内管的涂层是介于一端与另一端的外管的密封层里面。
This coated inner tube is closed at one end and sealed at the other end to the outer tube.
水结冰时发生膨胀，所以冰会浮在水面上形成一个密封层。
Water expands when it freezes, causing ice to float and form aninsulating layer.
PE铝箔封口膜由密封层、铝箔、胶粘层组成，适用于电磁感应封口，也可用于热封封口。
PE aluminum foil seal film compose of sealing layer, aluminum foil and glue layer. Through heat sealing or induction sealing.
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