Lab Press Design and Utilization: ASTM D3182 Vs. ISO 2393

Difference-Between-ASTM-and-ISO-Lab-Press-Specs_01-01

When preparing samples for testing, it is important to adhere to standards to both ensure that the results are accurate and to have certainty of compliance with regulations and laws. Depending on what is being manufactured, where a company is located geographically, and where the product is being shipped, a company could be required to adhere to several different standards.

The main standards that apply to companies within the United States are ISO and ASTM. As it relates to laboratory press specifications for use in preparation of vulcanized samples for testing, these two standards are very similar to one another. There are, however, several key differences. This means that a lab press that is designed to be ISO compliant may not be ASTM compliant, and vice versa. Differences in the standards also include procedural differences for the prescribed preparation and handling of the materials.

To make it easier to see the differences between the two standards, we have prepared a table for a side-by-side comparison of ASTM D3182 and ISO 2393 as it pertains to preparing standard vulcanized samples for physical testing. Rows that are highlighted in green indicate that the two standards are identical in their specifications. Rows that are not highlighted denote deviation between the two standards (sometimes very small).

PRESS SPECIFICATIONS
Specification ISO 2393 ASTM
Pressure Requirement Not less than 3.5 MPa (500 psi) Not less than 3.5 MPa (500 psi)
Platen Size Sufficient size that no portion of rubber is nearer than 30 mm (1.18 in) to the edge of platen Sufficient size that no portion of rubber is nearer than 75 mm (3 in) to the edge of platen
Platen Composition Preferably made of rolled steel, machined for electric, steam, or thermofluid heating. Preferably made of rolled steel, machined for electric or steam heating.
Steam Platen Requirements
  • Each platen supplied individually
  • Self-bleeding trap or small vent shall be placed in exit steam line to allow steam to flow continuously through platens.
  • For chamber-type platens: steam outlet shall be placed slightly below steam chamber to ensure good drainage
  • Self-bleeding trap or small vent shall be placed in exit steam line to allow steam to flow continuously through platens.
  • For chamber-type platens: steam outlet shall be placed slightly below steam chamber to ensure good drainage
Heat Conduction Conduction of heat from platens to cross-head shall be reduced as much as practicable by means of steel grid or other means. Platens should be shielded from drafts. Conduction of heat from platens to cross-head shall be reduced as much as practicable by means of steel grid or other means. Platens should be shielded from drafts.
Parallelism Platens’ pressing surfaces shall be plane parallel to within 0.25 mm/m when heated to 150°C and closed under full pressure with a grid of soft solder or lead between them Platens’ pressing surfaces shall be plane parallel to within 0.25 mm/m when heated to 150°C and closed under full pressure with a grid of soft solder or lead between them
Temperature Uniformity Temperature over the mold area shall be uniform. Maximum deviation at the center of the platen shall not exceed ±0.5°C. Between adjacent platens, temperature difference between corresponding points shall not exceed 1°C, and the mean difference in platen temperatures shall not exceed 0.5°C Temperature over the mold area shall be uniform. Maximum deviation at the center of the platen shall not exceed ±0.5°C. Between adjacent platens, temperature difference between corresponding points shall not exceed 0.5°C

SPECIMEN SPECIFICATIONS

Specification

ISO

ASTM

Specimen Conditioning

• Between 2 and 24 hours,

• Standard lab temp. (ISO 23529),

• Pref. closed container or in room w/ humidity less than 50%

• Between 1 and 24 hours,

• At 23 ± 3°C (73.4 ± 5.4°F)

• At humidity less than 55% or for max precision, in closed container with humidity less than 35 ± 5%

Specimen Size

Cut to corresponding dimensions of mold cavity

4.5 ± 1.5mm (0.18 ± 0.06 in.) shorter in width and length than corresponding dimensions of mold cavity
Mass of Unvulcanized Sheet (150 x 150 mm)

