Natural rubber nanocomposites using polystyrene-encapsulated nanosilica prepared by differential microemulsion polymerization

In this study, nanocomposites of natural rubber (NR) and polystyrene (PS)-encapsulated nanosilica were prepared by latex compounding method. The nanolatex of PS-encapsulated silica was synthesized via in situ differential microemulsion polymerization. The resulted hybrid nanoparticles showed core-shell morphology with an average diameter of 40 nm. The silica hybrid nanoparticles were subsequently used as filler for the NR nanocomposite. The properties of NR were found to be improved as a result of the incorporation of PS-encapsulated nanosilica at 3 and 3-9 parts per hundred rubber (phr) for tensile strength and modulus at 300% strain, respectively, except the elongation at break, and up to 9 phr for flammability. The results from dynamic mechanical analyzer showed that the elastic properties of NR near the glass transition temperature increased with the inclusion of increasing concentration of the PS-encapsulated nanosilica, causing by the semi-interpenetrating nanostructure in the NR nanocomposites.     

Enhanced mechanical properties of bamboo fiber/HDPE composites by grafting poly(amido amine) onto fiber surface

The mechanical properties of bamboo fiber composites depend on the interfacial strength between fiber and high-density polyethylene (HDPE) matrix. Different poly (amido amine) (PAMAM) dendrimers were grafted onto bamboo fiber to improve the interfacial strength of the resulting composites. The surface morphology of the resulting materials was characterized by scanning electron microscopy and atomic force microscope. Surface characteristic the bamboo fiber surface were examined by X-ray photoelectron spectroscopy and Fourier transform infrared (FT-IR). The characterization results revealed that PAMAM were chemically grafted onto the surface of bamboo fiber.     

Thermo-mechanical performance of PVC/ZnO nanocomposites

The present paper deals with the study of thermo-mechanical performance of PVC/ZnO nanocomposites. The samples have been prepared by solution casting technique with different (0, 2, 4, 6 and 8) wt. % of ZnO nanoparticles in poly (vinyl chloride) (PVC) matrix and structurally characterized through scanning electron microscopy. In thermo-mechanical analysis, dynamic mechanical analyzer gives the information about storage modulus and phase transition temperature (T_g). From these viscosities, profile at elevated temperature and activation energy of phase transition can be evaluated. This study reveals that dispersion of nano-ZnO significantly altered the thermo-mechanical properties of neat PVC but the effect is composition-dependent.     

Electromagnetic and mechanical properties of Fe3O4-coated amorphous carbon nanotube/polyvinyl chloride composites

Electromagnetic wave absorbing properties of absorbing composites depend on the dielectric and magnetic loss generally. In this paper, using Fe₃O₄-coated amorphous carbon nanotubes (ACNTs-Fe₃O₄) fabricated using a chemical synthesis–hydrothermal treatment method as an absorber and polyvinyl chloride (PVC) as a matrix, electromagnetic and mechanical properties of ACNT-Fe₃O₄/PVC composite were investigated. The results showed that the dielectric and magnetic losses of ACNT-Fe₃O₄/PVC composite were significantly enhanced in 8.2–12.4 GHz compared to ACNT/PVC composite, which improved absorbing properties, while slightly changing the mechanical properties.     

The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties

The PA66-based nanocomposites containing surface-modified nano-SiO₂ were prepared by melt compounding. The interface structure formed in composite system was investigated by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The influence of interface structure on material's mechanical and thermal properties was also studied. The results indicated that the PA66 chains were attached to the surface of modified-silica nanoparticles by chemical bonding and physical absorption mode, accompanying the formation of the composites network structure. With the addition of modified silica, the strength and stiffness of composites were all reinforced: the observed increase depended on the formation of the interface structure based on hydrogen bonding and covalent bonding. Furthermore, the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the presence of modified silica could affect the crystallization behavior of the PA66 matrix and lead to glass transition temperature of composites a shift to higher temperature.     

