Sage Journals: Discover world-class research

Abstract

In polymer nanocomposites, graphene is possibly the most promising nanofiller. Graphene produces impressive properties for polymers at very low filler content, which makes it highly interesting in building high-performance materials compared to other classes of polymer nanocomposites. Graphene-modified polymer nanocomposites have attracted much attention in scientific literature because of the need of superior materials with desirable properties such as electrical, mechanical, thermal, flame retardant, and gas barrier. Frequent studies have been attempted to produce graphene–polyamide (G-PA) nanocomposites with novel and improved properties. Based on this review, one can identify the synthesis technique and preparation for G-PA nanocomposites, which can further be useful in numerous applications.

Keywords

Graphene polyamide nanocomposites polymer composites polymerization

Introduction

Since the discovery of graphene by Geim and Novoselov, demand of graphene is increasing with wide array of applications, encompassing unique and remarkable properties like mechanical, electrical, thermal, physical, and optical. Graphene is considered as one of the most promising new materials.¹ However, researchers across the globe are still looking for a new dimension to produce lightweight, low-cost, and high-performance composite materials. Graphene have been used as one of the assuring nanofiller material to produce graphene–polyamide nanocomposites (G-PA). G-PA comprises a class of materials that are multiphase hybrid structures, where one of the phases has one, two, or three dimensions (1-D, 2-D, or 3-D) of less than 100 nm. Industrial and academic research on G-PA was pursued to provide added superior properties compared to the conventional polymer. Graphene provides substantial properties enhancements to G-PA, even at very low amount of nanofillers content. G-PA have been widely reported in the scientific literature.² Graphene is 2-D nanostructure in a hexagonal lattice or honeycomb lattice. Graphene is regarded as the fundamental building block for other allotropes, as shown in Figure 1.³ Graphene is a 2-D honeycomb lattice of carbon atoms, stacked up into many layers graphite, rolled up into 1-D carbon nanotube, and it can be wrapped up into zero-dimensional (0-D) fullerene.

Figure 1.

Graphene consists of carbon atoms in a honeycomb lattice on a 2-D plane. Three atomic orbitals from carbon atoms are hybridized into sp² orbitals. These sp² orbitals form covalent bonds with the carbon atoms. The carbon atoms separated by a distance of 1.42°A from each other and this hybridized sp² orbitals form hexagonal planar structure called honeycomb lattice (Figure 2). Graphene possesses excellent properties to its crystal structure. Due to the unique arrangement of atoms through sp² hybridization, graphene has many characteristics, such as thermal conductivity 5000 W m⁻¹ K⁻¹, electrical conductivity 6000 s cm⁻¹, strength 130 GPa, electron mobility 200,000 cm² Vs⁻¹, Young’s modulus 1.0 TPa, specific surface area 2630 m² g⁻¹, and optical transmittance approximately 98%.²

Figure 2.

Graphene derivatives. (a) Graphene, (b) few-layer graphene, (c) graphite, (d) reduced graphene oxide (rGO), and (e) graphene oxide (GO).

Polyamide (PA) is an attractive thermoplastic having repeating amide –CO–NH– linkages with better process ability and chemical resistance and is broadly used in engineering plastic. PA can be classified into two types such as aliphatic PA and aromatic PA (Figure 3). PAs are among the most important as they posed important material properties like high strength and stiffness. However, it has some weaknesses such as low thermal stability, poor dimensional stability, and low electrical conductivity as well as exceptionally its mechanical performance is varied with aromatic and aliphatic PA. Therefore, many works have been undertaken to improve its comparative properties through the nanofillers. PA known as nylons are used as fibers (80–90%), as engineering plastics, adhesives, and rubbers. PA can be obtained from ring opening polymerization, respectively, or polycondensation of diamine with dibasic acids. This review is a summary of the recent synthesis on G-PA nanocomposites.

Figure 3.

Polyamide nomenclature aromatic and aliphatic.

Preparation techniques for G-PA nanocomposites

In recent years, significant signs of progress have been made in synthesis and performances of G-PA. Graphene-filled PA materials have been considered as a stimulating route for creating a new type of high-performance material that combines the advantages of polymer and the merits of graphene. These materials provide unique behavior and improved properties at low nanoparticles content compared to the neat polymer.⁶ Basically, the selection of the synthetic techniques depends on uniform dispersion of graphene, exfoliation, and the interfacial interaction between the graphene and polymer. At present, solution blending, in situ polymerization, and melt blending are three main methods to prepare G-PA nanocomposites.² From the mentioned techniques, in situ polymerization and solution mixing have been used for the chemical interaction between the polymer and the graphene. Use of hazardous chemicals and low yield with high cost are two major demerits for solution mixing. To overcome this problem, scientists and researchers got fascinated toward melt mixing technique as it is solvent-free and environment-friendly, which can fabricate G-PA nanocomposites at a large scale. Melt route has been modified to influence the dispersion quality.⁷ Therefore, for better dispersion of graphene in polymeric material, a combined solution and melt route has been designed.⁸ G-PA nanocomposite obtained by combination approach has shown improved.

Moreover, the description summarizes the important preparation techniques of G-PA nanocomposites in recent years as mentioned in Table 1. Hence, we can see an obviously increase and improvement in the mentioned properties, which have been captivated by combination approach to work in this field fruitfully.

Table 1.

G-PA nanocomposites.

