Elaboration and relationships between structure and rheological properties of microtalc or nanotalc/polyamide composites

This study focuses on the elaboration of nanocomposites processed by melt mixing of a polyamide 12 matrix and a hydrogel filled with synthetic talc particles. The systems are obtained by simultaneous mixing using either an internal mixer or a lab twin‐screw extruder. The structure and rheological properties of synthetic talc/polyamide composites are compared with those of natural talc/polyamide microcomposites and modified montmorillonite/polyamide nanocomposites. A multiscale structure, composed of numerous nanometric particles but also few micrometric aggregates, is obtained for synthetic talc/polyamide composites. In terms of processability, the lab twin‐screw extruder is more adequate than the internal mixer for the elaboration of synthetic talc/polyamide composites with relatively high filler volume fractions. For composites elaborated with the extruder, the percolation threshold, estimated from linear viscoelastic measurements, is close to 1, 6, and 11%, respectively, with modified montmorillonite, synthetic talc, and natural talc particles, in agreement with structural results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42299.     

Dispersivity of modified ZnO and characterization of polyurethane/ZnO composites

The properties of inorganic nanoparticles/polymer composites depend on the dispersivity of nanoparticles in a polymer matrix. The effect of surface modification on the dispersivity of ZnO nanoparticles in a polyurethane (PU) resin matrix was investigated. The nanocomposites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X‐ray diffraction. The scanning electron micrographs show that ZnO nanoparticles (CDI–SA–APS–ZnO), which were modified by aminopropyltriethoxysilane (APS) and activated stearic acid (SA) by N,N′‐carbonyldiimidazole (CDI), can be homogeneously dispersed and had been encapsulated in the PU phase. The interfacial compatibility between ZnO nanoparticles and PU matrix was significantly improved by hydrophobically modifying ZnO nanoparticles with APS and SA. The tensile strength and elongation at break of PU/CDI–SA–APS–ZnO nanocomposites increased by 82 and 64% respectively, compared with the pure PU material. The thermal stability and ultraviolet‐shielding properties were also improved by incorporating ZnO nanoparticles into the PU matrix. POLYM. COMPOS., 35:237–244, 2014. © 2013 Society of Plastics Engineers     

Nanocrystalline Fe‐Ni alloy/polyamide 6 composites of high mechanical performance made by ultrasound‐assisted master batch technique

The focus of this study is to improve the dispersion state of nanocrystalline (nc) Fe‐Ni particles in polyamide 6 (PA6) matrix and the filler‐matrix interfacial interactions to provide Fe‐Ni alloy/PA6 nanocomposites of remarkable mechanical performance for engineering applications. nc Fe₄₀Ni₆₀ particles were chemically synthesized. Then Fe₄₀Ni₆₀/PA6 nanocomposites of various nanofiller loading were prepared by compounding via a newly modified master batch technique called ultrasound assisted master batch (UMB), followed by injection molding (IM). Their mechanical properties, morphology and structural parameters were characterized and compared with the corresponding properties of Fe₄₀Ni₆₀/PA6 nanocomposites made by solution mixing (SM) and IM. The study reveals that the UMB process is more cost effective and time efficient, simpler and easier to scale up compared with the SM process. In addition, UMB nanocomposites exhibit superior mechanical properties and distinctive morphology compared with the corresponding SM ones. Moreover, structural analyses indicate that physical structural changes occurred in PA6 due to presence of alloy particles are affected differently by the different compounding methods, profound understanding of such phenomenon is focused throughout the article. These distinctive advantages recommend that UMB technique can be of great potential in commercial production of polymer nanocomposites (PNCs). It is concluded that the sonication of nc Fe₄₀Ni₆₀ particles in dilute polymer solution during UMB compounding, a new step that is incorporated for the first time in the master batch process, is mainly responsible for the good wetting between nanoparticles and polymer chains, strong filler‐matrix interactions and consequently the remarkable mechanical performance of UMB PNCs. POLYM. COMPOS., 35:2343–2352, 2014. © 2014 Society of Plastics Engineers     

High performance epoxy resin nanocomposites containing both organic montmorillonite and castor oil-polyurethane

