Morphology and electrical conductivity of PS/PMMA/SMMA blends filled with carbon black

An alternative strategy to reduce the percolation threshold of carbon black (CB) in polymer blends was investigated using random copolymer ternary blends of polystyrene (PS), poly(methyl methacrylate) (PMMA), and a styrene-methyl methacrylate random copolymer (SMMA). The target morphology was to selectively locate CB particles in the encapsulating layer of SMMA during melt mixing. The CB used in this study is BP-2000 from Cabot and has a strong selective affinity to PS. Even when the CB was premixed with SMMA, it moves to the PS phase during the melt mixing. However, we also observed the CB particles located at the interface between SMMA and PS phases. Through this study it is found that the interaction between polymers and CB particles is critical for selectively localizing CB particles in multi-component polymer blends. Although appropriate processing condition may retard the movement of CB particles to the polymer phase with affinity, it cannot prevent it completely and locate them to the SMMA phase, which is not thermodynamically favored. To locate CB particles in an encapsulating layer of ternary polymer blends, first of all, polymers forming it should have selective affinity to CB.     

Preparation and UV-protective property of PVAc/ZnO and PVAc/TiO<Subscript>2</Subscript> microcapsules/poly(lactic acid) nanocomposites

The poly(vinyl acetate) (PVAc)/zinc oxide (ZnO) microcapsule and PVAc/titanium dioxide (TiO₂) microcapsule were synthesized via in-situ emulsion polymerization method. The PVAc/ZnO microcapsule and PVAc/TiO₂ microcapsule were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis(TG), transmission electron microscopy (TEM), and UV-visible spectroscopy (UV-vis). Effect of PVAc/ZnO microcapsule and PVAc/TiO₂ microcapsule on properties of poly(lactic acid) (PLA) was evaluated by UV-vis, SEM and mechanical properties test. The results showed that the addition of PVAc/ZnO and PVAc/TiO₂ microcapsules as a UV-blocking additive could significantly enhance UV-blocking property of PLA/PVAc/ZnO microcapsule composites and PLA/PVAc/TiO₂ microcapsule composites compared with pure PLA, PLA/ZnO composites and PLA/TiO₂ composites. The mechanical properties of PLA/PVAc/ZnO microcapsule composites were better than those of PLA/ZnO composites due to good dispersability and compatibility of PVAc/ZnO microcapsule in PLA matrix. Also, the mechanical properties of PLA/PVAc/TiO₂ microcapsule composites were better than those of pure PLA and PLA/TiO₂ composites. This study demonstrates the great potentials of the intrinsically UV shield additive PVAc/ZnO and PVAc/TiO₂ microcapsules in the application of high performance matrix resin and composite material.     

Miscibility and crystallization behaviors of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends of various compositions were prepared by the solution-blending and melt-blending methods. The changes in miscibility and crystallization behaviors of the blends upon thermal treatment above the melting temperature of the blends at 280°C were investigated by using DSC, DMA,¹H NMR, and SAXS analyses. Without any thermal treatment, the blend systems were not miscible, and the thermal transitions, such as glass transition, cold crystallization, and crystal melting of the individual components were observed in the DSC and DMA analyses. With thermal treatment, though, they became miscible as the thermal transitions of each component disappeared and single glass transition peaks were observed in the thermal analysis. The chain randomness determined using¹H NMR spectroscopy revealed that thermal treatment at 280°C for more than 30 min brought about transesterification reactions between the PTT and PEN segments resulting in an increase in their miscibility. These results were confirmed by the small angle X-ray analysis conducted to determine the long period (L), the thickness of the crystalline lamella stack (l _c ), and the thickness of the amorphous region (l _a ). After short thermal treatment, the melt-blended sample followed the values for the individual components. However, with extended thermal treatment, the blend became homogeneous, possessing different crystalline morphologies which resulted in different values ofL, l _c , andl _a .     