Polyamide	Nanofiller	Synthesis methods	Year	Reference
PA6	FG	Melt blending	2009	⁹
PA6	G	Solution mixing	2009	¹⁰
PA6	RGO	In situ polymerization	2010	¹¹
PA12	FG	Melt blending	2010	¹²
PA6	G	Melt blending	2010	¹³
PA6,6	G	In situ polymerization	2011	¹⁴
PA6	GO	In situ polymerization	2012	¹⁵
PA6	FG	In situ polymerization + melt spinning	2012	¹⁶
PA6,6	G	Solution mixing + electrospinning	2012	¹⁷
PA6	GO	In situ anionic ring-opening polymerization	2012	¹⁸
PA12	G	Melt blending	2012	¹⁹
PA46	GO	Solution mixing	2012	²⁰
PA6	G	Melt blending	2012	²¹
PA6	FG	In situ polymerization	2012	²²
PA11	G	Solution mixing	2012	²³
PA11	GNP	Solution mixing	2012	²⁴
PA6	GO	In situ polymerization	2013	²⁵
PA6	G	Melt blending	2013	²⁶
PA6	GNS-CO₃O₄	Melt blending	2013	²⁷
PA6	GNS-NiO	Melt blending	2013	²⁷
PA6,6	GO	Solution mixing + electrospinning	2013	²⁸
PA6	GO	Solution mixing + melt blending	2013	²⁹
PA11	GO	In situ melt polycondensation	2013	³⁰
PA11	FG	Melt blending	2013	³¹
PA12	FG	Melt blending	2013	³¹
PA11	GNP	Melt blending	2013	³²
PA6	RGO	Solution mixing + electrospinning	2013	³³
PA6	G	Solution mixing + electrospinning	2013	³⁴
PA6	FG	In situ polymerization	2013	³⁵
PA6	TiO₂-RGO	Solution mixing + electrospinning	2013	³⁶
PA6	RGO	In situ anionic ring-opening polymerization	2014	³⁷
PA6	G	Solution mixing	2014	³⁸
PA6	FG	Solution mixing + melt spinning	2014	³⁹
PA6	HNTs-RGO	Melt blending	2014	⁴⁰
PA1010	TRGO	Melt blending	2014	⁴¹
PA6	RGO	In situ thermal polycondensation	2014	⁴²
PA6	G	In situ polymerization	2014	⁴³
PA610	GO	In situ interfacial polymerization	2014	⁴⁴
PA6	GO, RGO	In situ ring opening polymerization	2014	⁴⁵
PA6/PA66	GNP	Melt blending	2014	⁴⁶
PA6	GO	In situ polymerization + melt blending	2014	⁴⁷
PA6	GO	In situ polymerization	2015	²⁵
PA1212	GO	Melt blending	2015	⁴⁸
PA6	G	Solution mixing	2015	⁴⁹
PA12	PEI-RGO	Melt blending	2015	⁵⁰
PA6	MLG	In situ polymerization	2015	⁵¹
PA6	FLG	Liquid reactive extrusion	2015	⁵²
PA6	GO	Melt blending	2015	⁵³
PA6	GNS	Melt blending	2015	⁵⁴
PA6	G	Solution mixing	2015	⁵⁵
PA6	GNP	Melt blending	2015	⁵⁶
PA12	G	Selective laser sintering	2015	⁵⁷
MC-PA	GO	In situ ring opening polymerization	2015	⁵⁸
PA6	SMA-FG	In situ polymerization + melt blending	2015	⁵⁹
PA6	SG+CF	Melt blending	2015	⁶⁰
PA6	MWNT-GO	Melt blending	2015	⁶¹
PA6	FG	Melt blending	2015	⁶²
PA6	GNP	Melt blending	2016	⁶³
CO-PA	G	Solution mixing	2016	⁶⁴
PA6,6	GNP	Solution mixing	2016	⁶⁵
PA6	SGR	In situ hydrolytic ring-opening polymerization	2016	⁶⁶
PA6	Amide-GO	In situ polymerization	2016	⁶⁷
PA6	G	Melt blending	2016	⁶⁸
PA11	GNP	Melt extrusion	2016	⁶⁹
PA6	G-GO	In situ polymerization	2016	⁷⁰
PA6	GF	In situ polymerization	2016	⁷¹
PA6	RGO	Melt blending	2016	⁷²
PA6	RGO	Solution mixing	2017	⁷³
CO-PA	CRGO	In situ reduction	2017	⁷⁴
PA66	GNP	Melt blending	2017	⁷⁵
PA6	GOS	Melt blending	2017	⁷⁶
PA6	GO	In situ ring opening polymerization	2017	⁷⁷
PA6	GO	Solution mixing	2017	⁷⁸
PA1010/FPA	GO	Solution mixing	2017	⁷⁹
PA6/EPR	GO	Solution mixing	2017	⁸⁰
MC-PA6	RGO	In situ synthesis	2017	⁸¹
MC-PA6	GN-PEG	In situ synthesis	2017	⁸¹
PA12	GNP	Melt blending	2017	⁸²
PA11	GO	In situ polymerization	2017	⁸³
PA6,6	GNP	Melt blending	2017	⁸⁴
PA6	GO	Melt blending	2017	⁸⁵
PA12	GNP	Melt blending	2017	⁸⁶
MC-PA6	G-APDMC	In situ synthesis	2017	⁸⁷
PA6	G	Melt blending	2017	⁸⁸
PEA	GO	In situ anionic copolymerization	2017	⁸⁹
PA6	G	In situ polymerization	2017	⁹⁰
PA1010/PTA	GNP	Solution mixing	2017	⁹¹
PA6	G	Melt blending	2018	⁹²
PA11	G	In-situ polymerization	2018	⁹³
PA12	G	Solution mixing	2018	⁹⁴
PA6	AMG	Melt blending	2018	⁹⁵
PA6	G	In situ polymerization	2018	⁹⁶
PA6	GO	Solution mixing	2018	⁹⁷
PA66	RGO	In situ polymerization	2018	⁹⁸
PA12	RGO	Melt blending	2018	⁹⁹
PA6	GOHP	Melt blending	2018	¹⁰⁰
PA	GO	In situ polymerization	2018	¹⁰¹
PA6	CORG	Melt blending	2019	¹⁰²
PA6T/6	G	In situ polymerization	2019	¹⁰³
MC PA	G	Solution mixing	2019	¹⁰⁴
PA6	RGO	Melt blending	2019	¹⁰⁵

G: graphene; PA: polyamide; G-PA: graphene–polyamide nanocomposites; FG: functionalized graphene; RGO: reduced graphene oxide; GO: graphene oxide; GNP: graphene nanoplatelet; PEG: polyethylene glycol; GF: graphene foam; GOS: graphene oxide-silica nanohybrid; PEI: polyethylenimine; HNT: halloysite nanotubes; CORG: carbon monoxide reduced graphene; GOHP: graphene oxide hindered phenol; MC PA: monomer casting polyamide; AMG: amino-modified graphene oxide; PTA: polythioamide G-APDMC: graphene 3-aminopropyl-terminated poly- (dimethyl siloxane); EPR: ethene-propene elastomer; CRGO: chemically reduced graphene oxide; SGR: sulfonated graphene; SMA: poly (styrene–maleic anhydride); SG+CF: solar graphene carbon fiber; MWNT: multi-walled carbon nanotubes; FLG: few-layer graphene; MLG: multi-layer graphene; TRGO: thermally reduced graphene oxide.

In situ polymerization

In situ polymerization is a suitable technique for the preparation of polymer nanocomposites based on graphene. In this method, monomers present in and out of the graphene interlayers to polymerize to form polymer nanocomposites. In situ polymerization is the important technique for graphene/PA6 nanocomposites. Xu et al.¹¹ Prepared graphene/PA6 nanocomposites using in situ ring-opening polymerization of caprolactam in the presence of GO. This technique opens a new possibility to fabricate graphene-based nanocomposites of polymers and offers wide range of applications. The nanocomposite prepared by condensation reaction between carboxylic graphene oxide (GO) and amino ends of PA6 chains. Graphene showed good solubility and compatibility to PA6. The blue bonds in the PA6-grafted graphene represent restored conjugated bonds through high-temperature reduction and the red curves represent the grafted PA6 macromolecular chains (Figure 4).

Figure 4.

Schematic of PA graphene composites by in situ ring-opening polymerization of caprolactam in the presence of GO.

Das et al.¹⁴ have reported a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets and successfully coat the graphene noncovalently with PA610 and PA66, and the stability of the graphene dispersion in water is enhanced. Zheng et al.¹⁵ have also reported the in situ polymerization of GO/PA6 nanocomposites. These nanocomposites show a low percolation threshold of approximately 0.41 vol% and high electrical conductivity of approximately 0.028 S m⁻¹ with only approximately 1.64 vol% of GO. This method showed potential for the mass production of electrically conductive polymer/reduced graphene oxide (RGO) nanocomposites. Dixon et al.²⁵ developed GO-PA6 nanocomposites by in situ polymerization technique. The nanocomposite prepared by direct synthesis of the polymer in the presence of the GO/water dispersion. High levels of interfacial interaction improved degradation temperature and tensile strength 64.9 MPa at 0.65 wt% was obtained.