Summary Epoxy resin/polyurethane interpenetrating polymer network nanocomposites with various contents of organophilic montmorillonite (oM-EP/PU nanocomposites) were prepared by a sequential polymeric technique and an in situ intercalation method. X-ray diffraction(XRD), and transmission electronic microscopy(TEM) analysis showed that organophilic montmorillonite (oMMT) disperses uniformly in epoxy resin/polyurethane interpenetrating networks(IPNs), and the intercalated or exfoliated microstructures of oMMT are formed. Differential scanning calorimetry(DSC) test proved that oMMT promotes the compatibility of EP phase and PU phase, and glass transition temperature(T_g) of oM-EP/PU nanocomposites improves with increasing oMMT content. Mechanical properties tests and thermal gravity analysis (TGA) indicated that oMMT and the IPNs of EP and PU exhibit synergistic effect on improving mechanical and thermal properties of pure EP. The mechanism of toughing and reinforcing of oM-EP/PU nanocomposites was further discussed by scanning electronic microscope(SEM).     

Polyethylene with MoS2 nanoparticles toward antibacterial active packaging

Molybdenum disulfide (MoS₂) nanoparticles, obtained from liquid phase exfoliation in the presence of chitosan, were melt mixed with a linear low-density polyethylene (LLDPE) matrix to produce novel antimicrobial active packaging materials. The LLDPE/MoS₂ composites presented exfoliated nanoparticles forming aggregates that are well dispersed in the polymer matrix. These 2D-layered MoS₂ nanoparticles at concentrations of 0.5, 1.0, and 3.0 wt% rendered several functionalities to the LLDPE, as for example an antimicrobial behavior against Salmonella typhi and Listeria monocytogenes bacteria that can be explained not only by the photoactivity of the filler but also by changes in the composite surface. For instance, the composites presented a reduction in the water contact angle (i.e., an increased hydrophilicity) and relevant changes in the surface topography (i.e., reduced roughness) as compared with pure LLDPE. Regarding the barrier properties, while MoS₂ dramatically increased the water vapor permeation (WVP) of the polymer matrix, until 15 times for composite with 3.0 wt% of filler, the oxygen permeation decreased around 25%. All these novel functionalities in the nanocomposites were obtained without significantly affecting the tensile mechanical properties of the pure LLDPE matrix. These results show that MoS₂ is a promising filler for the development of antibacterial active packaging films with behaviors as similar as other 2D-layered fillers such as graphene derivatives.     

Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization,mechanical, and fracture behavior of mullite fiber‐reinforced polypropylene nanocomposites

This study describes the reinforcement effect of surface modified mullite fibers on the crystallization, thermal stability, and mechanical properties of polypropylene (PP). The nanocomposites were developed using polypropylene‐grafted‐maleic anhydride (PP‐g‐MA) as compatibilizer with different weight ratios (0.5, 1.0, 1.5, 2.5, 5.0, and 10.0 wt %) of amine functionalized mullite fibers (AMUF) via solution blending method. Chemical grafting of AMUF with PP‐g‐MA resulted in enhanced filler dispersion in the polymer as well as effective filler‐polymer interactions. The dispersion of nanofiller in the polymer matrix was identified using scanning electron microscopy (SEM) elemental mapping and transmission electron microscopy (TEM) analysis. AMUF increased the Young's modulus of PP in the nanocomposites up to a 5 wt % filler content, however, at 10 wt % loading, a decrease in the modulus resulted due to agglomeration of AMUF. The impact strength of PP increased simultaneously with the modulus as a function of AMUF content (up to 5 wt %). The mechanical properties of PP‐AMUF nanocomposites exhibited improved thermal performance as compared to pure PP matrix, thus, confirming the overall potential of the generated composites for a variety of structural applications. The mechanical properties of 5 wt % of AMUF filled PP nanocomposite were also compared with PP nanocomposites generated with unmodified MUF and the results confirmed superior mechanical properties on incorporation of modified filler. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43725.     

