Why I say double layers SUP have higher chance explosion than other layers?
Because double layers SUP manufacturing process is: Adhesive top&bottom PVC sheet first, then begin sealing the board, this caused two problems:
-1. Adhesived PVC sheet can not ensure it is 100% on center, it's a handwork, maybe workers make it left have more space, right have less space or conversely. When sealing it caused left and right have different adhesive area, the intesity also difference.
-2. Extra top&bottom adhesived PVC sheet encroached sealing rail space, but single layer/MSL/Woven layer only has one layer, so do not encroached sealing area. Double layers can not compacte by tool as other layers did.
Besides that, the cost make double layers similar as make MSL layer board, at same time more heavy more glue, so we suggest customer choose other layers if possible.