The adhesion layer of the non stick pot affects the application effect, and the contact angle measurement is the most reliable index to characterize the performance of the non stick pot. For the contact angle measurement of non stick pan, the main problem is that the bottom of the pan can not be observed by the method of side view. Compared with the side view method, another typical method is the top view method, and the corresponding analysis method is ADSA-D. This method was proposed by A.W. Neumann team of the University of Toronto, Canada. ADSA-D uses droplet volume as boundary condition, and uses young Laplace equation to fit contact angle. The defects of the top view method are: (1) it can only be used to analyze the contact angle of the axisymmetric image; however, 98% of the sample surface is not axisymmetric due to the chemical diversity and surface structure; (2) due to various reasons, the accuracy of the calculated contact angle value is not high.
Therefore, we suggest to use portable contact angle measuring instrument for most of the pot shaped samples. In order to improve the accuracy of contact angle measurement, we suggest that the portable contact angle meter has the following functions:
1，Telecentric lens is used，
2，A 1/2 or lager size of camera is used,
3, A prism instead of a mirror is used as the light path turning structure，
4，The angle of view of prism can be adjusted with micron precision, such as one-dimensional tilted adjustment positioning stage with micrometer,
5，At the same time, the more droplets can be tested, the better. Three drops are recommended, which can be used to measure the surface free energy of multi drop method such as acid base method. Two drop method can be only used for Owens method for surface free energy, and this method can not be used to estimate the surface free energy of three droplets. It can only be used for two droplets and is not the most widely used method.
The actual test image of the portable contact angle meter (contact angle goniometry) with three drops which measures contact angle of the non stick pan is shown below.
For this pan, the contact angle value is shown as the drop shape image:
Values of contact angle show us:
1, Three drops of water have different value of contact angle means surface of sample is not clean at all.
2, The deviation value of contact angle is more than 2 degree means sample is not clean or “At the level of nanometer or micron, the sample surface has structure"
3, The result is value of contact angle by three drops tells us this sample is not as good as we expect it.
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