Reinforcement of Si3N4 nanoparticles in polypropylene single fibers through melt extrusion process and their properties

We have successfully aligned/dispersed the rod and spherical‐shaped Si₃N₄ nanoparticles in the polypropylene (PP) fibers through melt extrusion process to fabricate polymer nanocomposite (PNC) single fibers. The alignment/dispersion of Si₃N₄ nanoparticles in PP/Si₃N₄ PNC fibers has been carried out in a systematic manner to produce uniform single fibers. The PNC fibers were first uniformly stretched and stabilized using a two‐set Godet machine. The as‐extruded single PNC fibers were tested for their thermal and tensile properties. The test results of PNC fibers were compared to neat PP polymer single fibers fabricated using the same procedure as PNC fibers. These results show that the PNC fibers are much (307%) higher in tensile strength and modulus (>1000%) when compared with the neat PP polymer single fibers. The field emission scanning electron microscope results clearly show the alignment of rod‐Si₃N₄ nanoparticles in polymer matrix. The differential scanning calorimetry results show ～ 12% increase in crystallinity for rod‐Si₃N₄ PNCs when compared with the neat PP single fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Surface functionalization of aramid fibers via constructing different zinc oxide nanostructures for improved UV resistance

Aramid fibers (AFs) with high strength and modulus have a vital application in harsh outdoor bulletproof protection and ship ropes; however, solar radiation, especially ultraviolet (UV) radiation, is one of the main factors for affecting their service life. Herein, different zinc oxide (ZnO) nanostructures were constructed on the surface of AFs by the growth of ZnO nanowires (AF-ZnO NW) and coating of waterborne polyurethane/ZnO nanoparticles composite emulsion (AF/ZnO), respectively. The surface functionalized AFs exhibited enhanced mechanical properties retention after UV radiation. Nevertheless, the tensile strength of AF-ZnO NW before UV aging was already lower than the tensile strength of original AFs due to the surface structure damage from chemical grafting modification. The tensile strength and elongation retention rates of AF/ZnO-5% reached 74.4% and 84.4% after UV exposure for 168 h, respectively, which were much higher than the value of 48.3% and 60.5% of the neat AFs. These results provide an effective and low-cost strategy for improving the UV-resistance of advanced high-performance fibers.     

ZnO nanocrystallites/cellulose hybrid nanofibers fabricated by electrospinning and solvothermal techniques and their photocatalytic activity

ZnO nanocrystallites have been in situ embedded in cellulose nanofibers by a novel method that combines electrospinning and solvothermal techniques. Zn(OAc)₂/cellulose acetate (CA) precursor hybrid nanofibers with diameter in the range of 160–330 nm were first fabricated via the electrospinning technique using zinc acetate as precursor, CA as the carrier, and dimethylformamide (DMF)/acetone(2 : 1) mixture as cosolvent. The precursor nanofibers were transformed into ZnO/cellulose hybrid fibers by hydrolysis in 0.1 mol/L NaOH aqueous solution. Subsequently, these hybrid fibers were further solvothermally treated in 180°C glycerol oil bath to improve the crystallite structure of the ZnO nanoparticles containing in the nanofibers. The structure and morphology of nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. It was found that hexagonal structured ZnO nanocrystallites with the size of ～ 30 nm were dispersed on the nanofiber surfaces and within the nanofibers with diameter of about 80 nm. The photocatalytic property of the ZnO/cellulose hybrid nanofibers toward Rhodamine (RhB) was tested under the irradiation of visible light. As a catalyst, it inherits not only the photocatalytic ability of nano‐ZnO, but also the thermal stability, good mechanical property, and solvent‐resistibility of cellulose nanofibers. The key advantages of this hybrid nanofiber over neat ZnO nanoparticles are its elasticity, dimensional stability, durability, and easy recyclability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A facile approach to fabricate porous nylon 6 nanofibers using silica nanotemplate

