ASTM D5289 – 95 R01

Designation: D 5289 – 95 (Reapproved 2001) Standard Test Method for Rubber Property—Vulcanization Using Rotorless Cure Meters1 This standard is issued under the fixed designation D 5289; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. 1. Scope 1.1 This test method specifies a method for the measure- ment of selected vulcanization characteristics of rubber com- pounds using rotorless linear shear, unsealed torsion shear, and sealed torsion shear cure meters. The three types of instruments may not give the same results. NOTE 1—An alternative method for the measurement of vulcanization characteristics is given in Test Method D 2084. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility 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. 2. Referenced Documents 2.1 ASTM Standards: D 1349 Practice for Rubber—Standard Temperatures for Testing2 D 1556 Test Method for Density and Unit Weight of Soil in Place by the Sand-Cone Method3 D 2084 Test Method for Rubber Property—Vulcanization Using Oscillating Disk Cure Meter2 D 4483 Practice for Determining Precision for Test Method Standards in the Rubber and Carbon Black Industries2 2.2 ISO Standard:4 ISO 6502 Rubber—Measurement of Vulcanization Charac- teristics with Rotorless Curemeters 3. Terminology 3.1 Definitions of Terms Specific to This Standard: 3.1.1 rotorless cure meter—a name for a class of cure meters that uses one of the two specimen shaping members or dies to sense the torque or stress during strain application. Rotorless cure meters do not have a third member in the form of a rotor (see definitions of cure meter in Test Methods D 1556 and D 2084). 3.1.2 torque—for an oscillating shear cure meter, the value measured by a torque transducer at the peak strain amplitude of the oscillating cycle. 3.1.3 The following measurements may be taken from the recorded curve of force or torque as a function of time (see Fig. 1). 3.1.3.1 minimum force or torque—measure of the stiffness of the unvulcanized test specimen at the specified vulcanizing temperature, taken at the lowest point in the vulcanization curve. 3.1.3.2 maximum, plateau, or highest force or torque— measure of the stiffness or shear modulus of the vulcanized test specimen at the vulcanization temperature, measured within a specified period of time. 3.1.3.3 time to incipient cure (scorch time)—measure of the time at which a specified small increase in force or torque has occurred; it indicates the beginning of vulcanization. 3.1.3.4 time to a percentage of full cure—measure of cure based on the time to develop some percentage of the difference in force or torque from the minimum to the maximum. 4. Summary of Test Method 4.1 A rubber test piece is contained in a die cavity which may be closed or almost closed and maintained at an elevated temperature. The cavity is formed by two dies, one of which is oscillated through a small linear or rotary amplitude. This action produces a sinusoidal alternating linear or torsional strain in the test piece and a sinusoidal shear force or torque which depends on the stiffness (shear modulus) of the rubber compound. The envelope curve, which is defined as the amplitude of the oscillating force or torque, is continuously recorded as a function of time (see Fig. 2). 4.2 The stiffness of the rubber test piece increases as vulcanization proceeds. The test is completed when the re- corded force or torque rises to either an equilibrium or maximum value, or when a predetermined time has elapsed (see Fig. 1). The time required to obtain a vulcanization curve is a function of the test temperature and the characteristics of the rubber compound. 1 This test method is under the jurisdiction of ASTM Committee D11 on Rubber and is the direct responsibility of Subcommittee D11.12 on Processability Tests. Current edition approved Sept. 10, 1995. Published November 1995. Originally published as D 5289 – 92. Last previous edition D 5289 – 93a. 2 Annual Book of ASTM Standards, Vol 09.01. 3 Annual Book of ASTM Standards, Vol 04.08. 4 Available from American National Standards Institute, 25 W. 43rd St., 4th Floor, New York, NY 10036. 1 Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. 5. Significance and Use 5.1 This test method is used to determine the vulcanization characteristics of (vulcanizable) rubber compounds. 5.2 This test method may be used for quality control in rubber manufacturing processes, for research and development testing of raw-rubber compounded in an evaluation formula- tion, and for evaluating various raw materials used in preparing (vulcanizable) rubber compounds. 5.3 The test piece in a rotorless cure meter approaches the test temperature in a shorter time and there is a better temperature distribution in the test piece due to the elimination of the unheated rotor found in oscillating disk cure meters. 