High Mechanical and Thermal Properties of Epoxy Composites with Liquid Crystalline Polyurethane Modified Graphene.

Yuqi Li,Xu Xu,Xiuyun Li,Jian Gao,Shaorong Lu

doi:10.3390/polym10050485

Abstract

Graphene nanosheets (GNs) often result in incompatibility with the hydrophobic polymer matrix, and the tendency to form aggregates during processing. Herein, liquid crystalline polyurethane modified GNs (GPLP) were obtained by π–π stacking interactions between GNs and perylene bisimide derivatives, and then in-situ polymerization of liquid-crystalline polyurethane. Spectroscopic studies, elemental analysis, and thermal properties confirmed the successful π–π stacking and the integrated structure of GPLP. The good dispersion state of GPLP in the epoxy matrix (EP), and the strong interactions between GPLP and EP, lead to the significant improvement of the thermal and mechanical performance of the GPLP/EP composites. The impact strength, Young’s modulus, tensile strength, and toughness of the GPLP/EP composites with 1.47 wt % GNs reached the highest values of 54.31 kJ/m2, 530.8 MPa, 112.33 MPa and 863 J/m3, which significantly increased by 210%, 57%, 143%, and 122% compared to that of neat epoxy, respectively. As well, the glass transition temperature increased by a notable 33 °C. It is hoped that this work can be used to exploit more efficient methods to overcome the poor adhesion between GNs and polymers.

Highlights

InstructionA single layer of sp hybridized carbon atoms packed densely in a two-dimensional honeycomb crystal lattice, has attracted tremendous attention because of its novel properties and potential application in many technological fields such as polymer composites, supercapacitors, lithium batteries, and sensors [1,2,3]
Graphene nanosheets (GNs) often result in incompatibility with the hydrophobic polymer matrix, and the tendency to form aggregates during processing
Liquid crystal polyurethane modified graphene nanosheets were prepared by π–π stacking interactions method

Summary

Instruction

A single layer of sp hybridized carbon atoms packed densely in a two-dimensional honeycomb crystal lattice, has attracted tremendous attention because of its novel properties and potential application in many technological fields such as polymer composites, supercapacitors, lithium batteries, and sensors [1,2,3]. It was suggested that graphene can be used as a nanofiller for carbon filler-based polymer composites as a result of its good chemical stability, huge specific surface area, electrical properties, and remarkable mechanical [4,5,6]. Yang et al [14] used a facile covalent functionalization method to obtain polydisperse, functionalized, chemically converted graphene nanosheets (f-CCG) They demonstrated that the compressive failure strength and the toughness of f-CCG-reinforced monoliths at 0.1 wt %, compared with the neat monolith, were greatly improved by 19.9% and 92%, respectively. The introduction of the liquid crystal units endow the GNLP/EP composites with excellent mechanical and thermal properties, due to the enhanced interactions between the GNs and EP

Materials

Synthesis of the Perylene Bisimide Derivatives

The fractions of GPLP were of

Characterization

Results and Discussion

Conclusions