Milk, jelly, bean curd box, can't these packages be well torn?

Jelly and milk lovers are hurt a lot.

(this article is first published in the fruit shell)

for a long time, I have some opinions about the milk carton packaging called "fresh house".

these boxes are clearly printed with diagrams of the steps to open it, but it is not always easy to get a neat opening. Sometimes, pushing hard forward as shown in the picture did not open the seal, but split the packaging cardboard in the middle, making a mess.

(I can open it like this when I play well)

not only milk boxes, but also when tearing open packages sealed with plastic film. The seals of a jelly, a cup of yogurt or a box of tofu can sometimes be so tight that people doubt life.

(a box of tofu that tore the lid film and failed to open it)

this makes me wonder: can't these packaging seals be made to open better?

is it torn? blame the heat seal for being too strong

the similarity between the jelly lid and the milk house carton is that they are both heat-sealed, and consumers need to open the package from the heat-seal position. The same is true when you want to tear it neatly from the top of the snack bag instead of tearing it along the sawtooth.

the essence of heat sealing is to use some thermoplastics as "glue" to stick the opening. These plastic films, which act as adhesives, are located in the inner layer of the package, and the thermal seal heats the parts and presses them together, allowing the partially melted plastic to stick to the seal.

(machine encapsulated jelly | sezmak makina)

ideally, these wrappers should be separated from the heat seal again when opened. And if the heat seal is very strong, then hard tearing will cause the package to be destroyed first in other locations.

contradictory demand

the strength of the heat seal can be adjusted by adjusting the heat seal temperature and the composition of the heat seal layer, but it is not so easy to find the most ideal heat seal strength. This is because these seals need to meet two contradictory needs at the same time: it has to be closely matched in transportation and storage in order to maintain the quality of the product, but it has to be not so strong in order to uncover it smoothly.

the seal is not easy to tear open, and seal failure is a more serious problem-which directly leads to the birth of unqualified products. As a result, people who design packaging always want to make the heat seal as tight as possible as far as it can be torn apart. In this way, it may not be so easy to tear open the seal neatly.

moreover, in order to speed up production, the producer may also increase the temperature of the heat-sealing equipment, so that the heat-sealed interface can reach a high enough temperature in a shorter time to seal faster [1]. If the sealing temperature becomes too high, it will cause the heat seal to combine too closely.

(encapsulated milk carton Alan Chiong)

how to solve this problem?

how to balance the heat seal in contradiction? Some experiments show that the most important factor affecting the heat sealing strength is the temperature, compared with the change of sealing pressure and time is not very great. Therefore, if you do not change the formula of the heat seal, then accurate control of the temperature is a solution.

however, it is not easy to accurately control the heat sealing temperature on a fast pipeline. Fortunately, there are several techniques to change the design of the thermal seal, which can be lowered in the loose temperature control and the contradiction between "sealing" and "easy to tear".

Are you puzzled how to buy the appropriate dress but of the right price? lilac-colored bridal party attire is the solution. Let them shower you with a display of exquisite taste.

for example, in the production of heat-sealed films, two polymer materials that are not very compatible can be mixed together, which reduces the strength of the heat-sealing layer and makes it easy to "split" from the inside. In this way, even if the two layers of heat-sealing materials are fully integrated and difficult to separate from each other during heating, the heat-sealing materials can still be split from the inside when the force is applied, which is called "cohesion peeling". In addition, there are also design options to make the bonding strength between the hot seal layer and the core layer of the packaging material not too large, easy to peel off. For the packaging of jelly cups with different lid and body materials, it is also important to consider the consistency of the two materials.

(cohesion peel diagram, the white part is mixed with another polymer (usually polybutene), it makes it easier for the heat seal to crack from the inside (drawn by the author)

and for the milk roof carton, there is also a patent that provides a simpler solution: a small weakly sealed area can be left in the following image to facilitate opening [2]. (according to my observation, there is often a small piece of fresh house in the three-yuan 250ml that is not sealed, but I don't know if it is a deliberate design.)

(a design idea of the easy-to-open house carton: leave a weak sealing area in the red area in the picture.

of course, another simple, rough and very effective way to open

is to give up separating the hot seal. Open it directly from somewhere else. For example, producers can put extra lids on roof-shaped cartons and add easy-to-tear sawtooth to hot-sealed snack bags. In this way, the heat seal only needs to ensure that the seal is firm.

(some jagged bags can also be opened from the heat-sealed position, but this one in the picture is really sealed like welding. But anyway, people have left you sawtooth.)

or in the end, at least we have scissors.

references

httPs://journals.sagepub.com/doi/abs/10.1177/8756087906071351

https://patents.google.com/patent/EP0331792A2/en

http://www.bomotong.com/a/hangyezhiku/zhikuguandian/2018/0417/238.html

https://www.mitsuichemicals.cn/techno/feature/feature04.htm