LLDPE/Graphene Nano-composites: Synthesis and Characterization

Abstract

The development of nano-composite materials is making a significant impact on modern technology due to their wide range of applications and their superior properties1. Several methods have been proposed and developed to prepare polymer nano-composites. Graphene nano-composites, in particular, have attracted the interest of researchers because of their excellent properties, such as high electrical conductivity, high thermal stability and excellent mechanical strength 2–3. Graphene, a two-dimensional carbon atoms structure, exhibits exceptional properties4–5. Incorporating these nano-fillers with high performance polymers results in a unique combinations of properties.This paper reports on the synthesis and characterization of graphene and LLDPE (Linear Low Density Polyethylene)/graphene nano-composites with different weight ratios of graphene. Graphene was synthesized from graphene oxide, which was prepared by using modified hammers method. The obtained few layers of graphene were confirmed by different characterization methods such as FTIR, XRD, Raman spectroscopy and SEM. LLDPE/Graphene composites at different weight ratios of graphene, i.e. 1, 4, and 8 wt% were compounded in twin screw extruder. Extruded granules of LLDPE/Graphene materials were used in the preparation of nano-composites by compression molding. In this research, we used the LLDPE as the polymer matrix, because PE (polyethylene) is one of the most common plastic resins in the world and it is produced on a large scale in the State of Qatar by Qatar Petrochemical Company (QAPCO). LLDPE has grown most rapidly within the PE family due to its good balance of mechanical properties and process-ability compared to other types of PE. The effect of graphene ratio on the mechanical, thermal and electrical properties were investigated. LLDPE/Graphene composites with 4% graphene showed higher tensile strength and tensile modulus than the other graphene loading composites. Agglomeration was a problem in the composites with high wt% of the graphene which caused the reduction in tensile properties. Graphene marginally increased the melting temperature of the nano-composites whereas crystallization temperature, thermal stability and electrical conductivity were increased with increase of graphene loading. The results obtained showed that the graphene can increase the thermal stability of the polymer mixture. Increment of thermal stability is due to the high thermal stability of the graphene and the formation of phonon and charge carrier networks in the matrix. The electrical conductivity of LLDPE is 4.28 × 10− 11 and for nano composites is 9.2 × 10− 05. The high electrical conductivity of the graphene converts the LLDPE polymer insulator to an electrical conductor. Electrically conductive PE based composite materials can be used as electron magnetic-reflective materials, as well as in high voltage cables. The enhancement in mechanical, thermal and electrical properties of LLDPE/Graphene nano-composites achieved by melt mixing of graphene into the polymer can enable mass production of new and low cost novel materials with superior tensile strength, thermal stability and electrical conductivity.