Hello,
This question is not naive and is easy to answer. But I would like to understand the basics of methods being followed across different laboratories where active/biopolymeric films are being developed. How do you make sure the uniform thickness? Ideal molds for casting biopolymeric films? Ideal temperature being used for drying? How long do you keep the dried films after peeling before you start film analysis? Please share basics that you use in your laboratories (can be facility pictures also)
Thank you
Dear Mandeep Gulati
Although casting biopolymeric films is not my speciality, maybe some of these suggestions can help you a bit:
The substrate on which you are depositing the biopolymer should be inert, and do not stick to the polymer (so it is easy to remove after casting). A colleague at my lab uses a little PTFE box. PTFE is very inert, and the surface is normally smooth, and the parts can be machined easily to ensure that is it levelled correctly (this is to have uniform thickness when casting).
When it comes to drying, it depends a lot on the solvent where the biopolymer is. If it is water, you need to be sure that the temperature is high enough (above 100C, at ambient pressure). I remember removing solvents and so by using vacuum. This, during the process, will generate bubbles, but if the biopolymer is not crosslinked, you might finish with a very smooth surface. If this does not work, then drying slowly in an oven I think would be the best option to pursue.
Finally, there is a way of seeing when the polymer is totally dried before peeling, and it is by comparing the weights before and after drying. Something like this: imagine that you cast your biopolymer in a PTFE box and you weight that. Great. Now you put it in the oven and let it dry for, let's say, 12 hours, and you record the weight again. And the you do it after 24 hours, and so on, until the weight is constant. That means that all the solvent that could be evaporated is gone (once the weight becomes constant). This time will be very dependent on the film thickness, of course.
Hope this helps
Biopolymeric films are developed through precise casting methods using defined molds to ensure uniform thickness. Drying temperatures are typically between 25°C and 60°C. After peeling, films should be stored at room temperature for several hours to days before analysis to allow moisture equilibrium.
To produce bubble-free films you can use a vacuum pump and ultrasonic bath. After plasticization, it keeps the solution at a temperature of 60 °C (to thermoplastic starch for ex.) transferring it to a kitassato. A vacuum pump is used in conjunction with the ultrasonic bath to facilitate the removal of bubbles.
- To achieve optimal results in film fabrication, prepare a precise volume of the casting solution based on the dimensions of the mold to ensure uniform thickness. Allow the films to dry at ambient temperature instead of using an oven or applying vacuum, as this minimizes bubble formation and ensures even drying. Once dried, measure the thickness of the peeled-off films using a thickness gauge for accuracy and consistency. To maintain the integrity of the films, store them in a desiccator to prevent moisture absorption.
Hey guys,
Just wanted to ask you all that I dissolved PLA (4043D) in DCM. I solvent cast the same on a glass petri dish and kept it for drying without covering it under a fume hood. I saw some white flaky-like things form. I don't know what that is. Can someone please tell me how to overcome this problem at the earliest? Thanks
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