This article has been devoted to investigation of the tribological properties of ultra‐high molecular polyethylene/graphene oxide nanocomposite. The nanocomposite of ultra‐high molecular polyethylene/graphene oxide was prepared with 0.5, 1.5, and 2.5 wt% of graphene oxide and with a molecular weight of 3.7 × 106 by in‐situ polymerization using Ziegler–Natta catalyst. In this method, graphene oxide was used along with magnesium ethoxide as a novel bi‐support of the Ziegler–Natta catalyst. Analyzing the pin‐on‐disk test, the tribological properties of the nanocomposite, such as wear rate and mean friction coefficient, were investigated under the mentioned contents of graphene oxide. The results showed that an increase in graphene oxide content causes a reduction in both wear rate and mean coefficient friction. For instance, by adding only 5 wt% graphene oxide to the polymeric matrix, the wear rate and mean coefficient friction decreased about 34% and 3.8%, respectively. Also, the morphological properties of the nanocomposite were investigated by using X‐ray diffraction and scanning electron microscopy. In addition, thermal properties of the nanocomposite were analyzed using differential scanning calorimetry, under various contents of graphene oxide. The results of the morphological test indicated that the graphene oxide was completely exfoliated into the polymeric matrix without any agglomeration. Copyright © 2016 John Wiley & Sons, Ltd.

The graphene‐based Ziegler–Natta catalyst has been used to prepare ultrahigh molecular weight polyethylene/graphene oxide (UHMWPE/GO) nanocomposite via in situ polymerization. The morphological investigations have been conducted using X‐ray diffraction patterns and scanning electron microscopy method. The obtained results indicated that no diffraction peak is detected in a GO pattern, which could be due to the exfoliation of graphene nanosheets in the UHMWPE matrix. Morphological investigations indicated that GO nanosheets are dispersed almost uniformly in polymeric matrix, and that there should exist a good interaction between nanofillers and matrix. The mechanical properties of the nanocomposites were studied, and the results showed that the Young (tensile) modulus and tensile strength of the prepared nanocomposites were significantly increased by increasing the filler content, which should be due to the high aspect ratio of GO plates and their uniform dispersion in the UHMWPE matrix. The thermogravimetery investigations reveal that the thermal stability of nanocomposites increase with increasing GO content and that initiation thermal decomposition temperature shifts to higher values.

The synthesis of mono-and bi-supported Ziegler-Natta catalysts using magnesium etoxide Mg(OEt) 2 and graphene oxide (GO) as catalyst support for production of Ultra High Molecular Weight Polyethylene (UHMWPE) is reported in this investigation. Nano-graphene oxide was prepared by the modified Hummer's method and its structure was analyzed by XRD and FTIR indicating the presence of hydroxyl groups on graphene oxide and the formation of an exfoliated structure. The activity of TiCl 4 /Mg(OEt) 2 , TiCl 4 /Mg(OEt) 2 -GO, and TiCl 4 /GO catalysts in terms of grams of PE produced per mmol of Ti per hour was experimentally obtained for catalysts with different ratios of co-catalyst (triisobutylaluminium) to TiCl 4 . For all three series of catalysts, the activity curve showed an optimum point at a specific Al/Ti molar ratio. Catalyst activity was highest for TiCl 4 /Mg(OEt) 2 and lowest for TiCl 4 /GO. The characterization of UHMWPE products indicated that the viscosity average molecular weight (Mv) was highest for the polymer produced by TiCl 4 /Mg(OEt) 2 and lowest for the polymer produced by TiCl 4 /GO. Furthermore, thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and mechanical tensile testing were conducted on the prepared polymers indicating that the polymer produced by TiCl 4 /GO had the highest thermal and mechanical properties, while these properties were at their minimum for polymers produced by TiCl 4 /Mg(OEt) 2 .

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