How to choose high quality carton adhesive (3)

Adhesive strength

The adhesive must first have sufficient adhesive strength to ensure that the adhesive does not affect the function of the paper product. To determine whether the bonding strength of the adhesive is acceptable, the two adhered materials can be torn along the adhesive interface. If it is found that the adhered material is damaged after tearing, it is proved that the adhesive strength is sufficient; if only the adhesive interface is separated, it indicates that Adhesive strength is insufficient.

Sometimes the binder with poor performance will be debonded and the film will be brittle after being stored in high temperature or low temperature environment for a period of time. Therefore, it is necessary to perform high temperature thermal deformation and low temperature embrittlement experiments to determine whether the quality is reliable.

The test method of high temperature heat change is to put the carton that has been completely cured at the bonding place in a constant temperature oven at 60° C. and bake it for 24 hours. After cooling, the hand taps the joint of the carton until it separates, and tears if adhered. It shows that the heat resistance of the adhesive is good. If the adhesive material is intact, only the bonding interface is disengaged, indicating that the heat resistance is not enough; the low-temperature embrittlement test method is to put the paperboard with the completely cured adhesive at -15°C. In the environment, it was frozen for 24 hours. The method of determination was the same as that of the high temperature thermal deformation test method.

Drying speed

When choosing an adhesive, it must be measured whether the drying speed matches the bonding process. The general hand-bonding process is slower and requires a longer initial drying time, while the machine-bonding process is faster and requires a shorter initial drying time. In terms of thorough time, the vast majority of cases require the sooner the better, so that we can enter the next process as soon as possible.

Viscosity

Viscosity is the most important factor affecting the quality of adhesives. If the viscosity is too large, the coating is thick, the amount of glue is large, drying is slowed down, and the wetting and penetration of the adhesive on the surface of the adherend are also affected, thereby directly affecting the adhesive strength; if the viscosity is too low, the coating is applied. The layers are thin, dry quickly, and are prone to problems such as poor adhesion. Therefore, packaging companies must constantly check the viscosity to ensure that the bond strength is within the desired range. The ideal viscosity range for various adhesives is not the same, such as 50 ± 15 seconds for corrugated paper board adhesive, 50 ± 10 seconds for automatic paper glue, 70 ± 15 seconds for manual paper glue, and glue for stick boxes. 4000mPa. S～7000mPa. S and so on.

Solid content

Solid content is also one of the important factors affecting the quality of the binder. The higher the solids content, the stronger the adhesion and the faster the drying speed. In particular, for the corrugated board processing technology and the affixing process, the higher the solid content of the binder, the quicker the initial dry and dry time of the cardboard and the higher the production efficiency. Cardboard with a binder with a high solid content absorbs less water, and the cardboard produced has good hardness and is not easily warped and deformed. Therefore, under the same conditions of other technical indicators, high solid content will help improve production efficiency and maintain the quality of paper products.

pH value

Synthetic resin adhesives are mostly weakly acidic and do not negatively affect the bonding process and paper products, but water glass and starch binders are more basic. The high alkalinity not only causes corrosion to workers and equipment, but also sometimes corrodes the adherends, forms marks that affect the appearance, and reduces the moisture resistance of the paper products. Therefore, the impact of pH on the product must be taken into consideration when purchasing the adhesive.

For corrugated paperboard adhesives, it is necessary to purchase starch, caustic soda, borax and other materials for self-adhesives. The quality of starch materials should be strictly controlled. The water content of starch should not be too high and should generally be maintained at 12% to 18%; the protein in starch The content should not exceed 1% of the content is better than 0.5%.

At present, the most commonly used starches include corn starch and tapioca starch, corn starch binders are more prone to retrogradation, but strong adhesion; tapioca starch binders are more stable, but the adhesion is not as good as corn starch binders. In the procurement of starch, may wish to do occasional testing of starch to ensure the quality of the adhesive. (Finish)