How to test plastic material properties

Technology

Different foods need different types of packaging. Both foods and packaging materials have different sets of properties and it is important to understand what those are when determining the optimum solution, as discussed in selecting optimal solutions: property-based decision making.

Let us have a closer look at packaging. How to test plastic material properties? The answer is simple: by performing laboratory for testing plastics that measure each property individually. Would you like to learn more about these types of tests? Read on to discover which tests we perform at SP Group.

Key plastic material tests:

1. FRICTION TESTS

Some plastics require specific friction properties in order to be used in packaging solutions and packaging devices. Why do the properties of plastic materials change when subjected to friction? This is due to the following factors: the type of polymer or additive(s) used; the manufacturing process; the type of surface structure; and environmental conditions.

We use a coefficient friction measurement device  plastic by bringing into contact a specimen (or two specimens) of plastic with a specimen of metal.

2. TENSILE TESTS

Tensile tests are used to determine the maximum resistance and elongation at rupture thresholds of plastics.

How do you perform this test? By applying a constant axial tension load to a standard test piece until it fractures. You will then be able to study the test results on the graphic.

3. PEEL RESISTANCE TESTS

The purpose of this very useful test is to measure the resistance of adhesive bonds. To perform this test, we use two test pieces and place two bonded materials together (or glued) on one end, and the same unbonded materials on the other end. The resulting graph will illustrate the average peel resistance, indicating if the adhesive bond between the two materials is adequate.

4. WELD STRENGTH TEST

We run this test to make sure containers are leak free – a key property when protecting food, especially food products containing liquids or those that need high barriers. This test is essential when testing the quality of a material used in food packaging, such as top film and bags or pouches.

5. CHROMATORGRAPHY GAS TESTS

This test is performed to ensure residual solvents in plastics do not exceed 10 mg/dm2 as per EU Regulation No. 10/2011 on plastic materials and articles intended to come into contact with food.

This test can detect up to 15 different types of solvents, in addition to the substance used as the internal standard. Our solvent retention limit is 20 times lower than that stipulated by the Regulation.

6. HOT-TACK TESTS

In an earlier post we explained hot-tack testing and how it is key in determining filling efficiency. This test assesses the hot sealing performance of packaging materials during production and when it is most critical.

7. OXYGEN PERMABILITY TESTS

This test measures oxygen permeation in plastic films and packaging, a key property in ensuring adequate food preservation.

8. PUNCTURE TESTS

This is one of the most important tests because it helps determine the penetration or the puncture strength of plastic materials. Punctures may be caused by the shape of the food, or even external causes, so it is important to understand the maximum stress a material can withstand when selecting between materials.

9. TEAR RESISTANCE TESTS

This test is performed at a constant speed and measures the force required to tear multi-layer or laminated plastic films. The test results are very useful when deciding on the type of material to use for bags and pouches that are manually opened.

10. PASTEURISATION AND STERILISATION TESTS

Foods are usually pasteurised or sterilised once packaged. This is why packaging materials need to be able to withstand high temperatures for specific amounts of time. This test can be performed in a bath or autoclave to observe how the material reacts to specific temperatures during specific time periods.

11. ROBINSON TESTS

This is a sensorial analysis method used to determine the possible influence of odour of packaging materials on packaged foods and to ensure the organoleptic properties are not altered. This test must be performed by specialised personnel.

12. PLASTIC BAG PRESSURE TESTS

This test is performed by introducing compressed air into a plastic bag or pouch to identify possible defects along the weld lines. The bag can also be submerged in water which yields faster test results.

13. ANTI-FOG TESTS

This test is performed to determine the anti-fog properties of materials and ensure condensation does not form on the inner surface of the packaging material. A specimen is placed in a refrigerator between 7 and 10 degrees and monitored for 24 hours. This is a testing method we use on a wide range of materials at SP Group.

14. MICROSCOPY ANALYSIS

This type of test allows to determine the structure of materials and research new materials.

15. LAYER MEASURING

This test is very useful to determine the thickness and number of layers that make up films. This test can also detect in microns the thinnest of layers and identify the types of materials that make up the specimen.

16. DIFFERENTIAL SCANNING CALORIMETRY ANALYSIS

This testing technique is used to determine what happens when a polymer is exposed to high temperatures. It evaluates thermal transition properties, such as fusion, crystallisation, glass transition and melting.

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