HeatSeal Reliability - Gasoline Test

Test Purpose: To determine the effect of gasoline on the switch bodies of membrane switches constructed with a Bergquist HeatSeal spacer and with a pressure sensitive acrylic spacer.

Set Up
Standard 3 x 4 matrix switches 2.6” x 3.0” with 3” tails are used for testing. All switches are constructed one month prior to any testing. Spacers tested are as follows:

1) Bergquist HeatSeal spacer - .008” total thickness (.005” base polyester with .0015” of HeatSeal adhesive on each side).
2) Pressure sensitive acrylic spacer - .009” total thickness (.005” base polyester with .002” of pressure sensitive acrylic adhesive on each side).

Pre-testing of switches is performed as in the General Purpose Cleaners Test.

Results
HeatSeal Spacer - After 14 days of immersion in gasoline there were no visual signs of degradation. There were no measurable changes, throughout the 180 hours (14 days) duration of the test, in the insulation resistance measurements.

Pressure Sensitive Acrylic Spacer - Severe dissolving of the PSA adhesive and ingression of the gasoline occurred within the first 2 hours of the test. After 2 hours the parts had failed the insulation resistance test. After fourteen days switches were completely delaminated with only some gelatinous masses of PSA adhesive left.

FIGURE 1: PSA switch soaked in gasoline and green dye for 10 hours indicates substantial fluid ingression and switch delamination.