Someone please advise how to get films of uniform thickness by solvent casting method. I am using petri dish to pour the PLA/chloroform solution but the thickness is not uniform.
It depends on the viscosity of your solution and the viscosity of your solution will control the thickness of the film.If you want films with a very thin thickness(less than 100 micrometer), then prepare a 5to 10 weight percent of PLA solution in chloroform. then using a small beaker you pour the solution in your petridish. remember that your petridish must be on an even surface and this will control the uniformity of your film and also the way you pour the solution on your petridish,after trying a couple of times you get uniform films.
I used a wet film applicator (bird type: https://www.gardco.com/pages/application/ap/birdtypeapp.cfm).
Dissolved polymer can be evenly spread on a glass plate with this applicator which can be peeled out after drying, it helps in obtaining a highly uniform thickness of films. In my case wet film thickness was around 700 micron which produced 40-50 micron thickness films after drying. One can get this type of applicator from local vendors also. there are other variations of this kind of applicator.