The strength of the joints in corrugated box directly affects its overall structural strength and safety, and the bonding process is the core factor determining the quality of the connection. By optimizing adhesive formulations, adjusting equipment parameters, improving application methods, and strengthening environmental control, the peel strength and durability of corrugated box joints can be significantly improved.
Adhesive performance is the primary factor affecting strength. Traditional starch-based adhesives require dynamic formulation adjustments based on season and production speed. For example, in winter, the gelatinization temperature needs to be lowered to 55-60℃ to avoid insufficient flowability, while in summer it needs to be increased to 61-66℃ to prevent premature gelatinization and decreased tack. Simultaneously, adding crosslinking agents (such as borax) can enhance initial tack, allowing the cardboard to quickly solidify during high-speed production and reducing the risk of misalignment due to movement. Furthermore, the solid content must be controlled to match the production line speed; during high-speed production, the water-to-starch ratio should be adjusted to 2.5:1 to 3:1 to reduce the impact of moisture on cardboard warping.
Equipment precision plays a decisive role in the bonding effect. The gap between the gluing roller and the corrugating roller must be strictly controlled between 0.2-0.25 mm to ensure even glue application and avoid splattering. If the gap is too large, insufficient glue will result; if it is too small, glue accumulation may cause cardboard deformation. Furthermore, the position and wear condition of the guide claw baffles must be checked regularly to prevent glue gaps or vacuum marks due to component aging, which could lead to localized bonding failure. Using a high-precision gluing system can avoid lateral glue splattering or localized accumulation, reducing the risk of cardboard warping and strength reduction.
Optimizing the gluing process is a key step in improving strength. For double- or triple-layer corrugated cardboard, a layered gluing technique must be used to ensure even adhesive penetration of the linerboard, core paper, and linerboard. For example, the amount of glue applied to the linerboard and core paper needs to be adjusted according to material characteristics. For straw pulp corrugated paper with poor water absorption, the glue application amount needs to be increased or a water-resistant adhesive should be used to avoid bonding failure due to insufficient penetration. At the same time, a low viscosity should be maintained during gluing to improve fluidity and ensure that the glue can penetrate deep into the cardboard fibers to form a strong mechanical bond. The quality of the base paper directly affects the bonding process. Base paper with excessively high or low moisture content will lead to poor bonding. For example, base paper with a moisture content below 6% will absorb moisture from the adhesive, resulting in incomplete gelatinization of the glue; while base paper with a moisture content above 12% may absorb heat due to excess moisture, preventing the adhesive from fully curing. Therefore, it is necessary to strictly control the moisture content of the base paper and regulate its temperature and humidity using a preheater and flatbed drying cylinder to ensure the base paper reaches its optimal state before bonding. Furthermore, the water absorption and permeability of the base paper must match the adhesive characteristics to avoid glue seepage or false bonding due to material incompatibility.
Environmental control is a crucial aspect of ensuring bonding quality. The temperature and humidity in the production workshop must comply with GB/T 10739 standards, i.e., temperature controlled at 23±1℃ and humidity maintained at 50±2%, to prevent high humidity from causing the adhesive to absorb moisture or the cardboard to absorb moisture and delaminate. Finished cardboard must be stored in a dry environment to avoid prolonged exposure to a humid environment, which can reduce bonding strength. For pre-formed cartons, avoid stacking them under high temperature and humidity conditions to prevent softening of the joints due to moisture penetration.
Dynamic adjustment of process parameters can further improve adhesion strength. By monitoring parameters such as adhesive application rate, temperature, and pressure online, and combining edge crush strength and compressive strength test results, adhesive ratios and equipment settings can be optimized in real time. For example, in high-speed production, the solid content of the top layer adhesive needs to be increased and the gelatinization temperature lowered to compensate for heat loss during temperature transfer and ensure synchronous curing of the upper and lower layers of cardboard. Simultaneously, using pressure rollers instead of traditional pressure rollers can avoid corrugated deformation caused by uneven pressure, improving the flatness and peel strength of the joints.
Improving the adhesion strength of corrugated boxes requires a multi-dimensional approach, including adhesive optimization, improved equipment precision, improved adhesive application processes, control of raw paper quality, enhanced environmental management, and dynamic adjustment of process parameters. Through systematic improvements, the compressive strength and durability of cartons can be significantly improved, meeting the high-strength requirements of modern logistics for packaging materials.
