Yuanfang Luo

Reinforcing and Flame-Retardant Effects of Halloysite Nanotubes on LLDPE

Halloysite nanotubes (HNTs) were used to compound with linear low density polyethylene (LLDPE) to prepare composites with better mechanical properties and higher flame retardancy. The PE graft was used as interfacial modifier in the LLDPE/HNTs composites. HNTs were showed to be a promising reinforcing and flame retardant nano-filler for LLDPE. The mechanical properties and flame retardancy as well as thermal stability of the composites can be further enhanced by the addition of the graft copolymer. Morphological observation revealed that the graft copolymer could facilitate the dispersion of HNTs in LLDPE matrix and enhance the interfacial bonding.

One-step synthesis of metal nanoparticle decorated graphene by liquid phase exfoliation

A novel method for the fabrication of a metal nanoparticle (NP)–graphene hybrid based on the pristine graphene from liquid-phase exfoliation in organic solvents is essential. In the present work, 1-cyanoethyl-2-ethyl-4-methylimidazole (2E4MZ-CN) was employed as a novel stabilizer for graphene sheets in an acetonitrile solution and simultaneously as a reducing agent for metal NPs deposited on the graphene sheets. A homogeneous pristine graphene dispersion is achieved by sonication of natural graphite in an acetonitrile solution of 2E4MZ-CN. Once exfoliated from natural graphite under sonication, the graphene sheets can be stabilized by 2E4MZ-CN through the π–π interaction. Atomic force microscopy, Raman spectroscopy and transmission electron microscopy (TEM) confirm the presence of monolayer and few-layer graphene sheets. The absence of oxidation or destruction of the sp2 character of the carbon is demonstrated by Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Silver NP (AgNP) decorated graphene hybrid is in situ synthesized during the curing process of epoxy resin. Scanning electron microscopy, X-ray diffraction and TEM show that the small particle size and good distribution of AgNPs are realized due to the stabilization of epoxy network. The synthesized AgNP decorated graphene is used as nanoscale filler to prepare highly conductive epoxy-based composites (4 × 10−5 Ω cm). The low temperature sintering of AgNPs attached on the graphene constructs effective electrical network in the epoxy matrix. This method facilitates the preparation of graphene-based materials for various applications.

MORPHOLOGY, INTERFACIAL INTERACTION AND PROPERTIES OF STYRENE-BUTADIENE RUBBER/MODIFIED HALLOYSITE NANOTUBE NANOCOMPOSITES

A natural nanotubular material, halloysite nanotubes (HNTs), was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube (SBR/m-HNT) nanocomposites. Complex of resorcinol and hexamethylenetetramine (RH) was used as the interfacial modifier. The structure, morphology and mechanical properties of SBR/m-HNT nanocomposites, especially the interfacial interactions, were investigated. SEM and TEM observations showed that RH can not only facilitate the dispersion and orientation of HNTs in SBR matrix at nanometer scale, but also enhance the interfacial combination between HNTs and rubber matrix. FTIR and XPS investigations confirmed that a number of hydrogen bonds were formed between the phenol hydroxyl groups in resorcinol-formaldehyde resin derived from RH and the oxygen atoms in Si–O bonds or hydroxyl groups on HNTs surfaces. The m-HNTs modified with RH have significant reinforcing effect on SBR vulcanizates. RH as a good interfacial modifier can remarkably improve mechanical properties of...

The Effect of Dy(III) Complex with 2-Mercaptobenzimidazole on the Thermo-Oxidation Aging Behavior of Natural Rubber Vulcanizates

A novel kind of Dy(III) complex with 2-mercaptobenzimidazole was prepared. The antioxidative properties and mechanisms of the Dy(III) complex in the NR vulcanizates were investigated by attenuated total-reflectance Fourier transform infrared (FTIR-ATR) spectroscopy, crosslinking density determination, mechanical properties testing and thermogravimetric analysis. The thermo-oxidative stability of the NR vulcanizates was found to be improved markedly by the addition of Dy(III) complex. It can be attributed to the thioether bonds, which can decompose the hydroperoxide, and the Dy(III) ions, which can capture and inactivate the oxy radicals. The apparent thermo-oxidation activation energy of the NR vulcanizates was calculated by the Kissinger and Flynn-Wall-Ozawa methods, respectively. The results show that the NR vulcanizates with the Dy(III) complex have higher thermo-oxidation activation energy than that of the samples with antioxidant MB and antioxidant 4010NA.

Synthesis and Characterization of a New Trimethacrylate Monomer with Low Polymerization Shrinkage and its Application in Dental Restoration Materials

In this study, a new trimethacrylate monomer α,α,α′-tri[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)phenyl]-1-ethyl-4-isopropylbenzene (α,α,α′-THMPEIB) with a molecular weight of 850 and a large molecular volume was designed and synthesized. The structure of monomer α,α,α′-THMPEIB was confirmed by FT-IR, 1H NMR, and elemental analysis. Degree of double-bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, and flexure strength of α,α,α′-THMPEIB/tri(ethylene glycol) dimethacrylate- (TEGDMA) based resin were measured. 2,2-Bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)-phenyl]-propane (bis-GMA)/TEGDMA monomer mixture was used as reference. The result showed that the α,α,α′-THMPEIB/TEGDMA-based resin had the lower double-bond conversion, polymerization shrinkage, and water solubility than bis-GMA/TEGDMA-based resin. Water sorption and diffusion coefficient value of α,α,α′-THMPEIB/TEGDMA-based resin were nearly the same as those of bis-GMA/TEGDMA-based resin. Flexural strength of α,α,α′-THMPEIB/TEGDMA-based resin was higher than that of bis-GMA/ TEGDMA-based resin.

