Search

In this study, the morphology and thermo-mechanical behavior of composites formed by a polyoxymethylene (POM) matrix and monosilanolisobutyl polyhedral oligomeric silsesquioxane (msib-POSS) filler have been studied. The msib- POSS molecules were added to the POM by direct melt blending at loadings between 0 and 10 wt.%. Hydrogen bonding interactions were detected between POM and msib-POSS Si–OH groups, increasing their mutual compatibility and leading to nanometer-size dispersion of some msib-POSS molecules. These interactions do not prevent POSS aggregation during blending, but lead to micron-scale msib-POSS domains. The thermal decomposition temperature of the composites remained practically constant under inert and oxidative conditions. The low temperature thermal transition (g) and glass transition temperature (Tg) of POM were found to move to higher temperatures only when 2.5 wt.% of msib-POSS was added, indicating that POSS is physically linked to the POM chains, restricting their motion under those conditions. Low content (2.5 wt.%) of msib-POSS results in antiplastization, whereas higher levels of POSS lead to a decrease in the storage modulus of the polymer. The relationships among these effects and the morphological characteristics of the systems will be discussed herein

A multilayer “smart pellet” additive composed of layered polymers, and capable of exfoliating in a manner similar to that of smectite clays, was demonstrated to be an effective reinforcing agent for bulk polymers processed in the melt. Polysulfone (PSF) and Ethylene-octene (PEOC-1) copolymer were chosen as one of the model systems. PSF/PEOC-1 smart pellets were added to PEOC-1 as masterbatches during injection-molding. This methodology allowed for high glass transition temperature PSF to function as a reinforcing agent during injection-molding of matrix polymers processed below their glass transition temperature. Mechanical properties of the composites were studied by performing tensile and flexural tests. Tensile modulus was fitted to the Halpin–Tsai model, and this model was used to predict the optimum tensile modulus that PSF/PEOC-1 smart pellets could achieve. The morphology of smart pellet and polymer composites were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical microscopy (OM). The PSF layers were observed to resemble clay platelet morphology in PEOC-1 matrix.

The influence of the functionalization of fully condensed POSS cages on the properties of POMbased nanocomposites is studied. POSS with different organic substituents [glycidylethyl, aminopropylisobutyl, and poly(ethylene glycol)] are taken into account and melt mixed with POM. Good dispersion was achieved upon the addition of amino functionalized POSS, leading to an increase on the thermal decomposition temperature under nitrogen atmosphere up to 50 8C. However, mm-size aggregates were observed for other nanocomposites. There is no significant change in other thermal properties of the nanocomposites. The relationships among these effects and the morphological characteristics of the systems were analyzed.

Oil absorption performance of aerogels produced from poly(amide-imides), epoxies, and acrylic polymers were dependent upon freezing conditions, which in turn dictated solid state structures of these materials. Denser aerogels have less void space, and are more efficient at filling that space with oil, supporting the hypothesis that capillary spacing plays a vital role in determining oil absorption. Lower molecular weight epoxy-based polymers produced aerogels with small capillary radii, again allowing increasing amounts of the liquid to penetrate between the aerogel layers. Aerogels produced from acrylic emulsions outperformed the other two systems tested in terms of volume per volume absorption. The initial difficulty with these materials, the fact that they still retain some hydrophilicy and absorb water, was overcome by simple post curing treatment, which was able to reduce water absorption to near zero levels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45844.

A series of polysulfone/phenyl trisilanol POSS nanocomposites were produced by melt blending by twin screw batch mixing. These materials were then injec- tion molded, and their thermal, mechanical, and morpho- logical properties were tested. The tensile properties of polysulfone were moderately compromised by the addition of phenyl TPOSS, because of the formation of large ( 1 l m) voided POSS aggregates. These domains however did cause the improvement of the impact resistance of the composites as described by the mechanism of crack pinning and bow- ing. Flexural properties remained essentially unchanged, which is attributed to the formation of an aggregate free- skin layer, which formed in the injection molded parts. Thermal behavior of the composites also remained largely unchanged due to the lack of POSS-polymer interactions on the molecular/chain segment scale. Initially, it was hypothesized that a high degree of POSS-polymer interac- tions would be present in these composited based on exami- nation of their chemical structures. This however, was not the case as phase separation was clearly present. This work highlights the need for a better understanding of the predic- tion of POSS-polymer interaction.