Analyzing the influence of different synthetic talcs in waterborne polyurethane nanocomposites obtainment

Waterborne polyurethane (WPU) nanocomposites were produced utilizing synthetic talc in gel form in order to improve its physical–chemical properties. Synthetic talc manufactured in nano‐gel form are interesting because their interaction with water occurs through hydrogen bonding favoring fillers dispersion within the WPU matrix. WPUs are environmental friendly materials because no organic solvents are used in its production. The nanocomposites obtained with the three synthetic talc nano‐gel fillers presented a good dispersion even when higher amounts of fillers were added, as seen by X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy analyses. The addition of synthetic talcs improved WPU nanocomposites mechanical properties. Storage and loss modulus results proved fillers incorporation into the WPU matrix corroborating with Fourier transform infrared spectroscopy results. Results demonstrated that synthetic talcs in nano‐gel form are interesting to obtain WPU nanocomposites with superior mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46107.     

PMMA‐grafted‐silica/PVC nanocomposites: Mechanical performance and barrier properties

Poly(vinyl chloride) (PVC)/SiO₂ nanocomposites were prepared via melt mixture using a twin‐screw mixing method. To improve the dispersion degree of the nanoparticles and endow the compatibility between polymeric matrix and nanosilica, SiO₂ surface was grafted with polymethyl methacrylate (PMMA). The interfacial adhesion was enhanced with filling the resulting PMMA‐grafted‐SiO₂ hybrid nanoparticles characterized by scanning electron microscopy. Both storage modulus and glass transition temperature of prepared nanocomposites measured by dynamic mechanical thermal analysis were increased compared with untreated nanosilica‐treated PVC composite. A much more efficient transfer of stresses was permitted from the polymer matrix to the hybrid silica nanoparticles. The filling of the hybrid nanoparticles caused the improved mechanical properties (tensile strength, notched impact strength, and rigidity) when the filler content was not more than 3 wt %. Permeability rates of O₂ and H₂O through films of PMMA‐grafted‐SiO₂/PVC were also measured. Lower rates were observed when compared with that of neat PVC. This was attributed to the more tortuous path which must be covered by the gas molecules, since SiO₂ nanoparticles are considered impenetrable by gas molecules. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization, and mechanical performance of various functionalized carbon nanotubes-polyurethanes nanocomposites

Nanocomposites of functionalized carbon nanotubes (CNTs_f) used as a reinforcement agent, and a polyurethane (PU), as a polymeric matrix were synthesized via in situ polymerization. Carbon nanotubes (CNTs) were chemically functionalized using four different chemical treatments to obtain (1) oxidized CNTs (CNTs_{OH, COOH}), (2) CNTs containing aliphatic amine groups (CNTs_{et diam}), (3) CNTs attached to an aromatic amine group (CNTs_4AB), and (4) CNTs containing a combination of aromatic amine, hydroxyl, and carboxyl functional groups (CNTs_{4AB, OH, COOH}). The nanocomposites (prepared using 0.25, 0.5 or 1.0 wt % CNTs_f) were synthesized by two processes: (1) one-step using a PU made from PCL-diol (α-ω-telechelic polyester diol) obtained by biocatalysis from ε-caprolactone (ε-CL) and diethylene glycol (DEG) and 4,4′-methylenebis (cyclohexyl isocyanate) (H₁₂MDI) in stoichiometric amounts, (2) two-step process (chain extended PU) using hexamethylene diamine (HMDA). Depending on the chemical route used to synthesized the nanocomposites, CNTs_f form, in some cases, covalent bonds and hydrogen bonding with the soft and/or hard segments of the PU matrix. Also, the presence of CNTs_f improves the thermal stability of the nanocomposites and some of their mechanical properties, compared to the pure PU properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47319.     

Reinforcement of polyurethane/epoxy interpenetrating network nanocomposites with an organically modified palygorskite

An organophilic palygorskite (o‐PGS) prepared by the treatment of natural palygorskite with hexadecyl trimethyl ammonium bromide was incorporated into interpenetrating polymer networks (IPNs) of polyurethane (PU) and epoxy resin (EP), and a series of PU/EP/clay nanocomposites were obtained by a sequential polymeric technique and compression‐molding method. X‐ray diffraction and scanning electron microscopy analysis showed that adding nanosize o‐PGS could promote the compatibility and phase structure of PU/EP IPN matrices. Tensile testing and thermal analysis proved that the mechanical and thermal properties of the PU/EP IPN nanocomposites were superior to those of the pure PU/EP IPN. This was attributed to the special fibrillar structure of palygorskite and the synergistic effect between o‐PGS and the IPN matrices. In addition, the swelling behavior studies indicated that the crosslink density of PU/EP IPN gradually increased with increasing o‐PGS content. The reason may be that o‐PGS made the chains more rigid and dense. As for the flame retardancy, the PU/EP nanocomposites had a higher limiting oxygen index than the pure PU. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermoplastic polyurethane and nitrile butadiene rubber blends with layered double hydroxide nanocomposites by solution blending

