Bottle packings are popular in every industry, from carrying liquids to powder and solids. They are fit to contain every form of product. Plastic and glass are two materials by far which are perfectly keeping the contents safe. You must have also seen metal bottles, like deodorant, insect killer spray, cleaning agents, etc. Metal bottles are fit for carrying chemicals, but they are prone to corrosion. This is why metal bottles are seldom used widely. Also, they contribute a lot in increasing the price of the product. Glass and plastic being cost effective is preferred choice.
Testing of PET bottles
A good bottle should have good balancing and stability, consistent wall thickness, no air bubbles or other deformities. To check all these parameters there is a wide range of testing instruments. But before all that, we need to check the preforms for perfect shape. Preforms are blown moulded to make full sized bottles. Sometime, these preforms have defects which further get passed to final product i.e. bottle. These defects might lead to product failure. To avoid that, polariscope is used. It’s an optical device with two polaroid lenses and an incident light. The PET preform allows the light to pass completely without any reflection or refraction. If there is any defect, the light would get refract doubly and create birefringence effect of light.
The preforms are tested at two angles, 45° and 90°.
Only defect free preforms are further blow moulded into bottles. A series of tests is performed on these bottles. This helps in assessing the working behaviour of the bottles in real conditions.
Testing of Glass bottles
Some of the testing procedures are as same as Pet bottle testing. However, glass bottles don’t undergo bursting tests etc. If the quality manager wants to do the same, there are specially designed machines with closed cavities, to avoid any mishap when bottle bursts.
Glass bottles are again check for any defects and air bubbles using polariscope strain viewer. In glass bottles also, it works with the same principle. But the strain viewer for glass has special features to analyse strain on glass.
Apart from strain, the bottles are tested for their balancing and wall thickness. All thickness gauges, like Magna Mike 8600 allows the operator to check the thickness without cutting the bottle into sections. The balancing property of the bottle can be analysed by checking the depth of the base with respect to height of the bottle. Base clearance tester accurate measures the depth of the base and circumference.
For more information about testing of glass and PET bottles, contact our experts.