A novel group of silsesquioxane derivatives, which are siloxane-silsesquioxane resins (S4SQ), was for the first time examined as possible flame retardants in polypropylene (PP) materials. Thermal stability of the PP/S4SQ composites compared to the S4SQ resins and neat PP was estimated using thermogravimetric (TG) analysis under nitrogen and in air atmosphere. The effects of the non-functionalized and n-alkyl-functionalized siloxane-silsesquioxane resins on thermostability and flame retardancy of PP materials were also evaluated by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) and by cone calorimeter tests. The results revealed that the functionalized S4SQ resins may form a continuous ceramic layer on the material surface during its combustion, which improves both thermal stability and flame retardancy of the PP materials. This beneficial effect was observed especially when small amounts of the S4SQ fillers were applied. The performed analyses allowed us to propose a possible mechanism for the degradation of the siloxane-silsesquioxane resins, as well as to explain their possible role during the combustion of the PP/S4SQ composites.

Synthesis and nucleation ability of a novel silsesquioxane‐based β‐nucleating agent for isotactic polypropylene (iPP) are presented. A silsesquioxane cage (POSS) was octa‐functionalized with a commercially used nucleating agent, namely N2,N6‐dicyclohexylnaphthalene‐2,6‐dicarboxamide (NU‐100), and used as a carrier with the ability to promote crystallization of β‐phase in polypropylene matrix. Presented results include the synthesis route of the β‐nucleating agent (SF‐B01) and a description of its nucleation ability in iPP. The influence of SF‐B01 on iPP matrix was examined using differential scanning calorimetry, wide‐angle X‐ray scattering and static tensile tests. Investigations were complemented with polarized light optical microscopy upon non‐isothermal crystallization of composites as well as scanning electron microscopy to qualitatively assess the filler distribution. Polypropylene samples modified with different amounts of NU‐100 were used as reference. Modification carried out with both nucleating agents reveals their comparable efficiency, i.e. a structure rich in β‐phase is obtained in both cases. © 2016 Society of Chemical Industry

A series of siloxane-silsesquioxane resins with Q 8 structures, as network nodes containing reactive Si-H groups in the siloxane backbone, connecting silsesquioxane moieties, were prepared in a hydrolytic condensation process and successfully functionalized by hydrosilylation of allyl alcohol. The proposed material being an alternative to the well-defined silsesquioxanes has been characterized and used for preparation of a series of polyurethane (PU)-based composites by simple reaction of 3-hydroxypropyl groups of siloxane-silsesquioxane resin with 1,6-diisocyanatohexane and subsequently with 1,6-hexanediol to get polyurethane composite. A series of composites based on PU and octakis(3-hydroxypropyldimethylsiloxy)octasilsesquioxane were prepared in the same manner to investigate the influence of the filler amount (1, 3 or 5%) and its structure on thermal properties of the obtained materials.

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Epoxy resin-based composites, also those containing POSS compounds, have been the subject of extensive research because of their attractive properties and broad practical applications. However, in some applications they suffer from too long curing times or not strong enough adhesion to metals. A solution to this problem is the use of episulfide (thiirane) derivatives or their combination with epoxies. In this paper, the synthesis of new octakis[(3-(thiiran-2-yloxy)propyl)dimethylsiloxy]octasilesquioxane from its 3-glycidoxypropyldimethylsiloxy analog is described. Results of study of its influence on thermal properties as well as curing processes of modified with this compound epoxy resins hardened with maleic, phthalic, and pyromellitic anhydrides are also presented. It is shown that addition of this new thiirane functional POSS compound can significantly increase thermal stability of obtained epoxy resin composites and decrease its curing temperatures.