Polymer blending coupled with nanofillers has been widely accepted as one of the cheaper methods to develop high‐performance polymeric materials for various applications. In the present work, dodecyl sulfate intercalated Mg? Al‐based layered double hydroxide (DS‐LDH) was used as nanofiller in the synthesis of polyurethane blended with nitrile butadiene rubber (PU/NBR; 1:1 w/w) nanocomposites, which were subsequently characterized. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the partial dispersion of Mg? Al layers in PU/NBR blends at lower filler content followed by aggregation at higher filler loading. In comparison to the neat PU/NBR blend, the tensile strength (156%) and elongation at break (21%) show maximum improvement for 1 wt% filler loading. The storage and loss moduli, thermal stability and limiting oxygen index of the nanocomposites are higher compared to the neat PU/NBR blend. Glass transition temperature and swelling measurements increase up to 3 wt% DS‐LDH loading in PU/NBR compared to either neat PU/NBR or its other corresponding nanocomposites. XRD and TEM analyses indicate the partial distribution of DS‐LDH in PU/NBR blends suggesting the formation of partially exfoliated nanocomposites. The improvements in mechanical, thermal and flame retardancy properties are much greater compared to the neat blend confirming the formation of high‐performance polymer nanocomposites. Copyright © 2009 Society of Chemical Industry     

Enhanced properties of phthalonitrile‐terminated polyarylene ether nitriles embedded with hybrid MWCNT–boehmite nanocomposites

The main motivation of the present work was to fabricate novel multifunctional polymer‐based nanocomposites. The nanocomposites embedded with multi‐walled carbon nanotube‐boehmite (MWCNT‐boehmite) were prepared via hot pressure casting technique. The MWCNT coated with boehmite were synthesized by hydrothermal synthesis. Subsequently, as‐prepared MWCNT‐boehmite was added into the phthalonitrile‐terminated polyarylene ether nitriles (PEN‐t‐CN) matrix in order to benefit from the synergetic effect of MWCNT and boehmite. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) X‐ray diffraction (XRD), and Fourier transform infrared (FTIR) were employed to confirm the existence of MWCNT‐boehmite in our article. Furthermore, the structures, fracture morphologies, thermal, mechanical and dielectric properties of the nanocomposites were investigated, respectively. SEM images indicated that the MWCNT‐boehmite was homogeneously dispersed in the polymer, which acted as an essential factor to ensure good physical properties. The TGA analysis showed that the incorporation of MWCNT‐boehmite enhanced the thermal stability of the nanocomposites with initial degradation temperature (T_id) increasing from 458 to 492°C, while that of the pure PEN‐t‐CN was 439°C. The mechanical testing proved that significant enhancement of mechanical properties has been achieved. The tensile strength of PEN‐t‐CN/MWCNT‐boehmite composites with 3 wt% MWCNT‐boehmite reached the maximum (78.33 MPa), with a 41.7 % increase compared to the pure polymer. More importantly, the unique dielectric properties were systematically discussed and the results demonstrated that dielectric properties exhibited little dependency on frequency. For the incorporation of hybrid filler, the positive impact of MWCNT‐boehmite hybrid material resulted in polymer‐based nanocomposites with enhanced physical properties. POLYM. COMPOS., 36:2193–2202, 2015. © 2014 Society of Plastics Engineers     

Polyurethane/amino‐grafted multiwalled carbon nanotube nanocomposites: Microstructure,thermal, mechanical,and rheological properties

