1.The migration of packaging printing inks can cause odors in the packaging and even contaminate the contents inside.
答：
The organic solvents (such as toluene, butanone, ethyl acetate) or photoinitiators contained in the ink printed on the outer layer of the packaging bag can migrate through the inner base film into the food, causing the contents to have a pungent "ink smell", even exceeding the food safety limit (total solvent residue > 10mg/m²). This has led to complaints from consumers or investigations by regulatory authorities.
Solutions:
Curing process control: After compounding, thorough curing (hardening) must be carried out. The temperature should be controlled at 40-50℃, and the duration should be no less than 48 hours to ensure that the residual solvents are fully evaporated. After curing, the total amount of residual solvents must be detected using a gas chromatograph. The standard is ≤ 5mg/m² (and no benzene should be detected).
Structural barrier: Between the printing layer and the food-contact layer, add a layer of aluminized PET or EVOH high-barrier material as a physical barrier, effectively preventing the migration of ink molecules to the interior.
2.The packaging was "squashed" or "burst and exploded" due to changes in air pressure during transportation.
答：
Products packaged in PET bottles, iron cans or inflatable containers (such as milk tea and potato chips) may burst and expand due to excessive internal pressure when transported by air or through high-altitude areas due to the decrease in external atmospheric pressure; or after being hot-filled, a negative pressure forms inside the container, causing the container to flatten and deform after cooling.
Solutions:
Inflation ratio adjustment: For inflated packaging (such as potato chips), adjust the inflation volume from "full inflation" to 70% - 80%. Leave sufficient buffer space to accommodate the volume expansion caused by altitude changes.
Pressure balance design: Design a one-way micropore valve on the bottle cap or sealing film (such as the one-way exhaust valve for coffee beans packaging), allowing internal gas to be discharged in one direction to balance the internal and external pressure differences; or use a pressure compensation sheet, which automatically introduces a small amount of air when under negative pressure. The test can be conducted by the leak tester LTY-01 (https://www.linktesting.org/903.html/leakage-tester/)
Packaging enhancement: Increase the wall thickness of PET bottles from the conventional 0.3mm to 0.4-0.5mm, or add reinforcing ribs (circumferential protrusions) to the can body to enhance the mechanical strength of the container against positive pressure and negative pressure. The packaging container’s wall thickness can be measure by wall thickness tester (https://www.linktesting.org/1665.html/wall-thickness-tester-chy-b2/)
3.The packaging becomes wrinkled, affecting its appearance and sealing strength.
答：
After the soft packaging bags are formed or filled, permanent creases (dead folds) that cannot be smoothed out appear on the surface. These creases not only affect the appearance but also often lead to a significant decrease in the heat sealing strength at the crease area, becoming a weak point for leakage. They are commonly found in thick films, multi-layer composite films, or aluminum foil bags.
Solutions:
Film roll flatness control: The supplier is required to control the curl of the film to be ≤ 5mm (that is, the height of the film sheet's warping on the horizontal plane after cutting), and use constant tension winding to avoid uneven internal tension in the film roll, which may cause forming wrinkles. The test can be conducted by the tensile tester (https://www.linktesting.org/7007.html/automatic-tensile-tester-xlw-500n/)
Adjustment of the forming machine angle: On the bag-making and filling machine, finely adjust the gap and angle between the former (forming device) and the guide plate to ensure that the film material folds uniformly and gradually, avoiding the occurrence of "one-step sharp turn" that causes dead folds.
Material heat shrinkage rate matching: For composite films, it is required that the difference in heat shrinkage rate between each layer of base film should be ≤ 2% (detected longitudinally and laterally respectively), to avoid wrinkling during bag making due to different shrinkage stresses after compounding. The shrinkage performance can be conducted by the shrink tester(https://www.linktesting.org/2334.html/thermal-shrinkage-tester-ltrsy-03/)
Preheating treatment: For thick film or aluminum foil composite films, a preheating plate or infrared heating zone (with a temperature set at 40-60℃) is added before entering the forming machine. This allows the film material to be moderately softened, enhancing the extensibility during forming and reducing the occurrence of dead folds.
4.The production date/batch number on the packaging is "blurred" or "has poor adhesion"
答：
The crucial information such as the production date, shelf life, batch number, etc., printed by ink printing or laser coding becomes blurred, smudged or incomplete due to transportation friction, refrigeration condensation water or hand rubbing, resulting in the products being regarded by consumers as "three-no products" or being rejected by supermarkets.
Solutions:
Ink/Substrate Compatibility: Based on the packaging material (PE/PP film, aluminum-coated film, paper box, glass bottle), select a high-adhesion ink with a specific formula (for example, PE/PP-specific ink should contain chlorinated polyolefin resin). Conduct a hundred-grid test during batch replacement to verify the adhesion. The test can be conducted by the Cross-Cut Tester.
Surface treatment before inkjet printing: For materials with low surface energy (such as PE and PP), an electrophoretic treatment machine or plasma treatment gun should be installed before inkjet printing to increase the surface energy from <34 dynes to ≥38 dynes, significantly enhancing the adhesion of the ink.
Complete drying and curing: After inkjet printing, ensure there is sufficient drying space (length ≥ 1 meter) or UV curing lamp irradiation to prevent the ink from being scratched or rubbed off during winding or packaging before it is completely dry.
Wear resistance verification: Conduct a rubbing test before each daily startup - rub the spray code area back and forth with standard cotton cloth 10 times, ensuring the content remains legible; carry out regular refrigeration condensate water tests (place at 4℃ for 24 hours and then remove) to verify durability in humid environments. The test can be conducted by the rub tester (https://www.linktesting.org/1361.html/rub-tester-mcj-05/)
5.After the carton is formed, it may "curl the edges" or "bend and deform" (due to moisture absorption and dampness)
答：
After the cartons have been stored in the warehouse for a period of time, the surface paper or inner paper may develop a wavy "upward curl" or the entire sheet of cardboard may become bent and deformed, preventing the automatic opening machine from picking up the cartons and causing inaccurate alignment during the packing process. The fundamental reason is that after the cardboard absorbs moisture in the storage environment, the moisture distribution among the layers of paper is uneven, resulting in stress deformation.
Solutions:
Moisture-proof packaging: After the arrival of the cartons, the supplier is required to use wrapping film to wrap or add a moisture-proof plastic bag to cover, to isolate from external moisture. During storage in the warehouse, add moisture-proof pallets at the bottom and keep a distance of ≥ 15 cm from the ground.
Paper moisture content control: During factory inspection, the moisture content of the paperboard is measured (using a moisture content tester), and it is required to be controlled within the standard range of 8% to 12% (in accordance with GB/T 6544). When the moisture content is too high (>14%), the paperboard is prone to warping and should be rejected or dried in advance before use. The test can be conducted by the moisture tester(https://www.linktesting.org/4295.html/cobb-absorption-tester-ltkbxs-01/)
Warehouse environment control: In the cardboard storage area, a dehumidifier is installed to maintain the relative humidity at 50% to 60%, especially during the rainy season. At the same time, the storage time of cardboard is limited to within 3 months, following the First In First Out (FIFO) principle.
Anti-softening reinforcement: During the production of cartons, the surface paper uses highly glazed kraft paper (with a glazing degree of ≥ 25g/m²) to reduce the rate of moisture absorption; or a layer of moisture-proof varnish or waterproof coating is applied to the surface of the paperboard. The test can be conducted by the moisture tester(https://www.linktesting.org/4295.html/cobb-absorption-tester-ltkbxs-01/).
