If the stretch film manufacturer’s ziplock bag loses its airtightness, it will be no different from a general plastic bag. Then, how to detect the packaging material How about the tightness of the stretch film?

1. Vacuum investigation method. After evacuating the vacuum, the internal and external pressure difference of the sample is generated, and the sample shape recovery after the expansion of the sample and the release of the vacuum is observed to determine the sealing performance of the sample.

2. In-water urban pressure method (vacuum method), after evacuating the vacuum chamber to make the sample immersed in water have internal and external pressure difference, and observe the gas escape or water ingress in the sample to determine The sealing performance of the sample.

3. Waterless immersion method, fill the sample with the test liquid, place the sample on the filter paper after sealing, and investigate the leakage of the test liquid from the inside to the outside of the sample. Both sides should be tested.

The stretch film manufacturer teaches you how to distinguish the toxicity of stretch film

The commonly used food stretch film is mostly made of polyethylene film, which is non-toxic and can be used to hold food. There is also a kind of film made of polyvinyl chloride, which is also non-toxic, but the additives added according to the use of the film are often harmful to the human body and have certain toxicity. Therefore, this kind of film and plastic bags made of the film are not suitable for holding food. If you want to distinguish between polyvinyl chloride plastic bags and polyethylene plastic bags, the following simple method can be used for identification.

Polyethylene film (non-toxic)

The film is milky white, semi-transparent (especially obvious in the investigation of several layers), and it feels smooth, like a wax layer on the surface, vibrates vigorously, the sound is brittle, it is flammable in fire, and the flame is yellow. Mucus drips and smells like candles burning.

Polyvinyl chloride film (generally toxic)

If the pigment is not added, it will be bright, and it will feel a little sticky to the touch, vibrate vigorously, and the sound will be low. It is not easy to burn in case of fire. It will go out immediately after leaving the flame, and the flame will be green.