Effect of Polyhedral Oligomeric Silsesquioxane on the Melting, Structure, and Mechanical Behavior of Polyoxymethylene

The effects of octakis[(3-glycidoxypropyl)dimethylsiloxy]octasilsesquioxane (GPOSS) on the crystallinity, crystal structure, morphology, and mechanical properties of polyoxymethylene (POM) and POM/GPOSS composites were investigated. The POM/GPOSS composites with varying concentrations of GPOSS nanoparticles (0.05⁻0.25 wt %) were prepared via melt blending. The structure of POM/GPOSS composites was characterized by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and polarized light microscopy (PLM). The mechanical properties were determined by standardized tensile tests. The morphology and dispersion of GPOSS nanoparticles in the POM matrix were investigated with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. It was observed that the dispersion of the GPOSS nanoparticles was uniform. Based on DSC studies, it was found that the melting temperature, lamellar thickness, and the degree of crystallinity of the POM/GPOSS composites increased. The POM/GPOSS composites showed an increased Young's modulus and tensile strength. Finally, compared with the pure POM, the addition of GPOSS reduced the spherulites' size and improved the crystallinity of the POM, which demonstrates that the nucleation effect of GPOSS is favorable for the mechanical properties of POM.

Polyoxymethylene/Polyhedral Oligomeric Silsesquioxane Composites: Processing, Crystallization, Morphology and Thermo-Mechanical Behavior

Polyoxymethylene composites with octakis (dimethylsiloxy, ethyl epoxycyclohexy)octasilsesquioxanes and octakis(dimethylsiloxy, vinyl)octasilsesquioxanes contents (0.5 and 1 wt.%) were studied. The effect of silsesquioxanes (POSS) on crystallization and melting behaviour of polyoxymethylene (POM) was investigated by polarized light microscope (PLM), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), with the aim to determine the structural properties like crystallization temperature, degree of crystallinity and lamellar thickness distributions. It was found that POSS as nucleating agent affects the crystallization process of POM, leading to a homogeneous structure, improving the thermo-mechanical properties of polyoxymethylene composites. Based on SEM observations it was found that the POSS particles in a concentration of 0.5 wt.% are uniformly dispersed in polyoxymethylene matrix. The storage modulus and relaxations temperatures of POM with POM/0.5 wt.% ehPOSS and vinPOSS are slightly increased.

Influence of polyhedral oligomeric silsesquioxanes on thermal and mechanical properties of melt-mixed poly(methyl methacrylate)/polyhedral oligomeric silsesquioxanes composites

In this study, the influence of the functionalization of fully or incomplete condensed polyhedral oligomeric silsesquioxanes composites (POSS) nanoparticles on the properties of poly(methyl methacrylate) (PMMA)-based composites has been studied. POSS with different organic substituents (methacryl, methacrylateisooctyl and trisilanolphenyl) are taken into account and added to the PMMA matrix by direct melt blending at loadings between 0 and 5 wt%. Significant differences in compatibility were observed depending on the structure of nanoparticles. POSS aggregation occurred during blending producing micron-sized aggregates in the composites. The thermal decomposition temperature of the composites with good dispersion of POSS aggregates increased under oxidative conditions. There were no significant changes in other thermal and mechanical properties of the composites. The relationships among these effects and the morphological characteristics of the systems were analysed.

Polyhedral Oligomeric Silsesquioxane (POSS)-Containing Polymer Nanocomposites

Hybrid materials with superior structural and functional properties can be obtained by incorporating nanofillers into polymer matrices. Polyhedral oligomeric silsesquioxane (POSS) nanoparticles have attracted much attention recently due to their nanometer size, the ease of which these particles can be incorporated into polymeric materials and the unique capability to reinforce polymers. We review here the state of POSS-containing polymer nanocomposites. We discuss the influence of the incorporation of POSS into polymer matrices via chemical cross-linking or physical blending on the structure of nanocomposites, as affected by surface functional groups, and the POSS concentration.