Viscosity may be a relatively unfamiliar word to most people, but it plays a very important role in our daily lives. Viscosity is a key property of liquids. It describes how the interaction between molecules hinders the relative movement of molecules under the action of external forces, which in turn affects the flow performance of liquids. The understanding and determination of this property is crucial for many fields, from chemical engineering to Coating production. In this article, we will delve into the concept of viscosity, the measurement method and its application in different industries.
Concept of viscosity
Viscosity, also known as internal friction, is a property of liquids that determines the resistance to flow under external forces. Usually, we use a simple ratio to express viscosity, which is the ratio between the external force and the layer that produces the flow velocity. Specifically, the viscosity of a liquid can be defined as the ratio of shear force to shear rate, or dynamic viscosity, in Pa · s. Taking into account the effect of the Density of the liquid on the viscosity, kinematic viscosity can also be used, which is defined as the ratio of dynamic viscosity to liquid Density in square meters per second (m ²/s).
The importance of viscosity is that it has a profound impact on the flow performance of liquids. In Coating production, viscosity is a key performance indicator, which reflects the molecular weight of the polymer in the paint. If the viscosity is too high, livering may occur during the paint making process, which will affect the mass of the Coating. If the viscosity is too low, it may lead to the inability to add enough solvent, which will seriously affect the performance of the paint film. Similarly, in the Coating construction process, viscosity also plays an important role. Coating with high viscosity can lead to construction difficulties, poor levelling of the paint film, and low viscosity can cause problems such as sag. Therefore, accurate determination of viscosity is crucial for process control of Coating production and mass assurance of the final Coating product.
Determination method of viscosity
In order to determine the viscosity of liquids, a variety of methods have been developed, and different methods are suitable for different types of liquids. The following are some commonly used viscosity determination methods:
1. Outflow method
The principle of the outflow method is to use the gravity of the liquid itself to measure the viscosity. The specific operation is to pour the sample into the Viscosity Cup, and then plug the outflow hole of the Viscosity Cup with a stopper or finger. The viscosity of the liquid can be calculated by measuring the time it takes from the start of the outflow to the interruption of the flow column, and the result is expressed in seconds (s). This method is suitable for liquid Coatings with Newtonian or near-Newtonian properties, such as low-viscosity varnishes and Paints.
2. Vertical ball drop method
The principle of the vertical ball drop method is to use the speed at which a solid ball falls vertically in a liquid under the action of gravity to determine the viscosity of the liquid. During the operation, the time required for the steel ball to pass the distance between the upper and lower scale lines of the falling ball Viscometer is measured, and the result is expressed in seconds (s).
3. Bubble method
The principle of the bubble method is to use the flow speed of the bubble in the liquid to determine the viscosity of the Coating product. The specific operation is to put the sample to be tested into the tube, leave the bubble space, and then quickly turn the testtube 180 ° vertically to observe the time required for the bubble to rise within the specified distance. The result is expressed in seconds (s).
4. Set shear rate method
The set shear rate method uses a cylinder, disc or blade to swirl/spin in a Coating specimen to generate a rotational flow. The viscosity can be calculated by measuring the stress required to bring it to a fixed shear rate. This method is often used to determine liquids such as high viscosity Paints. Results are expressed in Pa · s.
Application of viscosity in different industries
Viscosity is measured in a variety of ways, so it is widely used in a variety of industries. Here are some examples of viscosity applications in some major areas:
1. Coatings industry
In the Coatings industry, viscosity is a crucial parameter. By measuring the viscosity of Coatings, manufacturers can control the manufacturing process and ensure the conformity and mass of Coatings. This helps produce high-quality paints for various applications such as construction, automotive, furniture, and more.
2. Chemical industry
In the chemical industry, viscosity determination is used to control the rate and viscosity of chemical reactions to ensure the mass of the product. Especially in the polymer industry, viscosity is an important parameter, which is related to molecular weight and coalescence, and has an important influence on the performance of the final product.
3. Food and Beverage Industry
In the food and beverage industry, viscosity is a key quality indicator. For example, it is used to determine the texture and taste of sauces, jams and beverages. Determination of viscosity can help manufacturers adjust formulations to meet consumer tastes and preferences.
4. Pharmaceutical industry
In the pharmaceutical industry, viscosity determination is essential for the development and production of pharmaceutical formulations. Viscosity can affect the flowability, stability and injection performance of drugs and therefore requires precise control.
5. Petroleum and chemicals
In the field of petroleum and chemical industry, viscosity is an important parameter for the measurement of liquid petroleum products, which is of great significance for the storage, transportation and processing of oil products. In addition, in chemical processes, viscosity determination is also used to control the flowability of reaction materials.
Conclusion
Viscosity is a key property describing the flow performance of liquids, and it plays an important role in various fields. Different viscosity determination methods are suitable for different types of liquids, thus meeting the needs of different industries. In various fields such as Coatings, Chemicals, Food, Pharmaceuticals and Petroleum, accurate determination of viscosity is crucial to the control of product mass and production process. Therefore, it is very important for scientists, engineers and manufacturers to have an in-depth understanding and grasp of the concept and measurement method of viscosity. Through accurate determination of viscosity, we can better meet the needs of consumers and ensure a higher level of product performance and quality.