Porous Nylon 6 nanofibers were prepared using silica nanoparticles as the template. Firstly, Nylon 6/silica composite nanofibers were prepared as precursors by electrospinning Nylon 6 solutions containing different contents of silica nanoparticles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the surface morphology and the inner structure of composite nanofibers; where it was found that silica nanoparticles were distributed both inside and on the surface of nanofibers. Analytical techniques [Fourier transform infrared (FTIR), differential scanning calorimetry, thermal gravimetric analysis (TGA), and wide‐angle X‐ray diffraction) were used to study the structure and properties of these composite nanofibers. The glass transition, melting, and crystallization processes of the fibers were affected by the addition of silica nanoparticles. Secondly, porous Nylon 6 nanofibers were obtained by removing silica nanoparticles via hydrofluoric acid treatment. The removal of silica nanoparticles was confirmed using FTIR and TGA tests. SEM and TEM observations revealed the formation of the porous structure in these nanofibers. After the formation of the porous structure, Brunauer–Emmett–Teller specific surface areas of nanofibers were increased as compared to solid Nylon 6 and composite nanofibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effects of hybrid fillers on thermal,mechanical, physical,and antimicrobial properties of ultrahigh‐molecular‐weight polyethylene‐reinforced composites

The effects of hybrid filler of zinc oxide and chitosan (chitosan–ZnO) on thermal, flexural, antimicrobial, chemical resistance, and hardness properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE) composites with varying concentration of zinc oxide (ZnO) and further hybridized by chitosan (CS) were successfully studied. The composites were prepared using mechanical ball milling and followed by hot compression molding. The addition of ZnO to the UHMWPE matrix had lowered the melting temperature (T _m) of the composite but delayed its degradation temperature. Further investigation of dual filler incorporation was done by the addition of chitosan to the UHMWPE/ZnO composite and resulted in the reduction of UHMWPE crystallization. The flexural strength and modulus had a notably high improvement through ZnO addition up to 25 wt% as compared to neat UHMWPE. However, the addition of chitosan had resulted in lower flexural strength than that of 12 wt% ZnO UHMWPE composite but still higher than that of neat UHMWPE. It was experimentally proven that the incorporation of ZnO and chitosan particles within UHMWPE matrix had further enhanced the antimicrobial properties of neat UHMWPE. Chemical resistance was improved with higher ZnO content with a slight reduction of mass change after the incorporation of chitosan. The hardness value increased with ZnO addition but higher incorporation of chitosan had lowered the hardness value. These findings have significant implications for the commercial application of UHMWPE based products. It appears that these hybrid fillers (chitosan–ZnO)‐reinforced UHMWPE composites exhibit superior overall properties than that of conventional neat UHMWPE. POLYM. COMPOS., 38:1689–1697, 2017. © 2015 Society of Plastics Engineers     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

Structure and properties of polypropylene‐wrapped carbon nanotubes composite

By means of in situ graft method, polypropylene (PP)‐wrapped carbon nanotubes (CNTs) composite were prepared. Infrared spectroscopy (IR) results showed that there was covalent linkage between PP and CNTs via maleic anhydride (MAH) grafting. Owing to the uniform dispersion of CNTs and covalent adhesion between PP and CNTs, the tensile strength of PP‐wrapped CNTs composite was higher than that for neat PP by 110%, and a 74% increase as compared to the CNTs/PP (with the same CNTs content) composite. The further test showed a strong mechanical behavior with up to 113% increase in Young's modulus of the neat PP. Based on the uniform dispersion of CNTs, the electrical conductivity of PP‐wrapped CNTs composite increased sharply by up to seven orders of magnitude with 4 wt % CNT fillers. As a result, the volume resistivity was decreased with increase in the CNT content that could be governed in a percolation‐like power law with a relatively low percolation threshold. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fabrication of high strength PVA/SWCNT composite fibers by gel spinning

High-strength composite fibers were prepared from polyvinyl alcohol (PVA) (Degree of polymerization: 1500) reinforced by single-walled carbon nanotubes (SWCNTs) containing few defects. The SWCNTs were dispersed in a 10 wt.% PVA/dimethylsulfoxide solution using a mechanical homogenizer that reduced the size of SWCNT aggregations to smaller bundles. The macroscopically homogeneous dispersion was extruded into cold methanol to form fibers by gel spinning followed by a hot-drawing. The tensile strength of the well-oriented composite fibers with 0.3 wt.% SWCNTs was 2.2 GPa which is extremely high value among PVA composite fibers ever reported using a commercial grade PVA. The strength of neat PVA fibers prepared by the same procedure was 1.7 GPa. Structural analysis showed that the PVA component in the composite fibers possessed almost the same structure as that of neat PVA fibers. Hence a small amount of SWCNTs straightforward enhanced by 0.5 GPa the tensile strength of PVA fibers. The results of mechanical properties and Raman spectra for the SWCNT composites suggest the relatively good interfacial adhesion of the nanotubes and PVA that improves the load transfer from the polymer matrix to the reinforcing phase.     

