Analysis Of The Compressive Strength of Flexible Packaging Polyurethane Laminating Adhesives
2026,07,18
The composite strength is the core indicator for evaluating the bonding performance of flexible packaging polyurethane laminating adhesives. It directly determines the inter-layer stability of the composite film and is the key to preventing packaging problems such as delamination, glue separation, and bulging. It is widely used in the production of flexible packaging in fields such as food, cosmetics, and medicine. The industry usually uses the T-type peel strength as the testing standard. The peel strength of qualified products should be no less than 100 N/m to ensure the usability and storage reliability of the packaging.
The adhesive formula is the key internal factor influencing the strength of the composite. Polyurethane laminating adhesives consist of a main agent and a curing agent. The ratio of NCO (nitrile carbon-oxygen) groups to OH (hydroxyl) groups is crucial. The optimal industrial ratio range is 1.05:1 to 1.2:1. An imbalanced ratio will result in insufficient cross-linking reaction, decreased cohesion within the adhesive layer, directly reducing the composite strength, and may also cause abnormal curing, boiling delamination and other problems. At the same time, the molecular weight of the polyol and the structure of the resin will also affect the toughness and adhesion of the adhesive layer, determining the peel resistance and tensile strength of the composite film.
The production process and the environment are the key external factors. Insufficient surface tension of the substrate and failure to perform corona treatment will weaken the adhesion of the adhesive layer.Uneven coating thickness and inappropriate curing temperature and time will result in incomplete cross-linking and curing. In addition, the humidity in the workshop has a significant impact. In a high-humidity environment, water molecules will consume the active groups of the curing agent, destroying the network structure of the adhesive layer, causing the adhesive layer to become brittle and significantly reducing the composite strength.
In actual production, it is necessary to precisely control the ratio of the adhesive solution, optimize the coating and curing process, strictly control the temperature and humidity in the workshop, and cooperate with the activation treatment of the substrate surface. This will fully release the adhesive's bonding performance, stably enhance the bonding strength of the composite, and ensure the quality of the flexible packaging products.
