PETpla.net Insider 10 / 2016

CAPPING / CLOSURES 46 PET planet Insider Vol. 17 No. 10/16 www.petpla.net 4.8 Test Procedures Supply of closures for beverage containers involves a myriad of testing procedures to ensure that the caps perform satisfactorily in use and are safe for consumers. To become a supplier to a beverage bottler involves completing a thorough certification procedure. Once completed, there will be recertifications on a yearly basis as well as production audits. When a sig- nificant change in an existing design has been made, another extensive certification process may be required. Out of the large number of tests, we have chosen the most common ones for 28mm closures for carbon- ated beverages to give readers a good overview of what is involved. The values mentioned here might differ depending on the beverage company. 4.8.1 Proper ApplicationTest Filled and capped bottles are cut off underneath the support ring and placed in a pressure chamber. They are then pressurized to 6.9bar (100psi) and held there for 1 minute. No cap can leak at this position. Next the pres- sure is increased to 12bar (175psi) and held there for 1 minute. No cap can release any pressure at this point. After removal from the chamber, caps are closely inspected for any damage. 4.8.2 Top-load Vent Test Capped and filled bottles are con- ditioned for 48 hours in an environ- mental chamber at 40°C (104°F). A top load of 45.5kg (100lb) is applied. No headspace gas may vent during the loading of the bottle. 4.8.3 Cold Removal Torque Test Capped bottles are stored in an environmental chamber at 2-4°C (35- 40°F). Caps are examined after 24 hours and 1, 3, and 6 weeks. They are slowly unscrewed. When the maximum torque is reached, the value is noted as the seal torque. When the tamper band breaks, the value is noted as the band torque. Accept- able values for maximum torques are 19.6kg cm (17in lb). 4.8.4 Ambient Removal Torque Test Capped bottles are stored at 20-24°C (68-75°F). They are exam- ined for seal and band torque as described in the previous section in intervals of 24 hours and 1, 3, 6, 9, and 12 weeks. The same values obtained earlier are acceptable. 4.8.5 CycleTest at Elevated Temperature Capped bottles are placed in the controlled circulating air oven that is preheated to 42°C (108°F). The temperature is then increased to 60°C (140°F) and held for 6 hours. Then it is reduced to 32°C (90°F) and held for 18 hours. This temperature cycle is repeated three times. All caps must stay on the bottles, but leakers and cocked caps are allowed. 4.8.6 Vent/Flow Performance Test Filled and capped bottles are cut off underneath the support ring and placed in a pressure chamber. The current position of the cap on the bottle is marked, and a pressure of 5.5bar (80psi) is applied. Now the technician slowly opens the closure and notes the so-called vent angle when the closure starts emitting gas. The technician then notes flow rates at various angles until the closure comes off. There is no pass/grade in this test but these values are important to ensure that the clo- sure will vent all gas contained in the bottle before it comes off. 4.8.7 Strip Torque Test Bottles are conditioned at 38°C (100°F) for 1 hour. The warm bottle is then clamped and the cap rotated in clockwise direction until it jumps off the threads. The torque value is then recorded as the strip torque. A mini- mum strip torque of 34.6kg cm (30in lb) is required to pass. This test ensures that the closure will not fail during capping. product development caps & closures design high cavitation moulds multi-component moulds closure production systems after sales service competent – professional – inspiring Hoechster Strasse 8 | 6850 Dornbirn | Austria | www.z-moulds.com K-Show 2016 October 19th-26th meet us at the Eisbär booth in Hall10 / H46 Moulds at the K-Show 28mm 1881 FlipTop Fontana @KraussMaffei in H15 / C24 Cap 29/25mm 3-start water @Blue Air Systems in H10 / H60