At present, the price of polyethylene is about 1 1000, and the average grade of polystyrene is about 10500, with little difference. And the density of polyethylene is 0.92-0.95, while that of polystyrene is 1.05. From the perspective of material cost alone, polyethylene has more advantages. As for PTFE, the price of the material itself is at least three times higher than the above two kinds, and the processing is not easy and the processing cost is much higher.

Ptfe has many characteristics far beyond ordinary plastics, just because it is a soft spot in mechanical properties and its hardness is low. It is rarely used to make stress-bearing structural parts, and it is really used in the wrong place.

If you make a PH pen, is there any transparency requirement? Then only polystyrene is transparent, polyethylene is translucent and PTFE is opaque. However, polystyrene itself has poor mechanical properties, too brittle, easy to break, and poor acid and alkali resistance. If the product requirements are high, it is recommended to use PMMA (plexiglass, commonly known as acrylic).