Zhang et al.¹⁸ prepared GO-reinforced PA6 composites via in situ anionic ring-opening polymerization. A two-step new and facile method was employed in the synthesis of PA6-GO nanocomposites. The ε-caprolactam (CL) was firstly fixed onto the GO sheets coupling by 4,4′-methylenebis (phenyl isocyanate), and then PA6 was grafted from the GO surface by in situ anionic ring-opening polymerization. The polymerization processing was effectively carried out at relatively low reaction temperature (150^°C) and in a short reaction time (20–40 min) by using a caprolactam magnesium bromide (C1) initiator in combination with a difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) activator (Figure 5).

Figure 5.

Schematic representation of graphene oxide with caprolactam and subsequent grafting of PA6 by in situ anionic ring-opening polymerization.

Ding et al.³⁷ reported the thermal conductive PA6/graphene (PG) composite was synthesized by in situ ring-opening polymerization reaction using CL as the monomer, 6-aminocaproic acid as the initiator, and RGO as the thermal conductive filler. The uniform dispersion and interconnected structure of RGO sheets in the nanocomposite helped to improve the λ from 0.196 W m⁻¹ K⁻¹ of neat PA6 to 0.416 W m⁻¹ K⁻¹ of PG-10.0 composite. The application of PG in thermal interface materials, connectors, and thermal management systems. The brown bonds in PG composite represent the restored sp² C after the thermal reduction at 250 C and the red curves represent the grafting PA6 chains (Figure 6).

Figure 6.

Schematic representation of synthesis of graphene/PA6 nanocomposites by in situ polymerization with simultaneous thermal reduction from GO to RGO.

Lee et al.⁴⁴ developed PA610/PA610-grafted GO composites by using acyl-functionalized GO and in situ interfacial polymerization. The PA610 grafted on GO enhanced the dispersion of GO in the PA610 matrix and the interfacial adhesion between GO and PA610. The thermal properties of PA610/GO-g-PA610 and PA610/GO composites were improved with increasing GO-g-PA610 and GO contents, respectively, compared with pure PA610. O’Neill et al.^45,67 presented an efficient method to prepare PA6 nanocomposites containing highly dispersed oxidized graphene by in situ polymerization. The technique apparently maintained the single-layer nature of GO in the nanocomposite by direct synthesis of the polymer in the presence of the GO/water dispersion. Nguyễn et al.⁴⁷ reported the preparation of PA6 and GO nanocomposites. PA6-grafted GO was prepared using an in situ polymerization method with GO dispersed in an CL monomer with 6-aminocaproic acid as the initiator and in situ polymerization with GO dispersed in an CL monomer with 6-aminocaproic acid as the initiator. The MB chips were well compounded with the virgin PA6 chips with good processability.

Fu et al.⁵¹ have reported the effective method to prepare PA6 multilayer graphene nanocomposites via in situ polymerization. The mechanical and thermal properties of PA6 nanocomposites were investigated with low unmodified multilayer graphene content of 0.01–0.5 wt%. The dispersion of multilayer graphene sheets in the polymer matrix was studied in extensive detail. The mechanical properties of the nanocomposites were significantly enhanced; the flexural modulus, flexural strength, and impact strength increased by approximately 97%, approximately 69%, and approximately 76% relative to pristine PA6. Furthermore, multilayer graphene can increase the crystallization speed and improving the crystallization temperature of PA6/multilayer graphene nanocomposites. Wang et al.⁵⁸ have prepared MC PA/GO-CTAB composites by in situ ring-opening polymerization. The tensile strength of the composites was greatly improved even though at very low containing of GO-CTAB. The mechanical properties and the thermal decomposition temperature were increased at various degrees. Wang et al.⁶⁶ developed PA6/sulfonated graphene composites using sulfonated graphene by in situ hydrolytic ring-opening polymerization of CL. The PA6 chains were covalently grafted onto sulfonated graphene sheets by the condensation reaction between the active amino groups at PA6 chain terminals and the sulfonic acid groups on sulfonated graphene sheets (Figure 7). These composites have simple preparation process, good mechanical properties, high-thermal conductivity, and excellent processability, providing great promises for the large-scale application in thermal conductive materials. Li et al.⁷¹ demonstrated that 3-D graphene structures constructed by graphene foam were introduced into PA6 for enhancing the thermal-conductive and anti-dripping properties of PA6 composites.

Figure 7.

Schematic representation of PA6/sulfonated graphene composites by in situ polymerization process.

Hocker et al.⁸³ prepared GO-based PA11 via in situ polymerization. These nanocomposites had elevated resistance to hydrolytic degradation. The results show 40% increase over PA11’s equilibrium molecular weight when aged in water at 100°C and 120°C, concentration 1 mg°g⁻¹ GO in PA11, and slight decrease in the amount of PA11 crystallinity prior to aging. The crystallinity of the PA11 was similarly affected by a reduction in chain mobility during annealing due to the GO nanoparticles and highly asymmetric nano-planar sheet structure. Li et al.⁸⁷ have produced MC PA6/graphene (GN)–3-aminopropyl-terminated poly-(dimethyl siloxane) (APDMS) nanocomposite via in situ polymerization by incorporation of polyethylene glycol (PEG) as a solid lubricant. Addition of PEG led to more effective grafting of PA6 molecules on GN surface. The tensile strength increased 12% and impact strength increased 20.6% with 0.5 wt% GN addition, while over 75% reduction in specific wear rate and 13% reduction in friction coefficient were obtained with 0.7 wt% GN addition. This work provides outstanding anti-wear MC PA6 nanocomposites to expand the applications of GN in the engineering plastic (Figure 8).

Figure 8.

Synthesis of MC PA6/GN-APDMS nanocomposite via in situ polymerization.

Yousefian-Arani et al.¹⁰¹ developed semi-aromatic PA-based GO nanocomposites by in situ polymerization. In this preparation, GO or SGO nanosheets mixed into the PA matrix, during interfacial polymerization. There were significant improvements observed in thermal stability, electrical conductivity, and dielectric constant of PA by adding 0.1% SGO in the PA matrix. Duan et al.⁹⁸ have produced PA66/RGO nanocomposite by a one-step process of in situ polymerization. The nanocomposites produced by a condensation reaction between the carboxylic acid groups on the GO surface and the terminal amino ends of PA66 chains. The Young’s modulus and tensile strength of the nanocomposites were increased to 660 MPa and 84 MPa, respectively, which offered a wider application of the PA66 materials.

Wang et al.⁹⁶ have prepared PA6 nanocomposite with low graphene content by in situ polymerization. A 3-D graphene network was created in PA6 through the reduction and self-assembly of GO, and then PA6 nanocomposites with low graphene content were fabricated through in situ polymerization. The 3-D graphene network can suggestively improve the thermal conductivity of PA6. In the case of the PA6 with only 0.25 wt% graphene, its thermal conductivity is 0.69 W m⁻¹ K⁻¹, about 2.88 times of that of the neat PA6. Moreover, the mechanical properties and water resistance of PA6 also have increased with the incorporation of the 3-D graphene network (Figure 9).

Figure 9.

Schematic representation of GNPA6 nanocomposites: (a) fabrication of PA6 monomer filled 3-D graphene network by self-assembly of reduced GO and (b) in situ polymerization of PA6 in the resultant 3-D graphene network.

Zhuang et al.¹⁰⁴ prepared monomer-casting PA/graphene nanocomposite by in situ polymerization (Figure 10). The pre-dispersion method led to good dispersion of graphene in MC PA. The results of nanocomposites indicated that thermal conductivity and thermal stability increased.

Figure 10.

Schematic representation of MC-PA/graphene nanocomposite by in situ polymerization: (a) pre-dispersion process and (b) preparation of nanocomposites.

