Nanoparticles based on Al(III) and Zr(IV) melamine phosphate and sulfate, respectively, are prepared. Cone calorimeter measurements reveal that compared to an unfilled polyacrylate matrix the polyacrylate‐based nanocomposites containing the novel nanoparticles display significantly improved flame‐retardant properties as evidenced by the corresponding values for the peak heat release rate, the time‐to‐ignition, the values for the peak rate of heat release, the total heat evolved, the time to the CO peak and the CO yield. Concomitantly, the mechanical properties of the acrylate‐based composite coatings, i.e., the Martens and surface hardness, can also be significantly improved.
Novel fluoroalkyl end‐capped oligomer/hydroxyapatite nanocomposites have been easily prepared by the reaction of disodium hydrogenphosphate and calcium chloride in the presence of self‐assembled molecular aggregates formed by fluoroalkyl end‐capped oligomers in aqueous media. The fluorinated hydroxyapatite nanocomposites thus obtained were found to exhibit a good dispersibility in a variety of media, and were applied to the surface modification of glass.
Acrylic‐epoxy interpenetrating polymer networks were prepared by means of UV curing. The photopolymerization process was investigated via real‐time FTIR spectroscopy. The hybrid, cured films showed a broad tan δ peak in DMTA demonstrating the high damping properties of the hybrid, cured formulations. A decrease on shrinkage was achieved by increasing the epoxy‐resin content in the photocurable formulation, with a consequent increase in adhesion properties.
Organoclay–polyolefin nanocomposites have been shown to exhibit slightly increased thermal stability and decreased flammability, compared to unfilled polyolefins. In contrast, we find that when the clay has not been organically modified, the resulting polyolefin nanocomposites are less thermally stable and, unexpectedly, also much less flammable. In this contribution, we investigate the mechanistic origins of these effects. Clay–polyolefin nanocomposites were prepared by in situ polymerization of ethylene or propylene, using a catalyst adsorbed onto the clay. Decreased thermal stability is attributed to clay‐catalyzed polymer decomposition, while decreased flammability arises in part from clay‐catalyzed formation of a polyaromatic char from olefins trapped in the material by the dispersed nanofiller.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
The solid and thermally instable azoinitiators V‐65 and VR‐110 were embedded within a polymer particle by using the miniemulsion process and afterwards quickly decomposed by thermal treatment below the glass temperature of the polymer. The resulting nitrogen gas overpressure inside the particles leads to a disruption of the polymer particle and a possible sudden release of encapsulated substances. It is shown, by electron microscopic measurements, that the number of burst particles correlates with the applied temperatures as well as the heating time. The surface deformation could be verified by scanning electron microscope analyses.
A novel zirconia polyester nanocomposite is prepared using an in situ approach. Surface‐functionalized zirconia nanoparticles are obtained by attaching 3‐phosphonopropionic acid to the metal oxide. Neat and surface‐covered metal oxide particles are incorporated at the beginning of the polyesterification reaction of isophthalic acid and neopentyl glycol resulting in zirconia/poly(neopentyl isophthalate) (PNI) nanocomposites. TEM shows that the dispersibility of the inorganic filler is improved by covering the zirconia surface with carboxylic acid groups. These results are verified by SAXS. Rheological measurements reveal that the viscosities are increasing compared to pristine PNI at particle loads of 10 wt% (neat zirconia) and 5 wt% (phosphonic‐acid‐capped zirconia), respectively.
PVDF nanocomposites are prepared through solution mixing of Au‐NPs or Au‐NSs with PVDF. The novel optical properties of Au‐NPs and ‐NSs are retained as confirmed from UV‐Vis spectra. Analysis of resulting nanocomposites by FT‐IR, XRD, and DSC shows an obvious polymorphism change from α‐ to β‐form compared to PVDF prepared under the same conditions. The β‐polymorph seems to be more prominent with higher concentration of Au‐NPs (0.5%) and even more so with Au‐NSs. Thermogravimetric analysis shows that both nanocomposites have better resistance toward thermal degradation. Combination of novel optical properties of Au‐NPs or Au‐NSs with induced ferroelectric‐active β‐polymorph in PVDF can lead to new design of optical, piezoelectric devices.
Thermo‐responsive PNIPAAm/PLLA nanofibrous films with tunable surface morphologies and better biocompatibility were prepared by electrospinning technique. The electrospun composite films possessed a “bead‐on‐string” structure. The wettability of nanofibrous films was observed by water CA measurements. The results showed that the electrospinning process and addition of PLLA did not change the thermo‐sensitivity of PNIPAAm. The wettability of electrospun PNIPAAm/PLLA composite films could switch from superhydrophilic to superhydrophobic when the temperature increased from 20 to 50 °C. Electrospinning is a promising way to create stimuli‐responsive surfaces with potential application in the design and tactics of controllable drug delivery system.
The influence of the functionalization of fully condensed POSS cages on the properties of POM‐based 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 °C. However, µm‐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.
Both α‐cyclodextrin and linear dextrin are used to prepare biocomposites with poly(3,4‐ethylenedioxythiophene). Materials are prepared electrochemically in aqueous solution. Comparison with the pure polymer indicates that the electroactivity and electrostability decrease with the incorporation of the dextrins while the electrical conductivity is retained. The different properties of the two biocomposites suggest that the linear dextrin is mainly located at the surface, whereas the cyclodextrin is homogeneously distributed in the polymeric matrix. Cell adhesion and proliferation assays indicate that the cellular activity is significantly higher in the dextrin‐containing biocomposites.
