Filled compounds with properties

SE-BR has several outstanding properties. Above all it has improved processability. Carbon black-filled compounds based on commercial BR show the well known bagging and sagging effects on the batch-off mill (13) unless the BR is blended with NR or SBR. Figure 5 shows a compound based entirely on Ti-BR and containing 50 parts of carbon black, at various times on the roll mill. 

The use of irradiated PTFE powder in EPDM gives enhanced mechanical properties as compared to composites containing nonirradiated PTFE. The existence of compatibility between modified PTFE powder and EPDM is indirectly revealed by , DSC, and SEM. shows that modified PTFE powder (500 kGy-irradiated) is obviously but partially enwrapped by EPDM as compared to nonirradiated PTFE powder. This leads to a characteristic compatible interphase around the modified PTFE. The resultant chemically coupled PTFE-filled EPDM demonstrates exceptionally enhanced mechanical properties. Crystallization studies by DSC also reveal the existence of a compatible interphase in the modified-PTFE-coupled EPDM. The synergistic effect of enhanced compatibility by chemical coupling and microdispersion of PTFE agglomerates results in improvement of mechanical properties of PTFE-coupled EPDM compounds. In summary, an effective procedure both for the modification of PTFE powder as well as for the crosslinking of PTFE-filled EPDM by electron treatment has been developed for the preparation of PTFE-coupled EPDM compounds with desired properties. 

The state of the art in friction and wear of PTFE-filled rubbers include the effects of many important system parameters, such as the composition of the rubber formulation, particle dispersion, bulk mechanical properties, ability of transfer film formation, and the chemistry between PTFE powder and the rubber matrix. Although the present study has explicitly highlighted the potential of PTFE powder in rubber matrixes with significant property improvements in the friction, wear, and physical properties, it has simultaneously opened a new field regarding the use of PTFE powder in rubber compounds, with some challenging tasks for chemists, engineers, and material scientists. 

The probable existence of protactinium was predicted as early as 1871 by Mendeleev to fill up the space on his peiiodic table between thorium (at, no. 90) and uranium (at. no, 92). He termed the unconfirmed element ekatantalum. In 1926, O. Hahn predicted the properties of the element in considerable detail, including descriptions of its compounds. In 1930, Aristid v. Grosse isolated 2 milligrams of what then was termed ekatantalum pentoxide and showed that element 91 differed m all reactions with comparable amounts of tantalum compounds with exception of precipitation by NH3. However, credit for the discovery of protactinium generally is attributed to Lise Meitner and Otto Hahn in 1917,... 

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