Wang et al.¹⁰³ produced semi-aromatic PA6T-co-6(PA6T/6)/GO composites by in situ polymerization (Figure 11). PA6T chain grafted on graphene sheets by strong hydrogen bonding produces polymer-bridged graphene network structure which enhanced mechanical properties of nanocomposites at small amount of GO (2 wt%).

Figure 11.

Schematic representation of PA6T-graphene nanocomposite by in situ polymerization. PA: polyamide. Source: Reproduced from Wang et al.¹⁰³ with permission from Elsevier.

Melt blending

Melt blending is one of the useful techniques to produce G-PA nanocomposites. In melt blending, graphene is mixed up with polymer by mechanically or using extruder, melt spinning to prepare G-PA nanocomposites. Rafiq et al.¹² prepared ultra-toughened functionalized graphene (FG)/PA12 composite by melt blending and investigated the effect of FG on the mechanical properties of PA12. With small amount of FG caused significant improvement in the toughness of the PA12 due to increase in γ-phase of PA12. Tensile strength and elongation at break of the PA12 is improved by approximately 35% and approximately 200%, respectively. Yan et al.¹⁹ prepared electrically conductive PA12/graphene binary nanocomposites with maleated polyethylene-octene rubber by melt blending. Zhang et al.²¹ synthesized graphene/PA6 composites by melt processing. With the use of graphene, the crystalline temperature improved due to heterogeneous nucleation and thermal properties of PA6 also increased.

Hong et al.²⁷ prepared graphene/PA6 nanocomposites by melt mixing. The graphene nanosheets coated with Co₃O₄ and NiO (denoted as GNSeCo₃O₄ and GNSeNiO) and then melt blend with PA6. The GNSeCo₃O₄ and GNSeNiO are well dispersed in PA6 and significantly decrease the gaseous products from PA6. The thermal stability of the composites was improved as evidenced by the increase in decomposition temperature and reduction in maximum decomposition rate. jin et al.³¹ prepared high performance of graphene/PA11 and PA12 nanocomposites by direct melt compounding. The ultimate tensile strength, fracture toughness, elongation at break, and impact failure energy of the PA12 were significantly increased by approximately 35%, approximately 75%, approximately 200%, and approximately 85%, respectively, when only 0.6 wt% FG was incorporated, and the tensile and fracture toughness of PA11 were slightly improved compared to PA12. Barrier resistances of the PA11 were improved.

Gaikwad et al.³² developed PA11/nanographene platelets (NGPs) nanocomposites by melt blending with using co-rotating twin-screw extruder to produce nanocomposite master batch pellets. The tensile modulus and flexure modulus with increases in the wt% of NGPs within PA11 matrix. There was no change in the flammability properties with increase in the NGP wt%. Co-rotating twin-screw extrusion and high shear action involved in mixing resulted in uniform dispersion of NGPs in PA11. Li et al.⁴⁰ synthesized a novel RGO decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite as the additive in PA6. The flame-retardant properties of PA6 were significantly improved. Xu et al.⁴⁶ developed PA6/PA66/GNP thermal composites by melt-blending method. The thermal conductivity of composite containing 50 wt% of GNP was measured as 5.03 W m^–1 K^–1 at 30°C, indicating an increase of more than 15 times compared with that of the neat PA6. Cai et al.⁴⁸ prepared PA1212/GO composites by two-step melt-blending process. GO solution was mixed with an ethanol-soluble PA solution then melt-compounded with a PA1212. With the addition of GO, crystallinity in the composites increased slightly.

Roy et al.⁵⁰ prepared PA12/polyethylenimine (PEI)-RGO composites by melt mixing process. The thermal stability of PA12 significantly improved with the addition of PEI-RGO and glass transition temperature increased. Mayoral et al.⁵⁶ prepared PA6/graphene nanoplatelet composites via twin-screw extrusion. A small increase in crystallinity and a maximum enhancement of 420% in Young’s modulus were achieved at 20 wt% loading of GNPs. Liu et al.⁶² reported graphene non-covalently functionalized with amino-terminated dendronized PA (DPA-GNs) filled into the PA6 to prepare nanocomposites. The functionalization of graphene enhanced dispersion and interface interaction between graphene and PA6. The thermal conductivity of DPA-GNs/PA6 composite approximately increased by 200% with low graphene content, compared with neat PA6. The decomposition temperatures of DPA-GNs/PA6 were approximately increased by 20°C. Wu et al.⁶⁸ prepared graphene/PA6 nanocomposites by masterbatch melt mixing with a kneader mixer. The rheological behavior and viscous activation energy of these nanocomposites were investigated. Graphene/PA6 masterbatch (10 wt%) produced by twin-screw extruder. The viscosities of the graphene/PA6 composites improved with increasing graphene concentration. As the concentration of graphene increased, the flow behavior changed from Newtonian to pseudo-plastic flow. They found most suitable processing parameters for maximizing the exfoliation stress level, the range from 25 kPa to 30 kPa at a 100 s⁻¹ shear rate and 240°C.

Rashmi et al.⁶⁹ developed production technique for multifunctional bio-based PA11/graphene nanocomposites by melt extrusion processes via masterbatch dilution. Addition of graphene improves the electrical conductivity, crystallization temperature, degree of crystallinity, tensile strength, and dielectric constant of PA11. The tensile strength increases by approximately 14–25% and modulus by approximately 35–56% for 0.5–5 wt% GNP, respectively. With extensive usage of carbon-based nanofillers will cause emissions to the environment and increase in human exposure to nanofillers. Therefore, manufacturing of carbon-based nanofillers in plastic parts often a key issue. This production process of a GNP masterbatch in PA is dust-free processing method with lower risks compared to the bulk carbon nanofillers as well as an easier method for handling the material. Cho et al.⁷² prepared the PA/reduced graphene nanocomposites by melting blending. The chemical compatibility between RGO and PA enhanced by using titanate coupling agent (TCA). Covalent bonds can be formed by the chemical reaction between hydroxyl groups on the GO and alkoxy group of titanate molecules. The TCA molecule can replace of water of hydration at the RGO surface, which can improved thermal conductivity. With using RGO loading level (5 wt%), PA/TCA RGO composite has 53% higher thermal conductivity. Moreover, PA/TCA-RGO composite material can be used in thermal management for electronic as well as photonic applications. The LED lamp combined with PA/TCA-RGO composite as heat sink also displays better strength due to its excellent thermal dissipation.

Scaffaro and Maio⁷⁶ have prepared GO-silica nanohybrid (GOS)/PA6 nanocomposites by melt blending process. GOS was prepared in water and used as a filler for PA6-based nanocomposites. This method can be considered green because the reactions in aqueous environment which reduces the time and avoid toxic solvents. GOS prepared by 150 mL of water under mild operative conditions (T = 120°C for about 30 min at atmospheric pressure). Moreover, GOS provides toughening at low filler contents (up to +210%), the simultaneous stiffening (up to +180%), and strengthening (up to +210%) (Figure 12).

Figure 12.

Schematic representation of nanocomposites (a) (direct melt mixing of PA6 and GO), nanocomposites (b) (melt mixing of PA6, GO and nanosilica), and nanocomposites (c) (synthesis of lasagna-like self-assembled GOS nanohybrids and melt mixing with PA6).

