Toughening of polymers by graphene

Abstract

IntroductionDue to the rapid development of nanoscience and nanotechnology in the past 20 years, improvement of polymer properties by nanofillers has become a vital topic in the field of material science. [1][2][3] The polymer nanocomposites show enhanced properties by the incorporation of low amount of nanofillers such as carbon black (CB), carbon nanotubes (CNTs), graphene and nanoclay. [4][5][6][7] Due to the high surface to volume ratio and/or high aspect ratio, the nanofillers are more efficient than the traditional fillers in reinforcing polymers. 8,9 Among the nanofillers, graphene is an atomically thick, 2D nanomaterial that is the strongest materials measured so far. it has intensively attracted a great deal of interest in extensively exploring its applications. The superior properties of graphene also reflected in the graphene/polymer nanocomposites. It has been widely reported that the mechanical, thermal, electrical, gas-barrier and flame-retardant properties of polymer can be significantly improved by the addition of graphene. 3,6,[18][19][20][21][22][23][24] Its advantages over other nanofillers have been discussed. 3,19,[25][26][27][28] However, the reinforcing efficiency of graphene highly depends on the dispersion and distribution of graphene sheets in the polymer matrix. 29 An optimized graphene-polymer interface is critical in the property transfer. [30][31][32] Pristine graphene sheets are not compatible with organic polymers and have a great tendency to agglomerate in the matrix. 3,33,34 To resolve this problem, functionalization of graphene is an essential step to achieve a molecular level dispersion.3,35 The functionalized graphene (FG) sheets could form strong interfacial bonding with polymer chains, which is favorable for load transfer, but it also confines the motion of interfacial polymer segments. [36][37][38] Thus, the enhancements in stiffness, tensile strength and hardness of polymer are frequently reported, while the elongation at break and ductility is always decreased. 3,6,39 Toughness of polymer is extremely important in the critical structural applications and highperformance areas such as automotive, aerospace and defence. 9,40 Enhancing the toughness of polymer has been a challenging issue, especially for thermosets that have highly cross-linked structure. 9Traditional fillers, such as rubber particles, can improve the toughness, but they show negative impact on mechanical properties and manufacturability. 38,41 In the past few years, toughening of polymers by graphene has been explored and reported in a few publications. 25,[29][30][31][32]38,[42][43][44][45][46][47][48][49][50][51][52][53][54][55] According to the results, it is believed that the incorporation of FG can toughen polymers including both thermoplastics and thermosets, although the understanding of the mechanism is still insufficient. In this review, the authors try to focus on the recent development on the Toughening of polymers by graphene Wang and Song ICE Publishing: All rights reserved

Graphene as a Prototypical Model for Two-Dimensional Continuous Mechanics

“…According to Equation (7), the critical pressure P c (d) increases with increasing d, reaches a maximum at d = √ 5/3β ≈ 0.57 nm, and then decreases. Asymptotically, P c (d) ∼ 24D/d 3 , which is what continuous-mechanics predicts for a thin-wall elastic ring (Lévy-Carrier law) [51].…”

“…Besides its many potential applications [1], including the improvement of polymer properties and those of other host materials [2,3], graphene is an interesting model material for testing the prediction of two-dimensional (2D) mechanics [4]. In linear elasticity, the simplest formulation of the elastic energy of a 2D medium is the surface integral (1) involving the elements of the 2 × 2 strain tensor and the 2 × 2 curvature tensor κ.…”

High performance graphene oxide/epoxy nanocomposites fabricated through the solvent exchange method

“…This significant enhancement in elongation at break is attributed to the uniform dispersion of GO, strong interfacial interaction between GO and epoxy and reduction of epoxy crosslink density. However, at higher GO loading, the strong interactions between the GO sheet and epoxy matrix leads to diminishing epoxy molecular mobility and slightly reduces the elongation at break .…”

Effect of antioxidant grafted graphene oxides on the mechanical and thermal properties of polyketone composites

“…Although GO has good interfacial interaction with PK due to the oxygen functional groups in GO, since HA-GO and HP-GO contain additional surface functional groups, larger interfacial interactions between HA-GO or HP-GO and the PK matrix could be expected. Similarly, it was reported that when GO derivatives containing organic functional groups that have a specific interaction with the polymer matrix were used as fillers for polymer composites, they could increase the toughness of polymers [14,46].…”

“…Although the content difference of the organic moieties between HA-GO and HP-GO is only 1 wt.%, the mechanical strength values of HP-GO/PK are quite larger than those of HA-GO/PK because HP-GO contains larger content of rigid conjugated carbon units; more oxygen functional groups in HP-GO could be reduced because HP-GO is prepared using a longer reaction time (3 days) than HA-GO (12 h). Others also reported that the polymer composites containing more oxidized GOs have the smaller mechanical strength values [45][46][47]. Therefore, the carbon nanomaterials can increase the mechanical strength of the PK, while CNT, GO, and HP-GO having a relatively larger content of rigid conjugated carbon units are more effective than HA-GO in increasing the mechanical strength of PK.…”