1、Designation: D7997 15Standard Practice forPolyurethane Raw Materials: Gel Tests for PolyurethaneNon-Foam Formulations1This standard is issued under the fixed designation D7997; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers procedures for determining the geltimes of polyurethane non-foam formulations using commer-
3、cially available gel test equipment.1.2 Definitions, terms, and techniques are described alongwith procedures for calculating sample weights.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport
4、to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1There is no known ISO equivalent to this sta
5、ndard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to Plastics3. Terminology3.1 DefinitionsFor general definitions of terms used in thispractice see Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 gel pointthe extent of polymerization at which theupp
6、er limit, as defined by the procedure being run, is reached.3.2.2 gel timethe time from the initiation of the reaction tothe gel point.3.2.3 resin blend (formulated polyol)complete ingredientformulation without the isocyanate component.3.2.4 indexthe ratio of the equivalents of the isocyanatecompone
7、nt to the equivalents of the resin blend of a polyure-thane formulation.4. Summary of Practice4.1 The gel time of a polyurethane non-foam formulation isdetermined by measuring the time required for the viscosity ofthe polymerizing system to increase to a set level using a gelmeter. It is recommended
8、 that the torque of the gel meter beverified with a gauge certified to NIST standards.5. Significance and Use5.1 General Utility:5.1.1 This practice is suitable for research, quality control,specification testing and process control.5.1.2 It is useful to define and verify the reactivity ofnon-foam p
9、olyurethane formulations.5.2 Limitations:5.2.1 Operator-to-operator variability and lab-to-lab vari-ability can be significant.5.2.2 The variability of this practice is dependent on theequipment used to measure the gel time. It is recommendedthat the testing laboratory and the client agree on the eq
10、uipmentand the conditions to be used that include the following:5.2.2.1 Gel Tester and gel point criteria,5.2.2.2 Speed/rpm of the mixer,5.2.2.3 Type and shape of the mix blades,5.2.2.4 Size and type (for example, shape, lined or unlined)of container for mixing the components and for measuring thege
11、l time, and5.2.2.5 The volume (or height) of material to be placed inthe container for measuring the gel time and the depth of themeasuring wire or spindle of the gel tester from the bottom ofthe container.5.2.3 The estimation of precision in this practice is verylimited. Users of this practice shal
12、l develop their own precisiondata to determine if these procedures meet their requirements.5.2.4 It is possible that low-levels (ppm, ppb) of contami-nants will not be detected using this practice.6. Sampling6.1 Since organic isocyanates react with atmosphericmoisture, take special precautions in sa
13、mpling. Usual sampling1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved Nov. 15, 2015. Published December 2015. DOI:10.1520/D799715.2For referenc
14、ed ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
15、shohocken, PA 19428-2959. United States1methods, even when conducted rapidly, can cause contamina-tion of the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times. (WarningDiisocyanates are eye, skin and respiratory irritants at concen-trations above the occ
16、upational exposure limit (TLV or PEL).Diisocyanates can cause skin and respiratory sensitization(asthma) in some people. Once sensitized, it is essential to limitfurther exposure to diisocyanates. Use a combination ofengineering controls and personal protective equipment, in-cluding respiratory, ski
17、n and eye protection, to prevent over-exposure to diisocyanates. Consult the product suppliersSafety Data Sheet (SDS) for more detailed information aboutpotential health effects and other specific safety and handlinginstructions for the product.)7. Test Conditions7.1 Isocyanate samples shall remain
18、sealed against moistureuntil immediately before testing.8. Equipment and Reagents8.1 Commercial gel meter or other equipment capable ofdetermining a large increase in viscosity that occurs in apolymerizing urethane system at or near the gel point.8.2 Balance, capable of weighing to 0.1 mg.8.3 Contai
19、ners appropriate for the particular gel test beingrun.8.4 Stopwatch or electronic timer.8.5 Heating device as described in the specific procedure.8.6 Methyl ethyl ketone (MEK) or other solvent appropriatefor cleaning the equipment after use.8.7 Motorized mixer with blades (or spatula for manualmixin
