The opacity of the paper

Update:24 Nov 2018
Summary:

How does the filler affect the opacity of the paper? A: […]

How does the filler affect the opacity of the paper?

A: Paper without filler is made up of fiber and air. Air is present in the pores between the fibers. Because the refractive index of the fibers is different from that of air, when the beam is irradiated onto the surface of the paper, some of the light is scattered at the interface between the fibers and the air, giving the paper a certain (lower) opacity. Reflected in the printing, the main performance is extremely easy to print. Adding a filler with a refractive index greater than cellulose in the paper increases the number of light scattering interfaces inside the paper, that is, there are three different interfaces between the fiber and the air, between the filler and the fiber, and between the filler and the air. In the middle, the difference in refractive index between the filler and the air is large. Therefore, the light is maximally scattered at the interface between the filler and the air, resulting in an increase in opacity.

How does the filler improve the smoothness of the paper surface?

Answer: The network formed by the interweaving of fibers always has a large number of pores and unevenness on the surface. The addition of fine particle filler can improve the softness and plasticity of the paper, and can perform better calendering treatment, thereby improving the paper after calendering. Smoothness.

What is the effect of filler on paper strength?

A: The combination of fibers is the basis of the strength of the paper. The addition of fillers reduces the bond between the fibers, so adding a large amount of filler will significantly reduce the strength of the paper. Among them, the tensile strength, the folding endurance and the bursting resistance are greatly reduced, the tearing degree is decreased, and the amount of the filler used is limited.

How does the filler affect the bulk of the paper?

A: The density of paper fibers is about 1g/cm3, and the density of fillers is mostly 2.5-3.0g/cm3. Therefore, the addition of filler will reduce the bulk of the paper. However, when the amount of filler added is small, the bulk thickness increases as the amount of filler increases, and the staple fiber paper is particularly noticeable.

How does the filler affect the stiffness of the paper?

A: The stiffness of the paper is a function of the thickness of the paper and the modulus of elasticity. The effect of the filler on the stiffness should be considered in combination with the effect of the filler on bulk and tensile strength. When the amount of filler is small, the addition of the filler does not substantially affect the stiffness of the paper. When the amount of filler is increased, the stiffness decreases remarkably as the amount of filler increases.