Recently, a friend asked me that the surface of the sample polished with worn old sandpaper looks smoother and better reflective than the surface of the new sandpaper, so is the old sandpaper better than the new sandpaper?
Conclusion: No, there is no doubt that the new sandpaper grinding effect is better than the old sandpaper grinding effect!
Here's why:
Taking the most common silicon carbide sandpaper as an example, the production of sandpaper uses an adhesive (generally a resin) to fix sharp abrasive particles to the paper base. Because the grinding of sandpaper is a micro-grinding process, the damage or shaping flow of worn abrasive to the sample is greater than that of sharp abrasive particles. It can be clearly seen from the section comparison diagram of the new and old sandpaper below that the abrasive on the new sandpaper is sharp and protruding, and after a period of use, the abrasive will be broken, the corners are cut off, and the abrasive particles are completely in the bonding layer. At this time, the removal rate of the material is relatively slow, and the chance of rubbing contact is increased.
The abrasion marks below are made with new and old sandpaper. Which do you think is the better preparation surface? What about the kind that comes from fresh sandpaper?
Here's a hint: the new sandpaper will have a clear, three-dimensional image of one abrasion on top of another. The abrasion marks of the old sandpaper no longer have a clear three-dimensional shape, and they all seem to be in a plane; However, in this case, the depth of the deformation layer of the sample will be multiplied. It is only because the abrasion marks are more flat and the reflection of the sample is better that it gives the illusion of more successful preparation.
I'm sure you already know the right answer. Therefore, in the grinding process, do not be afraid of scratches, the clear, three-dimensional, regular scratches brought by the new sandpaper represent the successful removal of the material. Changing the sandpaper in time will help you get a sample with less residual damage.
