The relationship between the thermal adhesion of packaging materials and filling efficiency

      The heat sealing performance of packaging materials is the main index to evaluate the packaging performance of materials, including hot adhesion and heat sealing strength, and the peeling force of the heat sealing part of the material in a short time after heat sealing (has not yet cooled) is the hot adhesion of the material (HotTack), and the heat sealing strength (UltimateStrength) is the peeling strength of the heat sealing part after complete cooling, and these two indicators of the same material are very different. However, in fact, the good application of these two indicators is often directly related to the selection of packaging materials and the actual filling efficiency, this paper takes the selection of packaging materials in the filling production line as an example to introduce the application and analysis and evaluation of the thermal adhesion of the materials.

1. The use of hot adhesion

Today, most flexible packaging filling in food, medicine, cosmetics, and other fields uses Form-Fill-Seal Machine. In these filling production lines, the production process of flexible packaging bags and the filling process are carried out at the same time, and the way of product filling is basically that the product falls into the packaging bag from a certain height and has a strong impact on the bottom of the packaging bag, if the bottom of the packaging bag can not withstand the impact force will appear bottom cracking - broken bags, not only will affect the cleaning of the production environment, but also affect the filling efficiency. Since the interval between the two-step operation of heat sealing bag and content filling in the filling production line is very short, and it is impossible to completely cool the heat sealing part of the packaging bag in such a short time interval, it can be seen that the heat sealing strength of the packaging material is not suitable for the evaluation of the heat sealing performance of the material here, and the thermal adhesion of the material should be used. Optimizing the heat sealing process during packaging is widely recognized as an effective way to shorten packaging cycle times, and thermotack testing can help operators select the optimal heat sealing parameters.

Therefore, the difference between the application of hot adhesion and heat sealing strength is very clear, hot tack performance is used to ensure the normal operation of the filling production line, and its suitability directly affects the filling efficiency and bag breaking rate; The heat sealing performance is mainly used to evaluate the storage performance of the material to ensure that the heat sealing part will not leak during transportation, storage and display, which is the premise for realizing the functionality of packaging materials.

2. Case study

By detecting the thermal adhesion of materials, how should the optimal line heat sealing parameters be selected? Let's take the customer test commission accepted by Labthink Lab as an example to introduce the relationship between hot adhesion and the selection of heat sealing parameters in the production line.

The customer is a food production enterprise in Southeast Asia, and wants to choose one of the two kinds of films A and B with similar performance indicators to meet the bag-making requirements of the production line and make the production line have high filling efficiency. Due to other factors, the hot tack time and seal pressure that the line can provide have been determined, and the hot cover of the material has also been determined. The customer requires that the heat sealing temperature of the packaging material is not higher than 133 °C, the hot adhesion is not less than 2N, and the heat sealing time should be shortened as much as possible on the basis of meeting the above requirements, while taking into account the principle of energy saving.

We use LabthinkHTT-L1 thermotactic tensile tester to detect the hot adhesion of A and B films, the heat sealing time is set to 0.3s, 0.5s, 0.7s, the heat sealing temperature is set to 115°C, 118°C, 121°C, 124°C, 127°C, 130°C, 133°C, other indicators are set according to customer requirements, and the width of the test specimen is 25mm according to customer requirements.

In fact, there is a most suitable temperature point to achieve the optimal thermal adhesion of the film material, and when the heat sealing temperature exceeds this temperature point, the thermal adhesion will show a downward trend. From Figures 1 and 2, we can see that the optimal heat sealing temperature for film A is about 130°C, while the optimal heat sealing temperature for film B is about 127°C.

Data analysis, for film A, when the heat sealing time is 0.3s, the thermal adhesion does not meet the customer's requirements; When the heat sealing time is 0.5s, the hot adhesion of the material when the heat sealing temperature is between 127 °C ~ 133 °C can just meet customer requirements; When the heat sealing time is 0.7s, the heat adhesion of the material in the range of 127 °C ~ 133 °C can better meet the requirements.

Therefore, for film A, only when the heat sealing time is greater than 0.5s and the heat sealing temperature is 127 °C ~ 133 °C can meet the customer's requirements for the thermal adhesion of the material. The hot adhesion of film B under the same heat sealing parameters is much better than that of film A, when the heat sealing time is not less than 0.3s and the heat sealing temperature is between 118 °C ~ 133 °C, it can meet the customer's requirements for hot adhesion; And with the increase of heat sealing time, the required heat sealing temperature drops significantly, when the heat sealing time increases to 0.7s, the heat sealing temperature is at any temperature point in 115 °C ~ 133 °C, film B can meet customer requirements.

Referring to the above test data, we believe that film B should be used, and the heat sealing parameters of the production line can be set to: heat sealing time of 0.3s~0.5s, heat sealing temperature of 118 °C. Of course, the heat sealing temperature point should also be determined by further testing to determine the optimal value, but it should be noted that the hot adhesion should leave a certain margin to avoid the problem of insufficient strength due to uneven heat sealing caused by heat sealing mechanism factors or material factors. From the material analysis alone, we believe that the use of A specimen will reduce the filling efficiency and increase the energy consumption of the production line, but further data analysis should also take into account the cost of packaging materials and the optimal working efficiency of the entire production line.

3. Summary

If you want to reasonably set the heat sealing process parameters of the filling line, you should mainly consider the thermal adhesion of the material. Using the hot viscosity tensile tester, we can adjust the heat sealing time, hot viscosity time, heat sealing temperature and heat sealing pressure at will, and analyze the best parameter combination mode from the test data chart combined with the actual situation of the production line. Of course, material costs should also be taken into account to achieve the optimization of production costs and production efficiency.