1、 FORD LABORATORY TEST METHOD AV 102-01 Date Action Revisions 2000 08 30 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockman 1989 10 23 Printed copies are uncontrolled Page 1 of 6 Copyright 2000, Ford Global Technologies, Inc. DETERMINATION OF PERCENT
2、SILICA-PRODUCING VOLATILES IN SILICONE RUBBER ADHESIVES/SEALERS WHICH CURE AT ROOM TEMPERATURE Application This test method establishes a procedure to determine the percent silica - producing volatiles present in an RTV sealant. Silica - producing volatiles are contributors to the fouling of oxygen
3、sensor systems used in the control of vehicle emissions. As a contributing source of contamination, the volatile potential of TRV sealants can be accurately monitored by the use of this procedure. Utilizing this method in conjunction with the realistic maximum volatility tolerance level can help min
4、imize the risk of oxygen sensor disfunction from formed - in - place sealants. Scope The procedure consists of four basic steps: 1) the RTV s ealant is cured to its elastomeric form; 2) the volatiles are extracted from the cured sealant; 3) the extract is separated and measured by gas chromatography
5、; and, 4) the GC results are quantified using a siloxane calibration. The volatile silicones from a commercial RTV sealant are primarily cyclodimethyl - siloxane. Other species present having GC retention times similar to those of the cyclics are assumed to be silicone as well. Apparatus and Materia
6、ls Required Gas Chromatograph Varian Model 2720 or equivalent, equipped with a thermal conductivity or flame ionization detector and linear temperature programmer. Column A column capable of separating cyclosiloxanes, e.g. 3.0 m x 3.0 mm stainless steel standard wall packed with 5 % OV - 101 on Chro
7、mosorb W , HP grade, 80/100 mesh. Inlet packing should be Chromosorb W, HP grade 80/100 mesh. The maximum operating temperature for OV - 101 in 350 C. Use of other phase materials with maximum operating temperatures closer to the 290 C procedure temperature may r esult in column bleed and a shift in
8、 the base line. A base line shift will affect integration of the higher cyclics and linears. Recorder-Integrator (1 MV) Hewlett - Packard Model 3390 A or equivalent, for data acquisition. Glass Plates 0.89 mm thick, for curing the wet formed - in - place sealant (see Figure 1). FORD LABORATORY TEST
9、METHOD AV 102-01 Page 2 of 6 Copyright 2000, Ford Global Technologies, Inc. Teflon Slab (see Figure 1) Humidity Chamber A humidity chamber for curing samples, or a controlled laboratory environment with a relative humidity of 40 to 60 %. Wrist-Action Mechanical Shaker VWR Catalog Number 57040 - 027
10、or equivalent. Vials Flint glass, 30 mL, VWR Catalog Number 66011 - 165 or equivalent. Screw cap, size 22 - 400 with polyethylene cone liner, VWR Catalog Number 16217 - 067 or equivalent. Syringe Capable of accurately delivering 20 + 0.1/ - 0.0 microlitre (no plastic elements due to solvents used).
11、Serum Bottles/Hypodermic Vials Due to the volatility of pentane, the standard solution should be sealed to minimize evaporative loss. Use capped serum bottles, Fisher Catalog Number 06406E or 1 mL disposable hypodermic vials with septums. Balance Top load balance with glass draft shield capable of 0
12、.0001 g accuracy. Reagents All must be reagent grade. Silicone Standards Polydimethylcyclosiloxanes can be obtained from base manufacturers (G E, Wacher Silicones, Huls America or Silar). Pentane Dodecane Spectral grade (99 %). Helium For carrier gas. Conditioning and Test Conditions All test values
13、 indicated herein are based on material conditioned in a controlled atmosphere of 23 +/ - 2 C and 50 +/ - 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. FORD LABORATORY TEST METHOD AV 102-01 Page 3 of 6 Copyright 2000, F
14、ord Global Technologies, Inc. Procedure A. Preparations 1. Cured Sample. Tape two 0.889 + 0.051/ - 0.000 mm thick glass plates to the Teflon slab so they are approximately parallel and about 50 mm apart. Place a quantity of RTV sealant on the Teflon slab between the two plates and near one end. Draw
15、 a third plate across the deposited RTV, spreading it to an even thickness (0.889 mm) between the t aped plates. The spreading plate riding on the parallel plates maintains the necessary sample thickness. Avoid entrapped air and knit lines when preparing the sample. Allow this sample to cure for 24
16、hours at 25 C and 50 % relative humidity (see Figure 1). Cut three (3) strip specimens for each candidate material that produce the desired sample weight (1 g) in one piece. The cured sample thickness should be 0.899 mm. Make the cuts in the following locations on the cured slabs (see Figure 2). 2.
