Conductivity of microfibrillar polymer-polymer composites with CNT-loaded microfibrils or compatibilizer: A comparative study

Conductive polymer composites have wide ranging applications, but when they are produced by conventional melt blending, high conductive filler loadings are normally required, hindering their processability and reducing mechanical properties. In this study, two types of polymer-polymer composites were studied: i) microfibrillar composites (MFC) of polypropylene (PP) and 5 wt% carbon nanotube (CNT) loaded poly(butylene terephthalate) (PBT) as reinforcement, and ii) maleic anhydride-grafted polypropylene (PP-g-MA) compatibilizer, loaded with 5 wt% CNTs introduced into an MFC of PP and poly(ethylene terephthalate) (PET) in concentrations of 5 and 10 wt%. For the compatibilized composite type, PP and PET were melt-blended, cold-drawn and pelletized, followed by dry-mixing with PP-g-MA/CNT, re-extrusion at 200°C, and cold-drawing. The drawn blends produced were compression moulded to produce sheets with MFC structure. Using scanning electron microscopy, CNTs coated with PP-g-MA could be observed at the interface between PP matrix and PET microfibrils in the compatibilized blends. The volume resistivities tested by four-point test method were: 2.87•108 and 9.93•107 Ω•cm for the 66.5/28.5/5 and 63/27/10 (by wt%) PP/PET/(PP-g-MA/CNT) blends, corresponding to total CNT loadings (in the composites) of 0.07 vol% (0.24 wt%) and 0.14 vol% (0.46 wt%), respectively. For the non-compatibilized MFC types based on PP/(PBT/CNT) with higher and lower melt flow grades of PP, the resistivities of 70/(95/5) blends were 1.9•106 and 1.5•107 Ω•cm, respectively, corresponding to a total filler loading (in the composite) of 0.44 vol% (1.5 wt%) in both MFCs

Effect of encapsulated SWNT on the mechanical properties of melt mixed PA12/SWNT composites

Styrene maleic anhydride copolymer (SMA) encapsulated single wall carbon nanotubes (SWNT) are melt mixed with PA12 in order to disperse SANT more homogeneously. The mechanism is found to be a reactive coupling between amine end groups of PA12 and maleic anhydride functionality of SMA during melt mixing of PA12 with SMA modified SWNT. This leads next to a better dispersion to an enhanced interfacial adhesion between PA12 and SWNT as indicated by enhanced rheological, dynamic mechanical, and tensile properties of the PA12/SWNT composites. (C) 200

Reactive compatibilization of melt mixed PA6/SWNT composites: Mechanical properties and morphology

Styrene maleic anhydride copolymer (SMA) encapsulated single wall carbon nanotubes (SWNT) were melt mixed with polyamide 6 (PA6) utilizing an interfacial reaction in order to disperse SWNT homogeneously and to enhance interfacial adhesion. The intended reactive coupling between PA6 and SMA was evident from IR spectroscopy. Raman spectroscopy was used to characterize the SWNT and the nanocomposites. Studies on crystallization behavior showed the nucleating behavior of SWNT in the composites, as found using DSC and WAXD. The encapsulation of SWNT by SMA copolymer leads to increased elongation at break in the composites, which can be attributed to the enhanced interfacial adhesion between PA6 and SMA modified SWNT as observed from the SEM investigation of tensile fractured surfaces of PA6/SWNT+SMA composites. The glass transition temperature of PA6 increased significantly in the composites

Styrene maleic anhydride copolymer mediated dispersion of single wall carbon nanotubes in polyamide 12: Crystallization Behavior and morphology

Melt mixed composites based on polyamide 12 (PA12) were prepared using single wall carbon nanotubes (SWNT), which were encapsulated by styrene maleic anhydride copolymer (SMA). The aim was to achieve a reactive coupling between the maleic anhydride functionality of SMA at the surface of the SWNT and the amine end groups of PA12 during the melt mixing. The reaction could be proven by infrared spectroscopy. The modified nanocomposites exhibited a better SWNT dispersion. An enhanced interfacial adhesion between PA12 and SWNT was detected from SEM investigations of tensile fractured surfaces of the SMA encapsulated PA12/SWNT composites. Electrical conductivity measurements revealed the formation of "network-like" structure formation at 6 wt % SWNT content in PA12/SWNT composites, however, PA12/SWNT + SMA composites showed insulating behavior due to encapsulating SMA layer on SWNT surface. Studies on crystallization behavior indicated the nucleating action of unmodified and SMA encapsulated SWNT in the respective composites as found in the increase of crystallization temperature and the change in the crystalline morphology of PA12 as observed from DSC, WAXD, and SAXS. However, the degree of crystallinity of PA12 increased only marginally on incorporation of either unmodified or SMA encapsulated SWNT. (c) 2007