Density

Mg / m3

Mass

g
0.94 47
0.96 48
0.98 49
1.00 50
1.02 51
1.04 52
1.06 53
1.08 54
1.10 55
1.12 56
1.14 57
1.16 58
1.18 59
1.20 60
1.22 61
1.24 62
1.26 63
1.28 64
1.30 65

 

Density

Mg / m3

Mass

g

(150 x 150mm)

Mass

g

(150 x 75mm)
0.94 52 ± 3 26 ± 1.5
0.96 53 27
0.98 54 27
1.00 55 28
1.02 56 28
1.04 57 29
1.06 58 29
1.08 59 30
1.10 60 30
1.12 61 31
1.14 62 31
1.16 63 32
1.18 64 32
1.20 65 33
1.22 66 33
1.24 67 34
1.26 68 34
1.28 69 35
1.30 70 35

 

VULCANIZATION PROCEDURE
Specification ISO ASTM
Temperature Tolerance Bring mold to within 0.5°C (1°F) of curing temperature for at least 20 minutes before inserting unvulcanized rubber Bring mold to within 0.5°C (1°F) of curing temperature for at least 20 minutes before inserting unvulcanized rubber
Mold Temperature Verification Verify mold temperature using thermocouple or other suitable device inserted into overflow grooves, and in intimate contact with the mold Verify mold temperature using thermocouple or other suitable device inserted into overflow grooves, and in intimate contact with the mold
Inserting Unvulcanized Material into Mold / Press Open the press, insert the unvulcanized pieces in the mold, and close the press in the minimum time possible. If necessary, open and close the press a few times to remove trapped air. The time taken for this process shall not be part of the vulcanization time. When the mould is removed from the press to insert the blanks, take any precautions necessary to prevent excessive cooling of the mould by contact with cool metal surfaces or by exposure to air drafts. Open the press, insert the unvulcanized pieces into the mold, and close the press in the minimum time possible. When the mold is removed from the press to insert the pieces, take precautions to prevent excessive cooling of the mold by contact with cool metal surfaces or by exposure to air drafts.
Vulcanization Time Vulcanization time is considered the instant that pressure is fully applied to the instant that pressure is released. The mold is to be held under a minimum of 3.5 MPa (500 psi) of pressure Vulcanization time is considered the instant that pressure is fully applied to the instant that pressure is released. The mold is to be held under a minimum of 3.5 MPa (500 psi) of pressure
Removal and Cooling / Conditioning Samples

As soon as the press is opened, remove the vulcanized sheets from the mold and cool in water (at room temperature or lower) or on a metal surface (for items used for electrical measurements) for 10 min to 15 min. Wipe dry the sheets cooled in water and reserve for testing. Be careful to prevent stretching or deformation.

Alternatively, the molds may be cooled in water before the vulcanized sheets are removed.

Store vulcanizates at one of the standard laboratory temperatures (ISO 23529). Separate vulcanizates with aluminum foil or other suitable material to prevent contamination during storage. The minimum time between vulcanization and testing shall be 16 h. The maximum time between vulcanization and testing shall be 96 h.

As soon as the press is opened, remove the vulcanized sheets from the mold and cool in water (room temperature or lower) or on a metal surface (for items used for electrical measurements) for 10 to 15 min. Designate in the report the type of cooling used.

Condition vulcanizates of compounds at a temperature of 23 ± 2°C (73 ± 3.6°F) for at least 16 h and for not more than 96 h before preparing and testing, unless otherwise specified.
Report Preparation

A report shall be prepared for each batch mixed. These reports shall include:

  • Vulcanization temperature
  • Vulcanization time
  • Molding pressure
  • Type of mold release agent, if used
  • Number of the International Standard specifying the evaluation procedure in which the test mix is to be used.

The ASTM only specifies recording the method of sample cooling used in the report. However, it can be assumed that it is good practice to also record:

  • Vulcanization temperature
  • Vulcanization time
  • Molding pressure
  • Type of mold release agent, if used
  • ASTM number of the test procedure in which the material is to be used.

 

MonTech Lab Presses meet or exceed all of the specifications listed above. To learn more about MonTech Lab Presses visit: www.montechusa.com/lab-presses

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