Surface Preparation for PVC and Rubber Specimens

As some members of the user community know well, strain gages are applied to a wide range of material surfaces.  During the training of strain gage installation, examples and projects are generally undertaken with aluminum beams for convenience.  However, there may be significant variation in surface preparation when one moves away from the metallic materials to those having less frequent strain gage testing.    

Two such materials requiring different surface preparation for strain gage installation are polyvinyl chloride (PVC), frequently used for producing water pipe, and rubber.  Both have a smooth finish that must be “roughened“ for good adhesion to the strain gage but must not be abraded in the conventional way as done with metals.

The section of the specimen to which strain gages are to be installed should first be cleaned with an isopropyl alcohol,  then by scouring with a household cleanser like Comet, followed by rinsing with water.  This takes the place of standard abrading steps with abrasive papers and M-Prep Conditioner A, neither of which is suitable for PVC or rubber surfaces.

Continue by marking the specimen with gage alignment marks as needed, scrub with a cotton-tipped applicator and M-Prep Neutralizer 5A, and carefully dry the surface using a single, slow wiping motion with a gauze sponge.  Without the use of abrasive papers or acidic conditioner, the surface is now fully prepared for gage installation.   
As some members of the user community know well, strain gages are applied to a wide range of material surfaces.  During the training of strain gage installation, examples and projects are generally undertaken with aluminum beams for convenience.  However, there may be significant variation in surface preparation when one moves away from the metallic materials to those having less frequent strain gage testing.    

Two such materials requiring different surface preparation for strain gage installation are polyvinyl chloride (PVC), frequently used for producing water pipe, and rubber.  Both have a smooth finish that must be “roughened“ for good adhesion to the strain gage but must not be abraded in the conventional way as done with metals.

The section of the specimen to which strain gages are to be installed should first be cleaned with an isopropyl alcohol,  then by scouring with a household cleanser like Comet, followed by rinsing with water.  This takes the place of standard abrading steps with abrasive papers and M-Prep Conditioner A, neither of which is suitable for PVC or rubber surfaces.

Continue by marking the specimen with gage alignment marks as needed, scrub with a cotton-tipped applicator and M-Prep Neutralizer 5A, and carefully dry the surface using a single, slow wiping motion with a gauze sponge.  Without the use of abrasive papers or acidic conditioner, the surface is now fully prepared for gage installation.