Dynamic and transient shear start‐up flow experiments along with TEM, WAXS, and SEM analyses are performed on PP/PET blends and nanocomposites. The TEM results along with a theoretical analysis based on a thermodynamic model reveal that the clay particles are mainly localized in the PET phase. The localization of nanoclay in PET as the matrix phase leads to a refinement of morphology. The localization of clay is also studied by analyzing changes in complex viscosity and storage modulus in oscillation mode as well as the changes in power law index obtained from steady‐state and transient shear start‐up flow experiments. The changes in the rheological behavior of the blends are attributed to formation of clay network‐like structures.
A systematic study of the effects of , flow rate, voltage, and composition on the morphology of electrospun PLGA nanofibers is reported. It is shown that changes of voltage and flow rate do not appreciably affect the morphology. However, the of PLGA predominantly determines the formation of bead structures. Uniform electrospun PLGA nanofibers with controllable diameters can be formed through optimization. Further, multi‐walled carbon nanotubes can be incorporated into the PLGA nanofibers, significantly enhancing their tensile strength and elasticity without compromising the uniform morphology. The variable size, porosity, and composition of the nanofibers are essential for their applications in regenerative medicine.
Nanocomposite UV coatings with adjustable properties for use on wood substrates in outdoor conditions were developed. Nanoscale ZnO was shown to be an efficient light absorber. Coatings were characterized in terms of elongation at brake, residual PI and double bond conversion, universal hardness, transparency, hydrophobicity, and yellowing. Coated samples were artificially weathered and studied with regard to their optical and mechanical properties, as well as to changes in brightness, transparency, hydrophobicity, and water permeability. The prepared wood coatings showed an increased weather fastness and improved optical properties. The suitability for use in outdoor conditions was assured by optimizing the elasticity of the coating and decreasing its water permeability.
A new technique for design and preparation of self‐reinforced starch films is introduced. The films were based on a high‐amylose corn starch that was chemically modified in different ways. Hydroxypropylation was used to decrease gelatinization temperature and improve processability. The reinforcing component consisted of cross‐linked starch granules, where the crosslinking increased granule thermal stability and moisture resistance. Distribution of the cross‐linked starch was imaged by CLSM, and the matrix/particle interface was studied by SEM. Modulus and tensile properties of the starch film were increased by about 30 and 20%, respectively, after addition of rigid cross‐linked starch particles. A perfect interface between matrix and reinforce agent was obtained.
A new class of polymer materials is reviewed, the SPCs, in which the matrix and the reinforcement share the same chemical composition. In addition to their milder environmental impact as compared to traditional polymer composites, they show superior mechanical performance mainly due to the improved adhesion between matrix and reinforcement. Another advantage of SPCs is the missing dispersion step in their production, thus contrasting the common polymer nanocomposites. Definition, manufacturing, classification, and the application opportunities of SPCs are described. Special attention is paid on the very new members of the SPC family, the micro‐ and nanofibrillar SPCs, including the techniques for preparation of their starting neat micro‐ and nanofibrils using bulk polymers.
Morphological analyses of nanocomposites based on TPU and polyhedral oligomeric silsesquioxanes (POSS) was performed using different techniques (transmission electron microscopy, small‐ and wide‐angle X‐ray scattering, differential scanning calorimetry) as a function of molecular weight of poly(ethylene glycol) (PEG) and PEG/POSS mol ratio. A strong interdependence in crystallisation behaviour between the two (POSS and the soft segments of TPU) specified to be able to crystallise in TPU/POSS was found. The mechanical properties determined by using recording microindentation techniques at room temperature were significantly improved by POSS for two material formulations.
Poly(lactic acid) plasticized with 15 and 20 wt.‐% of polyadipate was melt‐blended with different amounts of an O‐MMT (1–5 wt.‐%) to prepare nano‐biocomposites. The effect of plasticizer and nanofiller contents on the morphology and on thermal, mechanical and barrier properties of PLA‐based nano‐biocomposites was evaluated in order to understand their structure‐properties relationships. The oxygen transmission rate was notably reduced (around 45%) with increasing amount of clay due to an increased tortuosity. However, for clay concentrations above 3 wt.‐%, a significant detriment in ductile properties could also be observed. For a given amount of nanofiller, the increasing plasticizer concentration improved the clay dispersion through the polymeric matrix.
Toughness enhancement of S‐(S/B)‐S triblock copolymers via a molecular‐weight‐controlled pathway is demonstrated. The post‐yield crack toughness behavior of the triblock copolymers uniquely reveal a brittle‐to‐semiductile‐to‐ductile transition with increasing while keeping the basic molecular architecture fixed. TEM and SAXS investigations indicated three distinct morphologies as a function of χeffN as a consequence of the increase in : (i) a homogeneous structure without phase‐separation, (ii) a weakly segregated structure, and (iii) a lamellar structure. The increase in crack toughness is also reaffirmed from kinetic and strain field analysis studies concerning dynamics of crack growth in block copolymers with high PS content.
This work aims at improving the interfacial bonding between polyamide‐12 and CNFs. CNFs were oxidized and dispersed in polyamide‐12 giving rise to polymer nanocomposites. The oxidation caused an increase in the specific surface area and structural defects of the fibers, as indicated by surface area and Fourier‐transform Raman spectroscopy. The nanocomposites exhibited improved thermal and thermo‐oxidative stabilities. The oxidized nanofibers had marginal effect on the crystallinity and crystallization of the polyamide‐12. An over‐proportional enhancement of stiffness due to the fibers could be achieved. In spite of these improvements the fiber/polymer adhesion should be further improved.
