1. I intend to do composite cans with a top heat seal concept, so I need to curl out the top portion before sealing. What is the paper I should use (thinkness, grade, etc.)?
The grade of paper depends on several aspects. The required strength of the composite can, the environment it will be subject to and several other attributes. Also, within a given grade of paper some attributes such as moisture and smoothness are tailored to the end use.
A well seamed “tin can end” should meet most packaging applications per sealing intergrity.