This standard specifies the method for determining the water absorption capacity (cobb value) of paper and board with a cobb water absorption determinator.
This standard is applicable to the determination of water absorption on the surface of sized paper and board.
This standard is not applicable to body paper and embossed paper with a quantify of less than 50 g/m2, lower sizing or more pinholes, unsized paper and board and accurate evaluation of writing performance of paper and board.
2 Normative reference
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions cited are valid. All normative documents are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below.
GB/T 450-2002 Paper and board - Sampling for testing (eqv ISO 186: 1994)
GB/T 461.1-2002 Paper and board - Determination of capillary rise - Klemn method (idt ISO 8787: 1989)
GB/T 10739-2002 Paper,board and pulps - Standard atmosphere for conditioning and testing (eqv ISO 187: 1990)
3 Definition
For the purposes of this standard, the following definitions apply.
3.1
cobb value
under certain conditions, the mass of water absorbed by the surface of paper and board per unit area within the specified time, which is expressed in g/m2
3.2
absorption time
the time from the initial contact of water with the specimen to the end of absorption. This time can be selected according to the different water absorption capacity of paper and board, which shall meet those specified in Table 1 in Sub-clause 7.2.1.3, and if necessary, can be shortened or extended as appropriate.
