Why the drying unit of the density meter should consist of polycarbonate instead of plexiglas


The demands on the „pots“ are high: they have to stand the sometimes hard conditions in a laboratory. The thread must not break when treated ruggedly and the container should resist blows and being dropped on the floor.
Could that work with plexiglas? The slight difference in colour wouldn’t be a problem. Polycarbonate PC (Brandname among others „Makrolon“) is slightly bluish while plexiglas PMMA appears somewhat lighter or even slightly yellowish.
Heating the 2 materials to their softening points provided first interesting distinctions – the acrylic glas deformed strongly while polycarbonate kept its shape to a much greater extent.


polycarbonate keeps its shape


The brittleness test led to the final decision: Swarfs from both materials were rubbed in the palm. The swarfs from polycarbonate looked the same way after the treatment as before, while swarf from plexiglas was entirely crumbled.

swarfs in brittleness test


The different reaction to fire was also demonstrated – PC stops burning outside the flame, but PMMA keeps burning on its own.

reaction to fire


Only then the – obvious – idea came up: it was easy to prove the 2 different refractive indexes (polycarbonate 1.491 and plexiglas 1.586) by using an A.KRÜSS AR4 refractometer.
Conclusion: production of drying units will stay with the higher quality polycarbonate.