5.4 Several manufacturers produce rotorless cure meters with design differences that may result in different torque responses and curve times for each design. Correlations of test results between cure meters of different designs should be established for each compound tested, and for each set of test conditions. 6. Apparatus 6.1 Rotorless cure meters of three types can be used. In each case, an oscillation of small amplitude is applied to one die. 6.1.1 Linear Strain Rotorless Cure Meter—This type of cure meter measures the force produced by a linear strain of constant amplitude (see Fig. 3(a)). 6.1.2 Unsealed Torsion Strain Rotorless Cure Meter—This type of cure meter measures the torque produced by an angular strain of constant amplitude in a cavity that is not completely closed (see Fig. 3(c)). 6.1.3 Sealed Torsion Strain Rotorless Cure Meter—This type of cure meter measures the torque produced by an angular strain of constant amplitude in a cavity that is completely closed and sealed (see Fig. 4(a)). 6.2 Die Cavity—The die cavity is formed by two dies. In the measuring position, the two dies are fixed a specified distance apart so that the cavity is almost closed (see Fig. 3(b) and 3(d)), or closed and sealed (see Fig. 4(a)). 6.2.1 The dimensions for typical linear shear curemeter dies include a diameter of 30 mm (1.18 in.), and a total depth of 4 mm (0.16 in.). The dimensions for typical torsional shear curemeters include biconical-shaped dies having a diameter of 40 6 2 mm (1.57 6 0.08 in.), and an angle of separation ranging from 7 to 18°, depending on the manufacturer’s design. In the center of the dies, a separation equal to 0.5 mm (0.02 in.) plus the die gap should be maintained (see Fig. 3(b), Fig. 3(d), or Fig. 4(b)). Manufacturer’s guidelines should be followed to determine if the dies have been excessively worn and should be replaced. 6.2.2 Die Gap—The gap between the edges of the dies in the closed position shall be between 0.05 and 0.20 mm (0.002 to 0.008 in.), preferably 0.1 mm (0.004 in.) for unsealed cavities. For sealed cavities, no gap should exist at the edges of the dies. 6.2.3 Die Closing Mechanism—A pneumatic cylinder or other device shall close the dies and hold them closed during the test with a force of not less than 8.0 kN (1820 lbf). 6.3 Die Oscillating System—The die oscillating system consists of a rigid eccentric drive, which imparts a linear or torsional oscillating movement to one of the dies, in the plane of the cavity. 6.3.1 The amplitude of the oscillation should be either 60.01 to 60.1 mm, preferably 60.05 mm (60.0004 to 60.0039 in., preferably 60.0020 in.) for linear shear; or 60.1° to 63.0°, preferably 60.5° of arc for torsional shear cure meters. 6.3.2 The frequency of oscillation should be between 0.5 and 2 Hz, preferably 1.7 6 0.1 Hz. 6.4 Force or Torque Measuring System—A force or torque measuring system shall measure the resultant shear force or torque. 6.4.1 The force or torque measuring device shall be rigidly coupled to one of the dies and any deformation shall be negligibly small and shall generate a signal which is propor- tional to the force or torque. The total error resulting from zero point error, sensitivity error, linearity, and reproducibility errors shall not exceed 1 % of the measuring range selected. NOTE 2—The elastic deformation of the oscillating and measuring system should not be more than 1 % of the oscillating amplitude; otherwise, the curemeter curves must be corrected. 6.4.2 The force or torque recorder device shall be used to record the signal from the force or torque measuring device. It shall record the envelope (see Fig. 2) and shall have a response time for full-scale deflection on the force or torque scale of 1 s or less. The force or torque shall be recorded with an accuracy of 60.5 % of the range. Torque recording devices may include analog chart recorders, printers, plotters, or computers. 6.5 Torque or force calibration equipment is required to measure the linear or angular strain amplitude and to calibrate the force or torque measuring device. Examples of calibration FIG. 1 Types of Vulcanization Curves FIG. 2 Envelope Vulcanization Curve D 5289 2 equipment are shown in Fig. 5, Fig. 6, and Fig. 7. The amplitude of oscillation of the device shall be checked with no test piece in it. A displacement transducer shall be used to measure the amplitude and torque measurements shall be checked against standard masses using a device as shown in Fig. 5 or Fig. 6. An alternate technique shall use a torque standard. FIG. 3 (a) and (b)—Typical Linear Shear Rotorless Curemeter; (c) and (d)—Typical Unsealed Torsion Shear Rotorless Curemeter D 5289 3 6.5.1 For calibrating linear strain curemeters, a displace- ment transducer shall be coupled by contact to one of the dies or blocks directly attached to it (see Fig. 5). The amplitude shall be checked with no test sample present. The force measuring system shall be checked by loading a wire, attached to the die or block by a pulley, with masses corresponding to the full-scale force to be measured. 