Electrospun titanium dioxide nanofibers: Fabrication,properties and its application in photo-oxidative degradation of methyl orange (MO)

In this study, we synthesed two kind of TiO₂ nanomaterial (nanoparticles and nanofiber) for photocatalitic degradation of methyl orange (MO) as pollutant. TiO₂ nanoparticles were synthesized by sol-gel technique using titanium (IV) isopropoxide as precursor. Polyvinyl acetate (PVAc)/TiO₂ hybrid nanofibers were fabricated by combining sol-gel process with electrospinning technology, which consisted of PVAc as organic segment and TiO₂ as inorganic part. Crystalline phase of TiO₂ nanomaterials was investigated by X-ray diffraction (XRD). The XRD results show that the TiO₂ nanomaterials crystallize in anatase with some rutile phase and these consist of titanium dioxide nano-crystals. The surface structures of TiO₂ nanomaterials were examined using scanning electron microscopy (SEM). SEM scanning revealed that the nanoparticle and nanofibrous structure was formed. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the chemical structures of the PVAc/TiO₂ hybrid nanofibers. The FTIR analysis indicated the newly formed associated hydrogen bond because of the hybrid effect between PVAc and TiO₂ sol. Finally, The photooxidative decomposition of methylene blue by using the titania nanomaterials was examined and compared.     

Crystallization of PVDF in graphene-filled electrospun PVDF/PMMA nanofibers processed at three different conditions

In this study, the morphology and crystal polymorphism of electrospun blend nanocomposite of graphene filled-polyvinylidene fluoride (PVDF)/poly(methyl methacrylate) (PMMA) nanofibers were investigated. The preparation of the nanofibers was carried out by synthesis of PMMA/graphene as a masterbatch through in-situ polymerization, and then followed by compounding with PVDF solution in the different ratios. The process of electrospinning was done at three selective conditions of temperature, moist and ordinary environment. Crystallinity, morphology and thermal properties of nanofibers were characterized by X-ray diffraction spectroscopy (XRD), differential scanning calorimetric (DSC), Transmittance Electron Microscopy (TEM), Thermogravimetric Analyses (TGA), and Field Emission Scanning Electron Microscopic (FE-SEM). The enhancement of β crystal formation in the electrospun graphene-filled blend nanofibers was confirmed by XRD and DSC results. This can be ascribed by the benefits of solution casting, mechanical stretching, high electric field, PMMA interactions and graphene restrictions, altogether in one simple process. Also, presence of water molecules during the electrospinning causes the orientation of fluorine atoms in PVDF due to polar-polar interactions which enhance the polar conformation even in the pure PVDF nanofibers.     

Functionalization of graphene nanosheets and its dispersion in PMMA/PEO blend: Thermal,electrical, morphological and rheological analyses

Graphene nanoplatelet (GnP) was chemically functionalized by amine groups for improvement of compatibility in poly(methyl methacrylate) (PMMA)/poly(ethylene oxide) (PEO) blend. PMMA/PEO (90/10) nanocomposites with non-functionalized GnP and functionalized GnP (FGnP) were prepared by solution casting method. Successful grafting of amine groups on the GnP surface was confirmed by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) analysis. The Transmission electron microscopy (TEM) images showed that the dispersion state of FGnP was better than that of GnP in PMMA/PEO nanocomposites. The effects of FGnP and GnP on rheological, thermal and electrical properties of PMMA/PEO nanocomposites were investigated by various methods. The results indicated that the FGnP-based nanocomposites had higher storage modulus, glass transition temperature and thermal stability as compared to the GnP-based nanocomposites. The electrical conductivity of the nanocomposites with FGnP was better than that of GnP-based nanocomposites. The higher conductivity was attributed to homogeneous and well dispersion state of FGnP in PMMA/PEO nanocomposites.     

Preparation of high molecular weight poly(methyl methacrylate) with high yield by room temperature suspension polymerization of methyl methacrylate

To obtain high molecular weight (HMW) poly(methyl methacrylate) (PMMA) with high conversion, methyl methacrylate (MMA) was polymerized in suspension using a room temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN), and the effects of polymerization conditions on the polymerization behavior of MMA and the molecular parameters of PMMA were investigated. On the whole, the experimental results well corresponded to the theoretically predicted tendencies. These effects could be explained by a kinetic order of ADMVN concentration calculated by an initial rate method and an activation energy difference of polymerization obtained from the Arrhenius plot. Suspension polymerization at 25 °C by adopting ADMVN proved to be successful in obtaining PMMA of HMW (number-average degree of polymerization (P_n): 30,900–36,100) and of high yield (ultimate conversion of MMA into PMMA: 83–93 %) with diminishing heat generated during polymerization. The P_n and lightness were higher and polydispersity index was lower with PMMA polymerized at lower temperatures.     

