Omega Products SG401 Installation Manual

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SG401 and SG496

Rapid Cure Strain Gauge

Adhesives

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User’s Guide

SG401 and SG496 Rapid Cure Strain Gauge Adhesives

1

SECTION 1 - INTRODUCTION

OMEGA’s Rapid Cure Adhesives, SG401 and SG496 are modified
versions of a solvent-free cyanide-acrylate adhesive specially developed
to apply strain gauges of the bonded-resistance type. They are suitable
for all series of strain gauges and compatible with most metals of
common use and with most synthetic materials. They are not suitable,
however, for use with porous materials such as concrete, wood, foam
plastic, etc.

This series of Strain Gauge Adhesives is supplied in three different
packages. Their part numbers and weights are listed below:

SECTION 2 - SETTING AND CURING NOTES

Polymerization (setting) of cyanide-acrylate adhesives occurs by the
catalytic reaction of moisture absorbed from the air. The most favorable
conditions are given by a relative humidity (RH) between 40% and 70%.
In the case of RH less than 30%, the reaction is noticeably retarded and
in extreme cases, completely stopped. More than 80% RH causes shock
setting. Internal stresses in the adhesive layer caused by shock setting
reduce the maximum extensibility of the bond. One should, therefore,
always ensure that the limit values of 30% and 80% RH are not
exceeded.

Complete setting in the given time is achieved only with thin films.
Thick layers of adhesive set very slowly and incompletely; therefore,
extremely rough contact surfaces are unsuitable.

The setting speed depends on the chemical condition of the components
to be bonded. Alkaline materials accelerate polymerization, whereas
acid materials not only retard but can completely prevent setting. (In the
latter case, a neutralizer should be used.) Representative figures for the
setting time and its dependence upon the quoted materials at a
temperature of 20°C (68°F) and an RH of 65% are given in Table 2-1. At
the end of these periods, the adhesive will have set sufficiently to allow
cable connection to be initiated. Ultimate curing is achieved after some
24 hours. However, measurements can be taken after the periods quoted
in Table 2-2.

Part Number Net Weight

SG401 0.10 oz.
SG496 1.00 oz.

SG401 and SG496 Rapid Cure Strain Gauge Adhesives

2

TABLE 2-1

MINIMUM SETTING TIME FOR BONDING

TABLE 2-2

MINIMUM CURING TIME FOR MEASUREMENT

SECTION 3 - PREPARING THE SURFACE

The object of preparation is to create a smooth surface that can be
wetted. The following steps, which require attention or can be bypassed,
depends on the condition of the test piece.

3.1 Coarse Cleaning

Rust, scale, paint, and other such contaminants must be removed from
the test area and its surroundings.

3.2 Smoothing Surface

Pitting, protrusions, scratches, and other such imperfections must be
removed by grinding, filing, or other suitable methods.

3.3 De-greasing

The choice of a cleaning agent depends on the nature of the
contamination and whether the surface is adversely affected by a given
cleanser. Powerful grease solvents such as Freon TF, Chlorothene NU,
methyl-ethyl-ketone, acetone, and trichlorethylene are normally used.
Wax and similar substances dissolve in toluene.

The surface to be cleaned should be washed with gauze pads soaked in
solvent. Initial treatment should cover a somewhat larger area than that
which is ultimately required. As each new pad of gauze is taken, the
zone that receives attention should be progressively reduced to
minimize the possibility of continually introducing new particles of dirt
from the edges of the zone. Large areas can be brushed with water and
an abrasive powder (e.g. AJAX, COMET, etc.). After rinsing, there
should remain a surface which is completely wetted with an unbroken
film of water. The surface is then dried with a clean cloth (paper towel)
or by heat. Ultrasonic cleaning baths or steam degreasing apparatuses
can also be used with good effect.

Material Setting Time

Steel 60 to 120 sec.

Aluminum 50 to 100 sec.

Plastics 10 to 60 sec.

Type of Curing Time

Measurement At 5°C (41°F) 20°C (68°F)

Dynamic 90 min. 10 min.

Static 120 min. 15 min.