I understand there are multiple methods to accomplish this but I would greatly appreciate some insight as to how it is currently done. Thanks so much ahead of time.
There are two components to cure PDMS: the base and the curing agent. Mixing them in a certain volume ratio starts the curing process (I was using 1:10 curing agent:base, but certainly you can use different ratios). If you leave it as it is, it will cure probably about in one day. If you want faster curing, put the mixture inside an oven at about 100 Celcius. After 1-2 hours, it should be cured.
One thing to remember: after mixing the curing agent and the base, if there are air bubbles inside the mixture, it is better to put it inside a vacuum to get rid of the bubbles. After that, you can put it in the oven.
Well, the commercial PDMS is supplied with two components: Base Elastomer and Curing Agent. The appropriate mixing ratio is 1:10 where in, one part is constituted by the curing agent while rest of the ten parts is PDMS elastomer. The curing agent acts as a cross-linker, however, controlled heating surely expedites the cross-linking cum curing of the mixture. The curing time is directly linked with the temperature at which the mixture is fixed at, and the general trend is with higher temperatures, the curing times decreases. For example, the room temperature requires roughly two days for curing while as at fixed 100 degree Celsius, it takes 30-35 minutes to cure.
As rightly mentioned by Mr. Mustafa Eryürek, we often come across the air bubbles in the mixture at later stages of observation. Such bubbles create hindrance in optical observations owing to scattering and absorptive losses. Just to be on the safe side about your mixture, degasification of the mixture in the vacuum desiccator must be done prior to the curing. Also, remaining gas bubbles,if any left after curing, can be burst with the help of a sharp needle that is essentially free from any sort of contaminants.
You can use PMHS (Polymethylhydrosiloxane) as a cross-linking agent. It is generally taken in 1:10 PDMS : PMHS for cross-linking in the presence of tin catalyst. You can also use alkoxy silane (e.g. Tetrethyl ortho silicate) or chloro silane (Dimethyl dichloro silane) as cross-linking agent in the preseance of tin catalyst. You can vary curing temperature from 45 to 60 degree Celsius . Please see the following article published by our group.
Article Comparison of the Initial Reactant Structure and Crosslinked...
One of the most common curing agents for PDMS is
(3-Aminopropyl)triethoxysilane (APTES). It's used as 25% solution in ethylsilicate esther. We usually use 10-15% of that APTES solution for curing PDMS at room temperature. The curing is complete after two days.
Hi. A commercial PDMS comes usually with the base and the curing agent. With the mixing ratio of 1:10 (base:curing agent), the result will be better.
Hi. In addition to mentioned points, I should say that it is important to obey the recipes for special ratio of base and curing agent you use. Because, the time and temperature influence some properties of the final cured one such as elasticity which might be critical in some applications. Therefore, I suggest you do curing under correct recipe. I have referred to an article that I use for Sylgard 184. It might be useful.
doi:10.1088/0960-1317/24/3/035017
Check this link- it reviews the chemistry of cure the most common silicones. For academia it is dominated by platinum cure of vinylsiloxanes. For the consumer it is moisture cure of silanol siloxanes. For industrial it is peroxide cure.
https://www.gelest.com/themencode-pdf-viewer/?file=https://www.gelest.com/wp-content/uploads/Reactive_SIlicones.pdf
You might want to check this out:
http://blogs.rsc.org/chipsandtips/2012/04/18/easy-and-inexpensive-fabrication-of-pdms-films-of-different-thicknesses/?doing_wp_cron=1510851772.1185209751129150390625
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