Synthesis of poly(norbornene ester)s by using (<Emphasis Type="Italic">η</Emphasis><Superscript>3</Superscript>-substituted allyl) palladium (NHC) complex as catalyst and investigation of their chemical structure - Glass transition temperature - Refractive index relationships

The synthesis of poly(norbornene ester)s by using a (η ³-substituted allyl) palladium (N-heterocyclic carbene (NHC)) complex as catalyst was performed and the relationship between chemical structure and glass transition temperature or refractive index of poly(norbornene ester)s was investigated. Norbornene ester monomers were synthesized via esterification of 5-norbornene-2-methyl alcohol and aromatic carboxylic acids. The polymerization catalyst, (η ³-substituted allyl) palladium (NHC) complex, was synthesized according to a published procedure. ¹H-NMR spectroscopy was performed to determine chemical structure of monomers and polymers. The molecular weight of the polymers was measured via gel permeation chromatography and the thermal properties were analyzed via thermogravimetric analysis and dynamic mechanical analysis. Refractive indices of polymer films were measured using a prism coupler. Polymers with the highest M _n (between 100 kg/mol and 300 kg/mol) were synthesized when the ratio of monomer to catalyst was 2000:1. The glass transition temperature of synthesized polymers was about 100 °C lower than that of conventional norbornene polymers. Among the six polymers of different chemical structures, four polymers exhibited a refractive index of 1.6 or more at a wavelength in the visible light region.     

Preparation and photochromism of poly(methyl methacrylate) microspheres containing spirooxazine

Photochromic poly(methyl methacrylate) (PMMA)/spirooxazine microspheres were prepared by in situ suspension polymerization and those photochromic behaviors were investigated. When UV irradiation was subjected to the PMMA/spirooxazine microspheres, the reflection spectra generated by photochromic reaction was clearly observed and its reversible decoloration behaviors responded rapidly in the dark. Photochromic microspheres prepared in this work, could be used to photochromic fabrics such as microcapsules for fragrant finishing of fabrics, as well as those are could be applied in sensing materials.     

The effects of blend composition and blending time on the ester interchange reaction and tensile properties of PLA/LPCL/HPCL blends

PLA/LPCL/HPCL blends composed of poly(lactic acid) (PLA), low molecular weight poly(ε-caprolactone) (LPCL), and high molecular weight poly(ε-caprolactone) (HPCL) were prepared by melt blending for bioabsorbable filament sutures. The effects of blend composition and blending time on the ester interchange reaction by alcoholysis in the PLA/LPCL/HPCL blends were studied. Their thermal properties and the miscibility due to the ester interchange reaction were investigated by¹H-NMR, DSC, X-ray, and UTM analyses. The hydroxyl group contents of LPCL in the blends decreased by the ester interchange reaction due to alcoholysis. Thus, the copolymer was formed by the ester interchange reaction at 220 °C for 30–60 minutes. The thermal properties of PLA/LPCL/HPCL blends such as melting temperature and heat of fusion decreased with increasing ester interchange reaction levels. However, the miscibility among the three polymers was improved greatly by ester interchange reaction. Tensile strength and modulus of PLA/LPCL/HPCL blend fibers increased with increasing HPCL content, while the elongation at break of the blend fibers increased with increasing LPCL content.     

Enhancement of processability, stability and photoluminescence performance of poly(p-phenylene vinylene) containing diazine heterocycle unit

Two n-type conjugated polymers of pyrazine and quinoxaline containing poly(p-phenylene vinylene) (P-1) (P-2) have been synthesized through Wittig route. Formation of the polymers were confirmed by spectral (UV-Vis, PL, FT-IR and NMR), elemental and GPC analysis. These polymers were soluble in common organic solvents such as THF, CH₂Cl₂, CHCl₃ and CH₃CN. The resulting polymers have good thermal stability upto 308 and 361 °C with the 5 % weight loss. The absorption spectrum of the polymers displayed the maximum at 398 and 414 nm, corresponding to the ??-??* electronic transition of the conjugated polymer backbones. The optical band gap of these polymers found to have in the range of 2.5?C2.53 eV. The photoluminescence spectrum of the polymers was observed at 487 and 505 nm in CHCl₃ solution. AFM images depicted that the micrometer sized globular and triangular shaped particles can be seen from the polymer surfaces.     

