Introduction
In the packaging and labeling industry, the preparation of polyethylene terephthalate labels often involves the process of coating pressure-sensitive adhesives on the surface. As a key equipment to achieve uniform coating, the operating parameters and sample processing methods of the coating machine directly affect the adhesion, uniformity and durability of the coating. This paper aims to discuss the experimental sample preparation method of coating the surface of polyethylene terephthalate labels for coating machines, combined with relevant technical standards and process principles, to provide reference for industry practice.
Coating machine working principle
The coating machine controls the movement and pressure of the coating head through a precision mechanical structure to evenly apply the pressure-sensitive adhesive to the surface of the substrate. Its core process includes three stages: glue supply, coating and curing. The glue supply system ensures a stable flow of adhesive; The coating head (such as a scraper or roller) is applied at a set speed and gap; Subsequent curing can be promoted by heating or UV irradiation to promote the formation of the adhesive layer. Coating thicknessdIt is often roughly described by the following formula:
d = k × (v / ω)
Among themkis the constant related to the properties of the adhesive,vrepresents the coating speed,ωRepresents the angular velocity of the coating head rotation. This relationship shows that the coating thickness can be effectively controlled by adjusting the mechanical parameters.
Experimental sample preparation steps
A systematic process is required for the preparation of polyethylene terephthalate label coating samples. First, the substrate is cleaned and corona treated to improve surface energy. The applicator parameters are then set according to the adhesive characteristics, including coating speed, pressure and temperature. After coating, the sample is cured in a controlled environment and tested for thickness and uniformity. The key steps are summarized as follows:
| Substrate pretreatment | Clean and dust removal, corona treatment improves wettability |
| Adhesive blending | Mix in proportions and let stand to defoam |
| Coating parameter setting | Speed 1-10 m/min, gap 50-200 μm |
| curing conditions | The temperature is 60-80°C, and the time is 1-5 minutes |
| Performance Testing | Thickness measurement, peel strength test |
Impact analysis of key parameters
The coating quality is affected by a combination of factors. The coating speed directly affects the thickness and uniformity of the coating: too high a speed may lead to thinning or streaking of the adhesive layer, while too low a speed can easily cause buildup. The coating pressure needs to match the flatness of the substrate, and if the pressure is insufficient, the adhesive layer will not adhere firmly, and if it is too high, it may damage the substrate. Ambient temperature and humidity can also affect the rheological properties of the adhesive, and it is recommended to operate at a temperature of 23±2°C and a relative humidity of 50±5%. The combination of parameters can be optimized through orthogonal experiments to achieve the desired coating effect.
Frequently Asked Questions and Countermeasures
During the experiment, you may encounter phenomena such as uneven coatings, bubbles, or poor adhesion. Uneven coatings often stem from wear or parameter misalignment and can be mitigated by regular calibration of equipment. The bubble generation is mostly due to insufficient adhesive defoaming or too fast coating speed, which can be improved by vacuum defoaming and reducing the speed. Poor adhesion may be related to inadequate substrate treatment, and strengthening surface pretreatment or adjusting adhesive formulation are effective countermeasures. The system records operation logs to help trace back to the root cause of the problem.
Conclusion
In the experiment of coating the surface of polyethylene terephthalate labels on the coating of pressure-sensitive adhesive, the quality of the sample depends on the equipment parameter setting, substrate pretreatment and process control. By understanding the coating mechanism and standardizing the operation process, coating samples with uniform thickness and stable adhesion can be obtained. In the future, the application of automated control and real-time monitoring technology in improving coating consistency can be further explored.
References
1. Fundamentals of Coating Technology, Journal of Materials Processing, No. 3, 2020.
2. Pressure Sensitive Adhesive Performance Test Method, Industry Standard Compilation, 2022 Edition.
3. Research on Polymer Surface Coating Process Parameters, International Journal of Coating Technology, Vol. 5, 2019.