Unsaturated polyester/montmorillonite nanocomposites prepared by in situ intercalative copolyaddition Summary-New approach to the synthesis of unsaturated polyester/clay nanocomposites is described. Various forms of organically modified montmorillonite (OMMT) were introduced in situ during the copolyaddition of epichlorohydrin, maleic anhydride and phthalic anhydride. The catalytic effect of OMMT containing quaternary ammonium ions was observed. The introduction of clay leads to the increase in softening temperature, as well as melt or solution viscosity of unsaturated polyester. Cured unsaturated polyester/clay compositions exhibit increased hardness and heat resistance and, in some cases, decreased flammability. The best properties, including limiting oxygen index (LOI) values in the range of 27-29 %, were obtained for the compositions with OMMT functionalized with hydroxyl group. In that case, covalent bonds between clay surface and unsaturated polyester are likely to be formed. The dispersion of OMMT in the polyester matrix in form of exfoliated nanocomposite was indicated by X-ray diffraction study.
The cationic emulsion polymerization of octamethylcyclotetrasiloxane (D4) in mixtures with methyltriethoxysilane (MTES) and vinyltriethoxysilane (VTES) was studied by FTIR ATR, GC, the development of a toluene insoluble fraction of the polymer and a gravimetric analysis. The polymerization of D4 alone was also conducted for comparison and, additionally, the development of molecular weight of polydimethylsiloxane (PDMS) obtained in that process was studied by GPC. Dodecylbenzenesulphonic acid (DBSA) was used as a surfactant and catalyst. The process was carried out in a “starved feed” mode by adding dropwise the monomer mixture to the aqueous solution of DBSA. FTIR ATR spectra were recorded by the sensor placed in the probe tip of a ReactIR 15TM apparatus. It was found that the silicone polymer formation proceeded faster when D4 was polymerized in the mixture with alkoxysilanes, especially in the beginning of the process, and that already at the beginning of the process, the partly crosslinked polymer was formed. The induction period of ca. 30 min was observed and the concentration of cyclic siloxanes (D4 and decamethylcyclopentasiloxane—D5) remained at a very low level in the course of the reaction and only traces were detected in the final product. The particle size development in the course of the reaction was also studied and it was found that the particle size distribution was bimodal and was broadening as the reaction proceeded, though this phenomenon was less distinct when D4 was polymerized in the mixtures with alkoxysilanes. The structure of the reaction product was confirmed by 29Si NMR.
Graphite oxide as an intumescent flame retardant for polystyreneSummary -In this work the possibility to apply graphite oxide (GO) as an intumescent flame retardant added in situ during suspension polymerization of styrene was studied. Synthesis of GO was carried out starting from natural flake graphites with different carbon content and particle size (between 45 and 500 µm). The obtained products were examined using elemental and scanning electron microscopy (SEM) analysis, Fourier transform infrared spectroscopy (FT-IR) as well as X-ray powder diffractometry (XRD). Thermal stability and expansion properties of GO were also investigated. It was stated that with an increase in particle size GO exhibited a lower degree of oxidation while the temperature of maximum decomposition rate increased. The highest expansion volume at 600 °C was observed for GO prepared from graphite with large-sized plates (300 and 500 µm). In order to prevent the dispersion of hydrophilic GO in an aqueous phase during the polymerization of styrene, GO was modified with organofunctional silane. Polystyrene with added GO (15 wt. %) reached HF-1 rating in the UL 94 horizontal burning test, however it failed to pass the required vertical flame test. The modification with melamine-formaldehyde resin (MF) resulted in an increase of GO thermal stability. Polystyrene with 15 wt. % of GO-MF additive obtained maximum ratings HF-1 and V-O in the UL 94 flame test. An attention should be paid to safe handling of GO which, although stable at ambient conditions, may undergo highly exothermic decomposition, e.g. when subjected to mechanical impact at moderately elevated temperature.
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