1、FORD LABORATORY TEST METHOD BP 111-03 2001 O9 24 METHOD OF DETERMINING THE UNDERCURE OF HYDROGENATED NITRILE RUBBER IMPREGNATING THE FACING FABRIC OF TOOTHED TIMING BELTS Revised Editorial - no technical change A. Cockman Application The Hydrogenated Nitrile Rubber (HNBR) used to impregnate the poly
2、amide facing fabric covering the tooth profile of HNBR toothed timing belts is susceptible to under-curing during manufacture due to factors as yet unknown. This causes the rubber to be transferred to the surfaces of driving and driven pulleys leading to a build-up of material. This manifests itself
3、 as noisy running and increased wear due to tooth misengagement in the pulleys. HNBR contains additives with carbonyl groups in their chemical composition which are constant for a given HNBR compound whether it is under-cured or not. These additives can be extracted from the HNBR by acetone and subs
4、equent infrared spectroscopic analysis of the extract will show the presence of carbonyl groups at approximately 5.8 microns. If the HNBR is fully cured, there should be no nitrile groups from the rubber in the acetone extract. Thus by measuring the ratio of the infrared peaks attributable to carbon
5、yl groups at 5.8 microns and nitrile groups from under-cured HNBR at 4.4 microns, an assessment of the degree of under-cure of the HNBR can be made. Apparatus Required Round Bottom Flasks 250 mL with ground glass joint. Sohxlet Extraction Apparatus With ground glass joint to fit the round bottom fla
6、sk. Hot Plate, Heating Block or Other Means of Heating Suitable for heating the round bottom flask with the Sohxlet extractor to reflux the solvent. Water Bath or Evaporator To remove solvent. Vacuum Oven (60 C10.1 mm Hg) To dry extracts. Amber Glass Vial with PTFE Faced Septum - 2 mL I I Date I Act
7、ion I Revisions Copyright O 2001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BP 111-03 Roller Mixer Glass Syringe - 250 microlitres Infrared Spectrophotometer Demountable KBr or NaC1 Cell Acetone Analytical reagent grade. Chloroform Analytical reagent grade. Conditioning and Test Cond
8、itions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 OC and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. 1. 2. 3. 4. 5. 6. Procedure Peel a length of o
9、uter fabric from the belt without the aid of solvent to soften the rubber. Place approximately 1.0 to 1.5 grams of fabric in a sohxlet extraction thimble and extract 4 times with fresh 200 mL portions of acetone refluxed for 4 hours each until complete extraction has taken place. (Place glass antibu
10、mping granules in the bottom of the flask.) After extraction, evaporate the acetone from each flask over a water bath to leave the extracted residue from the rubbedfabric sample. Dry each extract in the flask in a vacuum oven at 60 OC, 0.1 mm Hg for at least 30 minutes. Redissolve the extracts with
11、chloroform and combine them. Concentrate the combined extract by evaporation to approximately 0.5 mL. Transfer the chloroform solution to a 2 mL amber glass vial fitted with a PTFE faced septum. Page 2 of 3 Copyright O 2001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BP 111-03 7. 8. 9
12、. 1 o. 11. 12. 13. Before testing, mix the solution on a roller mixer for 30 minutes. Using a syringe transfer 50 to 250 microlitres of sample into a demountable cell fitted with sodium chloride or potassium bromide plates and a spacer of suitable thickness to give a carbonyl peak transmittance of 2
13、0 to 30 %. Ensure that there re no air bubbles in the film. Produce an infrared spectroscopic trace of the absorption peaks attributable to the nitrile group (CN) at approximately 4.4 microns and the carbonyl group (CO) at approximately 5.8 microns. Measure the areas of these peaks between 2214 and
14、2264 wave numbers (CN) and 1690 and 1770 wave numbers (CO) respectively. Calculate the ratio of the CN area and the CO area. Repeat steps 8 to a further 4 times, cleaning the cell thoroughly with clean chloroform between each sample. Calculate the mean CN/CO peak area ratio for the five measurements
15、. Note: When using a single beam FTIR spectrophotometer ensure that o carbon dioxide from breath is introduced into the sample chamber either during the background scan or sample scan as this causes an error in the CO peak value. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper useand handling in its facilities. Page 3 of 3 Copyright O 2001, Ford Global Technologies, Inc