The viscosity anomaly of polymer mixture solution in extremely dilute concentration region

Abstract The measured reduced viscosity–concentration ( η sp / C – C ) curves of compatible PPO/PS incompatible PMMA/PS mixtures with different composition in toluene all deviate linear and reveal downward turn in extremely dilute concentration region. Moreover, with the variation of composition, the η sp / C – C curve of PS/PMMA/ m -xylene solution bends downwards sometimes and bends upwards sometimes in the extremely dilute concentration region. It indicates that such viscosity anomaly should not be attributed simply to incompatibility, but be related to solvent, composition and so on. It is further suggested that, like the single polymer solution, the viscosity anomaly of polymer mixture solution be resulted mainly from the interference of wall effects on viscosity measurement, which could be eliminated quantitatively with a proposed theoretical formula.

Structure and Properties of Natural Rubber-Organoclay Nanocomposites Prepared by Grafting and Intercalating Method in Latex

The nanocomposites of natural rubber (NR) and organoclay with unsaturated carbon-carbon double bonds (C1/4C) on interlayer surfaces (USMMT) are prepared by the grafting and intercalating method in latex in the presence of butyl acrylate (BA) monomer. The conversion, grafting efficiency, and grafting percentage of BA onto NR and USMMT are determined. The structure and morphology of the nanocomposites are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmitted electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling experiments. The mechanical properties of the nanocomposites are measured. The results show that graft copolymerization of BA monomer onto NR molecular chains can take place with high conversion, grafting percentage, and grafting efficiency. At the same time, BA can intercalate into the interlayer galleries of USMMT and polymerize in situ together with C1/4C bonds on the interlayer surfaces. As a result, the interlayer spacing of organoclay is increased and the interfacial combination between the silicate layers and rubber is strengthened. The results of XRD and TEM demonstrate the formation of the nanocomposites of NR-M-USMMT. The glass transition temperatures of the nanocomposites are higher than that of the NR vulcanizate. The mechanical properties of the nanocomposites are remarkably improved compared with those of the NR and NR-USMMT vulcanizate.

Thermal Degradation Behaviors of Poly(vinyl chloride)/Halloysite Nanotubes Nanocomposites

Poly(vinyl chloride) (PVC)/halloysite nanotubes (HNTs) nanocomposites were prepared by melt blending. Transmission electron microscopy (TEM) results showed that HNTs were uniformly dispersed in the PVC matrix. The thermal properties of PVC/HNTs nanocomposites were investigated in detail. The apparent activation energies (Ea) were analyzed by means of Kissinger and Flynn-Wall-Ozawa methods. Thermogravimetric analysis results showed that the thermal properties of PVC/HNTs nanocomposites were improved. Cone calorimetry was used to measure the smoke evolution and fire properties. The addition of HNTs led to a remarkable reduction in the smoke production rate, the total smoke production, and the peak heat release rate.

Effect of Alkali Treatment on Structure and Mechanical Properties of Acrylonitrile–Butadiene–Styrene/Bamboo Fiber Composites

The preparation and properties of wood–plastic composites (WPCs) based on acrylonitrile–butadiene–styrene (ABS) and bamboo fibers (BFs) are described. The BFs were first modified by alkali treatment in order to improve their adhesion to an ABS matrix. The BF modifications were monitored by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Styrene–maleic anhydride (SMA) copolymer, as a compatibilizer, was added to both the untreated and alkali-treated composites. The changes in the structure and the properties resulting from these treatments were observed by the SEM and mechanical tests. The experimental results indicated that both the alkali treatment of the BF and the inclusion of the SMA copolymer improved the interactions between the BF and ABS matrix, and promoted better mechanical properties of the composites.

Effect of Curing Procedures on the Electrical Properties of Epoxy-Based Isotropic Conductive Adhesives

In this paper, a typical isotropic conductive adhesives (ICAs) composed of an epoxy-based binder containing micro-sized silver flakes was prepared and the effects of different curing procedures on the electrical properties of conductive adhesives were investigated. The results showed that there a greater influence of the curing temperature on 55% silver fill loading, the volume resistivity of ICAs decreased to 4.7×10-from 1.0×10-3 cured at 180 °C and 250 °C, respectively. However, there is almost no effect on the high silver fill loading. The in situ monitoring the variations in electrical resistance of ICAs with 65% silver fill loading was studied during the curing process, and it was found that the resistance reached to 1.99 MΩ at 180 °C after cured for 27 min, and reached to 1.39 KΩ for 40 min, and 18.8 Ω for 60 min and the cooling process almost no effect on the electrical resistance of ICAs. The reasons for the dependence of bulk resistivity on temperatures were also discussed in terms of the dispersing of the silver flakes in ICAs by SEM.