Transparent nanocomposites with enhanced performances from poly(propylene carbonate) and silica

In this study, silica nanoparticles with a refractive index matching PPC and a diameter smaller than the visible light wavelength were chosen to prepare enhanced PPC/silica nanocomposites by a simple melt compounding method. The result exhibited all the nanocomposites possessed excellent transparency (about 90%), even in the nanocomposite with a silica content of 10 wt%. For PPC/silica nanocomposites, the percolation threshold was determined to be 7.5 wt% based on the dynamic rheological behavior and percolation theory. Moreover, the overall performance of the PPC-based nanocomposite with a silica content of 7.5% is the best. The optimal nanocomposite showed a Young's modulus of 3792 MPa, a yield strength of 46.5 MPa, a storage modulus of 3812 MPa and a highest temperature at maximum weight-loss rate (T_max, 309°C). These characteristics are very important for potential commodity applications of PPC.     

Interaction of dendronized polymeric nanocomposites with isomeric cyclohexanediols

Dendronized poly(diethylaminoethyl methacrylamide) (PEAM) was studied in blends containing isomeric cyclic dialcohols. Monomers and polymers were characterized by spectroscopic measurements. The phase behaviors of blends of PEAM with 1,2‐, 1,3‐ and 1,4‐cyclohexanediols (1,2‐CHD, 1,3‐CHD and 1,4‐CHD, respectively) were established. Transparent films of the blends exhibited a single glass‐transition temperature (T_g). Thermogravimetric analysis (TGA) revealed the temperature at which the polymer releases the small molecules. UV‐vis spectra of 1,3‐CHD and 1,4‐CHD derivatives showed an isosbestic point that indicated the association of the alcohols. FT‐IR measurements showed shifts in several absorption bands. The results were analyzed in terms of the side‐chain structure and the interactions involved. AFM measurements revealed differences between the polymer and the blends. Compatibilization of blends of PEAM/CHDs occurred via the formation of hydrogen bonds, although hydrophobic interactions could not be disregarded. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42267.     

Influence of fullerenes on the thermal and flame-retardant properties of polymeric materials

At present, the application of fullerene in polymer materials has become an attractive issue. Fullerene can enhance the thermal and flame-retardant properties of polymers due to its high capacity to trap free radicals. Fullerene also has good synergistic effect with inorganic metal flame retardant, intumescent flame retardant, brominated flame retardant (BFR), clay, carbon nanotubes, graphene oxide, and so on. In this review, the impact and mechanism of fullerene and its derivatives on the thermal and flame-retardant properties of polymeric materials are discussed. And the prospect of fullerene in flame-retardant polymer composites is also briefly introduced by analyzing the research progress in the recent years. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47538.     

Electromagnetic interference shielding behavior of chemically and thermally reduced graphene based multifunctional polyurethane nanocomposites: A comparative study

This article presents the effect of exfoliation, dispersion, and electrical conductivity of graphene sheets onto the electrical, electromagnetic interference (EMI) shielding, and gas barrier properties of thermoplastic polyurethane (TPU) based nanocomposite films. The chemically reduced graphene (CRG) and thermally reduced/annealed graphene (TRG) having Brunauer–Emmett–Teller surface areas of 18.2 and 159.6 m²/g, respectively, when solution blended with TPU matrix using N,N-dimethylformamide as a solvent. Graphene sheets based TPU nanocomposites have been evaluated and compared for EMI shielding in Ku band, electrical conductivity, and gas barrier property. TRG/TPU nanocomposite films showed excellent gas barrier against N₂ gas as compared to CRG/TPU. The EMI shielding effectiveness for neat CRG and TRG graphene sheets is found to be −80, −45 dB, respectively, at 2 mm thickness. The EMI shielding data revealed that TRG/TPU nanocomposites showed better shielding at lower concentration (10 wt %), while CRG displayed better attenuation at higher concentrations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47666.     