Titanium dioxide nanofibers prepared by using electrospinning method

The synthesis of titanium dioxide nanofibers with 200–300 nm diameter was presented. The new inorganic-organic hybrid nanofibers were prepared by sol-gel processing and electrospinning technique using a viscous solution of titanium isopropoxide (TiP)/poly(vinyl acetate) (PVAc). Pure titanium dioxide nanofibers were obtained by high temperature calcination of the inorganic-organic composite fibers. SEM, FT-IR, and WAXD techniques were employed to characterize these nanofibers. The titanium dioxide nanostructured fibers have rougher surface and smaller diameter compare with PVAc/TiP composite nanofibers. The anatase to rutile phase transformation occurred when the calcination temperature was increased from 600 °C to 1000 °C.     

Preparation of aminated polyacrylonitrile porous fiber mat and its Application for Cr(VI) ion removal

Porous polyacrylonitrile (PAN) fiber mat was prepared by electrospinning PAN in N,N-dimethylformide solution with poly(methyl methacrylate) (PMMA) as pore-forming agent. Then, the porous PAN fiber mat was chemical modified by the tetraethylenepentamine to acquire aminated porous polyacrylonitrile (APPAN) fiber mat. Common aminated PAN fiber mat was also prepared for comparison. The surface morphologies of the APPAN and PAN fiber mat were characterized by scanning electron microscopy (SEM) and the corresponding specific surface areas were also measured. FT-IR/ATR spectra of the APPAN and PAN fiber mat were recorded for analysis of the surface chemical structures. The Cr(VI) absorption results demonstrated that the porous structure in the fiber could obviously increase the absorption capacity of the fiber mat.     

Preparation of SAN/silicate nanocomposites using PMMA as a compatibilizer

Polymer/silicate nanocomposites were prepared via two-step manufacturing process: a master batch preparation and then mixing with matrix polymer. A hybrid of PMMA and Na-MMT with exfoliated structure was first prepared by emulsion polymerization of MMA in the presence of Na-MMT. For the case that SAN24, miscible with PMMA, is used as matrix, we could prepare a nanocomposite with exfoliated structure. However, SAN31 nanocomposite shows the aggregation and/or reordering of the silicate layers due to the immiscibility between SAN31 and PMMA.     

Fabrication of structure-preserving monodisperse particles of PMMA-<Emphasis Type="Italic">grafted</Emphasis> fullerenes

Fullerene has fascinated characteristics and the fabrication of fullerene-containing assembly of high solubility in general solvents at facile way is immensely expected for the material processing. We aimed to control supramolecular structure of fullerene-containing molecules with arrested morphology, which would boost material potentials to wider application. In this study, we have synthesized poly(methyl methacrylate) (PMMA)-grafted fullerene and the association behavior of PMMA-grafted fullerene in solvent is utilized to obtain monodisperse assemblies with submicron size. Furthermore, we have succeeded to fix the assembly morphology by UV irradiation and recovered the assembly in another solvent in which the assembly basically does not form. This procedure enables us to obtain fullerene- dispersed materials at sub-μm order with various matrixes.     

Functionalized multi-walled carbon nanotubes with hyperbranched aromatic polyamide for poly(methyl methacrylate) composites

Multi-walled carbon nanotubes (MWCNTs) were functionalized with hyperbranched aromatic polyamide (HAP) by in situ polymerization and by the AB ₂ approach to enhance the mechanical properties of poly(methylmethacrylate) (PMMA) composites. Various concentrations of HAP-functionalized MWCNTs (HAP-f-MWCNTs) were used to prepare HAP-f-MWCNT-reinforced PMMA composite films. The covalent attachment of HAP to the MWCNTs, as achieved by in situ functionalization, resulted in effective dispersion of the MWCNTs in the PMMA matrix, thus enhancing the mechanical and thermal properties of the composite films. The breaking stress of the composites increased largely with the HAP-f-MWCNT loading.     

Processing and Characterisation of Hybrid Aramid Fabrics Reinforced with Cross-linked Electrospun PVB Composite Nanofibres

The aim of this study was to fabricate a new kind of hybrid fabric composites with the cross-linked electrospun poly(vinyl butyral) (PVB) composite nanofibres. The experiments were performed with the 10 wt.% PVB/ethanol solution for electrospinning where the modified silica nanoparticles (mSiO₂), the oxidised single-walled carbon nanotubes (o-SWCNT) and the o-SWCNT/mSiO₂ hybrid nanoparticles were added to the solution. The electrospun fibres were crosslinked with glutaraldehyde (GA) afterwards in order to reinforce the composite structure by bonding to the p-aramid fabrics. The chemical and thermo-mechanical properties of the hybrid fabric composites were evaluated. The greatest improvement in thermo-mechanical properties was achieved by the sample which contained the cross-linked PVB fibres with the o-SWCNT/mSiO₂ hybrid nanoparticles.     

