Most filter papers are made of cotton fibers and are made in different ways for different purposes. The key component of filter paper is cellulose. The pigments are a capillary function of cellulose.
The liquid rises along with the filter paper and shows very significant color bands: green is chlorophyll, yellow is lutein, and orange is carotene. Filter paper filtration is actually a chromatographic function. In experiments, the filter paper is used together with the filter funnel and Brinell funnel.
Because filter paper composition is fibers, there are numerous holes on its surface for liquid particles to pass through, while larger solid particles can not pass through. This property allows the separation of liquid and solid materials mixed together. The filter paper has good filtration and absorption performance and high compressive strength.
The technical indicators of filter paper can be divided into two aspects, one is the filtration characteristics of the filter paper, and the other is the physical characteristics. Filtration characteristics include air permeability, air resistance, maximum pore size, and average pore size. Physical properties include quantitative, thickness, stiffness, corrugation depth, burst resistance, resin content, etc.
Quantitative: refers to the quality of filter paper per square meter, unit: g/m2.
Thickness: refers to the thickness of filter paper, excluding corrugated depth. Unit: mm.
Air resistance: the resistance of the filter paper to airflow. Use 100cm2 filter paper to pass 85 liters of air in one minute to express the pressure drop value. The unit is mbar. or the height of the water column (mm).
Corrugated depth: the depth of the grooves suppressed to strengthen the longitudinal stiffness of the filter paper, in mm. Under normal circumstances, its value is 0.2mm.
Air permeability: The amount of air passing through the filter paper per unit time under a certain area and pressure (20 mm water column). The unit is L/m2·s.
Nominal filtration accuracy: refers to the retention capacity of the filter paper for particles of a certain size, and the particle size of the tiny spheres at 50% that can be retained or filtered out shall prevail. Unit: μm.
Maximum pore size: the size of the gap calculated by the pressure when the first bubble emerges on the filter paper sample during the test. Unit: μm.
Average pore diameter: The pore diameter calculated by the pressure during “dense” bubbling is called the average pore diameter. The unit is: μm.
Resin content: the percentage of resin in the weight of the filter paper. Generally 10%~30%.
Stiffness: the ability of filter paper to resist deformation. Unit: mg.
Bursting resistance: the maximum pressure that the filter paper can withstand per unit area. Unit: kPa.
At present, the filter paper is mainly used in petroleum, pharmaceutical, industrial oil, industrial organic suspension to separate solid and semi-solid impurities. The filter paper is mainly used in the ashing weighing analysis test after filtration. The ash weight of each filter paper after ashing is a fixed value, while the qualitative filter paper is used in the general filtering function.