Crystal structures and their effects on the properties of polyamide 12/clay and polyamide 6–polyamide 66/clay nanocomposites

Both polyamide 12 (PA 12)/clay and polyamide 6–polyamide 66 copolymer (PA 6/6,6)/clay nanocomposites were prepared by melt intercalation. The incorporation of 4–5 wt % modified clay largely increased the strength, modulus, heat distortion temperature (HDT), and permeation resistance to methanol of the polyamides but decreased the notched impact strength. Incorporation of the clay decreased the melt viscosities of both the PA 12 and PA 6/6,6 nanocomposites. Incorporation of the clay increased the crystallinity of PA 6/6,6 but had little effect on that of PA 12, which explained why the clay obviously increased the glass‐transition temperature of PA 6/6,6 but hardly had any effect on that of PA 12. The dispersion and orientation of both the clay and the polyamide crystals were studied with transmission electron microscopy, scanning electronic microscopy, and X‐ray diffraction. The clay was exfoliated into single layers in the nanocomposites, and the exfoliated clay layers had a preferred orientation parallel to the melt flow direction. Lamellar crystals but not spherulites were initiated on the exfoliated clay surfaces, which were much more compact and orderly than spherulites, and had the same orientation with that of the clay layers. The increase in the mechanical properties, HDT, and permeation resistance was attributed to the orientated exfoliated clay layers and the lamellar crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4782–4794, 2006     

Thermomechanical and optical properties of biodegradable poly(L‐lactide)/silica nanocomposites by melt compounding

Poly(L ‐lactide) (PLA)/silica (SiO₂) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO₂ nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO₂ nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO₂ nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass‐transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving C?O of PLA with Si? OH of SiO₂ was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO₂ nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO₂ concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mesua ferrea L. seed oil based highly branched polyester/epoxy blends and their nanocomposites

Mesua ferrea L. seed oil based highly branched polyester and epoxy resins blends were prepared by mechanical mixing at different weight ratios. The best performing blend was used as the matrix for the preparation of nanocomposites with different dose levels of organophilic montmorillonite (OMMT) nanoclay. The prepared nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Data resulting from the mechanical and thermal studies of the blends and nanocomposites indicated improvements in the tensile strength and thermal stability to appreciable extents for the nanocomposites with OMMT loading. The nanocomposites were characterized as well‐dispersed, partially exfoliated structures with good interfacial interactions. From the X‐ray diffraction analysis, the absence of d₀₀₁ reflections of the OMMT clay in the cured nanocomposites indicated the development of an exfoliated clay structure, which was confirmed by transmission electron microscopy. The homogeneous morphologies of the pure polyester/epoxy blend and clay hybrid systems were ascertained with scanning electron microscopy. The tensile strength of the 5 wt % clay‐filled blend nanocomposite system was increased by 2.4 times compared to that of the pure blend resin system. The results suggest that the prepared nanocomposites have the potential to be used as active thin films for different applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Graphene-polymer nanocomposites for structural and functional applications

The introduction of graphene-based nanomaterials has prompted the development of flexible nanocomposites for emerging applications in need of superior mechanical, thermal, electrical, optical, and chemical performance. These nanocomposites exhibit outstanding structural performance and multifunctional properties by synergistically combining the characteristics of both components if proper structural and interfacial organization is achieved. Here, we briefly introduce the material designs and basic interfacial interactions in the graphene-polymer nanocomposites and the corresponding theoretical models for predicting the mechanical performances of such nanocomposites. Then, we discuss various assembly techniques available for effectively incorporating the strong and flexible graphene-based components into polymer matrices by utilization of weak and strong interfacial interactions available in functionalized graphene sheets. We discuss mechanical performance and briefly summarize other physical (thermal, electrical, barrier, and optical) properties, which are controlled by processing conditions and interfacial interactions. Finally, we present a brief outlook of the developments in graphene-based polymer nanocomposites by discussing the major progress, opportunities, and challenges.     

Dispersion and properties of cellulose nanowhiskers and layered silicates in cellulose acetate butyrate nanocomposites

The aim of this work was to develop well dispersed nanocomposites, in a non water soluble polymer using a non aqueous, low polarity solvent as a dispersion medium. The nanoreinforcements were cellulose whiskers and layered silicates (LSs) and matrix was cellulose acetate butyrate (CAB). Before nanocomposite processing, a homogenizer was used in combination with sonification to achieve full dispersion of the nanoreinforcements in a medium of low polarity (ethanol). After processing, the cellulose nanowhiskers (CNW) showed flow birefringence in both ethanol and dissolved CAB, which indicated well dispersed whiskers. The microscopy studies indicated that the processing was successful for both nanocomposites. The CNW showed a homogeneous dispersion on nanoscale. The LS nanocomposite contained areas with lower degree of dispersion and separation of the LS sheets and formed mainly an intercalated structure. The produced materials were completely transparent, which indicated good dispersion. Transparency measurements also indicated that the nanocomposite containing CNW showed similar performance as the pure CAB. Dynamic mechanical thermal analysis (DMTA) showed improved storage modulus for a wide temperature range for both nanocomposites compared with the pure CAB matrix. This study indicated that CNW have a potential application in transparent nanocomposites based on fully renewable resources. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Recent advancement in self-healing graphene polymer nanocomposites,shape memory,and coating materials