20、g).8.8 Two component non-foam polyurethane formulationconsisting of a resin blend as needed to obtain the desired geltime and an isocyanate component.NOTE 2Additional equipment may be listed in specific procedures inthe Appendixes.9. General Procedure9.1 A general procedure is outlined below with ex
21、amples ofspecific steps provided in the Appendixes.9.1.1 Charge the container used in the gel test with acarefully weighed amount of the resin blend and the isocyanatebeing reacted. A 1.05 index is typical for gel tests but can beadjusted for a specific test or formulation.9.1.2 Immediately start th
22、e timer or stopwatch and mix thecomponents thoroughly (the timer is to be started at thebeginning of the mix, that is, when the reaction is initiated).9.1.3 Introduce the container with the reacting system to thegel meter and monitor the reaction. Because some formulationssolidify, consider using di
23、sposable stirring paddles or probes.9.1.4 Stop the timer when the reaction reaches the gel point.Many commercial units will shut off automatically at thedefined gel point.9.1.5 Record the gel time.10. Sample Calculations10.1 Calculate the equivalent weight, EWp, of the resinblend as follows:EWp5100O
24、H1 Ac!100561001%W9(1)where:OH = the hydroxyl number of the resin blend in milli-grams of KOH per gram of sample,Ac = the acid number of the resin blend in milligrams ofKOH per gram of sample,%W = the percent water in the resin blend,56100 = the equivalent weight of KOH in milligrams ofKOH per equiva
25、lent, and9 = the equivalent weight of water in grams perequivalent.10.2 Calculate the equivalents of the resin blend, EQp,asfollows:EQp5 XpEWp(2)where:Xp= the amount of resin blend to be reacted with theisocyanate component in grams10.3 Calculate the equivalents, EQi, of the isocyanate com-ponent ne
26、eded to prepare the batch at an index of 1.05 asfollows:EQi5 1.05 3EQp(3)where:1.05 = the index of the batch10.4 Calculate the equivalent weight, EWi, of the isocyanatecomponent as follows:EWi542.02 3100%NCO(4)where:%NCO = the percent by weight of NCO groups present inthe sample and42.02 = grams NCO
27、 per equivalent of NCO.10.5 Calculate the weight, Wi, of isocyanate in gramsneeded to prepare the batch as follows:Wi5 EWi3EQi(5)11. Report11.1 Report the gel time and the procedure used.12. Keywords12.1 gel time; isocyanate; polyol; polyurethane; raw mate-rial; resin blendD7997 152APPENDIXESX1. EXA
28、MPLES OF GEL TIME TEST PROCEDURES FOR POLYURETHANE NON-FOAM FORMULATIONS(Nonmandatory Information)X1.1 The information in these nonmandatory appendices isgiven to provide the reader with examples of test conditions asdefined by individual companies. Other acceptable test condi-tions are possible.X1.
29、2 Specific suppliers are provided below as examples.Other suppliers are available and users of this practice areencouraged to identify suppliers and parts that meet theirspecific needs.X1.3 Test Procedure A is used to determine the gel time ofa polyester polyol with an isocyanate component using aSu
30、nshine Gel Meter.X1.4 Test Procedure B is used to determine the gel time ofan isocyanate component with a resin blend using a Gardco GelTester.X1.5 Test Procedure C is used to determine the gel time ofa two component elastomer system using a Shyodu Gel Timerand includes information on verifying the
31、torque of the ShyoduGel Timer with a desktop IMADA DTX-15B Torque Tester.X2. TEST PROCEDURE A: GEL TIME OF A POLYESTER POLYOL WITH AN ISOCYANATE COMPONENT USING A SUN-SHINE GEL METERX2.1 ScopeX2.1.1 This procedure determines the reactivity of a poly-ester polyol by measuring the gel time of a non-fo
32、am polyure-thane formulation using a Sunshine gel meter.X2.2 Summary of PracticeX2.2.1 A polyester polyol is reacted with an isocyanate andthe reactivity is determined by measuring the time required forthe viscosity of the polymerizing system to increase to a setlevel using a gel meter.X2.3 Equipmen
33、t and ChemicalsX2.3.1 Gel meter, Sunshine Scientific Instruments.X2.3.2 Balance, analytical, 0.01-g readability,.X2.3.3 Oven, circulating air, 110C.X2.3.4 Baths, oil, circulating high temperature.X2.3.5 Stopwatch.X2.3.6 Methyl ethyl ketone (MEK).X2.3.7 Polymeric MDI reagent.X2.3.8 Oil, high temperat
34、ure silicone bath.X2.3.9 Test tubes, 18-mm by 150-mm.X2.3.10 Jar, glass, 237-mL (8-oz).X2.3.11 Spatula.X2.4 ProcedureX2.4.1 Weigh 50 g of polyester polyol into a 237-mL (8-oz)jar. Cover and place the jar in the 110C oven for one hour.X2.4.2 Set the oil bath to the desired temperature (example:For a
35、polyester polyol with hydroxyl number of 35 mgKOH/g,set oil bath temperature to 130C). Set up the gel meter asdescribed in the operation manual.X2.4.3 Weigh the appropriate amount of isocyanate to thenearest 0.1 g. (See X2.5.) Remove the jar of polyester polyolfrom the circulating air oven and rapid
