Polymeric silane

Scheme 12.1.5 Modification of colloidal silica ultrafine particles with polymeric silane coupling agents in low polar solvent.

Interfacial shear strength and durability improvement by monomeric and polymeric silanes in basalt fiber/epoxy single-filament composite specimens J. M. Park and R. V. Subramanian 473... 

Nevertheless, it was decided to make the measurements of density and of refractive index for specimens after different times of curing. Since the molecular weight of the polymerized silane was not known, the molecular refractivity could not be calculated but only the ratio of this to the molecular weight. Nevertheless, interesting results were obtained with a linear relationship between the cure time and refractive index up to 18 h. The relationship between the cure time and the ratio of molecular refractivity to molecular weight is shown in Fig. 3 and indicates a steady increase in molecular complexity up to 24 h, when it approaches a constant value suggesting a final state of crosslinking. 

Polymeric silanes trimethaxysilyl-terminated polyfN -acetylethyleneimirie (PAEl)... 

Keywords Polymeric silanes basalt fiber epoxy composite acoustic emission. 

In recent work by Arkles el al. [4, 5], it has been proposed that, in comparison with monomeric silanes, polymeric silanes may react with substrates more efficiently. A typical polymeric silane is shown in Fig. la, in which pendant chains of siloxanes are attached through methylene chain spacers to a polyethyleneimine backbone. The film-forming polymeric silane thus provides a more continuous reactive surface to the polymer matrix in the composite. In this case, the recurring amino groups on the polymeric silane backbone can react with an epoxy resin matrix through chemical bond formation. 

Another noteworthy feature of the polymeric silane depicted in Fig. la is that the silane chains on the polymer backbone carry dialkoxy groups. In comparison with monomeric silanes which carry trialkoxy groups, these polymeric silanes are claimed to offer superior substrate reactivity and to provide further performance improvements [4, 5]. A probable explanation seems to be the difference in the number of siloxane bonds that can possibly be formed with the glass surface by the two types. 

Silane coupling agents. Monomeric and polymeric silane coupling agents were purchased from Petrarch Systems Co. (Bristol, PA) and used without further purification. Their chemical structures are given in Table 1. APS was obtained as the neat compound, and the polymeric silanes were supplied as 50% solution in isopropanol. The silanes were diluted to the required concentration in chosen solvents for application on fibers. 

Effects of solvents for polymeric silane PS076.5" application on dry/wet IFSS in basalt fiber-epoxy SFC specimens... 

It was shown above that the crosslinking observed with APS through selfcondensation and oxidation could be followed by changes in the IR spectra (Figs 3 and 4). A similar reaction with the polymeric silane would lead more easily to a tightly bound network because of the polymeric backbone to which the silanol groups are attached. These aspects of the silane reactions need further careful investigation. 

The acoustic energies of the pulses are shown in Fig. 11 and indicate the stress levels at which fracture has occurred in fibers of the same diameter. It is interesting to note here that fibers treated by the polymeric silane produce failure pulses at a higher energy than the untreated fibers. The protective effect of the polymeric silane coating in healing some surface flaws can be deduced from this observation. This effect is not significant when the monomeric silane is used. 

In figure 14.11, the C Is XPS spectra are given of the aminopropylsilica at different stages of thermal treatment. Experiments were performed using silica coated with a polymerized silane layer. Deconvoluted peak positions and relative percentages are indicated in the figure. 

Quite another type of imprinting on the surface of silica was used by Sagiv (102). Mixed monolayers of n-octadecyltrichlorosilane and surfactant dyes are absorbed and chemically bound to glass. The dye molecules are then removed, leaving holes entrapped within a stable network of chemisorbed and polymerized silane molecules. These layers show a preferred adsorption of Che dyes used as templates. Problems are encountered with Che kinetics of the sorption-desorption process which has to proceed through a channel formed from the dense arrangement of long alkyl chains in the monolayer. 

Bakalova and co-workers reported the synthesis of a 17 nm nanoparticle with a quantum dot (QD) core and a silica sheU. The encapsulation of the QD by silica involved the assembly of a polymerized micelle around the QD followed by the formation of polymerized silane shell around the precursors (Figure 7.1). By avoiding... 

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