Influence of zinc oxide on thermoplastic elastomer‐based composites: Synthesis,processing, structural,and thermal characterization

It was aimed to investigate how thermal conductivity and stability properties of synthesized thermoplastic elastomers were influenced by zinc oxide (ZnO) additives which differed in size and surface treatment. ZnO particles were prepared by the homogeneous precipitation method by mixing aqueous solutions of hexamethylenetetramine (HMT) and zinc nitrate. The obtained particles were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Poly(vinyl pyrrolidone) (PVP) was used as a modifier to reduce aggregation among the ZnO particles. The composites, prepared by melt compounding method, were characterized in terms of their morphology and thermal properties. Uniformly distributed surface treated particles caused an enhancement in thermal conductivity properties. At 10 wt% ZnO concentration the thermal conductivity of composite reached 1.7 W/mK compared with 0.3 W/mK for the neat polymer. At the same filler loading, ZnO nanoparticles exhibited a greater effect on thermal conductivity compared with submicron sized particles. It was found that the coefficient of thermal expansion of composites decreased at low temperature (55°C) with increasing ZnO content. Thermal gravimetric analysis (TGA) showed that the neat polymer and the composites were resistant up to 340°C without significant mass loss. POLYM. COMPOS., 37:2369–2376, 2016. © 2015 Society of Plastics Engineers     

Fibrous zinc oxide prepared by combined electrospinning and solvothermal techniques

The synthesis of novel zinc oxide (ZnO) nanostructure consisting of ZnO nanoparticles formed into the network of fibers was investigated. This structure was fabricated from the solvothermal reaction of the poly(vinyl alcohol) (PVA)/zinc acetate composite fibers, which were firstly prepared by electrospinning technique. It was found that zinc acetate within the PVA matrix was converted into ZnO nanoparticles in hexagonal wurtzite structure, while PVA was still retained within the structure. Therefore, the product was no longer easy to crumble into powder, easy to handle, yet it still possessed nanostructure feature. The growth mechanism of ZnO nanoclusters within the structure was also proposed by investigating the effects of various parameters, i.e. content of zinc acetate within the fibers, reaction temperature and reaction time.     

Study on the mechanical properties of hybrid reinforced rigid polyurethane composite foam

The mechanical properties of hybrid reinforced rigid polyurethane (PU) foams were investigated with the reinforcing agent SiO₂ and fibers. The effect of content of SiO₂ and fibers and the effect of length of fibers on the properties of the PU composite foam were emphatically analyzed. The experiment results show that the tensile strength of the PU composite foam is optimal when the content of SiO₂ and glass fiber is 20 and 7.8%, respectively. Furthermore, the reinforcing effect of glass fiber, Nylon‐66 fiber, and PAN‐matrix carbon fiber were compared and the results show that the tensile strength of the PU composite foam reinforced with 3–5% carbon fiber is optimal. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1493–1500, 2004     

Role of TiO2 and carbon nanotubes on polyethylene,and effect of accelerated weathering on photo oxidation and mechanical properties

In this work, LLDPE‐based composite films were prepared by melt mixing followed by compression molding to investigate the role of titanium oxide nanoparticles (TONPs) and/or multiwalled carbon nanotubes (CNTs) on the accelerated weathering samples (maximum of 39 days). Accelerating weathering caused the emerging of oxidation peaks in the FT‐IR spectra for LLDPE and LLDPE/TONPs. These peaks were not pronounced in the LLDPE/CNTs samples. The same prevention of oxidation peaks were noticed for the hybrid additives samples. Tensile properties decreased by exposing the composite samples to accelerating weathering. TONPs increased the tensile strength of the samples by 11.5% but deterioration of this property is the same as the pristine sample after accelerated weathering for 39 days. Addition of CNTs had negligible effect on the tensile strength but it kept the same approximate value of the original before the accelerated weathering (e.g., 23.2 MPa for 1 wt% of CNTs). CNTs also protected the samples even with the presence of TONPs because of the absorbance and antioxidants effects. The addition of CNTs into LLDPE network have not only retarded decomposition of LLDPE but also decreased catalytic activity of TONPs to activate degradation due to accelerated weathering. J. VINYL ADDIT. TECHNOL., 25:19–25, 2019. © 2018 Society of Plastics Engineers     

Surface‐graft hyperbranched polymer via self‐condensing atom transfer radical polymerization from zinc oxide nanoparticles