17、Stand ard Solution. Add 0.1 g (weighed to the nearest 0.1 mg) of each pure cyclic (98 %) to 1.0 g of dodecane (99 % - weighed to the nearest 0.1 mg). Add 10 +/ - 0.1 mL of pentane to the container and seal to prevent evaporation. 3. GC Operating Conditions. Use the following settings for this analys
18、is. Variation is allowed provided there is sufficient separation of peaks. Inlet: 290 C Detector: 290 C Column: 50 C to 320 C at 10 C/minute with 20 minutes hold at upper limit He Carrier Gas Flow Rate: 35 mL/ minute. 4. Calibration. Use the operating conditions described in A.3 and inject a one (1)
19、 microlitre sample of the standard solution. Response factors for the individual cyclics are calculated using the following equation: R f D n = Amt. D n in std. soln. x Area dodecane in chromatogm. Area D n in chromatogm. Wt. dodecane in Std. soln. Response factors for cyclic species vary in a relat
20、ively linear manner from D 5 through D 10 , so that response factors for cyclics not in the standard solution can be calculated from the known response factors of the cyclics in the standard solution. All unknowns which appear in the analysis are assumed to be siloxanes. All unknowns are given, as r
21、esponse factors, the average response factor calculated for the cycl osiloxanes from D 4 through D 1 0 . FORD LABORATORY TEST METHOD AV 102-01 Page 4 of 6 Copyright 2000, Ford Global Technologies, Inc. B. Test: 1. Extraction. Pre -weigh each cured sample (0.98 to 1.02 g). Weigh 0.015 to 0.025 g of d
22、odecane to the nearest 0.0001 g and place it in the 30 mL vial. Add about 10 mL of pentane. Place the curved sample into the vial and seal the container immediately to prevent evaporative loss. Shake for 16 hours. Note: The sequence is important due to the volatility of the solvents used. 2. Inject
23、40 microliters when using a thermal conductivity detector, or 1 to 5 mic roliters when using a flame ionization detector, into the column at the recommended test conditions (A.3). 3. After the elution is complete, about 35 minutes, identify the peaks and quantify them by integration using the follow
24、ing equations: % D n = R f D n (Area D n in chromgm) x Wt. of dodecane in sample x 100 Area dodecane in chromgm Wt. RTV in sample Perform the calculation for D 4 - D 10 . % Unkn.= R f D 4 - D 10 (Area unkn. in chrgm) x Wt. dodecane in sample x 100 Area dodecan e in chromgm Wt. RTV in sample R f D 4
25、- D 10 = Average response factors of D 4 - D 10 . Perform the calculation for all unknowns that elute between D 4 - D 10 . % Siloxane Volatiles = Sum of % cyclics D 4 - D 10 and sum of % unknowns eluting from D 4 - D 10 . Notes: Silicone volatiles below D 5 may not be detected at their correct level
26、s due to their loss from the sealant as it cures for 24 hours at 25 C and 50 % relative humidity. Dodecane can mask D 5 forms and the beginning of the first unknown. Any D 3 not lost would be masked by impurities in pentane. Weight precision is extremely important if the results are to be reproducib
27、le. C. Reporting: 1. Three data points shall be reported for each sample as % total volatiles. 2. Final results for siloxan e should be expressed as 0.00 %. Report D 4 through D 10 for total volatiles as cyclics plus unknowns (L 4 through L 10 ). 3. Automated devices for measuring and calculating pe
28、ak areas should be used. No planimeters. 4. All observed and recorded data on whi ch the calculations are based. 5. Date of the test, the conditions of cure and thickness of the sample. FORD LABORATORY TEST METHOD AV 102-01 Page 5 of 6 Copyright 2000, Ford Global Technologies, Inc. D. Precision and
29、Bias: 1. Statements on precision and bias were prepared in accordance with “Evaluating the Measurement Process“, D. J. Wheeler and R. W. Lyday, c.1984. 2. The results were determined from an inter laboratory program with six materials and six laboratories. Testing was conducted on three separate day
30、s within each laboratory. 3. Repeatability refers to within - laboratory variation (op erator) and reproducibility refers to between laboratory variation. 4. Bias, in statistical terminology, is the difference between an average test value and the reference, or true, test property value. Reference v
31、alues do not exist for this test method si nce the value or level of the test property is exclusively defined by the test method. Bias, therefore, cannot be determined. E. Calculations: 1. Total Volatiles - Est replication std. dev. = 0.0338 Est. uncert. for a single meas. (median uncert.) = 0.67 =
32、0.023 95 % upr. bound = 2.00 = 0.068 Repeatability (oper. effect) = 0.0399 Meas. error std. dev. = + = (0.0338) + (0.0399) = 0.052 Est. sample to sample std. dev. = 0.28 Signal to Noise ratio / = 5.38. Thus the number of distinct product categories that can be reliably distinguished is 1.41 x 5.38 =
33、 7.59 2. Percent Cyclics - Est. replication std. dev. = 0.031 Est. uncert. for a single meas. (median uncert.) = 0.67 = 0.02 95% upr. bound = 2.00 = 0.06 Repeatability (oper. effect) = 0.067 Meas. error std d ev. = + = (0.031) + (0.067) = 0.074 Est. sample to sample std. dev. = 0.33 Signal to Noise
34、ratio / = 4.46. Thus the number of distinct product categories that can be reliably distinguished is 1.41 x 4.46 = 6.29 Chemicals, materials, parts, and equipmen t referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD AV 102-01 Page 6 of 6 Copyright 2000, Ford Global Technologies, Inc. Figure 1 Apparatus to Make Cured Slabs Figure 2 Locations for Sample Cuts from Cured Slabs