A mixture of two different polyols, (polytetramethylene ether glycol and polydimethylsiloxane), were employed to synthesize a new structure of polyurethane (PU) with methylene diphenyl diisocyanate (MDI) and 1,4‐butanediol as chain extender. PU nanocomposites containing variable amount (0.3, 0.5, 1, and 3 wt %) of amino‐grafted multiwalled carbon nanotubes (NH₂‐MWNT) were prepared via in situ polymerization. The dispersion of NH₂‐MWNT into polymer matrix was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT‐IR) confirmed the urethane‐urea chemical bonding between the PU chains and the NH₂‐MWNT. Thermal stabilities of the nanocomposites were examined with thermogravimetric analysis (TGA) and the results indicated a remarkable improvement with increasing NH₂‐MWNT contents. The results of dynamic mechanical thermal analysis (DMTA) including storage modulus (E′) and glass transition temperature (T_g), as well as tensile properties demonstrated that the yield strength, strain‐at‐break, and young modulus were enhanced by increasing NH₂‐MWNT content. Rheological behavior including complex viscosity and storage and loss moduli of the PU nanocomposites improved with increasing NH₂‐MWNT loading, as well. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44411.     

Simultaneous full‐interpenetrating polymer networks of blocked polyurethane and vinyl ester. II. Static and dynamic mechanical properties

Simultaneous full‐interpenetrating polymer networks (full‐IPNs) based on blocked polyurethane (PU) and vinyl ester (VE) have been prepared. The static and dynamic properties of these IPNs have been examined. Results show that the tensile strength and flexural strength of IPNs increased with blocked PU content to a maximum value at 7.5 wt % PU content and then decreased. The tensile modulus, flexural modulus, and hardness of IPNs decreased with increasing blocked PU content. The impact strength of IPNs increased with increasing blocked PU content. The tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (kaolin) content to a maximum value at 20 to 25 phr filler content and then decreased. The higher the filler content, the greater the hardness, and the lower the impact strength of IPNs. The tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs increased with increasing VE initiator content. The dynamic technique was used to determined the damping behavior across a temperature range. Results show that the glass transition temperature (T_g) of IPNs are shifted inwardly compared with pure PU and VE, which indicated that the blocked PU–VE IPNs showed excellent compatible. Meanwhile, the glass transition temperature was shifted to a higher temperature with increased filler content. The dynamic storage modulus (E′) of IPNs increased with increasing VE and filler content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1977–1985, 1999     

An investigation on the mechanical and dynamic rheological properties of single and hybrid filler/polypropylene composites based on talc and calcium carbonate

Some results of experiments on the mechanical and rheological properties of mineral filled polypropylene were presented. Single filler and hybrid filler composites of talc and calcium carbonate (CaCO₃) were prepared in a co‐rotating twin‐screw extruder. The effect of filler type, filler content, and coupling agent on the mechanical and rheological properties of the polypropylene were studied. The coupling agent was maleic anhydride‐grafted polypropylene (PP‐g‐MA). It was found that the mechanical properties are affected by filler type, filler concentration, and the interaction between filler and matrix. The tensile strength of the composite is more affected by the talc while the impact strength is influenced mostly by CaCO₃ content. The elongation at break of PP/CaCO₃ composites was higher than that of PP/talc composites. The incorporation of coupling agent into PP/mineral filler composites increased the mechanical properties. Rheological properties indicated that the complex viscosity and storage modulus of talc filled samples were higher than those of calcium carbonate filled samples while the tan δ was lower. The rheological properties of hybrid‐filler filled sample were more affected by the talc than calcium carbonate. The PP‐g‐MA increased the complex viscosity and storage modulus of both single and hybrid composites. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Enhanced thermal conductivity of PLA‐based nanocomposites by incorporation of graphite nanoplatelets functionalized by tannic acid

Enhancing thermal conductivity of polymeric nanocomposites remains a great challenge because of the poor compatibility between nanofillers and the polymeric matrix and the aggregation effect of nanofillers. We report the enhanced thermal conductivity of poly(lactic acid) (PLA)‐based nanocomposites by incorporation of graphite nanoplatelets functionalized by tannic acid. Graphite nanoplatelets (GNPs) were noncovalently functionalized with tannic acid (TA) by van der Waals forces and π–π interaction without perturbing the conjugated sp² network, thus preserving the high thermal conductivity of GNPs. PLA‐based nanocomposites with different contents of TA‐functionalized GNPs (TA‐GNPs) were prepared and characterized, and the influences of TA‐GNPs content on the morphologies, mechanical properties, and thermal properties of the composites were investigated in detail. TA‐GNPs remarkably improved the thermal conductivity of PLA up to 0.77 W/(m K), showing its high potential as a thermally conductive filler for polymer‐based nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46397.     