Effect of Polyethylene Functionalization on Mechanical Properties and Morphology of PE/SiO2 Composites

In this study composites of high density polyethylene (HDPE) with various SiO₂ content were prepared by melt compounding using maleic anhydride grafted polyethylene (PE-g-MAH) as a compatibilizer. The composites containing 2, 4 and 6% by weight of SiO₂ particles were melt-blended in a co-rotating twin screw extruder. In all composites, polyethylene-graft-maleic anhydride copolymer (PE-g-MAH, with 0.85% maleic anhydride content) was added as a compatibilizer in the amount of 2% by weight. Morphology of inorganic silica filler precipitated from emulsion media was investigated. Mechanical properties and composite microstructure were determined by tensile tests and scanning electron microscopy technique (SEM). Tensile strength, yield stress, Young's modulus and elongation at break of PE/SiO₂ composites were mainly discussed against the properties of PE/PE-g-MAH/SiO₂ composites. The most pronounced increase in mechanical parameters was observed in Young's modulus for composites with polyethylene grafted with maleic anhydride. The increase in the E-modulus of PE/PE-g-MAH/SiO₂composites was associated with the compatibility and improvement of interfacial adhesion between the polyethylene matrix and the nanoparticles, leading to an increased degree of particle dispersion. This finding was verified on the basis of SEM micrographs for composites of PE/PE-g-MAH/4% by weight of SiO₂. The micrographs clearly documented that addition of only 2 wt% of the compatibilizer changed the composite morphology by reducing filler aggregates size as well as their number. Increased adhesion between the PE matrix and SiO₂ particles was interpreted to be a result of interactions taking place between the polar groups of maleic anhydride and silanol groups on the silica surface. These interactions are responsible for reduction of the size of silica aggregates, leading to improved mechanical properties.     

Mechanical Properties Comparison of Various Ratios of L-Lactide Grafted Sisal Fibers and Untreated Sisal Fibers Reinforced Poly (lactic acid) Composites

Composites composed of the mixed fibers of L-lactide (LA) grafted sisal fiber (SF-g-LA) and untreated sisal fiber (USF) in a poly (lactic acid) (PLA) matrix were prepared with SF-g-LA/USF fibers ratios of 0, 1:9, 3:7, 5:5, 7:3, 9:1, and 1. The mechanical properties and the interfacial performance of the mixed SF reinforced PLA composites were investigated. The results of the study showed that the introduction of SF-g-LA improved the tensile strength, tensile modulus, flexural strength and flexural modulus of the mixed SF reinforced PLA composites compared with pure PLA or PLA composites with only USF, resulting from the improved interfacial adhesion between SF-g-LA and the PLA matrix. In addition, the introduction of some amount of USF enhanced the reinforcing efficiency of the mixed SF in the composites compared to the PLA composites with only SF-g-LA, owing to the good mechanical properties of USF itself. Furthermore, as for the tensile strength and tensile modulus of the mixed SF reinforced PLA composites, the optimal ratio of SF-g-LA and USF was 7:3, whereas for the flexural modulus of the mixed SF reinforced PLA composites, the optimal mixed ratio of SF-g-LA and USF was 3:7.     

Poly‐L‐Arginine Grafted Silica Mesoporous Nanoparticles for Enhanced Cellular Uptake and their Application in DNA Delivery and Controlled Drug Release

Mesoporous silica nanoparticles (MSNs), that are capable of delivering gene and drugs to organisms in an effective and selective way have attracted much attention lately for its potential in the treatment of cancer. However, the successful application of MSNs for delivery of plasmid DNA or drugs requires surface modification of the silica with positively charged functional groups so that it binds to the negatively charged nucleic acids and also helps it penetrate through the cell membrane. We report for the first time the synthesis of a hybrid MSN where the cell penetrating cationic polypeptide poly‐L‐arginine synthesized by NCA polymerization is grafted onto the external surface of MSN using click chemistry. These poly‐L‐arginine grafted MSNs show low cytotoxity (85% cell viability at 100 μg/mL MSN concentration) and high cellular uptake by both HeLa and A549 (>90%). The poly‐L‐arginine grafted MSNs were used effectively to deliver mCherry DNA plasmid into cells leading to expression of the protein mCherry inside the cells (transfection efficiency 60%). In contrast, poly‐L‐arginine grafted non‐porous silica nanoparticles were unable to express the protein mCherry inside the cells although their uptake into the cells was as efficient as with poly‐L‐arginine grafted MSNs. We also show preliminary results to demonstrate that these hybrid MSNs can be used as a delivery vehicle for the anticancer drug Doxorubicin towards cancerous cells HeLa and A549. The biocompatibility of poly‐L‐arginine and its cell penetrating ability are expected to make these MSN conjugates very useful carriers for the delivery of genes and drugs into cancer cells.     

