632 testing, each rectangular piece is about 102 mm long and 25.4 mm wide.

Result:

Shear strength is reported in megapascals (Mpa).

Conclusion:

ASTM D3632 describes the test to compare the relative abilities of adhesive films and adhesive-bonded joints to resist deterioration in a high-pressure oxygen environment.