Is it scientific to determine the index by measuring the viscosity of Tu-4 cups?

Is it true that no one knows? :'(

The appearance of Tu 4 Cup is historic. It is mainly for the coatings at that time. It has a certain comparability on the relative size and amount of the base materials, additives and the molecular weight of the base materials in the coating. It is a relatively comparative testing method. It is fast and simple, and can reflect certain situations.； For the sample you measure, it depends on what your desired purpose is!

Very scientific! ! ! Especially for those who make high-performance coatings! ! !

Figure 4 cup, or other series of cups (iso, astm) is an orifice plate viscometer. Its basic working method is to flow out a certain amount of liquid through a small hole due to its own gravity, and determine the viscosity by measuring the time required for the flow out. The longer the time, the greater the viscosity. Normally the test is carried out at room temperature. Since the liquid level in the cup continues to decrease and the shear rate experienced by the liquid continues to change, the viscosity measured by this method can be understood as a viscosity index rather than the viscosity itself. This viscosity index can be compared with the actual viscosity to get a better corresponding curve. In this way, the Figure 4 cup can be used for a fast viscometer. Results are usually available within a few minutes. If the properties of the liquid to be measured are relatively stable, this method can be used for product quality testing. Some large paint companies or the painting departments of automobile companies use this method to check viscosity. Strictly speaking, this approach lacks scientific rigor. But for a single product, this method has strong practicality.

The viscosity of liquids has a close relationship with temperature. If there is no constant temperature room, for products with high viscosity and there is a large gap between the measured temperature and room temperature, you should be careful to use Tu4 Cup, because the measurement time is long and the temperature changes significantly. :)

There are regulations on the use of paint cups: 1) Viscosity range of material ； The measurement of low viscosity materials is possible, but high viscosity materials are generally not applicable. Secondly, the error may be larger, and the human and environmental impacts are large. 2) The fluidity of the material ； Paints with poor fluidity cannot be measured with a paint cup. 3) Whether the material is thixotropic. Specifically, if there are thixotropic materials, the fluidity will be affected, thus affecting the results. If you want to get precise and stable results without using a paint cup, there are two ways: 1) Ordinary spindle viscometer 2) Rheometer

Although it is used for coatings, it can still be used for low viscosity products. It can reflect the viscosity.

Sir, your question is very good. Let me share with you my personal opinion.: First, let’s talk about the significance of silicone oil viscosity measurement.: The apparent viscosity of silicone oil is an intuitive reflection of the molecular weight of polysiloxane. Annual rulings are usually used to guide industrial production and test application performance. The viscosity of silicone oil is generally expressed in rotational viscosity units, such as: poise, centipoise, etc., units of kinematic viscosity, such as: Meter 2/second, centimeter 2/second, millimeter 2/second, etc., and it is difficult to convert between the two. The method of measuring the viscosity of silicone oil usually uses a rotational viscometer, an Ubbelohde viscometer, etc. Because the rotational viscometer is easy to operate, it is usually widely used by industrial enterprises in production. Secondly, the Tu-4 cup viscometer used to measure paint viscosity is measured in units of time, which reflects the time it takes for paint with a certain viscosity to flow through a paint cup of a certain diameter. The length of time is directly proportional to the viscosity of the paint. The reason why the viscosity of paint is measured using this method is that a certain amount of solid filler has been compounded in the paint, such as: Matting materials, pigments, auxiliary film-forming fillers, etc. have serious viscous flow phenomena and cannot be measured with a rotational viscometer, let alone an Ubbelohde viscometer. But it can be used very well to monitor paint viscosity. Third, let’s look at the original poster’s question. Since the 4-cup viscometer can measure the viscosity of coatings, it can also be used to measure the viscosity of silicone oil. Under the same measurement conditions, based on the measurement data, the viscosity of the silicone oil sample can be compared. It is simple and has no problem. Fourth, is it scientific to use Tu-4 cup viscosity as the standard to determine whether silicone oil products are qualified or not? The answer is no, it is unscientific! Because the composition and structure of silicone oil and paint are very different, the apparent viscosity behavior is also completely inconsistent. Fifth, the viscosity data measured by rotational viscometer, Ubbelohde viscometer, etc. can reflect the interaction between molecular chains, especially the measurement data of Ubbelohde viscometer, which can be related to the molecular weight through the Mark-Houwink equation. ； However, the viscosity measured by the Tu-4 cup viscometer (note the unit: time) not only superficially reflects the interaction between molecular chains, but also includes the thickening effect of the filler, etc., so this is a fundamental difference! Sixth, as to how big the difference is, what is the margin of error? It should be said that it is impossible to talk about it. But I suggest you do some research: Through a series of silicone oils of different viscosities, the rotational viscosity and coated-4 cup viscosity were measured respectively, and the two sets of data were mathematically processed to compare and see if there was a correlation. If there is a correlation and a close relationship, this can be used to guide production, which makes sense. This post was last edited by bionics on 2008-8-4 22:41 ]

If it is scientific, first of all, if it is not scientific, no one will use this method. Second, there is the issue of accuracy. If the accuracy requirements are not high, there is no need to use high accuracy. Just like I need to weigh a ton of material, it doesn't need to be accurate to 0.0001 grams. Third, there is a scope of application, and as long as it is within this scope, it is scientific. It would be unscientific to measure low-viscosity liquids using this method.