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The Use of Chemical Additives to Protect SBS Rubbers Against Ozone Attack
(C . A . Moakes) 한국고무학회 1999 엘라스토머 및 콤포지트 Vol.34 No.2
N/A SBS thermoplastic elastomers offer an inexpensive alternative to vulcanised rubbers for many undemanding applications. They are, however, particularly susceptible to attack from atmospheric ozone leading to cracking as soon as any strain is applied. In most rubber applications some strain is unavoidable. In this paper a compounding approach to protecting SBS thermoplastic rubbers against ozone is described. An explanation is offered for why a protective effect is observed only when certain combinations of additive are used. SBS elastomers are the most affordable class of thermoplastic rubbers. To achieve finished products resistant to ozone and without compromising the light colours often demanded, recourse must be made to blending with other saturated elastomers or replacement by hydrogenated (SEBS) types. The latter is a significantly more expensive alternative. Under laboratory conditions where the rate of ozone attack is increased by several decades, unprotected SBS begins to crack within a few hours. Several different protective agents are examined here, the best of which, a cyclic enol ether, Vulkazon^ⓡ AFD, can extend the resistance to any cracking to several weeks by the use of a few percent by weight of additive. The systems reported neither discolour the polymer nor stain other materials with which it may be in contact. Use of the protective systems described here could enable SBS elastomers to compete in many applications with the more expensive SEBS polymers.
Kyou Hoon Han,Seung Moak Kim,Dong Ho Choung,Kyu Hwan Park,Tae Sung Moon,Dong Yeon Chae,Soo Kyung Kim,Hyun Jun Yoo 생화학분자생물학회 1994 BMB Reports Vol.27 No.4
A combination of the nuclear magnetic resonance (NMR) technique and the molecular modelling method has been successfully applied to determine high resolution solution conformations of a 17-residue oligopeptide LQARILAVERYLKDQQL (583-599) of gp41 from human immunodeficiency virus type I (HIV1), and its mutant with Ala→Thr at position 589. Vamous two-dimensional NMR methods such as NOESY (two-dimensional NOE SpectroscopY), ROESY (two-dimensional Rotating-frame nOE SpectroscopY), TOCSY (TOtal shift Correlation Spectroscopy), and COSY (shift Correlation Spectroscopy) have been used to obtain complete H-1 resonance assignments. Interproton distances obtained from NOE were input for a subsequent restrained molecular dynamics simulation. The overall shapes of both peptides are a-helical, except at the N- and C-termini. The threonyl side chain at position 589 in the mutant peptide protrudes outwards from the helical axis more than the alanyl side chain at the same position, which might account for differences in the antibody recognition patterns for the two peptides.