Effect of Surface Structure of Nano-CaCO3 Particles on Mechanical and Rheological Properties of PVC Composites

To study the effect of different surface structures on resultant mechanical and rheological properties, nano-CaCO₃ particles were treated with isopropyl tri-stearyl titanate (H928), isopropyl tri-(dodecylbenz-enesulfonyl) titanate (JN198), and isopropyl tri-(dioctylpyrophosphato) titanate (JN114). Scanning electron microscopy (SEM) and dynamic mechanic analysis (DMA), carried out to characterize the effective interfacial interaction between the nano-CaCO₃ particles and a poly(vinyl chloride) (PVC) matrix, indicated that JN114 treated nano-CaCO₃ particles had the strongest interfacial interaction with a PVC matrix, while H928 treated nano-CaCO₃ had the weakest. The rheological and mechanical properties of PVC/nano-CaCO₃ composites were investigated as a function of surface structure and filler volume fraction. The tensile yield stress and elongation at break decreased with the increasing of calcium carbonate content while tensile modulus increased. PVC filled with JN114 treated nano-CaCO₃ had the highest tensile modulus and tensile yield stress, while those filled with H928 treated nano-CaCO₃ had the highest elongation at break at the same filler content. The impact strength of PVC/nano-CaCO₃ composites increased with the increasing of CaCO₃ content, and PVC composites filled with JN198 treated nano-CaCO₃ particle had a higher impact strength than those with JN114 or H928 treated, with the value reaching 23.9 ± 0.7 kJ/m² at 11 vol% CaCO₃, four times as high as that of pure PVC. Rheological properties indicated that a suitable interfacial interaction and a good dispersion of inorganic filler in a PVC matrix could reduce the viscosity of PVC/nano-CaCO₃ composites. The interfacial interaction was quantitatively characterized by semiempirical parameters calculated from the tensile strength of PVC/nano-CaCO₃ composites to confirm the results from the SEM and DMA experiments.     

Influence of Fiber Surface Treatment on Mechanical Properties of CF/PET Composites

Carbon fiber (CF) / poly (ethylene terephthalate) (PET) composites were prepared with various contents (2–15wt%) of short carbon fibers. To investigate the effect of surface treatment of the CF on the mechanical properties of the composites, three specimens were prepared; those with short carbon fibers (called SCF), short carbon fibers oxidized with nitric acid (called NASCF) and the fibers oxidized with nitric acid and treated with silane coupling agent (called SCSCF). Flexural, tensile and impact tests were performed to observe mechanical behavior of the specimens. The morphology of the specimens was also studied with a scanning electron microscope (SEM). SCSCF composite had better mechanical properties than the other composites with the same content of carbon fibers since the coupling agent resulted in better interfacial adhesion between the fiber and the matrix.     

Flame-Retarding and Mechanical Properties of Flexible Polyvinyl Chloride with Surface-Treated Lamellar Magnesium Hydroxide

The effects of hydrophobic magnesium hydroxide (Mg(OH)₂) particles, prepared by a surface modification method with oleic acid, on the flame-retarding and mechanical properties of polyvinyl chloride (PVC) were investigated. Comparison between the use of modified and unmodified Mg(OH)₂ in the preparation of PVC composites showed that the former could provide excellent optical and flame-retarding properties. The dispersion of the modified Mg(OH)₂ particles in the PVC matrix was investigated through scanning electron microscopy. Compared with a composite containing unmodified Mg(OH)₂, the rheological and impact strength properties of that containing the modified Mg(OH)₂ filler were found to be significantly improved. These improvements were mostly attributed to the better dispersion of the modified Mg(OH)₂ particles and the strong adhesion between the filler and matrix.     

Preparation and Characterization of Composites Based on Poly (Butylene Succinate) and Poly (Lactic Acid) Grafted Tetracalcium Phosphate

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) was functionalized by poly (l-lactic acid) (PLLA) in order to improve the dispersion of TTCP particles in poly (butylene succinate) (PBS) matrices, and then a series of the PLLA grafted TTCP/PBS (g-TTCP/PBS) composites were prepared via melt processing. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (DTG/TGA) and melt rheological analysis were used to investigate the structure and properties of the g-TTCP/PBS composites. The results revealed that l-lactide could be grafted onto the surface of TTCP, and the g-TTCP/PBS composites showed the best mechanical properties when the content of g-TTCP was 10 wt%. The crystallization temperature of g-TTCP/PBS composites tended to increase with the increase of g-TTCP contents. The functionalized particles played an important role in augmenting the thermal degradation rate and the complex viscosity of the composites due to their unique structure and the reasonable interfacial interaction between the particles and PBS matrix.     

