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Why does the soft hardness of the PVC film change with the temperature?
Jan 26, 2018

The PVC bags made in summer will become hard and brittle in winter. Otherwise, the PVC bags made in winter will become soft and tough in summer. What is the reason?

It turns out that the PVC film is a kind of heat sensitive material, its soft hardness will change with the temperature change, the temperature will become softer, the temperature will become harder. Under the condition of constant temperature, the soft hardness of PVC film depends on its oil content, the higher the oil content is, the softer it is. This "oil" is the plasticizer in the PVC film. We often say the PVC membrane oil 27 PPA, 45 PA and so on, that is, the content of oil. For example, 100KGPVC film, if the plasticizer content is 30KG, then the corresponding oil is 30 PPA (writing 30P).

The formula of PVC film is usually divided into summer formula, winter formula and spring and autumn formula according to the oil content. In general, the PVC film 3 formulations do not use seasonal. Accordingly, 3 kinds of PVC films made of PVC bag, do not use the general season. If the PVC bags made in summer or spring and autumn are used in winter, brittle cracks tend to occur. On the other hand, if the bags made in winter or spring and autumn are used in summer, there will be soft and no bone conditions. Spring and autumn do bag should not be used in the two seasons of winter and summer.

What is the way to keep the soft hardness of the PVC film stable without the influence of the temperature? It's hard to do it absolutely without being affected, but we can mitigate this problem in 2 ways. One way is that the oil should not be done too high or too low to be moderate, but the bag making process will be difficult. Another way is to add proper amount of cold resistant agent (also called antifreeze) in the PVC film. The cold resistant agent can increase the toughness of the film, and it will not crack in the low temperature below zero. Some PVC bags used in low temperature areas, such as Russia, usually require a PVC bag to maintain a no brittle crack at minus 15 degrees centigrade.

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