4 kinds of paper "secrets" such as paper must use trees?

Why does wet paper wrinkle when it dries?

In general, the moisture contained in the paper (8%) should be in balance with the relative humidity in the surrounding air (that is, the moisture contained in the air). At this time, if the paper is wet by water, it will inevitably cause local changes. What kind of changes are these?

First, when liquid water is in local contact with the paper surface, there will be a physical change of "coarsening" in this part, that is, the fiber bulge and fiber warping occur. This phenomenon is an irreversible change in the shape of the fibers; Second, water molecules continue to penetrate into the paper, which will cause local deformation of the fiber network organization, resulting in stress release within and between the fibers. This deformation is also irreversible; Third, when the water on the paper evaporates, there is a "displacement" between the original fibers.

Along with the formation of new fiber bonding bonds, the possibility of reconnecting after the original network is destroyed is also lost, which is also an irreversible change. As a result, the paper that has been moistened and then dried by water not only decreases its tensile strength by about 10%, but also has wrinkles that are impossible to erase. This is the result of three irreversible changes.

Is there a way to make wet paper dry without wrinkling? It is impossible not to wrinkle at all. There is only one way to reduce this phenomenon, that is, when the paper is wet with water, immediately use absorbent paper or (good quality, flat surface) toilet paper, respectively, attached to both sides of the wet paper, and then press down with heavy weights. After 24 to 36 hours of time, when the paper dries, it will be found that the "wrinkles" are not so obvious.

Why can a paper pot boil water?

The key to boiling water in a paper pot is what kind of paper you use. In the past, some people used kraft paper folded into a paper box with water, put it on the electric stove to heat, and soon the water boiled. It's a physical phenomenon that can inspire people to think more. Because the paper is relatively thin, the specific surface area is large, the heat transfer rate is fast, and the temperature of the water is low, so even the thin paper can withstand the heating effect. However, strictly speaking, this "paper pot" boiling water is a scientific game and has no practical value.

Now, a paper pot made of thermal paper has been successfully developed. This paper must have the characteristics of high tightness, high break resistance, high physical strength and high fire resistance. Due to the low temperature of the water added, there is a temperature difference with the heat source under the paper pan; In addition, the paper has the strength, the thickness is small, and the heat transfer is good, so once it is heated (it is not appropriate to use an open fire, use an electric furnace), the water in the pot will be constantly heated and reach boiling. Therefore, this thermal paper can not only be waterproof, stress, but also can make tableware (such as hot pot).

The raw material used for thermal paper is coniferous wood pulp, after sticky beating, plus rosin, aluminum sulfate and waterproofing agent, etc., if necessary, it can also be coated with a layer of flame retardant to ensure that the waterproof, heat resistance and other functions of the paper are fully guaranteed. It is precisely because this paper has a good application, so it can become a tableware instead of copper or stainless steel POTS. The use of paper pot compared with other hot pot, its advantages are: one pot, to ensure health; Eliminate cleaning, reduce costs; Use up recycling (when waste paper), why not?