Preparation and characterization of a novel antistatic poly(vinyl chloride)/quaternary ammonium based ion-conductive acrylate copolymer composites

Antistatic poly(vinyl chloride)/quaternary ammonium salt based ion-conductive acrylate copolymer (PVC/QASI) composites were successfully prepared in a Haake torque rheometer. The surface resistivity of the PVC/QASI composites could be reduced to 10⁷ Ω sq^?1 order of magnitude when the QASI content reached 20 phr (parts per hundreds of resin). The surface resistivity of the composites was slightly sensitive to the relative humidity (RH), showing a good antistatic ability under an RH of 12%. Mechanical properties tests, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were also used to investigate the tensile strength, elongation at break, thermal properties, and morphology of the PVC/QASI composites, respectively.     

Effect of Carbon Nanotubes on the Mechanical Properties of Polypropylene/Wood Flour Composites: Reinforcement Mechanism

Maleic anhydride grafted polypropylene (PP-g-MA) was employed as the compatibilizer and carbon nanotubes (CNTs) or hydroxylated CNTs as reinforcements for polypropylene/wood flour composites. The results showed that when the PP-g-MA loading level was 10 wt%, the bending strength, tensile strength, Izod notched impact strength, and elongation at break of PP-wood composites were enhanced by 85% (66.3 MPa), 93% (33.7 MPa), 5.8% (2.01 kJ/m²), and 64% (23%), respectively, relative to the uncompatibilized composites. The introduction of pristine CNTs only improved slightly the overall mechanical properties of the compatibilized composites due to poor interfacial compatibility. Unlike CNTs, incorporating hydroxylated CNTs (CNT-OH) could significantly improve all of the mechanical properties; for instance, at 0.5 wt% CNT-OH loading, the flexural strength and tensile strength reached 68.5 MPa, and 40.4 MPa about 6.6% higher than that for the composites with the same CNT loading. Furthermore, CNT-OH also remarkably enhanced the storage modulus. Contact angle and morphology observations indicated that the increases in mechanical properties could be attributed to the improvements of interfacial interactions and adhesions of CNTs with the matrix and fillers.     

Effect of chemical modifications of the pineapple leaf fiber surfaces on the interfacial and mechanical properties of laminated biocomposites

Natural fiber reinforced renewable resource based laminated composites were prepared from biodegradable poly(lactic acid) (PLA) and untreated or surface-treated pineapple leaf fibers (PALF) by compression molding using the film stacking method. The objective of this study was to determine the effects of surface treatment of PALF on the performance of the fiber-reinforced composites. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to aid in the analysis. The mechanical properties of the PLA laminated composites were improved significantly after chemical treatment. It was found that both silane- and alkali-treated fiber reinforced composites offered superior mechanical properties compared to untreated fiber reinforced composites. The effects of temperature on the viscoelastic properties of composites were studied by dynamic mechanical analysis (DMA). From the DMA results, incorporation of the PALF fibers resulted in a considerable increase of the storage modulus (stiffness) values. The heat defection temperature (HDT) of the PALF fiber reinforced PLA laminated composites was significantly higher than the HDT of the neat PLA resin. The differential scanning calorimeter (DSC) results suggest that surface treatment of PALF affects the crystallization properties of the PLA matrix. Additionally, scanning electron microscopy (SEM) was used to investigate the distribution of PLA within the fiber network. SEM photographs of fiber surface and fracture surfaces of composites clearly indicated the extent of fiber–matrix interface adhesion. It was found that the interfacial properties between the reinforcing PALF fibers and the surrounding matrix of the laminated composite are very important to the performance of the composite materials and PALF fibers are good candidates for the reinforcement fiber of high performance laminated biodegradable biocomposites.     

Correlation between interfacial interactions and mechanical properties of PA-6 doped with surface-capped nano-silica

The polyamide-6 pellets were mixed with nano-SiO₂ particles surface-capped by 3-aminopropyltriethoxysilane (APS) via a melt blending route. PA-6 composites doped with surface-capped nano-SiO₂ (designated as PAMNS, where AMNS refers to APS surface-capped nano-SiO₂). AMNS and the silica samples (designated as EAMNS) extracted by acid etching from various PAMNS samples containing different concentration of amino functional groups on surface-capped nano-silica surfaces were characterized by means of Fourier transformation infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). This aims at revealing the interfacial interaction between AMNS and PA-6 matrix and its effect on the mechanical properties of the filled PA-6 composites. The chemical features and microstructures of the PAMNS composites were analyzed by means of FTIR and transmission electron microscopy (TEM), respectively, while their mechanical properties were evaluated using standardized test rigs. Results demonstrate that the surface-modified nano-SiO₂ particles were uniformly dispersed in PA-6 matrix. The residue silica extracted from various PAMNS samples showed characteristic FTIR absorbance peak of PA-6 and had larger weight losses than AMNS, implying that the polymeric matrix was chemically bonded with the nanofiller particles. The interfacial interactions are closely related to the concentration of functional groups in AMNS, and there might exist a critical concentration at which the strongest interfacial interactions could be reached. Beyond the critical concentration of the functional groups in AMNS, the mechanical properties of the filled PA-6 composites tended to decrease to some extent.     

