Absorbent Paper
Absorbent paper, also called blotting paper, is used for a variety of purposes in the laboratory. Its soft surface is ideal for soaking up excess liquids and speeding up clean-up.
Several types of absorbent papers are available, but there are a few key properties to consider when choosing one. These include water absorbency, oil penetration, and porosity.
Water Absorbency
Water absorbency is an important property of any material. The ability of a material to absorb moisture affects many other characteristics, including skin comfort, static buildup, shrinkage, and wrinkle recovery.
To test the water absorption capacity of a material, the material is soaked with water and the amount of water that is absorbed can be measured. The Cobb sizing test is one of the most popular methods for testing the water absorption capacity of paper and related products.
Explain that paper, like felt and other natural fibers, is made from materials that have lots of tiny spaces where water can move into. These spaces are called capillaries. The spaces are similar to the holes in a sponge.
Tell students that they are going to use a sponge and a brown coffee filter to do an experiment about how much water is absorbed by different types of materials. Then they will try to do the same test with a paper towel and a terry cloth hand towel.
After students do the experiment, they will learn that each material has a different amount of water that it can absorb. This is important information to know since it will help them when they are testing other materials.
Next, students will take some paper towels and a terry cloth hand towel and place them in a jar of water. Then, they will use a stopwatch to measure how long it takes each one of them to absorb a single drop of water.
Once the students have completed their experiments, they will be able to compare the different materials and see which one absorbed the most water. They will also be able to understand that absorbent paper materials all need to be tested in the same way to determine their properties.
The water absorption of a paper product depends on the pulp that it is made from. Some pulps contain a high lignin content and absorb very little water while others have a low lignin content and have a higher water absorption capacity. Additionally, the beating of the pulp and the jordanning affect the water absorption capacity. The beating process of the pulp removes the primary wall of the cellulose and exposes the secondary wall layers. It also increases the fiber-water affinity of the cellulose by allowing more water to reach the surface of the paper.
Oil Penetration
The oil penetration capacity of absorbent paper is a factor that is often considered when choosing a product to use on a particular surface. This is because it can help ensure that the product is able to effectively clean the surface and protect it from water damage.
Penetrating oils are commonly used to remove rust, adhesives, and other contaminants from surfaces. They can also help to loosen seized nuts and bolts, making it easier to turn them and get them off of a given item.
Most penetrating oils contain some kind of lubricant mixed with a solvent to make the fluid more mobile. This allows it to quickly penetrate crevices, grooves, and pores located on the surface of a given item.
These products can be found in liquid bottles, aerosol cans, and drip bottles. They are generally made to be easy to use and come in different sizes to suit a variety of needs.
They can also be found in a variety of different flavors, including ones that are specially designed to help with corrosion. These kinds of penetrating oils are usually formulated with ingredients that are specialized for specific uses, so it’s important to choose one that will work well for you.
If you want to make sure that your penetrating oil is going to work, you should look for an original version from a brand that you trust. Kroil is a great example of this, and they offer many different options that are perfect for removing stubborn nuts and bolts.
Another good option is one that contains PTFE or silicone. These ingredients can be used for both metal on plastic and plastic on rubber situations. PTFE is especially useful for damp situations, while silicone can make it extra slippery and repel water.
When you’re looking for a high-quality penetrating oil, be sure to check the manufacturer’s website for more information. They should be able to give you the information that you need, and they will also be able to provide you with a sample that you can test on to determine whether it’s the right product for your specific situation.
Porosity
Porosity is the percentage of pore spaces in a material that are able to contain fluids. This varies depending on the type of paper and can be determined either by measuring how quickly air flows through a sample (using a Gurley densometre) or by using a Sheffield porosimetre.
Porosity may also be determined by observing the morphology of fibres. For example, if the strands of your hair are bumpy and rough, it is likely that they have high porosity, while a smooth strand is likely to have low porosity.
In paper sheets, inter-fibers spaces constitute capillaries that enable water to lift itself up through the paper to a certain height. This characteristic pore radius tends to be greater in a paper sheet that is made up of softwood pulp fibers than it is for a corresponding hardwood sheet.
As a result, the absorbency of water in a paper strip is directly proportional to the pore radius. Moreover, the COP is affected by pulp beating and by the degree of collapse of the paper structure during sheet pressing. In addition, the use of 4% NaHCO3 solution during manufacturing of absorbent grade paper increases water absorbency and oil penetration (COP) and improves its porosity.
The use of a NaHCO3 solution during sheet making increases surface tension forces that cause the fibers to come closer together. This increase in the surface tension forces leads to an increase in the density of the cellulose fibrils.
This increase in the density of the cellulose fibrils can also help improve the strength of the paper. This is because the bonded area of cellulose fibrils increases, which in turn increases the load that the fibers can carry.
A simple test to determine the porosity of a material is to grab a small section of the material and feel it with your fingers. If it is rough and bumpy, it is probably high in porosity; if it is smooth and glides easily on your fingertips, it is likely medium or low in porosity.
Porosity is often measured by comparing the amount of time it takes for a particular quantity of air to pass through a sample (using a Gurley desometre) or by measuring how quickly air passes through a sample (using a Sheffield porosimetre). It can also be determined by examining the morphology of fibres.
Preservatives
One of the best known groups of preservative substances for paper are compounds commonly referred to as wetting agents, namely sulfonated and sulfated organic compounds (e.g. Turkey red oil and sulfonated neat’s foot oil).
The addition of as little as 0.2 percent based on the weight of the paper will prevent loss of absorbency over six months or more. The outward properties of the paper such as stiffness, softness, color, flexibility and tensile strength remain unchanged.
Moreover, I have found that the most effective preservatives for this absorbent paper purpose are those in which the cellulose is free of beta and gamma cellulose. Such paper does not develop the phenomenon of a great loss in absorbency on storage and this is due to the fact that these alpha celluloses do not pass-irreversibly to a hard, dried gel condition when stored indefinitely.
This is an important preservation technique which can be applied to most kinds of absorbent paper. A mild alkali such as calcium hydroxide, calcium hydrogen carbonate or magnesium hydrogen carbonate is soaked into the paper, and then dried. This neutralizes the acid in the cellulose, and re-forms some of the hydrogen bonds between the cellulose fibres.
When the paper is dried it is generally sprayed with a solution of these alkaline salts, or the same substances are added to it before it leaves the paper machine. This does not only deacidify the paper but also removes any residual acid in it, thereby acting as a preservative against future acidification.
Another good preservation method is the use of a mild alkali such as sodium hydrogen carbonate or potassium hydrogen carbonate, which is soaked into the paper and then dried. It not only re-forms some of the hydrogen bonding between the fibres but also removes any residual acid in it, thus acting as a preservative against future acidsification.
The addition of a mild alkaline salt to the paper can improve its water absorbency (Klemm test), oil penetration (COP) and porosity. It is a cost-effective preservation technique which can be used for most kinds of absorbent paper.
