Pranav

The silicones producer have all low viscosity oligomers-polymers.You have to chose the final cured polymer in account, i,e, the final use.Sylgards are adhesives and protectors.

There are the Silicone Rubbers, the RTV-Room Temperature , in one and two-components and also, very diferent kind off cure, the older tin catalysts and "newer "platin catalysts.

I recoment, Deep diving on the sites of, still, Dow Corning and Wacker Chemie.

Both have good intruduccions in the silicones fields, both sites are open to all visitants , to only, still to myself, challenges to work with.

Both are stting too, in INDIA, if not look to there homes, USA and Germany.

I still workes with silicones (siloxanes) getting my hands in , don't care the most arent toxic.

Good luck and keep contact, Roland

Thanks Roland. I did find some low viscous curable silicone by Wacker. But the problem with that is that they cure very fast at room temperatures. My work involves diffusing liquid silicone inside a porous substrate and curing it inside, and hence I would like to have a degree of control on when to initiate the curing process, maybe for example by UV. How do you suggest this to be done?

Well Pranav, can give me same information about the sustrate to work with?

How many fast or slow will you prefere the cur time and also pot life ?

Wath kind of silicone polymer you arefore, silicones can be

taloyred from soft geles to rubbers from 15 Shore A to 80 Shore A hardness and still more to resins, more ore less harder then the rubbers.

There are of course, differnt kind to cure and UV-Cure seems very aczeptable in terms of potlife.

Nice to see, that my former colleges by Wacker are quick, arent they?

Greetings, Roland

Thank you for the response Roland!

The substrate is a sugar based nano-porous system. I would prefer the pot life to be atleast 24 hours at room temperature conditions (without UV) so as to give sufficient time for silicone to diffuse inside the nano-pores. The initial viscosity of the system should be

I think for your purpose you must forget the usual approach to make silicon rubbers. It is difficult to combine long pot life, low viscosity and ambient temperature curing. One possibility is to use epoxy function silicon fluids like in the first link. I would chose a mixture of the first type (epoxy functional with lateral epoxy groups) and the third type (epoxy terminated). You can mix these liquids with a cationic photo initiator from the second link and make a UV hardening. With the product GP 55 from the first link you can increase the hardness, with GP 504 you can decrease it. 

http://www.gpcsilicones.com/epoxyfluids.html

http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=20396764

Thanks Burkhard! I'll definitely try out this approach!

Just to clarify, can you elaborate on the possible issues I can face in case I use a low viscous vinyl terminated pdms with a peroxide UV crosslinker like say for e.g. benzoyl peroxide?

Si-CH=CH2 containing silicons (vinyl lateral or as end group) are not suitable to UV curing with photoinitiators. Also for curing with peroxides this double bond need harsh conditions. A vinyl group directly on Si only gives a fast room temperature reaction in hydrosilylation with hydride functional silicons catalysed by Pt catalyst (Karstedt's catalysts) but in this case you have only a short pot life. If you want to make UV curing with normal photoinitiators you need acrylate or methacrylate functional silicons but they are not commercial. You can make it yourself by reacting the epoxy functional silicons with (meth)acrylic acid in presence of a catalyst like triphenylphosphine and an inhibitor like hydroquinone monomethylether, in doing so the epoxide ring is opened by the acid, but it is easier to make the UV curing directly with the epoxy functional silicons and the use of a cationic photoinitiator.