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Description / Abstract:
Introduction
Note: Nothing in this standard supercedes
applicable laws and regulations.
Note: In the event of conflict between the
English and domestic language, the English language shall take
precedence.
Purpose. Measure the percent silica producing
volatiles present in liquid injection molded silicone, heat cured
silicone rubber or one component room temperature vulcanizing (RTV)
silicone sealant regardless of cure system.
Applicability. Silica producing volatiles are
contributors to the fouling of oxygen sensor systems used to
control vehicle exhaust emissions. Encapsulating electronics in
silicone liquid injected molded products may result in these low
molecular weight extractable (cyclic dimethyl-siloxane) disrupting
electrical function. As a contributing source of contamination, the
volatile potential of silicone can be accurately monitored using
this procedure. Utilizing this procedure in conjunction with a
realistic maximum volatility tolerance level for end use silicones
can minimize risk of component dysfunction.
Consistency. To avoid variation in measurements
to production parts or sealant, and when comparing test results,
the following must be strictly controlled:
• Time from molding to test (3.3).
• Extraction or shake time (5.2.1).
• Specific gravity (5.3.2) of the silicone part or sealant
evaluated must be used to determine compliance to the maximum
percent specified on the release print.
Remarks. This procedure consists of the
following four (4) basic steps:
1.The silicone sealant is cured to its elastomeric form and
molded parts are sampled.
2.The volatiles (cyclic dimethyl-siloxane) are extracted from
the cured silicone.
3.The extract is separated and measured by gas chromatography
(GC).
4.The GC results are quantified using a siloxane standard
solution calibration.