Papers by Keyword: POSS

Abstract: The mechanical behavior of polyethylene (PE) co-polymerized with polyhedral oligomeric silsesquioxane (POSS) was studied by using molecular simulations. Simulation configurations consisted of aligned PE chains with POSS attached to the central chain and amorphous PE chains with different content POSS. From the simulations with aligned PE chains with POSS, it was found that the method for reinforcement was due to dislocation pile-up at POSS, and above a critical stress the dislocations traverse the POSS causing a sawtooth variation in the load-displacement curve. The stress-strain curves for amorphous PE-POSS bulk showed distinct elastic and plastic straining stages. Plastic straining consisted of hardening and slipping segments attributed to dislocation pile-up and chain sliding. Computational results were used to develop a reinforcement model to describe the mechanical response of PE-POSS bulk under uniaxial tension.

Abstract: Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with the humping semi-enclosed cage structure, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4’-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites, respectively. The polymer chain characteristics of these composites were investigated by wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing up to 22 wt% in hybrid composites, due to the humping semi-enclosed cage structure, distinct crystallite clusters are formed which lead to the micro-phase separation in composites. Meanwhile, the mobility of TSI-POSS cores and backbones in PU composites has been evaluated by the mean square displacement, which confirms that as the concentration of TSI-POSS increasing, the mobility of polymer chains are restricted apparently. Furthermore, it also indicates that the incorporation of TSI-POSS is as the rigid core in hybrid composites.

Abstract: Polyhedral oligemeric silsesquioxanes epoxy (POSS-EP) was prepared from 3-glycidyloxy-propyl-trimethoxysilane (KH-560) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSS-EP was characterized using fourier-transformed infrared spectroscopy (FTIR), thermal gravity analysis (TGA) and gel permeation chromatography (GPC). When the mass ratio of KH-560 and 25wt% TMAH was 20:1 and the temperature of hydrolytic condensation was 80°C, T8 was the majority and certain a mount of T10. The temperature of POSS-EP in weight loss 5wt% and the maximum degradation rate was approximately 200°C. The residual weight for POSS-EP at 800°C was 33.5wt%. After the cotton fabric was treated with 5wt% POSS-EP by using toluene as solvent, its carbon residue was improved 60 times than untreated .

Abstract: Poly(ethylene terephathalate)/1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (POSS) composites were prepared by in situ polymerization with 1.5-5.0 wt% loading of POSS. The dispersion of POSS in PET matrix was investigated by scanning electron microscope(SEM) the interaction between POSS and PET chains was studied by nuclear magnetic resonance(NMR) andX-ray photoelectron spectroscopy(XPS), and the thermal behavior of PET/POSS composites was investigated by DSC and TG as well as the melt rheological testing of PET/POSS. SEM observation suggests that POSS particles disperse evenly innanosize(80-100nm)in PET matrix, and this fine dispersion of POSS was further supported by XPS analysis, there is a covalent linkage presenting between POSS and PET chains. The crystallization temperature of the composites moved to high temperature as the POSS particles behave as the nucleating agent. The shear modulus(G’) increased apparently with the addition of POSS.

Abstract: Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with three hydroxyl functional groups pendent to a semi-enclosed cage, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4'-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites as a heavy linking node in backbone, respectively. The domain micro-structures of these composites were investigated by FTIR, wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing in hybrid composites, distinct crystallite clusters are formed which increase the volume of hard segments and lead to the micro-phase separation. Meanwhile, details of chain packing has been evaluated by radial distribution function, which shows that below 13wt% TSI-POSS concentration, the number of contacts between neighboring chains is decreased due to the humping semi-enclosed cage of TSI-POSS units. However, when TSI-POSS concentration is up to 22 wt%, the number of contacts is increased because the formation of crystallite cluster pulls neighboring chains closer to each other and significantly shortens their distance.

Abstract: In this work, octa(3-aminopropyl)polyhedral oligomeric silsesquioxane (Oap-POSS) [(NH₂CH₂CH₂CH₂)₈Si₈O₁₂] was synthesized through hydrolytic condensation of (3-aminopropyl)triethoxysilane, and incorporated into epoxy resin (EP) cured with methyl hexahydrophthalic anhydride (MHHPA) to offer a series of novel POSS/EP nanocomposites. The microstructure, thermal stabilities, electric insulation and dielectric behaviors of the epoxy nanocomposites were studied. The results showed that the thermal stability and dielectric property of the POSS/EP increases with the incorporation of Oap-POSS into EP.

Abstract: Polycarbonate/poly (lactic acid)/(PC/PLA) blends were modified by two kinds of POSS, glycidyl POSS (G-POSS) and Octa-ammonium POSS (O-POSS), respectively. The morphologies and mechanical properties of blends were investigated systematically. The results showed that the adding of O-POSS has a better effect on the compatibility of blend than adding G-POSS, the separate phase is invisible in the morphology of blends, and the mechanical properties of blends are improved significantly with the increase of added O-POSS.

Abstract: PAN/POSS nanofibers membrane with different content POSS have been prepared by electrospinning. The morphology and thermal properties of PAN/POSS nanofibers are characterized by SEM and DSC, respectively. The addition of different content of POSS into PAN matrix have a slight effect on the diameter of nanofibers. Compared to pure PAN fibers, the exothermic peak shift to higher temperatures by 6.8°C when POSS loading is 3wt%, and the corresponding Tg have increased 17.3°C.

Abstract: In this paper, different amounts of fluoropropyl polyhedral oligomeric silsesquioxanes (FP-POSS) were incorporated into the poly (vinylidene fluoride) (PVDF) matrix by the solvent evaporation method. Influence of FP-POSS on morphology and mechanical properties of PVDF matrix was investigated. Good dispersion between FP-POSS and PVDF was achieved up to 8 wt% of nanofiller. The mechanical testing and dynamic mechanical analysis showed that low FP-POSS content induced a positive reinforcement effect on mechanical property in the formed composites. The results also indicated the existence of the optimal formula for producing POSS polymer composites, and POSS owning to its unique organic-inorganic structure can act as a plasticizer or as a reinforcing agent on the basis of interactions between filler and polymer.

Abstract: Aliphatic polycarbonate Polycarbonate/poly (lactic acid)/(PPC/PLA) blends were prepared by melt blending, 1,2-propanediol isobutyl POSS (P-POSS) were added into the blends as a compatilizer and reinforcer. The morphologies, mechanical properties and rheological properties of blends were investigated systematically. The results showed that the adding of P-POSS could improve the compatibilization of PPC and PLA obviously. The thermal stability of the blends was enhanced but the crystallization was effected slightly. Moreover, the tensile strength and impact strength of blends exhibited a considerably increase.