We present the synthesis of hyperbranched polymer grafted zinc oxide (ZnO) hybrid nanoparticles by self‐condensing vinyl polymerization (SCVP) via surface‐initiated atom transfer radical polymerizations (SI‐ATRP) from ZnO surfaces. ATRP initiators were covalently linked to the surfaces of ZnO particles, followed by SCVP of an initiator‐monomer (“inimer”) which has both a polymerizable group and an initiating group in the same molecule. Well‐defined polymer chains were grown from the surfaces to yield hybrid nanoparticles comprised of ZnO cores and hyperbranched polymer shells having multifunctional chlorobenzyl functional end groups. The percentage of grafting (PG%) achieved 429% in 6 h, calculated from the elemental analysis results. The hybrid nanoparticles were also characterized using Fourier transform infrared spectroscopy, UV–vis absorption spectroscopy, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and transmission electron microscopy. POLYM. ENG. SCI., 47:1296–1301, 2007. © 2007 Society of Plastics Engineers     

Effect of spinning conditions on the mechanical properties of polyacrylonitrile fibers modified with carbon nanotubes

Carbon nanotubes (CNTs) were used to modify polyacrylonitrile (PAN) polymer. The PAN/CNT composite fibers were spun from dimethylformamide solutions containing different types of CNTs. The effect of nanotube addition to the fiber precursor on the resulting mechanical properties is discussed. In this study, we examined the relationship of the rheological properties of PAN spinning solutions containing various types of CNTs and the tensile strength of the resulting PAN fibers. The presence of CNTs in the PAN spinning solution enhanced its deformability during the drawing stage. This effect resulted in a higher tensile strength in the fibers containing nanotubes, as compared to the pure fibers. The use of a three‐stage drawing process resulted in a significant increase in the tensile strength of PAN fibers modified with multiwalled nanotubes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improved tribological properties of polyimide composites by micro–nano reinforcement

The hydroxylate carbon nanotubes (CNTs) were grafted by chemical method on the surface of the oxidized carbon fibers (CF) to improve the mechanical and tribological properties of polyimide (PI). The microstructure and fracture surface of the polyimide composites indicated that CF–CNTs hybrid as a multiscale reinforcement can distribute into the PI matrix homogeneously. Tribo-tests further showed that CF–CNTs hybrid had a better effect on hardness increment, impact strength enhancement, friction reduction, and wear resistance. Compared to the neat PI, the friction coefficient and wear rate of CF–CNTs/PI composite deceased by 23.2 and 55.9%, respectively. In particular, the loading capacity and high speed resistance of CF–CNTs/PI composite were greatly improved. The corresponding wear mechanisms were also discussed by observing the worn surface of the PI composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47900.     

Viscoelastic behavior of epoxy/carbon fiber/Zno nano‐rods hybrid composites

The insufficient viscoelastic resistance of fiber reinforced plastics can be retrofitted by the addition of more rigid nano fillers to the polymer matrix. In this study, carbon fibers plies were grafted with zinc oxide (ZnO) nano‐rods and the hybridized reinforcement was utilized in laminated composites. Flexural creep tests were carried out using dynamic mechanical analysis (DMA) and the time/temperature superposition principle was employed for accelerated testing. To verify the applicability of TTPS, prolonged stress relaxation tests were also carried out in flexural mode. Data from the DMA flexural creep tests revealed that the whiskerization of carbon fibers with ZnO nano rods reduced the creep compliance by 23% at elevated temperatures and prolonged durations. Also, the relaxation data confirmed the applicability of TTPS to these hybrid composites. The stress relaxation modulus improved by 65% in comparison to composites based on neat carbon fibers. POLYM. COMPOS., 36:1967–1972, 2015. © 2014 Society of Plastics Engineer     

Preparation and characterization of UV‐curable ZnO/polymer nanocomposite films

A series of novel nano‐ZnO/polymer composite films with different ZnO contents was prepared through incorporation of pre‐made colloidal ZnO particles into monomer mixtures of urethane‐methacrylate oligomer and 2‐hydroxyethyl methacrylate, followed by ultraviolet (UV) radiation‐initiated polymerization. The colloidal ZnO nanoparticles with a diameter of 3–5 nm were synthesized from zinc acetate and lithium hydroxide in ethanol via a wet chemical method. In order to stabilize and immobilize the ZnO particles into the polymer matrix, the ZnO nanoparticles were further capped using 3‐(trimethoxysilyl)propyl methacrylate. Thermogravimetric analyses show that the ZnO nanoparticles were successfully incorporated into the polymer matrix and these ZnO/polymer composites have a good thermal stability. Transmission electron microscopy studies indicate the ZnO nanoparticles were uniformly dispersed in the polymer and they remained at the original size (3–5 nm) before immobilization. All nanocomposite films with ZnO particle contents from 1 to 15 wt% show good transparency in the visible region and luminescent properties. In addition, composite films with high ZnO content (>7 wt%) are able to absorb UV irradiation below 350 nm, indicating that these composite films exhibit good UV screening effects. Copyright © 2006 Society of Chemical Industry     