Zhu et al.⁸² developed 3-D printable PA12/GNPs nanocomposites by melt blending. The thermal conductivity (k) and elastic modulus (E) of 3-D printed PA12/GNPs parts increased by 51.4% and 7%, respectively. The ultimate tensile strength, thermal conductivity, elastic modulus, and higher thermal stability of PA12/GNPs are improved. The crystallinity decreased by using GNPs content of 6 wt%. Furthermore, raster angle of 8° printed PA12/GNPs parts showing the reinforcement efficiency. Song et al.⁸⁸ prepared PA6/graphene (PG) composites by melting, stirring through an internal mixer. They demonstrated the bridge effect of silicon carbide whiskers (SiCw) on the enhancement of thermal conductivity in the experimental results. The thermal conductivity of PG composites increased with SiCw, particularly in the through-plane direction. The mechanical properties of the composites were synchronously enhanced. The thermal conductivity enhancement of the through-plane direction can reach as high as 199%, the maximum can reach 508% related to the PA matrix.

Scaffaro and Maio⁹² developed two-step synthesis technique for PA6 graphene nanocomposites by solvent-assisted melt blending (Figure 13). The nanocomposites prepared by three two-step methods and two different loading content of GO. Among the three techniques, method III was quick and involved less consumption of water.

Figure 13.

Schematic representation of preparation of PA6 graphene nanocomposites.

Chen et al.⁹⁵ prepared N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AAPS)-modified GO PA6 nanocomposite by melt blending (Figure 14). The nanocomposites revealed that the AMG owned improved dispersity, high thermal stability, tensile strength, and tribological properties such as friction behavior and wear rate.

Figure 14.

Schematic representation of the synthesis of AMG(AAPS)/PA nanocomposites.

Li et al.¹⁰⁰ prepared PA6/GO-g-hindered phenol antioxidant nanocomposites by melt blending. PA6 molecules onto GO surface were realized by forming hydrogen bonding, and GO was exfoliated and uniformly distributed in the matrix. The nanocomposite showed increase in the oxidation induction time and thermal degradation temperature. The retention of reduced viscosity and tensile strength were improved (Figure 15).

Figure 15.

Schematic representation of preparation of PA6/GO-HP nanocomposites.

Solution mixing

Perhaps the simplest applied processing technique for graphene-modified polymer nanocomposites is the solution mixing or solvent blending technique, which involves mixing of polymer and graphene in a suitable solvent. The nanocomposite is produced by precipitating or casting a film. During the solvent blending process, graphene dispersed in a suitable solvent with the polymer. The solvent removed by evaporation or distillation process. Chiu and Huang²⁰ prepared PA46/GO nanocomposites by solution mixing technique. The morphological observations showed the compatibility between PA46 and GO. With the small amounts of GO facilitate the nucleation and overall crystallization of PA 46. The stiffness of PA46 increased with GO. Pan et al.²³ presented preparation of PA11/graphene coatings. The wear life of composite coatings increased compared to the neat PA11 coating. Jacobs et al.²⁴ prepared PA11/NGP nanocomposites by solvent blending. The addition of NGPs showed an initial increase in thermal stability and crystallization temperature. Fathali et al.³⁸ developed new method of PA-decorated graphene sheet as a potential antimicrobial agent. The thermal stability and antibacterial properties of PA film increase with graphene. Hou et al.³⁹ synthesized amine FG/PA6 nanocomposites by solution mixing (Figure 16). Prepared nanocomposites GO, GO–NH₂, and GO–(CH2)₆ NH₂ showed that the nature of the functional groups affects the grafting chemistry of PA6 to graphene.

Figure 16.

Synthesis of amine FG/PA6 nanocomposites.

Gong et al.⁴⁹ prepared PA6/graphene composites modified through polymeric modification of graphene by solvent blending. Song et al.⁵⁵ have prepared PA6/graphene nanocomposites by solution blending and find effect of polymer modifier chain length on thermal conductive property of PA6/graphene nanocomposites (Figure 17).

Figure 17.

Synthesis of GA composites (GA represents PA 6).

Liu et al.⁶⁴ developed graphene/CO-PA nanocomposites by solution mixing method. They have prepared the simple method to make CO-PA nanocomposites with perfect properties. de Melo et al.⁹⁷ prepared GO-reinforced PA6 nanocomposites by solution mixing. Evie et al.⁶⁵ have prepared PA66/graphene nanoplatelet composite films obtained from a new solvent by solution blending technique. Ma et al.⁷³ reported preparation of highly conductive composites with segregated structure based on PA6 and reduced GO by solution mixing. Allahbakhsh et al.⁷⁸ prepared 3-aminopropyl-triethoxysilane-functionalized rice husk and rice husk ash-reinforced PA6/GO sustainable nanocomposites. Kausar⁹¹ prepared PA1010/PTA blend reinforced with GNP by solution mixing method. The nanocomposite revealed optimum tensile strength (40 MPa), impact strength (1.9 MPa), and flexural modulus (1373 MPa) to manufacture automotive part (Figure 18).

Figure 18.

PA1010/PTA/GNP nanocomposite.

Conclusion

The preparation of G-PA nanocomposites has been reviewed. There are three main methods to prepare G-PA nanocomposites such as in situ polymerization, solvent blending, and melt blending. In situ polymerization and solution blending produce composites with a high degree of consistency for research purposes, but these processes were very difficult to scale up, while the environmental concerns also need to be considered. On the other hand, making use of the conventional melt mixing process, nanocomposites can be produced that may still be performing enough for some applications. In situ polymerization and solvent blending can achieve a fine dispersion of graphene in polymer matrices nevertheless use of hazardous chemicals and removal of solvent lead to aggregation, which shows potential risks as these two methods are environment unfriendly. Melt blending is environmentally friendly and suitable for mass production, but the dispersion of graphene in the polymer matrix is not good. It has been shown that in the graphene structure, the number of layers, the specific surface, and the chemical functionalization of these fillers, all play a major role in the final performance of the G-PA nanocomposites.

Moreover, the variety of preparation methods that have been presented in this review offers different pathways, depending upon the perceived application of the material. The scaling-up of the production of high-quality graphene is a determinant factor for the production on commercial scale of these nanocomposites with useful properties. So far, the combination of graphene and PA has been playing a ubiquitous role in the field of research encompassing significant enhancement in the mechanical, thermal, electrical, and barrier properties. As future unfolds, the advancement in the achievement of the interaction between graphene and PA without modification process and cost of graphene. In this review, potential synthesis of G-PA nanocomposites has been highlighted. It concludes significant properties, synthesis, and preparation method. In the field of material science, G-PA nanocomposites are one of the most fortunate developments. Hence, we can say undoubtedly that G-PA nanocomposites are the materials for future innovation.

Future scope of work

A respectable amount of work has been done and important conclusions have been drawn. Continued overwhelming response from academicians and researches, graphene provides an exciting platform to study engineering, physics, chemistry, and materials science of unique 2-D systems as well as offers a route toward user friendly end products conducting polymer graphene composite. A reviewed research may lead to a new dimension for high-performance nanocomposite materials for a wide range of applications such as energy devices, electronics, automobiles, sports industries, aerospace, defense, solar cell, fuel cell, supercapacitor, gas detection, lithium ion batteries and functional conducting electrodes for technical relevance, and so on. Despite these interesting developments, a lot remains to be done about both essential understanding and the improvement in intrinsic methods, synthesis as well as properties. Appropriate surface modification of graphene to develop strong interaction between matrix and nanofillers is yet the blistering area of research. There are countless challenges that need to be addressed like to prepare single-layer graphene, development of fine interaction between graphene and matrix without any modification process, design of appropriate method for processing, and property improvement at very low loading levels are among the foremost argues. Although, some important parameters such as low-cost material with excellent quality and high production demand on large scale is yet to come. There is still room for broad fundamental research for basic understanding of the subject and their future commercial utilization. Besides the laboratory scale research to introduce graphene in PA for product applications, it is essential to scrutinize that how nanomaterials behave under industrial processing conditions. However, research is never ending task thus more future work on G-PA nanocomposite can be ultimately advanced by upgraded methods and technologies.

