Physical properties, mechanical properties and inspection of paper

Physical properties of paper

Quantitatively weighed commonly known as grammage, refers to the weight of paper per unit area, generally expressed in grams per square meter. In foreign countries, there are also the number of pounds or kilograms per ream, which can be converted into the number of grams per square meter according to the length and width specifications of the paper and the number of sheets per ream.

Quantification is the most basic physical index of paper. Its level of homogeneity influences all physical, mechanical, optical and printing properties of paper. The various performance indicators of general printing paper, such as thickness, tensile strength, bursting resistance, and opacity, are closely related to the quantification. If the basis weight of the paper is significantly lower than its standard, it will not only be liable to print defects, but will also be broken due to insufficient mechanical strength. On the other hand, if the ration is too high, the pulp will be wasted in production and the user will not be able to guarantee the usable area per ton of rolled paper. When the ration of a piece of paper and the next piece of paper is different, the printing adjustment work cannot be performed in such a paper interval, and problems such as misregistration and imprinting will occur. When the same piece of paper is unevenly quantified, it is more likely to result in illegible characters and inconsistent color.

Thickness and tightness indicate the thickness of the paper. The micrometer is used to measure the thickness of the paper under a certain area of ​​certain pressure. Generally, the pressure is 980 kPa. Generally, the thickness of a batch of paper or cardboard is required to be the same. Otherwise, the thickness of the finished product is inconsistent. Tightness refers to the weight of paper and cardboard per cubic centimeter. The result is expressed in g/cm3. Tightness is a measure of the degree of tightness of a paper or board structure and is a fundamental property of paper and board.

Smoothness smoothness refers to the time in seconds required for a given volume of air to pass through a gap between the surface of a sample subjected to a certain pressure and the glass surface under a certain degree of vacuum. The smoothness is determined by the surface condition of the paper. If the paper is uneven, the smoothness of the paper is poor.

Paper mechanical properties

Tensile Strength and Elongation Tensile strength refers to the tension experienced by paper or cardboard. It is usually expressed as absolute tensile resistance: the tensile strength (Newtons) of a sample of a certain width; or the length of a crack: the length of paper required for a certain width of a piece of paper to break when the paper is broken under its own weight. ); Or with the transverse section of the tensile strength; that is, the tensile strength of the sample unit cross-section (Newtons / meters 2) said. Tensile strength is one of the important parameters in physical properties. It is also a basic test. Long rate refers to the paper or cardboard after a certain tension. The percentage of extension to the length of the original sample up to the time of breaking. Elongation is an important indicator of the strength and toughness of paper.

Tear Tear refers to the force required to tear a pre-notched specimen to a certain length, expressed in kilotons (tons). The degree of paper breakage is the ability of paper and paperboard to resist cracking.

Folding resistance Folding resistance is the number of reciprocating folds that can withstand 180° under certain tension. Reciprocating folding times. The degree of folding resistance indicates the ability of the paper to resist folding.