ABSTRACT

Recently, self-healing polymeric materials has garnered much attention due to their ability to prolong materials shelf-life. Graphene, as a formidable nanoparticle, has garnered great interests due to accruable superior properties in polymer nanocomposites (PNC). Application of organic coatings is the most available, and cost-efficient technique of enhancing the shelf-life of metallic structures. Shape memory polymeric materials are capable of being deformed, and arranged into a temporary shape, while also recovering their original configuration on exposure to external stimulation. Hence, the advent of self-repairing graphene PNC, coatings, and polymeric shape memory materials has enlarged the applications scope of these materials.     

A brief review on fire retardants for polymeric foams

Fire retardants are briefly reviewed with reference to commonly available polymeric foams. Both physical and chemical aspects of intumescent fire retardants are summarized. New products based on nanocomposites are introduced as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 366–376, 2005     

Structure and properties of nanocomposites based on poly(butylene succinate) and organically modified montmorillonite

Poly(butylene succinate) and organically modified montmorillonite nanocomposites with there different compositions were prepared via melt blending in a twin‐screw extruder. The structure of the nanocomposites was studied with X‐ray diffraction and transmission electron microscopy, which revealed the formation of intercalated nanocomposites, regardless of the silicate loading. Dynamic mechanical analysis revealed a substantial increase in the storage modulus of the nanocomposites over the entire temperature range investigated. The tensile property measurements showed a relative increase in the stiffness with a simultaneous decrease in the yield strength in comparison with that of neat poly(butylene succinate). The oxygen gas barrier property of neat poly(butylene succinate) improved after nanocomposite preparation with organically modified montmorillonite. The effect of the layered‐silicate loading on the melt‐state linear viscoelastic behavior of the intercalated nanocomposites was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 777–785, 2006     

Dichroic nanocomposites based on polymers and metallic particles: from biology to materials science

Dichroic nanocomposites change their colors when they are viewed through a turning polarizer. In the case of polymer matrices containing inorganic nanoparticles, this color effect originates in anisotropic structures of inorganic moieties, such as uniaxially oriented linear assemblies of spherical nanoparticles or parallel oriented nanorods. The orientation of the particles or particle assemblies, respectively, is induced by the polymer matrix, either through oriented elongated hollow spaces or drawing. Matrices based on biopolymers (e.g. cellulose, polypeptides, chitin) as well as synthetic polymers (e.g. polyethylene, poly(vinyl alcohol)) have been employed. The dichroic colors have been generated so far mainly by silver or gold particles (including nanorods), but also other metals and occasionally also semiconductors (metalloids). Notably, dichroism is also disclosed in optical absorption spectra recorded with polarized light. Dichroism in biopolymer‐based objects with incorporated nanoparticles has been exploited for the cognition of biological fine structures, while dichroic films with technical polymers as matrices have been considered as optical switches in bicolored liquid crystal displays and authenticity cachets for documents, banknotes and packaging films. In this context, micropatterning of dichroic nanocomposites, which has been achieved by local heating procedures of materials composed of metal nanorods, is also of interest. © 2017 Society of Chemical Industry     

Preparation and characterization of high refractive index thin films of TiO2/epoxy resin nanocomposites

By using sol–gel method, amorphous titania was introduced into epoxy matrix to prepare a series of high refractive index TiO₂/epoxy resin nanocomposite films. To increase the refractive index of the hybrid films, triethoxysilane‐capped trimercaptothioethylamine (TCTMTEA), a new kind of high refractive index coupling agent was synthesized from trimercaptothioethylamine (TMTEA). In the experiment, TCTMTEA acted as the solidification agent together with TMTEA except being used as the coupling agent. The hybrid films have been characterized via FTIR, AFM, DSC, TGA, etc. The experimental results showed that the amorphous TiO₂ had been dispersed uniformly in the organic polymer matrix with the size smaller than 100 nm in each sample. More importantly, the refractive index of this kind of materials can be continuously adjusted from 1.61 to 1.797 with the content of TiO₂ increasing from 0% to 65% in mass, and the continuously adjusted refractive index is very important for the applications in optical antirefractive films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1631–1636, 2006     

Transparent conducting films based on nanofibrous polymeric membranes and single‐walled carbon nanotubes

