Why is the profit of high-end steamed bag twice as high as that of ordinary bag, There are a lot of problems caused by discoloration, peeling strength reduction, bag burst, etc. in light cases, downstream manufacturers will lose their orders when returning goods, and in serious cases, they will have to compensate a large amount of costs for the contents of downstream products. Now the author often encountered the problem of bag burst to do an analysis.
According to Raoult's law, the pressure of liquid vaporization in absolute space is determined by the amount of liquefiable substance. Under normal pressure, each mole of liquid can be given an atmospheric pressure of 22.4l space after complete vaporization. Taking GB / T 1o004-1998 "cooking resistant composite film and bag" as an example, it is required to pack 4% HAC, 1% sodium sulfide (Na2S), 5% sodium chloride (NaCI) aqueous solution and refined vegetable oil respectively in the packaging bag, and then conduct the exhaust sealing and put it into the back pressure cooking pot for test. We often think that the temperature has been accurately controlled, there is enough back pressure when cooling down, or there is often a bag burst phenomenon.
We know that the cooking performance of high-temperature cooking bags mainly includes whether the pattern changes color, whether the composite is open, whether the film is wrinkled, or whether the strength of the bag changes before and after cooking. It seems that whether the bag burst is not in the scope of investigation. However, as a manufacturer of cooking bags, the food factory will inspect your cooking bag rate when using your bags. If it exceeds 3%, it will be judged as unqualified as a whole. To be sure, the burst bag must be because the pressure inside the bag is higher than that outside the bag. The same problem is also explained in the water boiling test and ts-25c back pressure cooking test, that is, bag burst phenomenon. So why put the cooking bag into the cooking pot and hear the crackling sound when it is heated to nearly 100 ℃. Is it that the bag starts to burst when it is heated? What is the reason?

1. First analyze the boiling bag, put the water into the bag according to the regulations, and then exhaust and seal it. After careful observation, we found that the air was not discharged completely. The heating process before 100 ℃ shows that the time sealed glass ball represents the closed bag. It can be seen that the expansion of the boiling bag is normal during heating. The reason is: when the water is sealed at room temperature, the pressure inside and outside the bag is balanced. When the temperature is heated to 98 ℃, the liquid water itself will expand, and the air in the bag will expand. At this time, part of the water vapor generated will occupy part of the space, leading to expansion. At this time, the pressure in the bag will increase. In order to support the above conclusion, we used ZY-1 positive pressure tester and dk-98-1a water bath pot of Beijing landmec to carry out qualitative test. During heating process, the pressure in the bag did increase, and the degree of increase was related to the proportion of the sample and the residual air to the maximum volume of the bag, and to the amount of residual air. If the ratio of water to bag is high, the pressure is high; if there is much residual air, the pressure is high. The burst of the bag is caused by the creep of the polymer material at the sealing part under this thermal state, which is not enough to support the pressure. This strength is called the thermal burst strength. In order to compare the cold and hot burst strength, we tested the bursting strength at different temperatures with ZY-1 positive pressure tester at room temperature and 95 ℃. The comparison of two groups of samples showed that the bursting strength of the heat sealed bag at room temperature was significantly different from that at 95 ℃. The reason was that the strength decreased when heated, which is a normal situation in our production. If the bag is not heat sealed well, the burst strength at room temperature is very small, which belongs to the defective product in production. Although there is no leakage, it is easier to burst the bag when heated.

2. Cooking bag problem before heating to 100 ℃, the change of cooking bag is the same as that of boiling bag. When the cooking bag is heated to more than 1000 (2), because there is no instrument to observe the cooking process in China, and the sensor of ZY-1 positive pressure tester can not penetrate into the t-25c back pressure cooking pot, we can only speculate that the pressure in the bag is always higher than the pressure outside the bag when the temperature is higher than 100 ℃ (this conjecture is not supported by facts at present, we are developing a new type of pressure tester with Transparent observation window of the cooking pot, in order to solve this problem).
3. Can burst bag be avoided? If the pressure inside the bag is higher than that outside the bag, is there any way to avoid it? From the boiling process, we know that when the pressure inside the bag is high, the environmental pressure will not change before forming the differential pressure bag burst. If the environment changes synchronously, can it be avoided. We turn off the exhaust of ts-25c counter pressure cooking pot, and form a closed environment from the time the sample is put in. Set 115 ℃ (because of the safety valve, it can not be set higher) cooking. A total of 30 cooking bags were tested, and no burst was found. It can be imagined that this is equivalent to applying an external pressure to the bag from the beginning of heating to balance the internal and external pressure, so there is no bag burst.
4. Conclusion: (1) the problem of high temperature cooking bag explosion is actually the thermal burst strength of the bag, which is generally caused by the damage of the heat seal. (2) If an external pressure is added to the cooking bag in advance and the relative external pressure is maintained during the heating process, the bag burst will not occur. However, the pressure resistance of the boiler body is required to be high, such as 135 ℃, and the normal working pressure is required to increase from 2.2kg to 3.2kg. In this way, the bag burst is related to the test mode and the production mode. It is of great significance to improve the high temperature sterilization process to reduce the bag burst.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service. The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries. We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.