Physical properties of paper
ration
Quantitative commonly known as gram weight, refers to the weight of paper per unit area, generally expressed in grams per square meter. In foreign countries, it is also expressed by the number of pounds or kilograms per ream of paper, which can be converted into the number of grams per square meter according to the length and width of the paper and the number of sheets per ream.
Quantitative is the most basic physical index of paper. Its height and uniformity affect all the physical, mechanical, optical and printing properties of paper. In general, various performance indexes of printing paper, such as thickness, tensile strength, bursting strength and opacity, are closely related to quantitative analysis. If the paper weight is significantly lower than the standard, not only is it easy to pass through the printing failure, but also because of the mechanical strength is not enough to break the line. On the contrary, if the ration is too high, the paper pulp will be wasted in production, and the practical area per ton of paper can not be guaranteed. When the ration of one sheet of paper is different from that of the next sheet of paper, the printing adjustment can not be carried out in this paper interval, which will lead to the problems of incorrect overprint and different imprinting depth. When the quantity of the same paper is not uniform, it is easier to cause unclear writing and inconsistent picture color.
Thickness and tightness
Thickness indicates the thickness of the paper. A micrometer is used to measure the thickness of paper under a certain area and pressure. Generally, the pressure is 980 kPa. Generally, the thickness of a batch of paper or paperboard is required to be consistent, otherwise, the thickness of the products will be inconsistent. Tightness refers to the weight of paper and paperboard per cubic centimeter. The result is expressed in g / cm3. Tightness is an index to measure the tightness of paper or paperboard structure, which is the basic property of paper and paperboard.
Smoothness
Smoothness refers to the time required for a certain volume of air to pass through the gap between the sample surface and the glass surface under a certain pressure under a certain vacuum, expressed in seconds. Smoothness depends on the surface condition of the paper. If the paper surface is uneven, the smoothness of the paper is poor.
Mechanical properties of paper