In the same exercise book or a manuscript paper, a few sheets of paper are often found to have poor water resistance, there are a couple of sheets of waterproofing roll that are particularly good. what is the reason? 

Rubber permeation tester (HST) tests the sizing degree found that the outer sizing of each paper roll is much higher than the inner layer of the paper roll, the size of the sizing near the cut edge of the colored paper roll is also high. This phenomenon is called the migration of rubber, this migration is due to the cooling of the paper roll, which generated temperature gradient (The inner temperature of the paper coil is higher than the outer temperature of the paper roll), it causes rosin to move from the hotter inner layer of the roller core to the cooler outer layer and edge of the roll by force. The migration of the compound in a paper roll with a temperature gradient can also be demonstrated by the following facts: total amount of extractable rosin by TAPPI square method T408DS一74 determinates that the outer surface of each roll contains about 50 intestines higher than the inner core of extractable rosin, if rewinding after the paper is cooled, it will eliminate the temperature ladder of the paper roll towel, which can prevent the transfer of rubber in paper roll and ensure the consistency of sizing degree of finished products.