We herein report the synthesis of organic−inorganic hybrid poly(methyl methacrylate) containing polyhedral oligosilsesquioxanes. Octakis(3-hydroxypropyldimethylsiloxy)octasilsesquioxane (OHPS) was synthesized from octakis(hydridodimethylsiloxy)octasilsesquioxane [Si8O12(OSiMe2H)8, Q8M8 H] following literature procedures. Octakis(methacryloxypropyldimethylsiloxy) octasilsesquioxane (OMPS) was synthesized via the reaction of methacryloyl chloride or methacrylic acid anhydride with OHPS, with the latter giving improved purity. Polymerization of OMPS with methyl methacrylate using a dibenzoylperoxide initiator gave a highly cross-linked polymer. Characterization of the polymer was performed using Fourier transform IR spectroscopy, 29Si NMR, differential scanning calorimetry, thermogravimetric analysis, atomic force microscopy, and transmission electron microscopy with energy-dispersive X-ray analysis. The polymer was found to be largely homogeneous. Increasing the OMPS concentration in the polymer gave increased decomposition and glass transition temperatures.

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Flammability behavior of natural fiber polymer composites (NFPC) is an essential factor to define their scope of application. It was of great importance to quantitatively optimize the quantities of the flame retardants (FR) with respect to the corresponding mechanical properties as well as the flame retardance behavior. Flax/polypropylene (PP) system was selected in this study due to its diverse applications. Aluminum trihydroxide (ATH) which was an inorganic hydrate was used as a FR and smoke suppresser because of its environmentally–friendly nature. Flax and PP in the presence of a coupling agent were extruded together. Flax loading with respect to the host polymer was studied at 30% and 50%. Afterward, the compounds were mixed with three grades of ATH namely Apyral 32, 40CD, and 60CD which were loaded at different amounts ranging from 30 to 60 wt%. The synergetic effect of zinc borate (ZB) and ammonium polyphosphate Exolit AP‐422 was also investigated. Both mechanical and flammability behavior were assessed with respect to ATH and its synergists. It was found that 40 wt% of Apyral 60CD was enough to reach V‐0 level with a marginal loss of tensile strength namely 12.5% and 7% for samples of 30% and 50% flax, respectively. Higher loading of ATH at 60% results in strength reduction by 37%–40%. Cone calorimetry results proved the reduction of both heat release rate (HRR) and smoke release. Synergism with both additives improved the UL94 rating and decreased the HRR as well. POLYM. COMPOS., 37:3310–3325, 2016. © 2015 Society of Plastics Engineers

Influence of intumescent flame retardant and sepiolite on the mechanical and rheological behavior of polypropylene AIP Conference Proceedings 1736, 020157 (2016) Abstract. Adding the natural fibre thermoplastic composites NFTC to engineering plastics represents a challenge due to the high temperature processing which in turn could result in the natural fibre damage. Finding applications for NFTC depends not only on the mechanical properties but also on the physical ones and the flame retardance property has an utmost importance. However; the implementation of flame retardants FRs materials has to counteract another challenge which is the drop of the corresponding mechanical properties. A comprehensive study is carried out for optimising the compounding process of the three constituents namely the thermoplastic, the natural fibre and the FR. A mixture of halogen-free phosphor based intumescent and inorganic hydrates is used as the FR system. FR mixture does not exceed 20% limit to allow enough binding effect of the thermoplastic with both fibres and FR. After conducting a screening study, it found out that Polybutylene terephthalate (PBT) and Polyamide (PA6) are good candidates due to their relatively low melting point with respect to the candidate natural fibres namely flax and kenaf. Twin screw extruder is used to compound the polymer and the FR with the pellets of the natural fibres. Extruder configuration is adjusted to obtain a stable process at 10, 15 and 22.5 wt.-% fibre. Temperature and speed are optimised in order to avoid the thermal degradation of the natural fibres as much as possible. The prepared composites are subjected to tensile test, Charpy notched and un-notched impact test, UL94 and cone calorimetry. Results are promising especially for PA6 composites. Mechanical testing shows a decrease of 10% in strength and 15-25% in impact strength after the addition of 20% FR.V-0 rating is obtained by 20% FR according to UL94 test. The cone calorimetry show a reduction in heat release rate HRR to 50% after the application of FR.