Silicone mechanical properties variation 1

There's not just one flavor of silicone adhesive. Are you looking at an addition cure or a condensation cure silicone? What is the monomer used to build the chain? Is it ambient cure or elevated cure?

In other words, there is no one single answer to the question. Contact GE or Dow (silicone experts). They can direct you to an applications engineer who may have run tests on "a single" silicone adhesive where the bondline thickness was varied. This would be the only way (unless you want to make up and run the samples yourself) that you will get the answer you're looking for. Most literature will give a bond strength or modulus based on one thickness.

Actually, I have tried with Dow Corning but with no sucess (no tests were performed on this adhesive).
The silicone I am searching is the RTV 3145 (Dow). The problem is that I have experimental data for a thickness and I would like to have a full behavior variation for a range of thiknesses (graph or table...). To perform the tests for a big range of thicknesses is time dispending, which I do not have...

Dear Sirs,
I would be indebted to you if you could help me out with a small dilema. I have recently been in a discussion on a car forum and the issue revolves around vinyl protection. Vinyl as in your dashboard and other areas of your car. Tthe controversy is whether certain popular manufactured vinyl protectants (i.e. 303, Vinylex, ArmourAll, and so on) are bad for vinyl due to the type of silicones contained in them. The popular buzz words are PDMS (good silicone) and DMS (bad silicone). Below is several quotes from the board:

"Dimethal Silicones are migratory, they enter into the substrate and since they are an "oil" break down slowly the polymer substrate(binder/flim former resin for one) which is also derived from crude oil. They release the plastizers from vinyl,rubber and paint.Cause them to evaporate out of the substrate, leaving behind a "dry" unflexable surface."

"
There are many types of silicone the consensus is the oily ones are bad. They attract dust and do not last long IMO.

PDMS based protectants (water based) have a silicone in them but it is the good silicone not the evil one."

"The Vinylex contains the good silicone, its PDMS. The Armour All stuff has the DMS silicone which is bad."



1. Does this 'DMS is bad for vinyl' vs. 'PDMS is good for vinyl' debate make sense??

2. Is it true certain silicones cause the release of plastizers hence causing the vinyl to become weak, brittle, and dull?

3. Is there any other helpful facts you could give me in regards to how silicone and vinyl interact?

Thank You,

Kelly

Doyle, Genberg and Michels in “Integrated Optomechanical Analysis”, SPIE press, pages 86-98 discuss the geometrical effects that cause the apparent tensile modulus to vary between its true value and the bulk modulus depending the geometry of the sample. In thin large diameter adhesive joints the material is constrained from lateral motion and with the high Poisson’s ratio (0.49 or so) the joint becomes much stiffer in tension/compression.