Fabrication of high‐k poly(vinylidene fluoride)/Nylon 6/carbon nanotube nanocomposites through selective localization of carbon nanotubes in blends

The morphology as well as the distribution of conductive fillers in conductive filler/polymer nanocomposites have a decisive effect on the dielectric properties of blend composites. In this study, the relationship between morphology and properties was carefully investigated and the underlying mechanism is discussed based on the microcapacitor model. Multiwalled carbon nanotubes (CNTs) were introduced into an immiscible poly(vinylidene fluoride) (PVDF)/polyamide 6 (Nylon 6) blend and the morphologies of PVDF/Nylon 6 were tailored by changing the weight ratio of PVDF to Nylon 6, varying from sea‐island morphology to co‐continuous morphology. Interestingly, the CNTs are selectively localized in the Nylon 6 phase in both sea‐island and co‐continuous morphological blends, which is due to the finer interaction between Nylon 6 and CNTs. In the sea‐island morphological blend only, a strong increase of the dielectric permittivity can be found when the content of CNTs is increased. It is surprising that no effects of CNTs on the dielectric properties can be found in the co‐continuous morphological blend. The CNT filled Nylon 6 domains in the sea‐island morphological blend act as a microcapacitor with improved charge accumulation and interfacial polarization, resulting in a marked increase in dielectric permittivity. © 2016 Society of Chemical Industry     

Enhanced compatibilization and orientation of polyvinyl alcohol/gelatin composite fibers using carbon nanotubes

Polyvinyl alcohol (PVA)/gelatin composite fibers containing carbon nanotubes (CNTs) had been prepared by wet‐spinning method. A remarkable increase of tensile strength of the PVA/gelatin fibers was achieved by adding small amount of CNT. The mechanism of reinforcement has been studied using a combination of differential scanning calorimetry (DSC), 2D wide‐angle X‐ray diffraction (2D‐WAXD) and scanning electron microscopy (SEM). SEM showed a decreased gelatin domain size by adding CNTs, suggesting a possible compatibilization effect between PVA and gelatin. On the other hand, an increased crystallinity and degree of orientation of PVA/gelatin fibers has been observed by adding CNTs. Thus, the increased compatibilization, crystallinity and degree of orientation in PVA/gelatin/CNTs composite fibers should be the reasons for the observed increase of mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Simultaneous ultrasonication‐assisted internal mixing to prepare MWCNTs‐filled epoxy composites with increased strength and thermal conductivity

The uniform dispersion of carbon nanotubes in epoxy resin is one of the key factors to achieve the composites with desirable mechanical and physical property enforcement. However, the widely used dispersion methods have their own respective limitations in pursuing satisfactory nanotube dispersion. Herein, a new dispersion approach, based on the synergetic effect of combining high speed internal mixing with running simultaneously continuous ultrasonication treatment, has been proposed. The dispersion of nanotubes was carried out in a high speed internal mixer, consisting of twin kneading block structured rotors and an integrated ultrasonic horn, which was intercalated into the central position between the twin rotors. At first, the FEM simulation was conducted to optimize the kneading element assembly and illuminate the geometry influence of the ultrasonic horn intercalation on the mixing flow. Afterwards, to confirm the feasibility of the approach, pristine MWCNTs (P‐CNTs), oxidation modified MWCNTs (M‐CNTs) and M‐CNTs/multilayer graphene nanoplatelets (MGPs) hybrid are dispersed into epoxy resin. The dispersion of each sample in its liquid epoxy state is investigated under transparent optical microscopy. More characterizations, including SEM, TG/DTA, tensile test, and thermal conductivity measurements, were conducted on the cured composites. Competitive reinforcements on mechanical tensile property and thermal conductivity were observed. Especially, at a 1.5 wt% M‐CNTs/MGPs hybrid content, the composite mechanical tensile strength and thermal conductivity were 47% and 30% higher than those of neat epoxy. This preliminary study demonstrates the feasibility and practicability of the proposed approach to achieving good MWCNTs dispersion and distribution in epoxy resin. POLYM. COMPOS., 37:870–880, 2016. © 2014 Society of Plastics Engineers