A facile route to develop electrical conductivity with minimum possible multi‐wall carbon nanotube (MWCNT) loading in poly(methyl methacrylate)/MWCNT nanocomposites

Today, we stand at the threshold of exploring carbon nanotube (CNT) based conducting polymer nanocomposites as a new paradigm for the next generation multifunctional materials. However, irrespective of the reported methods of composite preparation, the use of CNTs in most polymer matrices to date has been limited by challenges in processing and insufficient dispersability of CNTs without chemical functionalization. Thus, development of an industrially feasible process for preparation of polymer/CNT conducting nanocomposites at very low CNT loading is essential prior to the commercialization of polymer/CNT nanocomposites. Here, we demonstrate a process technology that involves in situ bulk polymerization of methyl methacrylate monomer in the presence of multi‐wall carbon nanotubes (MWCNTs) and commercial poly(methyl methacrylate) (PMMA) beads, for the preparation of PMMA/MWCNT conducting nanocomposites with significantly lower (0.12 wt% MWCNT) percolation threshold than ever reported with unmodified commercial CNTs of similar qualities. Thus, a conductivity of 4.71 × 10^?5 and 2.04 × 10^?3 S cm^?1 was achieved in the PMMA/MWCNT nanocomposites through a homogeneous dispersion of 0.2 and 0.4 wt% CNT, respectively, selectively in the in situ polymerized PMMA region by using 70 wt% PMMA beads during the polymerization. At a constant CNT loading, the conductivity of the composites was increased with increasing weight percentage of PMMA beads, indicating the formation of a more continuous network structure of the CNTs in the PMMA matrix. Scanning and transmission electron microscopy studies revealed the dispersion of MWCNTs selectively in the in situ polymerized PMMA phase of the nanocomposites. Copyright © 2012 Society of Chemical Industry     

Synthesis and processing of PMMA carbon nanotube nanocomposite foams

Poly(methyl methacrylate) (PMMA) multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by several methods using both pristine and surface functionalized carbon nanotubes (CNTs). Fourier transform infrared (FTIR) spectroscopy was used to characterize the presence and types of functional groups in functionalized MWCNTs, while the dispersion of MWCNTs in PMMA was characterized using scanning electron microscopy (SEM). The prepared nanocomposites were foamed using carbon dioxide (CO₂) as the foaming agent. The cell morphology was observed by SEM, and the cell size and cell density were calculated via image analysis. It was found that both the synthesis methods and CNTs surface functionalization affect the MWCNTs dispersion in the polymer matrix, which in turn profoundly influences the cell nucleation mechanism and cell morphology. The MWCNTs are efficient heterogeneous nucleation agents leading to increased cell density at low particle concentrations. A mixed mode of nucleation mechanism was observed in nanocomposite foams in which polymer rich and particle rich region co-exist due to insufficient particle dispersion. This leads to a bimodal cell size distribution. Uniform dispersion of MWCNTs can be achieved via synergistic combination of improving synthesis methodology and CNTs surface functionalization. Foams from these nanocomposites exhibit single modal cell size distribution and remarkably increased cell density and reduced cell size. An increase in cell density of ∼70 times and reduction of cell size of ∼80% was observed in nanocomposite foam with 1% MWCNTs.     

Thermal and thermomechanical behavior of amino functionalized and metal decorated MWCNTs/PMMA nanocomposite films

The homogeneous nanocomposites (NC) films of amino modified and metal decorated multiwall carbon nanotubes (MWCNTs) with polymethylmethacrylate (PMMA) were synthesized through in‐situ free radical polymerization. Silver metal nanohybrids (Ag/MWCNTs) were prepared by two strategies, that is, reduction of metal salt in presence of sodium dodecyl sulfate and in‐situ growth from AgNO₃ aqueous solution. The amino functionalization by ball milling enhanced the dispersion of MWCNT in monomer and produced a new class of radiation resistant NC. These synthesized films were characterized by FTIR, TGA, TEM, EDX, TC, DMA, and optical microscopy to ascertain their structural morphologies, thermal stability, and mechanical strength. Microscopic studies reflect the homogeneous mixing of amino functionalized and metal decorated MWCNTs in polymer matrix contributing in the enhancement of thermal stability, thermo‐mechanical strength, glass transition temperatures, and thermal conductivity of NC even at 0.25 wt% addition of modified nanofiller. The thermal stability of NC film at 0.25 wt% loading was increased around ≂50°C and the raise of thermo‐mechanical properties was observed up to 85% at 100°C in the presence of adsorbed surfactant. Thermal and thermomechanical behavior of pre and post UV/O₃ irradiated NC films has been compared with neat polymer. The results revealed that amino modified nanofiller embedded network in polymer matrix can effectively disperse the radiation and has a dramatic reinforcement effect on the nature of degradation of PMMA matrix. POLYM. COMPOS., 35:1807–1817, 2014. © 2013 Society of Plastics Engineers     

Radiation resistant metal decorated MWCNTs/PMMA nanocomposite films with enhanced thermomechanical properties

UV/O₃ radiation and chemical resistant nanocomposite films of functionalized/metal decorated multiwall carbon nanotubes (MWCNTs) with polymethylmethacrylate (PMMA) are synthesized. Silver nanoparticles are decorated on the surface of UV/O₃ functionalized MWCNTs by both reduction and in situ growth from AgNO₃ aqueous solution. Microscopic studies reflect the better dispersion of UV/O₃ functionalized/silver decorated MWCNTs in polymer matrix contributing in enhancement of thermal stability, thermomechanical strength, glass transition temperatures, and thermal conductivity of nanocomposites even at 0.25 wt% MWCNTs additions. The thermal stability of nanocomposite film (0.25 wt% loading), prepared by using a surfactant (Sodium dodecyl sulfate) is increased to about 27°C while the thermomechanical properties are raised up to 76% at 100°C. Thermal and thermomechanical behavior of pre‐ and post‐UV/O₃ irradiated nanocomposite films are compared with neat polymer. The results reveal that UV/O₃ functionalized MWCNTs can effectively disperse the radiation and have a dramatic reinforcement effect on the nature of the degradation of PMMA matrix. POLYM. COMPOS., 36:969–978, 2014. © 2014 Society of Plastics Engineers     

