Q. Is a mesh taalit kattan, probably synthetic, kasher and can you make a bracha on it?

A. Shulchan Aruch (O.H. 9: 1) rules that only clothes made of linen or wool are Biblically liable for the mitzvah of tzitzit, any other material is at best only Rabbinical. Remah (ibid.) maintains that other materials are also included in the Biblical mitzvah. However, they all agree that the definition of clothing for the purpose of this mitzvah is that it has to be woven from threads; therefore clothing made of leather is exempt from tzitzis. (ibid. 10: 4). Chayei Adam 11: 6) adds that they are exempt even Rabbinically, even when threads were made from the leather and then woven into clothing (Igros Moshe O.H. 2: 1).
Poskim disagree in regards to clothing made from synthetic threads such as nylon, if it is comparable to leather and is exempt (from a pasuk that indicates that leather is not a begged), or it is different since normally this is now a type of common clothing. Mahari Shtaif O.H. 28, Halichos Shlomo 3: 16, Har Tzvi (1: 9), and others maintain that since they are woven and commonly used, they are liable at least Rabbinically. When the mesh, is not woven, but rather imprinted on a sheet of the synthetic material, Poskim maintain that it is exempt of tzitzis.
Horav Shlomo Miller’s Shlit’a opinion is that clothing made from synthetic threads is liable for tzitzis and one can recite a brocho on them.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a