No Child Left Behind in Art?

Interaction of Zinc Oxide Clusters with Molecules Related to the Sulfur Vulcanization of Polyolefins (“Rubber”)

“…In conventional vulcanization of natural rubber (cis-poly-A C H T U N G T R E N N U N G isoprene) approximately 1 mol of ZnS is produced per mol of cross-links formed, [3] which indicates that the ZnS originates from the H 2 S produced by substituting hydrogen atoms of the polyolefin by sulfur (see below).…”

“…The interaction energy of Lewis bases with Zn 4 O 4 increases in the following order: CO < S 6 < C 2 H 4 < C 3 H 6 < Me 2 S 2 < 1,4-C 5 H 8 < MeSH < Me 2 O < Me 2 S < Me 3 N ! CH 3 ). The NH form of free MBT is 36 kJ mol À1 more stable than the tautomeric SH form, while the sulfurized MBT derivative benzothiazolyl hydrodisulfide C 7 H 5 NS 3 (BtSSH) is most stable with the connectivity > CSSH.…”

“…The reaction energy given in Equation (22) applies to R = CH 3 , that is, to acetic acid as a model compound. The structure of the product 17 is shown in Figure 6.…”

“…[2] Typically, the vulcanization mixture consists of a natural or synthetic polyolefin (100 parts by weight), carbon black (50), elemental sulfur (0.5-4), zinc oxide (2-4), stearic acid (1-4), organic accelerators (0.5-2), and small amounts of antioxidants, retarders, and other chemicals (quantities given in parts per hundred of rubber). [3] The function of most of these constituents is reasonably well understood, [4] but the possible reactions of zinc oxide with the other components have not been studied to such an extent that the role of this material is clear. It is known that zinc thiolate complexes also accelerate the vulcanization process, [1] and most likely such compounds are formed from zinc oxide on heating with some of the chemicals mentioned above.…”

“…About 90 000 t of zinc oxide, together with smaller amounts of other zinc chemicals, are consumed annually by the rubber industry in the EU. [3] The wear of tire treads is the primary route by which zinc is released from rubber products to the environment. Therefore, there are ongoing efforts to reduce the zinc content of vulcanization mixtures without reducing the overall quality of the product.…”