Solvent-free lamination of PET/PE product structures with pressure boiling: why does delamination always occur?

A flexible packaging company: for solvent-free lamination of PET/PE product structures with pressure boiling, why does delamination always occur?

Composite Packaging — Zhang:

I guess it still has something to do with the PET heat-shrink film that Engineer Zhao mentioned.

Liu Hangen (formerly Huitian):

PET raw material is very good in terms of both corona treatment level and lamination strength. With normal PE raw material, the lamination strength of PET//PE material structures can be good.

In a very good boiling machine, the pressure is very well controlled during the boiling and cooling process, and the bag does not easily swell during the whole boiling process.

Conversely, with a poor boiling machine, the pressure is not well controlled during the boiling and cooling process, the pressure reduction outside the bag during boiling and cooling is poor, and bag bursting and delamination after the bag swells are very common. Pressure boiling places very high demands on the lamination strength of the product. If the heat resistance of the solvent-free adhesive meets the requirements, appropriately increasing the coating weight can improve the lamination strength, which should solve this problem.

But if this product is boiled under pressure, the probability of swelling during boiling is very high, and the PET//PE material structure is not a very good option, unless reinforced PET raw material or PE raw material is used, but this easily raises production costs. It is recommended to change the material and choose an NY//PE structure; the best direction for the solvent-free adhesive is an adhesive with high heat resistance and fast curing speed.

Zhao Shiliang of Beijing Gaomeng:

Pressure boiling is no longer boiling; it has entered the retort range. What does the delamination look like?

Composite Packaging — Zhang:

PET/PE pressure boiling means boiling with the bag filled with liquid; this type of packaging is widely used for lactic acid beverages on the market. Delamination means separation starting from the heat seal, where the PET and PE at the heat seal have separated. As shown in the figure.

Hainan Jiyao Apprentice:

We have encountered a similar situation. If it is not heat sealed, there is no problem; once it is heat sealed, it appears. Peeling starts from the heat seal. It was reported by the customer; no measurement data were taken, it just peeled apart directly.

Zhao Shiliang of Beijing Gaomeng:

Has this bag already swollen? Why?

Composite Packaging — Zhang:

It is pressure boiling, after all; this type of packaging requires it, and without pressure there would be no problem. Sometimes if the lamination strength is poor, it delaminates as soon as water is added, even without boiling.

Zhao Shiliang of Beijing Gaomeng:

The phenomenon in the picture shows that no back pressure was applied during retorting!

Composite Packaging — Zhang:

At present it is PET/PE, just ordinary pressure boiling.

Zhao Shiliang of Beijing Gaomeng:

This is the result of improper sterilization treatment.

Liu Xianxiang of Kangda New Materials:

Back-pressure boiling places relatively high demands on lamination strength, while atmospheric boiling does not require such high lamination strength. Boiling is divided into atmospheric and back-pressure; when releasing the back pressure, the speed should not be too fast.

Zhao Shiliang of Beijing Gaomeng:

Boiling does not require back pressure. Only retorting requires back pressure. The inevitable result of not applying back pressure during retorting is a swollen or burst bag! (For more technical content, see Packaging Frontier or the Packaging Frontier information website www.pack168.com. Different opinions are welcome; continue the discussion at www.pack168.com. Friends who provide more solutions can receive reading credits for technical articles on the website. To request credits, please contact Xiaoyang: 13316078351, Xiaolai: 18475695660)