Abstract
In this article, hyperbranched polyester grafted graphene oxide (GO) was successfully prepared. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were performed for its characterizations. On the other hand, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were also performed to study its influences on non-isothermal crystallization behaviors of β-nucleated isotactic polypropylene (β-iPP). The grafting ratios of hyperbranched polyester with different supermolecular structures were calculated to be 19.8–24.0 wt %, which increase with the degree of branching. The results showed that the grafting of hyperbranched polyester was advantageous in increasing the crystallization peak temperature Tp and decreasing the crystallization activation energy ΔE of β-iPP/GO composites, which contributed to the iPP’s crystallization process. Moreover, under all cooling rates (2, 5, 10, 20, 40 °C/min), crystallinities of β-iPP/GO were greatly improved after being grafted with hyperbranched polyester, because of the increase of the relative contents of α-phase αc and the average α-crystal sizes.
Highlights
With the excellent properties of low cost, light weight, excellent mechanical properties, good heat resistance, and superior processability [1], isotactic polypropylene has become one of the most widely used polymer materials [2] and has been extensively used in various areas
We studied the crystallization behaviors of β-nucleated isotactic polypropylene (iPP)/Graphene oxide (GO) composites cooled under different rates (2, 5, 10, 20, and 40 ◦ C/min) in order to investigate thoroughly the effect of hyperbranched polyester grafted GO on non-isothermal crystallization
Results of hyperbranched polyester is beneficial to increase the crystallinity of iPP/GO composites and 9 shows the The heating curves of samples cooled under differentpolyester, rates
Summary
With the excellent properties of low cost, light weight, excellent mechanical properties, good heat resistance, and superior processability [1], isotactic polypropylene (iPP) has become one of the most widely used polymer materials [2] and has been extensively used in various areas. Graphene is a single atomic layer consisting of sp carbon atoms, which are bonded in the hexagonal lattice [4], and it has attracted extensive attention in virtue of its extremely good thermal, mechanical, electrical, and crystallization performances [5,6,7] It has been extensively and thoroughly studied in catalysts, polymer composites, sensors, energy devices, electronic materials, drug delivery, etc. The existence of multitudinous functional groups, such as hydroxyl groups, provides high reactivity with reinforced fillers, which makes hyperbranched polyester suitable as the ideal surface modifier for graphene oxide, thereby further improving the dispersion and compatibility in iPP. It is presumed that the surface functionalization of GO by hyperbranched polyester can help to ameliorate the dispersion of GO in iPP, and improve the α-nucleation effect of GO, so as to further promote the iPP’s α-crystallization.
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