I used 2% to 10% polylactic acid in chloroform. I get a stronger film but whitening is there .The PLA I use is stored in polytheene cover under normal condition
In (semi)-crystalline polymers when polymer crystals are formed, an evident change in color and transparency occurs. This happens due to the fact that polymer crystals are impermeable to light.
Best Regards,
Apostolos
Although crystallinity is certainly a possibility, you may want to rule out the effects of moisture in your starting material. PLA is hydrophilic and will absorb up to ~ 0.5% H2O by weight under certain conditions. You may want to dry the PLA per the manufacturer's recommended conditions and then make your solution with dried chloroform (stored over CaH2 and freshly distilled). When casting your film, place it under a glass cover/box with a slight gap under the box so that the chloroform will slowly evaporate or in a low temperature vacuum oven.....best of luck, Phil
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