The degree of sizing of paper is a technical index indicating the water resistance of paper. The sizing degree of paper, that is, the water resistance ability, is determined by the paper sizing process, and both internal and external sizing have a great influence on the sizing degree.
From a method of measuring the degree of sizing, the concept of the degree of sizing can be more clearly understood. The Cobb (Cobb) method is measured with an absorbency Tester. The measured result is the water absorption on the surface of the paper, that is, the amount of water absorbed by the surface of the paper per unit area within a specified time under a certain pressure and temperature, and the unit is g/cm². The liquid penetration method is the time required for a certain liquid to penetrate the paper, and the degree of sizing of the paper is expressed in seconds.
The influence of paper sizing degree on printing is that it directly affects the surface strength of paper, paper shedding, powder shedding, paper deformation and other properties. For example, during the offset printing process, the paper is in contact with the dampening solution many times. If the sizing degree is poor, the water resistance will be low. The paper will be deformed due to the increase of water content, which will affect the registration accuracy, and will also cause the paper to drop hair and powder.
The tensile strength of paper refers to the ability of the paper to return to its original state when the fiber is stretched and the paper is deformed under the action of an external force, that is, the maximum tension it is subjected to. The tensile strength of paper depends on the properties of papermaking fibers, papermaking process, paper weight, paper moisture content, and also on the direction of paper. The transverse and longitudinal tensile strengths are different. The unit of tensile strength is N/m.
The impact of tensile strength on printing is mainly on web printing. The paper is moved by the tension between each color group of the roll paper and the winding and unwinding rolls, and the printing speed is fast and the tension is high. In order to make the latter unit have a certain pulling force on the paper relative to the former unit, the diameter of the roller of the latter unit is slightly larger than that of the former unit, so that the paper moving speed of the latter unit is slightly higher than that of the former unit, thus generating tension. If the tensile strength of the paper is poor, the paper will be broken and the operation cannot be carried out normally.
Break length is also a technical indicator of tensile strength. It is assumed that one end of the paper tape is fixed, and the other end hangs freely, and the length of the paper tape breaks due to the weight of the paper tape.