Limit, short term substitution

As an alternative to harmful fire retardant, nano-clay applications have recently been nsed very successfully, especially with PU foams that are used in furniture [23]. A draft list of Persistent, Bioaccumulative, and Toxic substances, providing limits under the proposed EU-REACH regulations for authorisation (targeted for control and/or substitution) in the short-term, as well as elimination in the longer term, is also available. 

About 70% of natural rubber consumption goes into tire production while the remaining 30% is used by the nontire sector. There is some substitutability of various synthetic elastomers for natural rubber, but it is rather limited. This substitutability is restricted for the tire sector, which globally uses almost half of its total rubber requirement as natural rubber. In the short term, it is technically very difHcult to make major substitutions of synthetic rubber for NR use. Some applications are very critical, such as the use of NR in wire adhesion compounds for the production of steel-belted radial tires. Also, the use of natural rubber is very critical in the production of very large off-the-road tires. However, the natural rubber requirements of the nontire sector were only 29% of its total rubber usage in the year 2000. The nontire sector only used about 22% of its total rubber requirement as natural rubber in 2010. Many times it is easier in the nontire sector to substitute specialty syn-... 

The stiffness of a biomaterial should be comparable to that of cortical and trabecular bone to support loading at the fracture site (Nilsson 2003). Therefore, bone substitutes have to be designed in order to withstand long-term or short-term compressive and bending forces. The main drawback of CaPs materials is their brittleness and poor strength, limiting their use as implants in loaded situations. 

Oxidation of unfunctionalized alkanes is notoriously difficult to perform selectively, because breaking of a C-H bond is required. Although oxidation is thermodynamically favourable, there are limited kinetic pathways for reaction to occur. For most alkanes, the hydrogens are not labile, and, as the carbon atom cannot expand its valence electron shell beyond eight electrons, there is no mechanism for electrophilic or nucleophilic substitution short of using extreme (superacid or superbase) conditions. Alkane oxidations are therefore normally radical processes, and thus difficult to control in terms of selectivity. Nonetheless, some oxidations of alkanes have been performed under supercritical conditions, although it is probable that these actually proceed via radical mechanisms. 

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