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How to Check Quality of PET Bottles?

PET bottles are widely used for packaging and storing. Due to its strong barrier properties against moisture, water, humidity and dust, PET bottles are perfect to use for liquids, powder and solid contents. Despite having some predefined parameters, the manufacturer has to do some mandatory tests, before declaring it fit to use. Before conducting any tests, the manufacturer should be aware of subjected real-life conditions, the storing conditions, warehouse conditions, transportation, etc. To satisfy the working conditions, a series of tests can be performed.


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Preform testing – Polariscope is used to determine the defects in the preforms. Usually, PET preforms allow the light to pass quickly through the medium. If there is any manufacturing defect, the incident light would refract from its path and create briefringes of colour waves. The preform is tested in two angles, 90° and 45°. This is actually not a test, instead, an inspection. Operator investigates the set up visually and takes the decision appropriately.

Top load testing – This test determines the load bearing capacity of the bottle or jar, depending upon the industrial demand. A top load tester applies force on the test sample from the top, until deformity occurs. The other way to assess the load bearing capacity is, preset the load in the machine and investigate if any deformity occurs when a certain load is applied to the bottle. This test is an important part of the quality check. If the buckling appears from similar spots, repeatedly, this means there is a defect in the moulding process or preforms are faulty. Thus, mass production can be postponed and
preforms can be sent for reconsideration.


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Sectional weight measurement – This is one of the most important tests of PET bottles. In this test, a hot wire bottle cutter cuts the bottle into 3 equal sections. The three sections of the bottle are neck, wall and base. The manufacturer knows that for getting perfectly balanced bottles, every section has a certain weight. Three sections are cut without any deformity and weighed separately. If there is any discrepancy in the weight, this requires to reconsidered the moulding process. This is a very important test when a newly shaped bottle is about to get manufactured or in R&D process.

Bottle burst testing – In this test, the bottle is tested for pressure bearing capacity. The bottle is clamped in bottle burst tester and a pneumatic pressure is created inside the bottle. The bottle is made to hold this pressure for some time or pressure is exerted till it bursts.

For more information regarding top load tester, bottle burst tester or any other PET bottle testing machine, contact us.


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