Packaging Quality Issue & Solutions XVIII

答：

Paperboard molded products (egg holders, fruit holders, food containers, industrial cushioning paper trays) may deform or collapse during storage stacking or transportation under pressure, failing to effectively protect the contents. The strength performance of paperboard molded products differs significantly from that of corrugated cardboard, and targeted testing is required.

Solution:

1) Resistance to pressure test: According to relevant standard methods, place the sample between two parallel pressure plates of the pressure testing machine, apply pressure at a relative speed of (10 ± 3) mm/min, and record the pressure value corresponding to the agreed deformation as the resistance to pressure. The pre-pressure and agreed deformation can be determined according to product design requirements. The test can be conducted by the BCT(box compression tester) KYJ-10K (https://www.linktesting.org/884.html/carton-compression-tester-kyj-10k/)

2) Auxiliary assessment of edge pressure/flat pressure strength: Cut a sample from the flat part of the paperboard molded product and use an edge pressure tester to measure the edge resistance to pressure; conduct compression tests on the flat area and record the yield or failure load.

答：

The folding paper boxes made of white cardstock and gray background white board paper have unstable paper feeding on the high-speed folding machine, incomplete folding, or the finished box bodies are floppy and lack rigidity. The bending stiffness of the paperboard directly determines the forming rigidity of the paper box and the adaptability to the automatic packaging line.

Solution:

1) Bending stiffness test: According to GB/T 22364, using the two-point loading method or the Taibai stiffness tester, measure the paperboard's ability to resist bending deformation, and evaluate its forming stiffness and paper feeding stability. The test can be conducted by the bending tester(https://www.linktesting.org/1858.html/microcomputer-bending-stiffness-tester-lttd-10s/)

2) Crease stiffness test: For the paperboard samples that have undergone die-cutting and creasing, perform small-angle bending along the crease line, measure the bending moment, and evaluate whether the creasing effect matches the folding requirements of the box-making machine to prevent "line bursting" or "incomplete folding". The test can be conducted by the bending stiffness tester (https://www.linktesting.org/1858.html/microcomputer-bending-stiffness-tester-lttd-10s/).

答：

Paperboard molded tableware (such as plates, bowls, and cup holders) will experience a significant decrease in strength when used to hold food containing water or oil. The surface will absorb water, causing the product to soften, deform, and even leak. The water resistance of paperboard molded products is a key performance for food-contact products.

Solution:

1) Water resistance (water droplet method) test: According to relevant standards, using a 0.1 mL non-flowing pipette, take 0.1 mL of distilled water at (20 ± 3) °C, drop it from a height of no more than 20mm onto the test area on the surface of the product, keep the water droplet still and use a stopwatch to time it. Observe whether the water droplet's mirror surface disappears within the specified time. At least 3 different positions should be tested. If any point fails the test, the product is judged as unqualified.

2) Cobb water absorption value determination: Refer to GB/T 1540. Evaluate the water absorption capacity of the paperboard molding surface. Note that the roughness of the paperboard molding surface may affect the consistency of the results. The test can be conducted by the cobb tester(https://www.linktesting.org/4295.html/cobb-absorption-tester-ltkbxs-01/)

答：

When printing paper-based packaging such as paper boxes, paper bags, and labels, problems like dot bleed, solid area exposure, and insufficient clarity of patterns often occur. The root cause is usually the insufficient smoothness of the paper surface, which prevents the ink from being evenly transferred on the uneven surface. Smoothness directly affects the printing performance and appearance quality.

Solution:

1) Smoothness Test: Using the Smoothness Tester, in accordance with GB/T 456, measure the flow rate of a certain volume of air passing through the gap between the sample surface and the glass plate under specified pressure and time. The smoothness is expressed in seconds. The detection range is wide, and it can distinguish the printing suitability of different grades of paper. The test can be conducted by the smoothness tester(https://www.linktesting.org/1019.html/automatic-smoothness-tester-ltbk-10a/)

2) Roughness Assisted Judgment: For samples with abnormal smoothness, roughness testing (air flow method or contact needle method) is conducted in addition to determine the specific features of surface unevenness, providing a direction for adjusting the papermaking or coating processes.

答：

After being slit or placed, the flexible packaging film shows obvious curling (curling towards the printing surface or the heat cover), which causes unstable film feeding, deviation, and misalignment of the seal on the automatic packaging machine. In severe cases, the machine cannot be started normally. The curling is caused by the internal stress on both sides of the film or the inconsistency in moisture absorption/drying degree. It is a common physical problem that affects the operational efficiency of the packaging line.

Solution:

1) Free curling method: Cut the film into specified size square or strip samples, place them flat in a standard temperature and humidity environment (23℃, 50% RH) and let them stand for a specified period of time. Measure the height of the edge curl or the curl angle of the sample to quantify the degree of curling.

2) Temperature and humidity condition comparison test: Test the curling behavior of the same batch of films in low humidity and high humidity environments to determine whether the curling is due to internal stress (independent of humidity) or moisture absorption difference (significant change with humidity), providing a direction for process adjustment.

3) Correlation analysis with friction coefficient/tenacity: Simultaneously measure the friction coefficient and tenacity of the film. Films with severe curling often have abnormal film running friction characteristics, and a comprehensive judgment can be made on the adaptability of the machine operation. The test can be conducted by the COF tester(https://www.linktesting.org/936.html/coefficient-of-friction-tester-ltmxs-06/)