Sulphur cement pre-composition and process for preparing such sulphur cement pre-composition

The invention provides a process for the preparation of a sulphur cement pre-composition comprising reacting sulphur modifier with polysulphide-containing organosilane to obtain in the presence of sulphur the sulphur cement pre-composition, wherein the organosilane has the general molecular formula: (X 3 Si) m H (2n+1) C n -S a -C n' H (2n'+1-m') (SiX' 3 ) m' (1) wherein a is an integer in the range of from 2 to 8, X and X' each are, independently, a hydrolysable group, n and n' each are, independently, an integer in the range of from 1 to 4, and m and m' each are, independently, an integer in the range of from 1 to (2n+1)

On the neutralization models in LEIS

Three different neutralization models are discussed. In the continuum limit their connection is clarified for ion trajectories with unspecified time-dependence. The unifying model is fitted to experiment for He+ → MgO scattering. It is pointed out how difficulties, related to the use of relative ion fractions, can be circumvented. Therefore the results of DISC-experiments, which are absolute intensities, are compared with calculations on the basis of the Muda-Newns model

Chemical structures assigned for the low molecular weight fractions from degradation of poly(styrene sulfides)

A non-destructive analysis is performed of thermally unstable sulfur-styrene reaction products, combining preparative size exclusion chromatography (P-SEC), ultraviolet-visible (UV-vis) and nuclear magnetic resonance (NMR). The crystallizing compounds are identified as be 2,4-diphenylthiophanes with short sulfur bridge (x ~ 2) contrary to earlier suggestions which were based on destructive analysis. A new cyclic structure (styrene polysulfide x = 1 up to 8) was assigned to the amorphous species containing a single styrene repeating unit. Comparison with the amorphous fractions suggests that the rigid ring of styrene repeating units in adjacent sequences is the characteristic feature for the crystallisability. The melting and crystallization behaviour of this crystalline component was observed, by optical microscopy (OM) and differential scanning calorimetry (DSC), to be step-wise as well as broad, due to the variation in the length of the sulfur bridge. © 2009 Elsevier Ltd. All rights reserved