Low temperature suspension polymerization of methyl methacrylate for the preparation of high molecular weight poly(methyl methacrylate)/silver nanocomposite microspheres

In order to prepare high molecular weight poly(methyl methacrylate) (PMMA)/silver nanocomposite microspheres, methyl methacrylate was suspension-polymerized in the presence of silver nanoparticles at low temperature with 2,2′-azobis(2,4-dimethylvaleronitrile) as an initiator. The rate of conversion was increased by increasing the initiator concentration. When silver nanoparticles were added, the rate of polymerization decreased slightly. High monomer conversion (about 85 %) was obtained in spite of low polymerization temperature of 30°C. Under controlled conditions, PMMA/silver microspheres with various number-average degrees of polymerization (6,000–37,000) were prepared. Morphology studies revealed that except for normal suspension microspheres with a smooth surface, a golf ball-like appearance of the microspheres was observed, due to the migration and aggregation of the hydrophilic silver nanoparticles at the sublayer beneath the microsphere’s surface.     

Preparation of monodisperse poly(vinyl alcohol) (PVA) nanoparticles by dispersion polymerization and heterogeneous surface saponification

Monodisperse poly(vinyl alcohol) (PVA)/poly(vinyl acetate) (PVAc) nanoparticles with a skin-core structure were prepared through heterogeneous surface saponification of PVAc nanoparticles. For the preparation of PVAc nanoparticles with a uniform particle size distribution, vinyl acetate (VAc) was dispersion polymerized in a mixed solvent of ethanol and water using PVA with a low degree of saponification as a stabilizer. Increase of the amount of ethanol in media, the resulting PVAc nanoparticle size increases due to increasing solubility of VAc and oligomer PVAc. To preserve the sphericity and size uniformity of PVAc nanoparticles, we restricted saponification to the surface of the nanoparticles by using a small amount of aqueous sodium hydroxide solution. To determine the proper concentration of alkali solution for heterogeneous saponification, monodisperse PVAc nanoparticles were saponified with different concentrations of alkali solution at 25 °C for 0.5–3.0 h. The PVA/PVAc nanoparticles obtained by the heterogeneous saponification with 4 % (relative to the amount of the VAc) alkali solution for 2.0 h were uniformly shaped and monodispersed with diameter ranging from 428 to 615 nm. Transmission electron microscopy (TEM) confirmed the spherical nature and regular skin-core structure of the PVA/PVAc nanoparticles.     

Soil Invertebrates Generate Microplastics From Polystyrene Foam Debris

To fully understand microplastics'' impact on soil ecosystems, one must recognize soil organisms as not just passively enduring their negative effects, but potentially contributing to microplastics'' formation, distribution, and dynamics in soil. We investigated the ability of four soil invertebrates, the cricket Gryllodes sigillatus Walker (Orthoptera: Gryllidae), the isopod Oniscus asellus L. (Isopoda: Oniscidae), larvae of the beetle Zophobas morio Fabricius (Coleoptera: Tenebrionidae), and the snail Cornu aspersum Müller (Stylommatophora: Helicidae) to fragment macroscopic pieces of weathered or pristine polystyrene (PS) foam. We placed invertebrates into arenas with single PS foam pieces for 24 h, then collected and assessed the microplastic content of each invertebrate''s fecal material, its cadaver, and the sand substrate of its arena via hydrogen peroxide digestion, filtration, and fluorescent staining. All taxa excreted PS particles, though snails only to a tiny extent. Beetle larvae produced significantly more microplastics than snails, and crickets and isopods fragmented the weathered PS foam pieces more than the pristine pieces, which they left untouched. A follow-up experiment with pristine PS foam assessed the effect of different treatments mimicking exposure to the elements on fragmentation by isopods. PS foam pieces soaked in a soil suspension were significantly more fragmented than untreated pieces or pieces exposed to UV light alone. These findings indicate that soil invertebrates may represent a source of microplastics to the environment in places polluted with PS foam trash, and that the condition of macroplastic debris likely affects its palatability to these organisms.