A Study on the Morphology and Mechanical Properties of PVC/nano‐SiO2 Composites

Three methods were used to modify nano‐SiO₂ particles with various interfaces and interfacial interactions between the particles and Poly(vinyl chloride) (PVC) matrix. The experimental results show that direct surface treatment of nano‐SiO₂ particles with a silane coupling agent (KH‐550) is not effective for improving the mechanical properties of PVC/SiO₂ composites. Both ultrasonic oscillations and high energy vibromilling improve the interfacial interactions between SiO₂ particles and PVC matrix. With these methods, the aggregation of SiO₂ particles was inhibited and a good dispersion of SiO₂ particles in PVC matrix was obtained, which improved the mechanical properties of the PVC/SiO₂ composite. The mechanical properties of the PVC/SiO₂ composite with high energy vibromilling modified SiO₂ particles were remarkably improved. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic mechanical analysis (DMA), and theoretical calculations demonstrate these improvements.     

Miscibility and Hydrogen Bonding Interactions in Blends of Poly(hydroxyether ketone) and Poly(4-vinyl pyridine)

The influence of silica nanoparticles on the tensile properties of poly(ethylene terephthalate)(PET) fibers was investigated. The results showed that mechanical properties of PET fibers were improved through nano‐silica incorporation. Two maxima of the modulus‐strain curves of PET/silica nanocomposites (PETS) fibers are always higher than those of pure PET (PET0) fibers. The results of microstructure investigations suggested that the amorphous orientation factor of PETS fibers is higher than that of PET0 fibers. It is suggested that the increase of amorphous orientation factor contributed to the improvement of tensile properties of PET fibers. Considering the difference in modulus‐strain curves of PET0 and PETS fibers, it is believed that the addition of nanoparticles not only improved the amorphous orientation factor but also changed the load units of PET fibers when strained, which also resulted in the improvement of tensile properties.     

Effects of enhanced hydrogen bonding on the mechanical properties of poly (vinyl alcohol)/carbon nanotubes nanocomposites

In this study, poly (vinyl alcohol) (PVA) composites reinforced by multiwall carbon nanotubes (MWCNTs) functionalized with either phenolic hydroxyl groups (MWCNTs-f-OH) or PVP molecule (PVP@MWCNTs) were fabricated. The objective was to elucidate the effect of different MWCNTs surface functionalization on the mechanical properties of the nanocomposites. It was found that both of PVP@MWCNTs and MWCNTs-f-OH had a good dispersion in PVA matrix. However, the MWCNTs-f-OH had stronger effective interfacial interaction with PVA matrix than PVP@MWCNTs, owe to the formation of hydrogen bonds between MWCNTs-f-OH and PVA. The stress-strain measurements showed that the Young’s modulus and tensile strength of MWCNTs-f-OH/PVA with only 1.0 wt.% contents increased by 200 and 100% compare with that of PVA, respectively. The findings of this experimental study emphasized the critical role of MWCNTs surface morphology in determining the mechanical properties of nanocomposites, and shed new light on understanding and advancing the properties of carbon nanotube based composites.     

Morphology,mechanical, rheological,and thermal properties study on the PTT/ABS/SCF composites

In order to improve the mechanical properties of the poly(trimethylene terephthalate) (PTT), both maleinized acrylonitrile–butadiene–styrene (ABS) and short carbon fiber (SCF) were melt-blended with PTT to prepare the composites and their morphology and properties were investigated in detail. When ABS content is fixed at 5?wt.% in composites, SCF can significantly improve the tensile and flexural strength as well as the impact strength of the matrix. The SCF has good interface adherence with the matrix. At glassy state, the storage modulus increases much with increasing SCF content. At rubbery state, the composites have larger cold-crystallization rate. At molten state, SCF first serves as lubricants and then as viscosity reinforcing agent for the matrix with increasing SCF. The composites melt exhibits increasing elastic behaviors with SCF. The composites have larger crystallization rate, but this accelerating effect decreases with excessive SCF content. The crystals formed in different composites are quite different in size or perfection.