Important!
Only A and B components with the same batch number should be processed together!
Material preparation:
ELASTOSIL® S 699 A/B contains a lightweight filler that might separate during transport or long storage. In order to ensure a homogeneous product composition, and hence an optimal product performance, it is recommended to thoroughly stirr up both component A and component B prior use. Note: since the lightweight filler can collapse when exposed to high shearing, the use of dissolver mixers or mixing devices with strong shear impact should be avoided.
To eliminate any air introduced during re-dispering the filler, it is necessary to de-aerate component A and B prior use. Applying vacuum (25-50 mbar) for some 10-15 min proved useful. Please note, that extended de-aeration under vacuum can alter the curing performance of ELASTOSIL® S 699 A/B; potential effects are a shortened potlife at room temperature, a lowered kick-off temperature and a faster curing under heat, for instance.
Surface preparation:
All surfaces must be clean and free of contaminants that will inhibit the cure of ELASTOSIL® S 699 A/B. Examples of inhibiting contaminants are sulfur containing materials, plasticizers, urethanes, amine containing materials and organometallic compounds – especially organotin compounds. If a substrate’s ability to inhibit cure is unknown, a small scale test should be run to determine compatibility.
ELASTOSIL® S 699 A/B is not self-adhesive. In order to make the rubber adhere to other materials (e. g. glass, aluminium, stainless steel, metal alloys and thermoplastics) it is necessary to treat the respective substrates with plasma, corona or a primer (such as WACKER® Primer G 790 TOLUENE FREE) prior to the application of the silicone.
Mixing:
Caution ! Component A of ELASTOSIL® S 699 A/B contains the platinum catalyst, component B comprises the crosslinker. Since even traces of platinum catalyst may cause gelling of component B, all tools (e. g. spatula, stirrers, mixing cups etc.) used for handling either component A or the A/B mix must not come into contact with component B by mistake.
The two components should be thoroughly mixed at a 1 : 1 ratio by weight or volume, preferably by automatic metering lines equipped with static or dynamic mixing devices.
Curing:
The curing time of addition-curing silicone rubber is highly dependent on temperature, size and heat sink properties of the respective substrates or of the assembly parts to be bonded, respectively. In order to secure a quick build-up of adhesion to the substrates, ELASTOSIL® S 699 A/B is vulcanized preferably between 100 °C and 200 °C. Typical curing temperatures and resulting curing times are given in adjacent table.
Detailed information about processing 2-part addition-curing silicones is given in our brochure “ROOM TEMPERATURE VULCANIZING (RTV) SILICONES - MATERIAL AND PROCESSING GUIDELINES”. We recommend running preliminary tests to optimize conditions for the particular application.
Chemical resistance:
Fully cured ELASTOSIL® S 699 is chemically resistant to most gases and many liquids (fluids, lubricants, cleaning agents, aqueous media, alcohols and other polar solvents). Long-chain esters or aromatic and alipatic hydrocarbons (e. g. fuels, gasoline, kerosene etc.), however, can result in a physical, but reversible swelling of the silicone rubber, which might have a temporary impact on both the dimensional and mechanical stability of the affected silicone article.
Removal:
If removal of the silicone from machines or dispensing equipment is necessary, white spirit or similar nonpolar solvents are recommended. However, cleaning ideally should take place before the silicone is fully vulcanized. Cured silicone rubber needs to be rubbed off or removed mechanically, if necessary in combination with a swelling agent (solvent) or a chemical silicone remover.
