Method and compositions that can be used for sealing and assembling components of a powertrain

A polyorganosiloxane composition X that is crosslinkable into elastomer in the presence of moisture provided by ambient air or by prior addition of water, via polycondensation reaction comprising:

• A) at least one polyorganosiloxane A comprising at least one alkoxylated group and comprising identical or different siloxyl units, of formula:
• (Z)b(R4)aSiO[4−(a+b)]/2 (1)
• in which:
• the symbol Z=[—(OCH2CH2)c—OR5], with c=0 or 1,
• a=0, 1, 2 or 3;
• b=0, 1, 2 or 3, a+b=0, 1, 2 or 3,
• the symbol R4 represents a C1 to C13 monovalent hydrocarbon-based radical,
• the symbol R5 represents a C1 to C6 monovalent hydrocarbon-based radical or an alkoxyalkyl radical optionally comprising an ester function, and
• with the condition that for at least one siloxyl unit, the index b≧1 such that the polyorganosiloxane A contains at least one alkoxylated group Z,
• B) optionally at least one polyalkoxylated silane B of formula:
• (R2)zSi(OR3)(4−z) (2)
• in which:
• z=0 or 1,
• the symbol R2 represents a C1 to C13 monovalent hydrocarbon-based radical, and
• the symbols R3, which may be identical or different, each represent a C1 to C6 monovalent hydrocarbon-based radical or an alkoxyalkyl radical optionally containing an ester function,
• C) at least one acetylene black D whose function is to absorb an oil used in a powertrain,
• D) at least one aluminum trihydrate E as mineral filler,
• E) at least one adhesion promoter F bearing at least one amine function,
• F) a catalytically effective amount of at least one guanidine G as condensation catalyst,
• G) optionally at least one unreactive linear polyorganosiloxane H,
• H) optionally at least one filler I, different from E, and
• I) optionally at least one additive J such as a coloring base, a pigment or a thixotropic agent,
• with the additional conditions that
• said polyorganosiloxane composition X contains neither any calcium carbonate nor any siloxane containing from 2 to 10 siloxyl units obtained by partial hydrolysis and condensation of a polyalkoxylated silane, and that
• the polyorganosiloxane A has a number of units strictly greater than 10, optionally greater than 20 and at most equal to 2000.