Qiuying Li

Synthesis and characterization of functionalized carbon black/poly(vinyl alcohol) high refractive index nanocomposites

Carbon black (CB)/polymer composites with high refractive index (RI) were fabricated from poly(vinyl alcohol) (PVA) and covalently functionalized nano-CB (PVA-es-CB) by simple esterification reaction. Transmission electron microscopy showed that uniform aggregates of PVA-es-CB nanoparticles with a size smaller than 100 nm formed in the nanocomposite films. Ellipsometric measurements indicated that the PVA-es-CB/PVA composite films had a RI in the range 1.520–1.598 linearly increased with the PVA-es-CB volume content. Theoretical equation based on Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The hybrid films also revealed relatively good surface planarity, thermal stability and optical transparency.

Synergistic effect between carbon black nanoparticles and polyimide on refractive indices of polyimide/carbon black nanocomposites

High refractive index polyimide (PI)–chloride modified carbon black hybrid materials were prepared. The introduction of chloride modified CBs endowed the PI/CB nanocomposites with high refractive index, and the effect of the interaction between the five-membered imide rings and aromatic rings of CBs on the high refractive indices and transparency of the resulting PI/CB nanocomposites was discussed. The refractive indices of the prepared hybrid films at 633 nm were in the range of 1.711–1.833, which increased with the CB content from 0 to 10 wt%. According to the comparison of the theoretical and experimental values, the higher refractive index is mainly due to the effective enhancement of intra- and intermolecular charge transfer (CT) interactions between the five-membered imide rings and chlorine atoms attached directly to the CBs and the adjacent benzene rings of CBs. A theoretical equation based on the modified Lorentz–Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values. Transmission electron microscopy results indicated that the incorporation of CBs into polymer matrices on the nanoscale would assure the optical transparency.

Phase Structure of Compatibilized Poly(Lactic Acid)/Linear Low-Density Polyethylene Blends

Blends of PLA and linear low-density polyethylene (LLDPE) were compatibilized with glycidyl methacrylate (GMA)–grafted poly(ethylene-octene) copolymer (mPOE). Effects of compatilizer on phase structure of compatibilized PLA/LLDPE were studied by spreading coefficient calculation prediction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) analysis. The spreading coefficient calculations, based on experimental and calculated surface tension data, show that mPOE spreads on LLDPE extensively to encapsulate LLDPE completely, which is in good agreement with the results of DSC, SEM, and WAXD analysis. The chemical reaction between the end carboxyl groups or end hydroxyl groups of PLA and epoxy groups of mPOE, which is suggested as the driving force leading to an ideal interfacial adhesion between PLA and the dispersed phase, was confirmed by Fourier transform infrared ray (FT-IR) spectroscopy analysis.

Crystallization Behavior of Poly(Lactic Acid) Filled with Modified Carbon Black

A novel method was employed to modify the surface of carbon black (CB) by an organic small molecule in a Haake Rheomix mixer. The modified carbon black (MCB) was dispersed uniformly in poly(lactic acid; PLA). The crystallization behaviors of PLA, PLA/CB and PLA/MCB composites were investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and polarizing optical microscopy. It is found that the addition of CB or MCB can influence the crystallization behavior of PLA. PLA/MCB has a faster crystallization rate and higher crystallization peak temperature than PLA/CB. For non-isothermal studies, Jeziorny and Mo equations were employed. The Mo equation can well describe the non-isothermal crystallization of the three samples. For PLA/CB and PLA/MCB composites containing 3wt% fillers, the nucleating activity for CB is about 0.32, and about 0.16 for MCB. All these results show that MCB is an effective nucleating agent. PLA/MCB has a higher nucleation rate than PLA/CB because of the finer dispersed particles size and improved interaction between MCB and PLA.

Thermal Conductivity and Mechanical Properties of Carbon Black Filled Silicone Rubber

The effects of two types of carbon blacks (CBs), N990 and Vulcan XC-72, on the mechanical properties and thermal conductivity of filled silicone rubber (SR) were investigated. It was found that the addition of CB particles increased the thermal conductivity, the thermal stability and the tensile strength of the silicone rubber composites. The scanning electron microscope showed that Vulcan XC-72 of higher structure was more liable to form conductive network within the matrix, and the thermal conductivity of the composites filled by Vulcan XC-72 was superior to that of the composites filled by N990 at the same filler loading. The Agari model and the Payne effect were used to explain the influence of N990 and Vulcan XC-72 on the formation of thermal conductive networks. Furthermore, Vulcan XC-72 also had better enhancing effects on the mechanical properties and the electrical conductivity of the composites. It was notable that at the high filler contents, silicone rubber filled with N990 also possessed good general properties.

