Why is the bubbling reason for the aluminum-plastic panel

Aluminum-plastic panel surface bubbling is the core plate extrusion with granular non-melt, these non-melt average diameter to a certain extent, will protrude on the surface of the core plate, composite will cause the board surface bubble phenomenon. When we peel off the aluminum plate, we will find that there are signs of poor adhesion around the bubbling, the reason for this sign is that when the bubbling is rolled and composited, the air around the bubbling part can not be completely squeezed out and sandwiched in the middle of the plate layer, and the extremely thin air layer blocks the full bonding of the plate layer, so the aluminum-plastic panel will appear bubbling.