Transparent and electrically conducting films were fabricated using a novel and simple method in which single‐walled carbon nanotubes (SWCNTs) adsorbed onto bacterial cellulose membranes were embedded into a transparent polymer resin. The bacterial cellulose membranes consisting of numerous nanofibrils were found to play important roles in this process. The bacterial cellulose membranes impart optical transparency to the nanocomposites due to the size of the materials during the synthesis of the nanocomposite using a transparent polymer resin. The membranes play a secondary role as a template for depositing uniformly dispersed SWCNTs. This results in not only electrically conducting pathways but also prevents interference from the transmittance of optically transparent nanocomposites. Transparent conducting films with a wide range of transmittances and surface resistances could be obtained by controlling the immersion time and SWCNT concentration in the SWCNT dispersions. A transparent conducting film with a transmittance and surface resistance of 77.1% at 550 nm and 2.8 kΩ/sq, respectively, was fabricated from a 0.01 wt %. SWCNT dispersion for an immersion time of 3 h. In addition, the transparent conducting films were quite flexible and maintained their properties even after crumpling. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, and ionic conductivity of nanocomposites: Polyelectrolyte systems

The synthesis, diffraction patterns, thermal stability, and ionic conductivity properties of methacrylate‐type polymers are analyzed here to assess their feasibility as polymer electrolytes. From the parent polymer, poly (N,N‐dimethylaminoethylmethacrylate), herein labeled PDMAEMA, a protonated derivative was used to prepare polymer/Montmorillonite nanocomposites with various clay contents (1, 3, and 5 wt %). AC spectroscopy provided the ionic conductivity data for the polymers and clay–polymer nanocomposites. Evidences of nanocomposite formation are shown using transmission electron microscopy and wide‐angle X‐ray diffraction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure–property correlation of polyurethane nanocomposites: Influence of loading and nature of nanosilica and microstructure of hyperbranched polyol

New generation polyurethane nanocomposites based on toluene diisocyanate, poly(propylene glycol), hyperbranched polymers (HBPs), and nanosilica were synthesized with the aim of determining the effect of the loading and nature of nanosilica and the functionality of HBP on the structure and properties of polyurethane nanocomposites. Good dispersion of nanosilica at 4 wt % loading in the polymer was confirmed from atomic force microscopy. The properties of the polyurethane nanocomposites were a function of content and nature of the nanosilica in the matrix. The optimum silica loading was 4 wt %. At this loading, tensile strength and storage modulus at 25°C of the nanocomposites increased by 52 and 40%, respectively over the pristine polyurethane. Organo‐treated nanosilica exhibited higher physico‐mechanical properties than the untreated one. With the increase of functionality in the hyperbranched polyol, the tensile strength, thermal stability, and dynamic mechanical properties of the nanocomposites improved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of novel copper nanoparticles/ternary polymer blend nanocomposites and their structural,thermal and rheological properties and AC impedance

Copper nanoparticles (Cu NPs)/ternary polymer blend nanocomposites were synthesized via a solution‐casting technique. The nanocomposites were studied for their structural, thermal, rheological and electric properties. Scanning electron micrographs and atomic force micrographs showed no phase separation between the polymers, a narrow size distribution of Cu NPs (in the range 25–43 nm) and good dispersion of Cu NPs in the polymer matrix. Energy‐dispersive X‐ray analysis confirmed the presences of Cu in the matrix. X‐ray diffraction data showed a characteristic face‐centred cubic architecture for Cu unit cell and interaction of the Cu NPs with oxygen‐carrying polymers. Thermogravimetric analysis showed an increase in the degradation temperature (from 254 to 268 °C) and three‐step degradation of the nanocomposites. Rheological analysis showed an increase in the complex viscosities and storage modulus for the nanocomposites. AC impedance studies showed increased ionic conductivities and decreased bulk resistance for the nanocomposites. All these studies suggested interactions between Cu NPs and polymer matrix and the formation of a network structure. © 2017 Society of Chemical Industry     

Preparation and properties of unsaturated polyester nanocomposites based on silylated sepiolite nanofibers

The novel surface‐modified sepiolite/unsaturated polyester (sepiolite/UP) nanocomposites were prepared by in situ polymerization. Sepiolite fibers were first organo‐modified by grafting of vinyltriethoxysilane (VTS) containing a double bond onto the surfaces and used as nanofillers. The morphology of sepiolites and nanocomposites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM). Moreover, the thermal properties were determined by thermogravimetric analysis (TGA) and the thermal degradation mechanism was discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010