the ring crush strength of the paperboard was not affected by biopolymer coating. There was no significant (Po0:05)
difference in ring crush force between control groups and biopolymer-coated groups right after coating.
However, ring crush force of all the paperboards decreased appreciably after 5 days storage at 30 1C and 98% RH condition. This decrease is mainly caused by the increase in the moisture content of paperboards.
It is notable that the degree of reduction varies depending on the coating materials. This result shows that the degree of water absorption changed depending on the coating material and had an influential effect on the ring crush force of the paperboards.