Role of surfactant molecular weight on morphology and properties of functionalized graphite oxide filled polypropylene nanocomposites

Abstract

Conductive polymer composites have aroused wide interests from both academia and industry in the field of functional materials. Addition of diverse conducting fillers such as carbon black [1,2], graphite [3], and metal fiber or powder [4] into thermoplastic polymers through melt mixing is an effective approach to fabricate conductive composites. Because a great amount of the fillers, generally greater than 15 wt% [5], were required for the host polymer to become conductive, resulting in both poor processability and inferior mechanical properties, the practical applications of these conventional composites were largely restricted. On the other hand, commercial exploitation of isotactic polypropylene has been expanded rapidly due to its attractive characters of low cost, low weight, heat distortion above 100°C, and extraordinary versatility in terms of properties, applications and recycling. The introduction of nanoscopic fillers of high anisotropy enhances a wide range of performance of the polypropylene nanocomposites, such as mechanical, thermal and conductive properties, at a relatively small loading [6]. Graphite is a layered mineral composed of weakly bonded graphene sheets with a large aspect ratio. Abstract. Various surfactants of different molecular weights, including alkylamine, poly(oxypropylene) diamine (POP), and maleic anhydride grafted polypropylene (PPgMA) oligomers, were used for simultaneous funtionalization and reduction of graphite oxide (fGO). In this study, the effect of molecular weight and compatibility of the surfactants on the morphology and properties of the nanocomposites are reported. Wide-angle X-ray diffraction (WAXD) exhibited a definite interlayer thickness for GOA (alkylamine intercalated GO), however, the diffraction peaks were nearly suppressed for fGOs combining ODA with either POP (GOAP) or PPgMA (GOAE). The uniform dispersion of the fGO flakes in the polypropylene matrix resulted in the significant increase in both the degradation temperature and the crystallization temperature. A single characteristic melting peak of monoclinic (!) crystalline phase was observed from DSC traces, which was consistent with WAXD results. Dynamic mechanical analysis clearly indicated increase in both the storage modulus and the glass transition temperature of the nanocomposites due to the enhanced affinity between fGO and the polypropylene matrix. However, GOAP composite showed lower E" and T g than GOAE because POP is less compatible with the matrix than PPgMA oligomer. Dielectric analysis also showed significant increase in both dielectric permittivity and dielectric loss at low frequency regimes with GOAE showing maximum dielectric properties. The finely dispersed GOAE and its compatibility with polymer matrix manifested the interfacial polarization, which gave rise to much greater #" and #$ than other nanocomposites.

Effect of Graphene Nanofibers on the Morphological, Structural, Thermal, Phase Transitions and Mechanical Characteristics in Metallocene iPP Based Nanocomposites

“…This shift up of T c is beneficial from an industrial point of view since it implies shorter cycle times during processing. This nucleation effect has been also observed in other iPPs composites incorporating different types of graphene or derivatives [24,[38][39][40][41]56,57]. The subsequent second melting curves are rather similar in both shape and T m location for all the different samples, independently of the type of nanofiber incorporated, GHS or GLS.…”

A DMA study of the interfacial changes on injection‐molded iPP/mica composites modified by a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene

“…Inherent to the success of the iPP based micro and nanocomposites is the need to assure that the desired interface performance remains available during the manufacturing and scaling compounding operations up to the macro (or final application) level of these composite materials. Indeed, the development of cheap and efficient interface agents obtained by grafting of an optimum number maleic anhydride like polar groups into the iPP backbone continues (from early developments) as one of the most competitive ways to optimize the mechanical performance of those engineering materials …”

The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

“…However, the viscosity of the HPP/NA-21 blend is lower than that of the HPP/NA-11 blend, since the interaction force between the molecular chains becomes weak due to the addition of NA-11. The sodium laurate components in NA-21 combine with the macromolecular chains through hydrogen bonding, which leads to more negative charge with large molecular chains, electrostatic repulsion and steric hindrance, resulting in the macromolecular stretch and the chain tangles weakening [41]. According to the molecular weight test results, it is also found that the effect of NA-21 on reducing intermolecular entanglement is more significant than NA-11, whether in HPP or LPP.…”