New ethylene standards for EPDM.

A consortium of European and North American ethylene-propylene rubber producers have cooperated under the joint leadership of the International Institute of Synthetic Rubber Producer's (IISRP) Technical/Operating Committee and the American Society for Testing & Materials (ASTM) to produce an updated ASTM D 3900 standard test method with expanded ethylene standards, the IISRP has announced.

The standard, first published in 1980, is broadly accepted within the industry for determining the chemical composition of ethylene-propylene(-diene) rubbers and, in particular, for determining the mass percent ethylene contained, according to Richard Killian, IISRP deputy managing director.

Killian said the method outlined in the standard developed in 1971 (ref. 1), utilized infrared spectroscopic techniques, centered on six calibration standards: ethylene-propylene copolymers whose ethylene content was determined with NMR tests of C14-tagged monomer.

He added that technical advancements in analytical techniques provided an opportunity to more precisely define the quality of the ethylene values assigned to the various calibrants and, at the same time, to expand the number of calibrants from six to ten improve accuracy.

International cooperation between European EPDM producers, represented by the IISPR's European section technical/operating committee, and North American EPDM producers, represented by ASTM, used 13C NMR to determine more accurately the ethylene contents of the calibrants, according to Dr. Jacques Noordermeer, chairman of the IISRP European technical/operating committee.

The ten new standards were adopted by ASTM and published in the July 1994 issue of ASTM Standard D 3900 [D 3900-94].

Dr. Noordermeer pointed out that the re-established mass percent values for the original six calibrants differ to some extent from the values assigned in 1971 (reference table and graph shown). He added that the use of the new mass percent ethylene calibrants will results in calculated ethylene values that differ from those previously determined.

Killian noted that EPDM producers may implement these new calibrants at their individual discretion and according to their own timetables.

Table 1
                Mass percent ethylene
Standard no.    Old    New
    1           37     40.1
    2           48     52.4
    3           55     58.6
    4           63     66.8
    5           69     70.8
    6           79     78.6
    7            -     44.8
    8            -     52.6
    9            -     69.5
   10            -     77.5

Samples of these calibrants are available from:

Exxon Chemical Co., Baytown Polymers Center

Vistalon Technology Manager

5200 Bayway Drive

P.O. Box 5200

Baytown, TX 77522 USA

[Figure 1 ILLUSTRATION OMITTED]

References

[1.] I.J. Gardner, C. Cozewith and G. Verstrate, "Infrared determination of composition of ethylene-propylene copolymers," Rubber Chemistry and Technology, 44, 1015-1024