Henry Kuo Feng Cheng

Poly(vinyl alcohol) Nanocomposites Filled with Poly(vinyl alcohol)-Grafted Graphene Oxide

We present a novel approach to the fabrication of advanced polymeric nanocomposites from poly(vinyl alcohol) (PVA) by incorporation of PVA-grafted graphene oxide. In this work, we have synthesized PVA-grafted graphene oxide (PVA-g-GO) for the strong interfacial adhesion of graphene oxide (GO) to the PVA matrix. It was found that the mechanical properties of PVA were greatly improved by incorporating PVA-g-GO. For example, the tensile strength and Youngs modulus of the PVA nanocomposite films containing 1 wt % net GO in the PVA-g-GO significantly increased by 88 and 150%, respectively, as compared to unfilled PVA. The elongation at break was also increased by 22%, whereas the GO/PVA nanocomposite containing 1 wt % pristine GO was decreased by 15%. Therefore, the presence of the PVA-g-GO in the PVA matrix could make the PVA not only stronger but also tougher. The strong interfacial adhesion between PVA-g-GO and the PVA matrix was attributed to the good compatibility between PVA-g-GO and the matrix PVA as well as the hydrogen-bonding between them.

Thermal kinetics of montmorillonite nanoclay/maleic anhydride-modified polypropylene nanocomposites

Thermal kinetics of montmorillonite nanoclay (MMT)/maleic anhydride-modified polypropylene (MAH-PP) composites (PPCNs) is reported here in terms of thermal stability, decomposition, and crystallization kinetics. The effects of MMT nanoclay on the thermal stability of PP in MMT/MAH-PP composites have been examined at different heating rates by means of thermogravimetric (TG) analysis. Based on the TG results, the Ozawa method was applied to determine the activation energies of decomposition for MMT/MAH-PP composites and the results were then verified by the Kissinger method. It was found that the thermal stability of PP was significantly improved in the presence of MMT nanoclay. Differential scanning calorimetry (DSC) was used to study the melting and crystallization behaviors of MMT/MAH-PP composites under various thermal conditions. Using the data from DSC, the Kissinger method was applied to estimate the activation energies of PPCNs which were required during their non-isothermal crystallization. The activation energies of crystallization showed that MMT nanoclay served as a nucleating agent in the non-isothermal crystallization of PP in the PPCNs and as a result, the crystallinity of PP was greatly enhanced. Therefore, the presence of MMT nanoclay in MMT/MAH-PP composites effectively modified the thermal kinetics of PP.

Covalent functionalization of carbon nanotubes for ultimate interfacial adhesion to liquid crystalline polymer

In this study, we have selectively introduced three types of chemical functional groups, namely nitrophenyl (C6H4NO2), aminophenyl (C6H4NH2) and benzoic acid (C6H4COOH), on the sidewalls of multiwalled carbon nanotubes (MWCNTs) with the aim to find the optimal functionalization of MWCNTs for the most desirable intermolecular interaction with a liquid crystalline polymer (LCP). We have investigated the effects of electron withdrawing (–NO2 and –COOH) and donating (–NH2) groups attached to the benzene rings of the functionalized MWCNTs on the dispersion of MWCNTs in the LCP matrix and the interaction with the LCP. FTIR analysis showed that the composite containing –C6H4NH2 functionalized MWCNTs exhibited the maximum intermolecular interactions (hydrogen bonding) between the –C6H4NH2 group of MWCNTs and –CO group of LCP. This strong intermolecular hydrogen bonding greatly improved the dispersion of p-C6H4NH2 functionalized MWCNTs in the polymer matrix as well as the interfacial adhesion. The highest complex viscosity, storage modulus and loss modulus were observed for the p-C6H4NH2-functionalized MWCNT/LCP composites among all the composites studied. The mechanical strength and electrical conductivity of this composite system were also the highest. Thus, these results testified that the extent of intermolecular interactions between the functionalized MWCNTs and the polymer matrix is key for an optimal improvement in the composite properties.

Thermal decomposition kinetics of multiwalled carbon nanotube/polypropylene nanocomposites

The multiwalled carbon nanotube (MWCNT)/polypropylene (PP) nanocomposites with different MWCNT contents were prepared by a melt-mixing method, and their thermal decomposition kinetics has been studied. As the properties of MWCNT/PP nanocomposites fundamentally depend on the dispersion state of MWCNTs in the PP matrix, rheological measurement and field emission electron microscopy were used to examine the dispersion state of MWCNTs in the PP matrix. The effect of MWCNTs on the thermal stability of PP in MWCNT/PP nanocomposites was studied at different heating rates by means of thermogravimetric (TG) analysis. Based on the TG results, the Ozawa’s method was used for the determination of the activation energies required in the thermal decomposition of MWCNT/PP nanocomposites. The Kissinger’s method was also applied to verify the results. Both methods proved that the thermal stability of PP could be significantly improved in the presence of MWCNTs.

Molecular Interactions in PA6, LCP and their Blend Incorporated with Functionalized Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxyl group (-COOH) to improve their dispersion in a nylon6 (PA6) matrix, a liquid crystal polymer (LCP) and their blend. This functionalized MWCNTs also achieved better interfacial adhesions with both polymer matrices and with both phases in the blend. The dispersion of MWCNT-COOH in the polymer matrices and their interfacial interactions with polymer molecules were found to be the most important factors affecting the properties of composites. Moreover, studies on morphological, rheological, and mechanical properties confirmed that a better miscibility between PA6 and LCP had been constituted in the presence of MWCNT-COOH. Therefore, it is observed that the functionalized MWCNTs not only played the traditional role as reinforcing fillers in the polymer matrices, but also performed a novel role as compatibilizers for their blend.

An innovative approach for the fabrication of highly conductive nanocomposites with different carbon

A novel approach to the preparation of a super-conductive polymeric nanocomposite system with different carbon fillers is presented. The ternary composites of polyamide 6 (PA6) and conductive carbon black (CCB) and multi-walled carbon nanotubes (MWCNTs) were fabricated by a melt-mixing technique. The ternary nanocomposites with the high filler contents showed extremely higher conductivity compared with the corresponding binary polymer composites. The effects of CCB and MWCNTs at different compositions on the rheological, physical, morphological, thermal, mechanical, and electrical properties of the ternary nanocomposites have been studied systematically. A mechanism for the complementary effects of CCB and MWCNTs has been proposed.