Influence of aspect ratio of fillers on the properties of acrylonitrile butadiene styrene composites

Aspect ratio (shape) of the filler is one of the key factors which play a vital role in determining the properties of the composites. Fillers like talc and calcium carbonate (CaCO₃) have different aspect ratios and affect the properties differently. This study was carried out to investigate the effect of aspect ratio of the filler on the properties of the acrylonitrile butadiene styrene (ABS) polymer. The rheological, mechanical, thermal properties, and fracture morphology were studied for the ABS composites filled with talc and CaCO₃ at various filler loading. Coupling agent was added to improve the interfacial adhesion between the filler and the ABS matrix. The aspect ratio of fillers affected the flow behavior at lower shear rate, and was insignificant at higher shear rates. The flow‐induced morphology was more effective in case of talc giving a significant increase in the bending modulus. Tensile and flexural strength showed a slight decrease in the values with talc showing better performance as compared to CaCO₃. The reverse was observed in case of impact strength, with CaCO₃ showing lower drop in the values. Aspect ratio of filler had no significant effect on the thermal properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46023.     

Template‐Free Synthesis of Porous Fe3O4/SiOC(H) Nanocomposites with Enhanced Catalytic Activity

We present a template‐free synthesis of Fe₃O₄/SiOC(H) nanocomposites with in situ formed Fe₃O₄ nanoparticles with a size of about 50 nm embedded in a nanoporous SiOC(H) matrix obtained via a polymer‐derived ceramic route. Firstly, a single‐source precursor (SSP) was synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with Fe‐acetylacetonate [Fe(acac)₃] at 140°C. The SSP was heat‐treated at 170°C to generate Fe₃O₄ nanocrystals in the cross‐linked polymeric matrix. Subsequently, the SSP was pyrolyzed at 600°C–700°C in argon atmosphere to yield porous Fe₃O₄/SiOC(H) nanocomposites with the high BET surface area up to 390 m²/g, a high micropore surface area of 301 m²/g, and a high micropore volume of 0.142 cm³/g. The Fe‐free SiOC(H) ceramic matrix derived from original AHPCS is nonporous. The in situ formation of Fe₃O₄ nanoparticles embedded homogeneously within a nanoporous SiOC(H) matrix shows significantly enhanced catalytic degradation of xylene orange in aqueous solution with H₂O₂ as oxidant as compared with pure commercial Fe₃O₄ nanoparticles.     

Enhanced Thermo‐Mechanical Stiffness,Thermal Stability,and Fire Retardant Performance of Surface‐Modified 2D MoS2 Nanosheet‐Reinforced Polyurethane Composites

This article reports new‐generation 2D‐MoS₂ nanosheet‐containing polyurethane (PU) composite materials with improved thermo‐mechanical stiffness, thermal stability, and fire retardation properties. The surface of 2D‐MoS₂ nanosheets is modified with melamine (M‐MoS₂), and then PU composites with varying M‐MoS₂ loadings are synthesized using an in situ polymerization method. During polymerization, 3‐amino‐propyl‐trimethoxy silane is introduced to create silicate functionality on the PU chains, which further improves the compatibility between PU and M‐MoS₂. Microscopy studies confirm the distribution of highly intercalated and agglomerated M‐MoS₂ nanosheets in the PU matrix. The PU composite containing 5 wt% M‐MoS₂ shows a 65% higher storage modulus (at 30 °C) than that of pure PU. The thermal stability of pure PU is significantly improved (62 °C) after composite formation. Thermogravimetric analysis in combination with FTIR spectroscopy shows that the PU/M‐MoS₂ composites release less toxic gases during thermal degradation compared to pure PU. Moreover, the composite containing 5 wt% M‐MoS₂ shows improved fire retardation properties, with 45% and 67.5% decrease in the peak heat and total heat release rates, respectively, as compared with those of pure PU. In summary, 2D‐MoS₂ is shown to have potential as an advanced nano‐filler to obtain stiffer PU composite with improved fire retardant property for structural application.