Cobb value
The Cobb value provides information about the water absorption capacity of paper and solid cardboard or corrugated cardboard . In the case of (corrugated) cardboard, this value is important for calculating the expected stability of a cardboard box or folding box. In the case of paper, the writability and printability with ink ( inkjet printer ) is only possible with papers that have certain water absorption values. Certain Cobb values must also be given for other printing processes .
In international goods handling, especially in tropical countries, packaging made of cardboard , solid and corrugated cardboard may only have a low level of moisture absorption, as the stability of the packaging decreases with increasing water absorption. The lower the Cobb value, the more stable the packaging remains even in high humidity.
Typical details of a GC1 box:
Water absorption according to DIN EN 20535 or ISO 535 (Cobb 60s): front side <35 g / m²
This means that 1 m² of the front of a GC1 carton absorbs up to 35 grams of water after 60 seconds.
Further characteristics for the stability of a cardboard are:
- Stack crush resistance (BCT)
- Edge crush resistance (ECT)
- Number and height of flutes for corrugated cardboard
- Material structure and thickness
- Fiber length
Paper and cardboard must be treated to achieve certain Cobb values. This is usually achieved by so-called gluing . Here, chemicals (sizing agents) are added or applied during production (bulk sizing) or on the finished paper (surface sizing), which cause partial hydrophobization .
Individual evidence
- ↑ DIN EN ISO 535 (2014-06-00) Paper and cardboard - Determination of the water absorption capacity - Cobb method (ISO 535: 2014) ; German version EN ISO 535: 2014