Footnotes

Acknowledgements

The authors are thankful to the Department of Chemistry, Gujarat University, Ahmedabad, for providing the essential facilities. UGC-Info net and Information and Library Network Centre, Gujarat University are acknowledged for providing the resource facilities.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Dilip V Vasava

References

Geim

Novoselov

. The rise of graphene. Nat Mater 2007; 6: 183–191.

Yao

Yang

. Recent advances in graphene/polyamide 6 composites: a review. RSC Advances 2015; 5: 61688–61702.

Wan

Huang

Chen

. Focusing on energy and optoelectronic applications: a journey for graphene and graphene oxide at large scale. Acc Chem Res 2012; 45: 598–607.

Kiew

Lee

, et al. Assessing biocompatibility of graphene oxide-based nanocarriers: a review. J Control Release 2016; 226: 217–228.

Sastri

. Engineering Thermoplastics. In: Sastri VR (ed) Plastics in Medical Devices. Boston: William Andrew Publishing, 2010, pp. 121–173.

Singh

Ohlan

Dhaw

. Polymer-graphene nanocomposites: preparation, characterization, properties, and applications. In: Nanocomposites - New Trends and Developments. 2012: 37–71.

Uyor

Popoola

API

Popoola

, et al. Enhanced dielectric performance and energy storage density of polymer/graphene nanocomposites prepared by dual fabrication. J Thermoplast Compos Mater. Epub ahead of print 11 October 2018. DOI: 10.1177/0892705718805522.

Kausar

. Trends in graphene reinforced polyamide nanocomposite for functional application: a review. Polym-Plast Technol Mater 2019; 58: 917–933.

Steurer

Wissert

Thomann

, et al. Functionalized graphenes and thermoplastic nanocomposites based upon expanded graphite oxide. Macromol Rapid Commun 2009; 30: 316–327.

10.

Scully

Bissessur

. Decomposition kinetics of nylon-6/graphite and nylon-6/graphite oxide composites. Thermochimica Acta 2009; 490: 32–36.

11.

Gao

. In situ polymerization approach to graphene-reinforced nylon-6 composites. Macromolecules 2010; 43: 6716–6723.

12.

Rafiq

Cai

Jin

, et al. Increasing the toughness of nylon 12 by the incorporation of functionalized graphene. Carbon 2010; 48: 4309–4314.

13.

Liu

I-H

Fukushima

, et al. Influence of processing on morphology, electrical conductivity and flexural properties of exfoliated graphite nanoplatelets-polyamide nanocomposites. Carbon letters 2010; 11: 279–284.

14.

Das

Wajid

Shelburne

, et al. Localized in situ polymerization on graphene surfaces for stabilized graphene dispersions. ACS Appl Mater Interfaces 2011; 3: 1844–1851.

15.

Zheng

Tang

Zhang

H-B

, et al. In situ thermal reduction of graphene oxide for high electrical conductivity and low percolation threshold in polyamide 6 nanocomposites. Compos Sci Technol 2012; 72: 284–289.

16.

Liu

Hou

Peng

, et al. Fabrication and characterization of polyamide 6-functionalized graphene nanocomposite fiber. J Mater Sci 2012; 47: 8052–8060.

17.

Albañil-Sanchez

Romo-Uribe

Flores

, et al. Electrospun nylon-graphene nanocomposites synthesis and microstructure. MRS Proceedings 2012; 1453: 1-8.

18.

Zhang

Fan

, et al. Facile preparation route for graphene oxide reinforced polyamide 6 composites via in situ anionic ring-opening polymerization. J Mater Chem 2012; 22: 24081–24091.

19.

Yan

Zhang

Jia

, et al. Improved electrical conductivity of polyamide 12/graphene nanocomposites with maleated polyethylene-octene rubber prepared by melt compounding. ACS Appl Mater Interfaces 2012; 4: 4740–4745.

20.

Chiu

F-C

Huang

. Phase morphology and enhanced thermal/mechanical properties of polyamide 46/graphene oxide nanocomposites. Polym Test 2012; 31: 953–962.

21.

Zhang

Zhu

, et al. Preparation and properties of graphene/polyamide 6 composites by Melt compounding. Adv Mater Res 2012; 621: 31–34.

22.

Liu

Peng

Tan

, et al. Preparation and properties of polyamide 6-functionalized nanometer-Sized graphene composite fiber. Key Eng Mater 2012; 519: 20–23.

23.

Pan

Zhang

, et al. Preparation and tribological properties of polyamide 11/Graphene coatings. Polym-Plast Technol Eng 2012; 51: 1163–1166.

24.

Jacobs

Tate

Olson

, et al. Thermal characterization of polyamide 11/nanographene platelet nanocomposites. J Nanosci Nanotechnol 2012; 12: 1799–1805.

25.

Dixon

Lemonine

Hamilton

, et al. Graphene oxide–polyamide 6 nanocomposites produced via in situ polymerization. J Thermoplast Compos Mater 2013; 28: 372–389.

26.

Mészáros

Szakács

. Elastic recovery at graphene reinforced pa 6 nanocomposites. In: 5th International Conference, Brno, Czech Republic, EU, 16–18 October 2013, pp. 51–55.

27.

Hong

Song

Hull

, et al. Facile preparation of graphene supported Co3O4 and NiO for reducing fire hazards of polyamide 6 composites. Mater Chem Phys 2013; 142: 531–538.

28.

Menchaca-Campos

García-Pérez

Castañeda

, et al. Nylon/Graphene oxide electrospun composite coating. Int J Polym Sci 2013; 2013: 1–9.

29.

Scaffaro AMaR. Polyamide 6/graphene oxide nanohybrids. In: Proceedings of the Polymer Processing Society 29th Annual Meeting, Nuremberg (Germany), 15–19 July 2013.

30.

Yuan

Wang

, et al. Unusual toughening effect of graphene oxide on the graphene oxide/nylon 11 composites prepared by in situ melt polycondensation. Compos B 2013; 55: 215–220.

31.

Jin

Rafiq

Gill

, et al. Preparation and characterization of high performance of graphene/nylon nanocomposites. Eur Polym J 2013; 49: 2617–2626.

32.

Gaikwad

Tate

Theodoropoulou

, et al. Electrical and mechanical properties of PA11 blended with nanographene platelets using industrial twin-screw extruder for selective laser sintering. J Compos Mater 2012; 47: 2973–2986.

33.

Pant

Park

, et al. RGO/Nylon-6 composite mat with unique structural features and electrical properties obtained from electrospinning and hydrothermal process. Fiber Polym 2013; 14: 970–975.

34.

Yuan

Zhang

. Transparent PMMA-based nanocomposite using electrospun graphene-incorporated PA-6 nanofibers as the reinforcement. Compos Sci Technol 2013; 89: 134–141.

35.

Liu

H-H

Peng

W-W

Hou

L-C

, et al. The production of a melt-spun functionalized graphene/poly(ε-caprolactam) nanocomposite fiber. Compos Sci Technol 2013; 81: 61–68.

