Packaging

Protective coatings ensure the long shelf life of drinks and foodstuffs or guarantee the sterility of medical products and medications. FISCHER offers proven measurement solutions for testing dividing layers, sealants or protective coatings for pores or fissures and ensuring the right coating thicknesses.

Packaging

Application notes

Testing for porosities in the hermetic sealing of food packaging

Using containers made of paperboard coated with polyethylene and aluminium foils (aseptic carton) is common practice for packaging beverages such as milk or fruit juices. But even tiny defects in the packaging coating systems can lead to spoilage of the product inside.

Beverage cartons must be hermetically sealed, solid, and must extend the shelf life of the contained product by shielding them from light and germs. Depending on the contents, various coating systems are used atop a paperboard base. To protect beverages against oxidation, an aluminium foil is used, while polyethylene foil in turn protects the aluminium against corrosion by acidic liquids such as fruit juices

It is crucial that the polyethylene foil is completely sealed; otherwise, corrosion of the aluminium foil is unavoidable. A well established, simple and effective method to test for the presence of gaps in the polyethylene layer is to use a porosity tester, also called a ‘holiday detector’.

FISCHER’s new POROSCOPE® HV5, equipped with a roller electrode, is ideal for monitoring the continuity of the polyethylene coating that protects the aluminium foil in aseptic carton packaging. The test method is based on the fact that all electrically insulating coating materials have a much higher disruptive strength than air does.

Operation is simple and can be performed by non-technical staff: the test voltage is set on the POROSCOPE® according to the disruptive strength and thickness of the innermost polyethylene layer. Alternatively, a test standard can be selected and a coating thickness can be set. The POROSCOPE® automatically adjusts for the appropriate high voltage. The specimen is grounded and then the electrode is moved slowly across its surface. The voltage drops briefly when the electrode passes a defective spot; a spark-over, accompanied by optical and acoustic signals, indicates the presence of a pore.

Fig.1: POROSCOPE® HV5 with roller electrode

Besides being easy to use, the POROSCOPE® is also compact and lightweight, making it an indispensable portable companion for anyone tasked with quality control on multi-coated food packaging.

The new FISCHER POROSCOPE® HV 5 with roller electrode is perfectly suited for performing the porosity testing required by the food packaging industry. For further information please contact your local partner for FISCHER products.

Measuring the thickness of protective layers inside aluminium cans and tubes

Aluminium tubes and cans are a commonly used as packaging for pharmaceutical, cosmetic or even food products. In order to prevent direct contact and chemical reactions between the container and the contents, the tubes are usually coated inside with a protective polymer layer. The thickness of the coating must be monitored regularly during the application process to ensure the proper function of the protective lining.

For aluminium cans and tubes filled with pharmaceuticals or food, the inner protective layer is critical for preventing chemical reactions between the packaging and the contents; this is why its thickness must be monitored carefully during manufacture. For quality assurance, random samples are periodically removed from the running production process and their linings are measured using the eddy current testing method. However, care and skill are required: these protective coatings are particularly sensitive to pressure. A "normal" probe can easily compress the layer, thus leading to incorrect measurement results.

After being cut, the samples are shaped to form a flat metal strip. For the measurement itself, FISCHER’s probe FTA2.4-SC is ideally suited because of its large contact area and spring-mounted measuring element, which exerts only low contact pressures. The stand V12 guarantees precise vertical guidance and controlled vertical touchdown. The probe can be operated and the results evaluated by the handheld measuring devices from the FISCHER FMP series.

Fig.1: Eddy current probe FTA2.4-SC, attached to the stand V12, measuring a protective layer inside an aerosol can made of aluminium

For processing larger sample quantities, an automated solution is also available with the FISCHERSCOPE® MMS® PC2 and a motorised, programmable stand. In addition to the inner protective layers, the outer skins and coatings can also be measured with these devices.

 

Tube 1

Tube 2

Tube 3

control point

Mean value

Std.
dev.

Mean value

Std.
dev.

Mean value

Std.
dev.

1

12.0

0.09

9.8

0.10

9.8

0.10

2

11.9

0.09

9.8

0.10

9.8

0.10

3

12.1

0.10

10.1

0.10

10.1

0.10

4

12.3

0.08

10.0

0.08

10.0

0.08

5

11.7

0.10

9.9

0.09

9.9

0.09

Mean value

12.0

0.09

9.8

0.10

9.8

0.10

Tab.1: Thickness measurement using the FTA2.4-SC probe on 3 different tubes, 10 measurements at each point. Readings in µm.

To check the thickness of protective coatings inside aluminium tubes and cans, the eddy current probe FTA2.4-SC is ideal due to its low contact pressure. Used together with a handheld or desktop device from FISCHER, the probe enables accurate measurements on these sensitive linings without compromising them with excessive pressure. For more information, please contact your local FISCHER representative.

Your contact to FISCHER

Fischer Technology Inc.
Windsor/United States

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Phone: (860) 683-0781
E-Mail: info@fischer-technology.com
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