Package strength and integrity
Adhesive bond strength testing
Delamination of flexible laminated packaging materials is a common cause of pack failure and print quality issues. Adhesive bond strength testing analyses the adhesive forces required to separate the laminated layers of flexible packaging materials.
Biotesting is a form of comparative container integrity testing used particularly during the development and introduction of new or modified forms of containers.
Containers are filled with a microbiological nutrient material and heat processed. The containers are then brought into contact with contaminated cooling water with a known microorganism. Samples are stored and checked for spoilage.
Campden BRI has facilities for packing the containers, processing, storage and microbiological testing.
The burst strength of a flexible pack is a measure of its seal strength and determined by inflating the package with air at a specified rate until it bursts. The position and type (seal or material) of failure is recorded in addition to the burst pressure value. The test is used as a means of evaluating the likelihood of pack failure when exposed to pressure differentials, such as may be experienced in during retorting or air transport. By placing the package between restraining plates, the weakest area of the seals are more likely to be detected as the stresses during pressurisation are more uniformly applied along the perimeter of the pack.
The compression strength of individual primary packaging samples such as cartons, bottles and cans is performed at Campden BRI using a Zwick Z3050 materials testing machine with a 50kN load capacity. Larger transit packaging, including fibreboard cases are also routinely tested for their compression strength.
Creep testing is conducted in a similar way to burst testing. However, a burst test is a measure of pack/seal strength, while a creep test is a measure of seal strength and pack integrity. During a creep test the pack is inflated to a percentage of its known burst pressure and held for 30 ora nominated time 60 seconds for a pass or fail result (in the case of seal leakage). The seals can also be measured for "seal yield" - narrowing of the seals before and after testing as an indication of internal seal peeling.
Drop tests can be conducted on packaging in various orientations and from a range of heights to determine its impact strength.
Dye penetration testing can detect leaks in packs down to approx 10 microns and are conducted over a period of 24 hours. These tests are especially effective for testing leaks in the seal area of the pack.
Internal pressure resistance testing is vital for containers that are intended for carbonated drinks or are otherwise subjected to changes in pressure during their intended use. This mechanical test determines whether the package meets applicable specifications and is fit for the intended use. Testing is carried out using a ramp internal pressure tester. Bottles are filled with water and the pressure is automatically increased until the bottle breaks or can deforms. The burst or deformation pressure value is recorded along with the location of the failure origin if applicable.
Seals are vital to many types of food packaging; however, the role of the seal will differ from one product to another. Depending on the type of package, it may need to have mechanical strength or hermetic integrity, or be easy to open. So, the amount of force required to peel a lidding material from a pack must balance the importance of seal integrity against the requirement of convenience for consumers wishing to open the packs. When designing new pack formats during product development, it is particularly important to keep food safety/integrity in mind. It is also vital to know how seal strength may alter over time or during/after distribution. At Campden BRI, as part of our package testing services, we have the equipment to measure the peel strength of a range of pack formats. The equipment is capable of running at different angles and speeds during a test cycle.
Pendulum impact testing is used to determine the impact resistance, strength and breakage characteristics of a range of different pack formats in order to ensure that they are fit for purpose. Impact testing can be carried out across a range of products including glass and plastic packaging and glassware. Typically, impacts are carried out at the contact point for that particular item, such as shoulder and heel for bottles or the rim of a pint glass and the testing is carried out until failure of the sample occurs. However, testing at other specific impact positions can also be undertaken.
Tear resistance testing can be conducted on sheet and film materials to measure the force perpendicular to the plane of the sheet required to tear single or multiple plies through a specified distance after tear initiation. A Zwick Z050 materials testing machine is used for this test and the results are stated in mN/ply.
A tensile strength test is a mechanical test performed on packaging materials to determine the maximum load force that can be applied to a material before it ruptures or tears. In essence it is a 'pulling' test used to measure the strength of paper, board and plastics. The material will show elastic behaviour up to a certain point and then rupture. The test can be adapted to different needs - it can be used to measure the strength or elongation of a material and its tearing resistance, as well as the force required to separate a seal. T-peel testing is a mechanical strength test conducted in a similar way as tensile testing, but it is performed on a section of a packaging seal to determine the maximum load force that can be applied to the seal before it separates.
Thrust testing is used in the determination of seal strength of pouches by use of a Thrust Pouch Pressure Tester. The thrust test involves the application of a constant pressure for a set period, and the observation of seal integrity after the pressure is released. This gives an indication of seal strength when a constant load is being applied at a set pressure.
Torque testing on (bottle and jar closures) measures the amount of force required to open a jar or bottle closure and should must balance the importance of closure integrity against the requirement of convenience for consumers wishing to open the packs. A Mecmesin Tornado digital closure torque tester is used for measuring application and removal closure torques.
Underwater vacuum / bubble emission testing can detect leaks in packs down to approx 250 microns. These tests are widely used in the food industry as quick off-line checks during production and packing.
You may also be interested in
Where we refer to UKAS Accreditation
Campden BRI (Chipping Campden) Limited is a UKAS accredited testing laboratory No. 1079 Campden BRI (Nutfield) is a UKAS accredited testing laboratory No. 1207