Lowering the percolation threshold of polymer matrix composite by using raspberry-like carbon black/polystyrene composite particles

Our previous studies of raspberry-like carbon black/polystyrene (CB/PS) composite particles suggested that their morphologies could be tailored as the coverage degree of CB on PS microspheres. Morphologies of these composite particles were investigated by scanning electron microscope. The CB/PS composites prepared by using raspberry-like CB/PS particles had lower percolation threshold than that of general CB/PS composites. Optical microscopy photographs indicated that hierarchical structure of composite particles enabled CB particles to form more effective networks within the matrix. Raspberry-like structure dispersed CB particles in the interfaces between polycarbonate (PC) and PS when CB/PS particles were introduced into PC as additives. The effects of concentration of PS, coverage degree of CB, and concentration of CB on electrical properties of CB/PS/PC composite were investigated. The results showed that the percolation threshold of CB/PS/PC composite was improved when PS concentration was at the range of 20–80% and coverage degree of CB was more than 5% simultaneously.

Effect of Carbon Black Nature on Vulcanization and Mechanical Properties of Rubber

The influence of the basic properties of carbon black, such as structure, panicle size, and surface activity on the vulcanization and mechanical properties of filled natural rubber compounds was investigated in detail. This is important for a better understanding of the rubber performance and the mechanism of reinforcement. In particular, the effect of carbon black surface activity, which was changed by introducing one kind of hindered amine light stabilizer on rubber reinforcement is emphasized.

Effect of electrostatic heterocoagulation of PVM/MA grafted carbon black and attapulgite nanorods on electrical and mechanical behaviors of waterborne polyurethane nanocomposites

In our previous report, poly(methyl vinyl ether-alt-maleic anhydride) grafted CB (GCB) with stable dispersion in water was successfully prepared. In the present study, waterborne polyurethane (WPU) nanocomposites including GCB and attapulgite (ATT) were prepared by liquid mixing method. Anionically charged GCB nanoparticles were heterocoagulated on the surface of cationically charged ATT nanorods at low pH value and improved the stabilization of ATT nanorods in water as a dispersing aid. The microstructure development in matrix that depended on various weight ratios of the nanoparticles ultimately influenced the electrical conductivity and mechanical properties of WPU nanocomposites. Composites containing equal concentrations of GCB and ATT showed reduced electrical conductivity, but significant increase in storage modulus. When the weight ratio of GCB to ATT was 5:1, both electrical conductivity and storage modulus of composite were improved simultaneously. The percolation threshold of composites containing a 5:1 (w/w) GCB/ATT ratio was lower than that of composites with GCB alone. The proposed mechanism for the effect of GCB and ATT on electrical or mechanical behaviors in composite was discussed in details. The clear evidence of microstructure development was also observed by transmission electron microscope.

Polytetrafluoroethylene (PTFE)/carbon black (CB) microporous membranes produced from PTFE/CB composite particles prepared by heterocoagulation process:

Polytetrafluoroethylene (PTFE)/carbon black (CB) microporous membranes with excellent properties were successfully prepared via heterocoagulation process and mechanical stretching method. Heterocoagulation was achieved using PTFE emulsion with 26% solid content, an intermediate product of the commercial PTFE dispersions with 60% solid content, and CB dispersions to prepare PTFE/CB composite particles by mechanical stirring, which is the unique content in this article. Furthermore, in order to obtain uniform distribution of CB particles within the membrane matrix as well as improve color uniformity and mechanical strength of the microporous membranes, CB was pretreated by a titanate coupling agent (NDZ-201). The PTFE/CB composite particles were then used to prepare the PTFE/CB microporous membranes via mechanical stretching operation. Several important properties of the prepared PTFE/CB microporous membranes, such as tensile strength, porosity, contact angles, morphology, and dynamic mechanical properties, were investigated. Results showed that the fabricated PTFE/CB microporous membranes possessed color uniformity, high tensile strength, and high hydrophobicity.

The Synergistic Effects of Carbon Black and Carbon Fibre on the Thermal Conductivity of Silicone Rubber

Silicone rubber (SR) composites filled with carbon black (CB) and carbon fibre (CF) were prepared. The effects of a single filler as well as hybrid fillers on the thermal conductivity (λ) and mechanical properties of SR composites were investigated. It was found that hybrid filler was more effective in increasing λ of the composite, and this effect was more pronounced when the weight ratio of CF:CB was 80:20. The scanning electron microscopy showed the hybrid filler formed a better filler network than single filler in the matrix. SR composites filled with hybrid fillers also possessed better mechanical properties compared with composites filled with only CF.