36、ly add the isocyanate.X2.4.4 Start the stopwatch as soon as the isocyanate isadded.X2.4.5 Immediately mix with a spatula for 1.5 min and fillan 18-mm by 150-mm test tube to a height of 9.5 cm from thebottom of the tube.X2.4.6 Place the tube in the gel meter bath and install thespindle so that it rem
37、ains 2.5 cm off the bottom of the tube.X2.4.7 Start the gel meter and stop the stopwatch at thesame time. Record the time, SW, on the stopwatch to thenearest second.X2.4.8 When the gel meter stops and the buzzer sounds,record the gel meter time, G, to the nearest second.X2.4.9 Immediately remove the
38、 spindle from the unit andclean it with MEK.X2.5 CalculationsX2.5.1 Calculate the equivalent weight, EWPE, of the poly-ester polyol as follows (see Note X2.1):EWPE556.1 31000OH(X2.1)where:EWPE= the equivalent weight of the polyester polyolsample,56.1 = the equivalent weight of KOH in milligrams perm
39、illiequivalents,1000 = the factor for converting milliequivalents toequivalents, andOH = the hydroxyl number of the polyester polyol samplein milligrams of KOH per gram of sample asdetermined by the appropriate specification method.NOTE X2.1Equation in X2.5.1 assumes negligible contribution fromD799
40、7 153the acid number and water content of the polyester polyol. The user of thispractice must validate this assumption for their particular systemX2.5.2 Calculate the equivalents, EPE,in50gofthepolyester polyol as follows:EPE550EWPE(X2.2)where:50 = the amount of the polyester polyol used in the reac
41、tivitytest in gramsX2.5.3 Calculate the equivalent weight, EWI, of the appro-priate isocyanate as follows:EWI542.02 3100%NCO(X2.3)where:42.02 = the equivalent weight of an NCO group in gramsper equivalent,100 = the factor for converting % NCO to grams ofNCO, and%NCO = the %NCO of the isocyanate as d
42、etermined by theappropriate specification method.X2.5.4 Calculate the weight, WI, of isocyanate to be used inthe reactivity test as follows:WI5 EPE3EWI(X2.4)where:WI= the weight of the isocyanate in gramsX2.5.5 Calculate the total reaction time, T, as follows:T 5 G1SW (X2.5)where:G = the time from t
43、he gel meter in seconds andSW = the time from the stopwatch in seconds.X2.6 ReportX2.6.1 Report gel time results, T, to the nearest one second.X2.7 PrecisionX2.7.1 The precision of this test method is not known at thistime because inter-laboratory data is not available.X3. TEST PROCEDURE B: GEL TIME
44、 OF AN ISOCYANATE COMPONENT WITH A RESIN BLEND USING A GARDCO GELTESTERX3.1 ScopeX3.1.1 This procedure is used to characterize the reactivityof Isocyanate X with a polyol blend.X3.2 Summary of PracticeX3.2.1 A sample of Isocyanate X is reacted with a polyolblend that consists of polytetrahydrofuran
45、diol and 1,4- butane-diol producing a product that is similar to one that is manu-factured by end users of Isocyanate X. Although the finalpolyurethane product has a moderately low average molecularweight, it can be classified as a thermoplastic. As the reactionproceeds, the viscosity of the reactio
46、n mixture increases andthis increase is monitored with a gel meter. The time requiredfor the mixture to reach the point where the wire stirrer makesonly one revolution in 60 seconds is reported as the gel time.X3.3 Equipment and ChemicalsX3.3.1 Gardco Hot Pot Gel Timer, Fast Cure (Paul N.Gardner, In
47、c.).X3.3.2 Oven, forced air, temperature control to 60.2C.X3.3.3 Oven, convection.X3.3.4 Balance, analytical, 0.1-mg readability.X3.3.5 Balance, top pan, 1-kg capacity.X3.3.6 Cup, aluminum, for Gardco gel timer.X3.3.7 Stirrer, wire.X3.3.8 Stopwatch, 1-s readability.X3.3.9 Polytetrahydrofuran diol, O
48、H No. ca. 112mgKOH/g.X3.3.10 1,4-Butanediol, anhydrous.X3.3.11 Xylene, raw material grade.X3.3.12 Dibutyltin dilaurate catalyst.X3.3.13 Syringe, glass, 50-L.X3.3.14 Bottle, screw-capped, 30-mL (1-oz).X3.3.15 Bottle, screw-capped, 120- mL (4-oz)X3.3.16 Pail, 2-L (0.5-gal).X3.3.17 Mixer, for 2-L (0.5-
49、gal) pail.X3.3.18 Nitrogen.X3.3.19 Polyol blend (17.8 to 1.0 weight ratio of polytetra-hydrofuran to to 1,4 butanediol).X3.3.20 Catalyst solution (4.75 w/w % dibutyltin dilauratecatalyst in xylene).X3.4 Instrument ConditionsX3.4.1 Gel meter conditions, 90C.X3.4.2 Oven, forced air, 60C.X3.4.3 Oven, convection, 90C.X3.5 ProcedureX3.5.1 Prepare the polyol blend. The steps to make a 500-gbatch are given below as an example.X3.5.1.1 Place the polytetrahydrofuran diol in a 40-50Coven until it is completely melted.D7997 154X3.5.1.2 Weigh 473.36 g of the well-mixed
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