6.5.2 For calibrating torsion shear curemeters, either a displacement transducer and wire-mass calibration or a torque standard shall be used. 6.5.2.1 A displacement transducer for checking angular displacement shall be coupled by a knife-edge bearing in contact with a rod fixed to one of the dies (see Fig. 6). The FIG. 4 Typical Sealed Torsion Shear Rotorless Curemeter FIG. 5 Calibration Equipment for Linear Shear Curemeter FIG. 6 Displacement Transducer and Wire-Mass Calibration Equipment for Torsion Shear Curemeters FIG. 7 Typical Torque Standard Calibration Device for Torsion Shear Curemeters D 5289 4 force measuring system shall be checked by loading a wire, attached to the die or block by a pulley, with masses corre- sponding to the full-scale force being measured. The torque shall be calculated in this case from the product of the applied force and the radius of the die block where the wire is attached. 6.5.2.2 Torque standard calibration checks the torque mea- surement at the selected angular displacement by clamping a reference steel torsion rod to the oscillating die and the torque measuring die of the torsion shear cure meter (see Fig. 7). The reference values for angular displacement and corresponding torque have been established by the manufacturer for each torque standard. 6.6 Temperature Controlling System—The method of tem- perature control shall maintain the following process param- eters: heating up time, curing temperature, temperature distri- bution, and reference temperature, which are necessary for reproducible measurement of the vulcanization curve. The temperature control system shall permit the reference tempera- ture to be varied between 110°C and 200°C with an accuracy of 60.3°C or better. 6.6.1 Die shall heat up in 1.5 min or less from closure of the die cavity. 6.6.2 Once heating up time hs been completed, die tempera- ture shall not vary by more than 60.3°C for the rest of the test. 6.6.3 The temperature distribution within the test piece shall be as uniform as possible. Within the deformation zone, a tolerance of 61°C of the average test piece temperature shall not be exceeded. 6.6.4 The reference temperature is determined by a tempera- ture sensor used for control. The difference between the reference temperature and the average test piece temperature shall not be more than 2°C. 6.6.5 Temperature measurement accuracy shall be 60.3°C for the reference temperature sensor. 6.7 Reference Test Temperature—The standard reference test temperature shall be 160°C (320°F). Tests may be carried out at other temperatures if required. Temperatures should be selected in accordance with Practice D 1349. 7. Sampling 7.1 The sample shall be taken from a vulcanizable rubber compound as required by the mixing method or other sampling instructions. 7.2 The sample shall be homogeneous, at room temperature, and as free of trapped air as possible. 8. Test Specimens 8.1 The recommended test specimen volume is between 3 and 5 cm3, depending on the model of instrument being used. The size of the test specimen should exceed the test chamber volume by a small amount, to be determined by preliminary tests. Typically, specimen volume should be 130 to 190 % of the test chamber volume. Once a target weight is established, the weight of specimens should be controlled to within 60.5 g for best repeatability. 8.2 The test specimen taken from the sample should be circular, with a diameter smaller than the test chamber of the instrument to be used. 9. Procedure 9.1 Preparation for Test—Bring the temperature of both dies to the reference temperature with the cavity closed. Adjust the zero of the force or torque measuring device, if necessary. 9.2 Loading the Curemeter: 9.2.1 Open the dies, unload the previous sample (if neces- sary), place the test piece in the cavity, and close the dies within 20 s. 9.2.2 The test time shall be counted from the instant that the dies are closed. Oscillation of the movable die shall be started at zero time or before. 