36.

Pant

Pokharel

, et al. Photocatalytic TiO2–RGO/nylon-6 spider-wave-like nano-nets via electrospinning and hydrothermal treatment. J Membrane Sci 2013; 429: 225–234.

37.

Ding

Song

, et al. Highly thermal conductive composites with polyamide-6 covalently-grafted graphene by an in situ polymerization and thermal reduction process. Carbon 2014; 66: 576–584.

38.

Fathali

Rahimnejad

Yousefi

. Polyamide decorated graphene sheet as a potential antimicrobial agent: synthesis, characterization. Adv Mater Res 2013; 829: 461–465.

39.

Hou

Tang

, et al. Preparation and physico-mechanical properties of amine-functionalized graphene/polyamide 6 nanocomposite fiber as a high performance material. RSC Adv 2014; 4: 4848–4855.

40.

Chen

, et al. A novel reduced graphene oxide decorated with halloysite nanotubes (HNTs-d-rGO) hybrid composite and its flame-retardant application for polyamide 6. Exp Polym Lett 2014; 8: 450–457.

41.

Mittal

Chaudhry

Luckachan

. Biopolymer – thermally reduced graphene nanocomposites: structural characterization and properties. Mater Chem Phys 2014; 147: 319–332.

42.

Ding

Song

, et al. Influence on thermal conductivity of polyamide-6 covalently-grafted graphene nanocomposites: varied grafting-structures by controllable macromolecular length. RSC Adv 2014; 4: 18782–18791.

43.

Zhang

Wang

Man

, et al. Isothermal crystallization kinetics of in situ nylon 6/graphene composites by differential scanning calorimetry. Polym Eng Sci 2014; 54: 2610–2616.

44.

Lee

Yun

Kim

, et al. Nylon 610/Graphene oxide composites prepared by in-situ interfacial polymerization. J Nanosci Nanotechnol 2014; 14: 5703–5707.

45.

O’Neill

Bakirtzis

Dixon

. Polyamide 6/graphene composites: the effect of in situ polymerisation on the structure and properties of graphene oxide and reduced graphene oxide. Eur Polym J 2014; 59: 353–362.

46.

Lin

Chen

, et al. Preparation and characterization of GNP/Nylon composites. Appl Mech Mater 2014; 556-562: 339–342.

47.

Nguyễn

Choi

S-M

Kim

D-H

, et al. Preparation and characterization of nylon 6 compounds using the nylon 6-grafted GO. Macromol Res 2014; 22: 257–263.

48.

Cai

Meng

Han

, et al. Reinforcing polyamide 1212 with graphene oxide via a two-step melt compounding process. Compos Part A: Appl Sci Manufac 2015; 69: 115–123.

49.

Gong

Yin

, et al. Nylon-6/Graphene composites modified through polymeric modification of graphene. Compos B: Eng 2015; 73: 49–56.

50.

Roy

Tang

Das

, et al. Enhanced molecular level dispersion and interface bonding at low loading of modified graphene oxide to fabricate super nylon 12 composites. ACS Appl Mater Interfaces 2015; 7: 3142–3151.

51.

Liu

Zhao

, et al. A commercial production route to prepare polymer-based nanocomposites by unmodified multilayer graphene. J Appl Polym Sci 2015; 132: 42742.

52.

Zhao

Yan

, et al. A facile route to prepare few-layer graphene/polyamide 6 nanocomposites by liquid reactive extrusion. RSC Adv 2015; 5: 77316–77323.

53.

Maio

Fucarino

Khatibi

, et al. A novel approach to prevent graphene oxide re-aggregation during the melt compounding with polymers. Compos Sci Technol 2015; 119: 131–137.

54.

Alirezaei Hoor

Morshedian

Ahmadi

, et al. Effect of graphene nanosheets on the morphology, crystallinity, and thermal and electrical properties of super tough polyamide 6 using SEBS compounds. J Chem 2015; 2015: 1–6.

55.

Song

Yang

Ding

, et al. Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites. Compos Part A: Appl Sci Manufact 2015; 73: 232–241.

56.

Mayoral

Harkin-Jones

Khanam

, et al. Melt processing and characterisation of polyamide 6/graphene nanoplatelet composites. RSC Adv 2015; 5: 52395–52409.

57.

Makuch

Trzaska

Skalski

, et al. PA-G composite powder for innovative additive techniques. Compos Theor Pract 2015; 15(3): 152–157.

58.

Wang

Liu

Zhang

, et al. In situ polymerization to prepare graphene-toughened monomer cast nylon composites. J Mater Sci 2015; 50: 6291–6301.

59.

Zhou

Liu

Zhang

. Poly(styrene-maleic anhydride) functionalized graphene oxide. J Appl Polym Sci 2015; 132: 41987.

60.

Zang

Zhu

Jiao

. Enhanced mechanical and electrical properties of nylon-6 composite by using carbon fiber/graphene multiscale structure as additive. J Appl Polym Sci 2015; 132: 41968.

61.

Biswas

Kar

Arora

, et al. A unique strategy towards high dielectric constant and low loss with multiwall carbon nanotubes anchored onto graphene oxide sheets. RSC Adv 2015; 5: 24132–24138.

62.

Liu

Hou

, et al. Thermal properties of PA6 nanocomposites by addition of graphene non-covalently functionalized with dendronized polyamide. J Thermal Analy Calorim 2015; 120: 1303–1310.

63.

Ferda

. Effect of crystalline form (γ) of polyamide 6 / graphene nanoplatelets (PA6/GN) nanocomposites on its structural and thermal properties. Mach Technol Mater 2016; 10: 56–59.

64.

Liu

Wang

Wan

, et al. Electrical conductivity and mechanical properties of ionic liquid modified shear exfoliation graphene/CO-PA nanocomposites at extremely low graphene loading. Polym Compos 2017; 38: E277–E284.

65.

Papadopoulou

Pignatelli

Marras

, et al. Nylon 6,6/graphene nanoplatelet composite films obtained from a new solvent. RSC Adv 2016; 6: 6823–6831.

66.

Wang

Yang

, et al. Preparation and properties of nylon 6/sulfonated graphene composites by an in situ polymerization process. RSC Adv 2016; 6: 45014–45022.

67.

O’Neill

Bishop

Dalton

, et al. Preparation and properties of polyamide 6 nanocomposites covalently linked with amide functional graphene oxide. J Thermoplast Compos Mater 2016; 31: 162–180.

68.

Cheong

S-

Chang

. Rheological properties of graphene/nylon 6 nanocomposites prepared by masterbatch melt mixing. J Polym Res 2016; 23: 242.

69.

Rashmi

Prashantha

Lacrampe

, et al. Scalable production of multifunctional bio-based polyamide 11/graphene nanocomposites by melt extrusion processes via masterbatch approach. Adv Polym Technol 2016; 37(4): 1067–1075.

70.

Chen

Meng

, et al. Super-high thermal conductivity of polyamide-6/graphene-graphene oxide composites through in situ polymerization. High Perform Polym 2016; 29: 585–594.

71.

Shao

Song

, et al. Enhanced thermal-conductive and anti-dripping properties of polyamide composites by 3D graphene structures at low filler content. Compos Part A: Appl Sci Manufact 2016; 88: 305–314.

72.

Cho

E-C

Huang

J-H

C-P

, et al. Graphene-based thermoplastic composites and their application for LED thermal management. Carbon 2016; 102: 66–73.

