Quality Guaranteed
Simple viscosity and texture tests can help to ensure the quality of both a product and its packaging. by Robert McGregor, Brookfield Engineering Laboratories, Inc.
Figure 1. The Brookfield CT3 texture analyzer in tension mode can evaluate the force required to tear a seal open. | R&D managers worry about how customers perceive their products, whether they be food, cosmetics, or personal care products. Thus, manufacturers perform quality-control (QC) checks for viscosity and texture to guarantee customers receive what they expect.
Food manufacturers, for example, measure viscosity to certify proper flow behavior of sauces and dressings and texture to ensure the chewing action feels right for cookies and crackers. Cosmetics suppliers measure viscosity to make sure skin lotion has the proper consistency, flows out of the tube or bottle without difficulty, and rubs onto the skin in a comfortable manner. This same method applies to any manufactured material used by consumers, such as shampoos, paints and lubricants.
Furthermore, the adhesives, inks and coatings used for these packaging materials also require viscosity measurement and control. Manufacturers want to provide durable, attractive packaging because customer-appeal is first satisfied by the appearance of the container.
The ease with which the consumer opens the package is an equally important issue and may warrant a QC check to ensure acceptable performance. A packaged food product should neither open too easily, suggesting an incomplete or loose seal, nor require the strength of Hercules to pull it apart. To avoid both of these scenarios, a texture analyzer (Figure 1) can be used in tension mode to evaluate the strength of the packaging’s seal, quantifying the amount of force required to pull a seal or wrapper apart or open a box or container.
The requirement for quantifying viscosity behavior is the same for all types of materials, including beverages, rubbing lotions, inks or adhesives. Measuring their viscosity determines the consistency of the materials. Suited for this purpose, a rotational benchtop viscometer provides a quick pass/fail indicator once the measurement is made. Normally a specification already exists for the choice of spindle, rotational speed, time of rotation, operating temperature, torque range and sample volume. If, however, there is no specification, then either supplier information or a characterization test run by R&D is used to create one. When implemented in QC, the approach is to define a target viscosity value and then specify acceptable limits around that number.
Spindle selection is one of the decisions that must be stated in the test specification. Products such as food items and shampoos can be measured with a standard cylindrical or disc spindle in a 600-mL beaker because there is plenty of material for testing.
Cosmetics, adhesives, and inks, however, may necessitate working with a small sample volume due to the limited availability of material. Consequently, an accessory device like Brookfield Engineering Laboratories’ Small Sample Adapter or a separate instrument such as the Cone/Plate Viscometer may be more appropriate for measuring viscosity. These devices use significantly smaller amounts of material and achieve temperature control more rapidly.
For some adhesive materials, such as hot melts, the viscosity measurement is made at elevated temperature. The Brookfield Thermosel system provides rapid heating to test small sample sizes quickly and efficiently.
In this competitive economy, the small details can move the consumer to choose one product over another. These simple tests will help to guarantee the quality of both the product and its packaging.
CONTACT
For more information, contact Robert McGregor at r_mcgregor@brookfieldengineering.com or 800-628-8139.
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