10. Report 10.1 Report the following information: 10.1.1 A full description of the sample, its origin and compound details, 10.1.2 Test method and test details, 10.1.2.1 Reference to this test method, 10.1.2.2 Type and model curemeter used (linear or torsion shear, manufacturer, die options, if any), 10.1.2.3 Amplitude of the die oscillation, in millimetres or degrees, 10.1.2.4 Frequency of oscillation, 10.1.2.5 Force or torque range selected, in Newtons (N) or deci Newton metres (dN·m). (The equation for conversion from dN·m to lbf·in. is 1.13 (dN·m) = 1.00 (lbf·in.)), 10.1.2.6 Time scale of the recording device, 10.1.2.7 Curing temperature in degrees Celsius, and 10.1.2.8 Date of the test. 10.2 Test results reported are normally chosen from the following parameters (refer to Fig. 1 for guidance): 10.2.1 FL or ML—Minimum force or torque, in N or dN·m (lbf·in.). 10.2.2 Maximum Force or Torque—All in N or dN·m (lbf·in.). 10.2.2.1 FHF or MHF—Maximum torque where curve plateaus. 10.2.2.2 FHR or MHR—Maximum torque of reverting curve. 10.2.2.3 FH or MH—Highest torque attained during a specified period of time when no plateau or maximum torque is obtained. 10.2.3 tsx—Scorch time, in minutes (time to an increase of x units of force or torque from FL or ML). The preferred scorch time for tests at an oscillation amplitude of 60.5° is tsl. 10.2.4 Cure Time, in minutes. 10.2.4.1 t8x—equal to the time to x % of torque increase or t8x = minutes to ML + x (MH − ML)/100 torque. NOTE 3—This method of determining the cure times is considered the standard method. The most commonly used values of x are 50 and 90. A cure time of t810 is sometimes used as a measure of scorch time. 10.2.4.2 tx—equal to the time to x % of maximum torque, or tx = minutes to (x·MH)/100 torque. NOTE 4—This is an alternate method for cure time determination. 10.2.5 Cure Rate Index—equal to 100/(cure time − scorch time). 10.2.6 “t10 % Rise” is the time for the force or torque to rise to 110 % of the minimum value. This may be used to measure D 5289 5 scorch in some cases. 11. Precision and Bias 11.1 This precision and bias section has been prepared in accordance with Practice D 4483. Refer to Practice D 4483 for terminology and other statistical calculation details. 11.2 Precision—The precision data presented in Table 1 were obtained using a sealed torsion type rotorless curemeter,5 with standard dies as illustrated in Fig. 5, at 175°C and 60.5° arc. 11.2.1 The precision results in this precision and bias section give an estimate of the precision of this test method with the materials (rubbers, etc.) used in the particular inter- laboratory program as described below. The precision param- eters should not be used for acceptance or rejection testing of any group of materials without documentation that they are applicable to those particular materials and the specific testing protocols that include this test method. 11.2.2 Type I precision results are given in Table 1. This is a short term precision study, covering a period of 1 month or less. In this study, three compounds based on SBR and SBR/NR polymers with sulfenamide cure systems and carbon black reinforcement were carefully mixed and prepared for testing. Precut specimens were sent to 11 laboratories along with instructions to test duplicate samples of each compound in one day, and repeat the testing, after checking calibration, one week later. Each determination yielded a test result (four per compound). 11.2.3 The precision of this test method may be expressed in the format of the following statements that use what is called an appropriate value of r, R, (r), or (R), that is, that value obtained from Table 1, to be used in decisions about results obtained with the test method. 11.2.4 Repeatability—The repeatability, r, of this test method has been established as the appropriate value for any parameter as tabulated in Table 1. Two single test results, obtained under normal test method procedures, that differ by more than this tabulated r must be considered as derived from different or nonidentical sample populations. 11.2.5 Reproducibility—The reproducibility, R, of this test method has been established as the appropriate value for any parameter as tabulated in Table 1. Two single test results obtained in two different laboratories, under normal test method procedures, that differ by more than the tabulated R must be considered to have come from different or nonidentical sample populations. 11.2.6 Repeatability and reproducibility expressed as a per- centage of the mean level, (r) and (R), have equivalent application statements as 11.2.4 and 11.2.5 for r and R. For the (r) and (R) statements, the difference in the two single test results is expressed as a percentage of the arithmetic mean of the two test results. 11.3 Bias—In test method terminology, bias is the differ- ence between an average test value and the reference (or true) test property value. Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method. Bias, therefore, cannot be deter- mined. NOTE 5—Another precision study is to be performed using a greater number of materials differing from each other as much as possible. 12. Keywo