73.

Zhu

, et al. Preparation of highly conductive composites with segregated structure based on polyamide-6 and reduced graphene oxide. Mater Lett 2017; 190: 71–74.

74.

Liu

Shao

Fang

, et al. Preparation and properties of chemically reduced graphene oxide/copolymer-polyamide nanocomposites. e-Polymers 2017; 17: 3–14.

75.

Sankara Narayana

Suman

KNS

Arun Vikram

. Investigation on dry sliding wear behavior of nylon66/GnP nano-composite. J Institut Eng (India): Ser D 2016; 98: 71–78.

76.

Scaffaro

Maio

. A green method to prepare nanosilica modified graphene oxide to inhibit nanoparticles re-aggregation during melt processing. Chem Eng J 2017; 308: 1034–1047.

77.

O’Neill

Archer

McIlhagger

, et al. Polymer nanocomposites: In situpolymerization of polyamide 6 in the presence of graphene oxide. Polym Compos 2017; 38: 528–537.

78.

Allahbakhsh

Noei Khodabadi

Hosseini

, et al. 3-Aminopropyl-triethoxysilane-functionalized rice husk and rice husk ash reinforced polyamide 6/graphene oxide sustainable nanocomposites. Eur Polym J 2017; 94: 417–430.

79.

Kausar

. Composite coatings of polyamide/graphene: microstructure, mechanical, thermal, and barrier properties. Compos Interface 2017; 25: 109–125.

80.

Kelnar

Kratochvíl

Kaprálková

, et al. Effect of graphene oxide on structure and properties of impact-modified polyamide 6. Polym-Plast Technol Eng 2018; 57: 827–835.

81.

Xiang

. Intercalation structure and highly enhancing tribological performance of monomer casting nylon-6/graphene nano-composites. Compos Part A: Appl Sci Manufact 2017; 95: 274–285.

82.

Zhu

Ren

Liao

, et al. Thermal and mechanical properties of polyamide 12/graphene nanoplatelets nanocomposites and parts fabricated by fused deposition modeling. J Appl Polym Sci 2017; 15: 45332.

83.

Hocker

SJA

Hudson-Smith

Smith

, et al. Graphene oxide reduces the hydrolytic degradation in polyamide-11. Polymer 2017; 126: 248–258.

84.

Sani

Manaf

MEA

Mohamad

, et al. Effects of nanographene addition on tensile and electrical properties of Nylon 6, 6 nanocomposites. In: Proceedings of Innovative Research and Industrial Dialogue’16, 2017, pp.35–36.

85.

Ayazi

Jaafarzadeh

. Graphene oxide/polyamide nanocomposite as a novel stir bar coating for sorptive extraction of organophosphorous pesticides in fruit juice and vegetable samples. Chromatographia 2017; 80: 1411–1422.

86.

Adel

El-Shazly

El-Wahidy

EWF

, et al. Eco-friendly produced lightweight structural graphene/polyamide 12 nanocomposite: Mechanical performance and the controlling microstructural mechanisms. Polym Eng Sci 2017; 58: 1201–1212.

87.

Xiang

Zhao

, et al. In situ synthesis of monomer casting nylon-6/graphene-polysiloxane nanocomposites: intercalation structure, synergistic reinforcing, and friction-reducing effect. ACS Appl Mater Interfaces 2017; 9: 33176–33190.

88.

Song

Pan

Hou

, et al. Enhancement of thermal conductivity in polyamide-6/graphene composites via a “bridge effect” of silicon carbide whiskers. RSC Adv 2017; 7: 46306–46312.

89.

Minář

Brožek

. Ε-Caprolactone as a medium for improving dispersability of graphene oxide in polyamide based composites. Eur Polym J 2017; 91: 212–220.

90.

Shi

, et al. Intercalation structure and enhanced thermal oxidative stability of polyamide 6/graphene nanocomposites prepared through in situ polymerization. Ind Eng Chem Res 2017; 56: 13715–13724.

91.

Kausar

. Polyamide 1010/polythioamide blend reinforced with graphene nanoplatelet for automotive part application. Adv Mater Sci 2017; 17: 24–36.

92.

Scaffaro

Maio

. Optimization of two-step techniques engineered for the preparation of polyamide 6 graphene oxide nanocomposites. Compos Part B: Eng 2019; 165: 55–64.

93.

Sisti

Totaro

Vannini

, et al. Bio-based PA11/graphene nanocomposites prepared by in situ polymerization. J Nanosci Nanotechnol 2018; 18: 1169–1175.

94.

Adel

El-Shazly

El-Wahidy

E-WF

, et al. Eco-friendly produced lightweight structural graphene/polyamide 12 nanocomposite: mechanical performance and the controlling microstructural mechanisms. Polym Eng Sci 2018; 58: 1201–1212.

95.

Chen

Yang

, et al. Enhancement of mechanical, thermal and tribological properties of AAPS-modified graphene oxide/polyamide 6 nanocomposites. Compos Part B: Eng 2018; 138: 55–65.

96.

Wang

Zhuo

, et al. Fabrication of polyamide 6 nanocomposite with improved thermal conductivity and mechanical properties via incorporation of low graphene content. Ind Eng Chem Res 2018; 57: 10967–10976.

97.

de Melo

CCN

Beatrice

CAG

Pessan

, et al. Analysis of nonisothermal crystallization kinetics of graphene oxide-reinforced polyamide 6 nanocomposites. Thermochimica Acta 2018; 667: 111–121.

98.

Duan

Yang

, et al. In situ polymerization of nylon 66/reduced graphene oxide nanocomposites. J Nanomaterials 2018; 2018: 1–9.

99.

Dorigato

Pegoretti

. Novel electroactive polyamide 12 based nanocomposites filled with reduced graphene oxide. Polym Eng Sci 2019; 59: 198–205.

100.

Shi

, et al. Polyamide 6/graphene oxide-g-hindered phenol antioxidant nano-composites: intercalation structure and synergistic thermal oxidative stabilization effect. Compos Part B: Eng 2019; 162: 11–20.

101.

Yousefian-Arani

Sharif

Bahramian

. Semi-aromatic polyamide-based nanocomposites: I. in-situ polymerization in the presence of graphene oxide. Polym Bull 2018; 75: 5387–5402.

102.

Lee

KPM

Czajka

Shanks

, et al. Mechanical properties of carbon monoxide reduced graphene–polyamide-6 nanocomposites prepared by melt-mixing. 2019; 2055: 090002.

103.

Wang

Tong

Yang

, et al. Improved strength and toughness of semi-aromatic polyamide 6T-co-6(PA6T/6)/GO composites via in situ polymerization. Compos Sci Technol 2019; 175: 6–17.

104.

Zhuang

Cao

Zhang

, et al. Monomer casting nylon/graphene nanocomposite with both improved thermal conductivity and mechanical performance. Compos Part A: Appl Sci Manufac 2019; 120: 49–55.

105.

Xiang

. Polyamide 6/reduced graphene oxide nano-composites prepared via reactive melt processing: formation of crystalline/network structure and electrically conductive properties. J Polym Res 2019; 26: 104.

Review on recent progress in synthesis of graphene–polyamide nanocomposites

Abstract

Keywords

Introduction

Preparation techniques for G-PA nanocomposites

In situ polymerization

Melt blending

Solution mixing

Conclusion

Future scope of work

Footnotes

Acknowledgements

Funding

ORCID iD

References