eli5: Glue container boasts Bonds: Metal, Plastic, Wood, Etc. So why does the plastic cap not firmly adhere to the metal tube? And why does the dried glue easily rub off the metal tube?

Question

eli5: Glue container boasts Bonds: Metal, Plastic, Wood, Etc. So why does the plastic cap not firmly adhere to the metal tube? And why does the dried glue easily rub off the metal tube?

In: 1

Answer 1

For glue to stick things together, it normally has to ‘dry’. Some glues literally dry out in open air, as their liquid content slowly becomes a gas and floats off. Some glues absorb water and use it to ‘dry’. Some more niche glues use other methods.