Microwave‐assisted synthesis and characterization of polyimide/functionalized MWCNT nanocomposites containing quinolyl moiety

Polyimide‐MWCNT nanocomposites were prepared by the reaction of a heterocyclic diamine monomer of bis(4‐amino‐3,5‐dimethylphenyl)‐2‐chloro‐3‐quinolylmethane (BACQM), pyromellitic dianhydride (PMDA) with unmodified MWCNT (MWCNT), acid‐functionalized MWCNT (acid‐MWCNT) or amine‐functionalized MWCNT (amine‐MWCNT) using microwave irradiation as well as by the conventional method. The structure of the monomer was confirmed by FTIR, ¹H‐NMR, and ¹³C‐NMR spectral techniques. The glass transition temperature (T_g) of the MWCNTs/polyimide nanocomposite was found to be higher than that of the unfilled polyimide system. The T_g's of both systems were higher when prepared with the microwave method than the conventional synthesis. The T_g's of the nanocomposites using acid and amine functionalized MWCNTs are greater than 300°C, in both methods. This is attributed to the presence of hydrogen bond and strong covalent bond in both the acid‐MWCNT/polyimide and amine‐MWCNT/polyimide systems. The morphological studies of the nanocomposites synthesized using microwave irradiation show that a distinct MWCNT nanofibrillar network is formed in the matrix when MWCNT or acid‐MWCNT is used. A homogeneous morphology, without distinct nanotube domains is seen when the amine‐MWCNT is covalently linked to the polymer. POLYM. COMPOS., 37:2417–2424, 2016. © 2015 Society of Plastics Engineers     

Low percolation threshold and high electrical conductivity in melt‐blended polycarbonate/multiwall carbon nanotube nanocomposites in the presence of poly(ε‐caprolactone)

This study focuses on the electrical properties of polycarbonate (PC)/poly(ε‐caprolactone) (PCL)‐multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL‐MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL‐MWCNT nanocomposites were studied in a broad frequency range, 10¹?10⁶ Hz and resulted in low percolation threshold (p_c) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσ_DC versus p^?1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers     

Crystallinity of biodegradable polymers reinforced with functionalized carbon nanotubes

Well-dispersed multiwall carbon nanotubes (MWCNTs) were prepared by grafting poly(L-lactide-co-ε-caprolactone) (PLACL) biodegradable copolymer onto the sidewall of hydroxylated MWCNTs using oligomeric L-lactide (LA) and ε-caprolactone (CL). After preparation of MWCNT/PLACL composites, the effect of functionalized MWCNTs on crystallinity of PLACL was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and polarized light optical microscopy (POM). The surface functionalization effectively improved the dispersion and adhesion of MWCNTs which acted as reinforcing filler in the PLACL polymer matrix and hence improved the physical and thermomechanical properties of the nanocomposites. The glass transition temperature (T _g) and the crystallinity of nanocomposites decreased in comparison with those of neat PLACL when the concentration of functionalized MWCNTs in nanocomposites was 0.5 wt%. With further increment in concentration of functionalized MWCNTs, the T _g of composites increased until the T _g of neat PLACL, and also the crystallinity of composites increased. The functionalized MWCNTs have no significant effect on the melting point of nanocomposites. The MWCNTs acted as heterogeneous nucleation points and increased the lamella size and therefore the crystallinity of PLACL. Furthermore, the larger agglomerated clusters of both kinds of MWCNTs (i.e., MWCNT-grafted-PLACL and pristine MWCNTs) are more effective than small clusters as nucleation points for growing the spherulites.     

Thermal‐Insulation,Electrical, and Mechanical Properties of Highly‐Expanded PMMA/MWCNT Nanocomposite Foams Fabricated by Supercritical CO2 Foaming

Foaming behavior of poly(methyl methacrylate) (PMMA)/multi‐walled carbon nanotubes (MWCNTs) nanocomposites and thermally‐insulating, electrical, and mechanical properties of the nanocomposite foams are investigated. PMMA/MWCNT nanocomposites containing various amounts of MWCNTs are first prepared by combining solution and melt blending methods, and then foamed using CO₂. The foaming temperature and MWCNT content are varied for regulating the structure of PMMA/MWCNT nanocomposite foams. The electrical conductivity measurement results show that MWCNTs have little effect on the electrical conductivity of foams with large expansion ratio. Thermal conductivities of both solid and foamed PMMA/MWCNT nanocomposites are measured to evaluate their thermally insulating properties. The gas conduction, solid conduction, and thermal radiation of the foams are calculated for clarifying the effects of cellular structure and MWCNT content on thermal insulation properties. The result demonstrates that MWCNTs endowed foams with enhanced thermal insulation performance by blocking thermal radiation. Moreover, the compressive testing shows that MWCNTs improve the compressive strength and rigidity of foams. This research is essential for optimizing environmentally friendly thermal insulation nanocomposite foams with enhanced thermal‐insulation and compressive mechanical properties.     

Synthesizing multi‐walled carbon nanotube‐polymethyl methacrylate conductive composites and poly(lactic acid) based composites

Multi‐walled carbon nanotube was modified with polymethyl methacrylate (MWCNT‐PMMA) by in situ solution radical polymerization in the presence of 2,2′‐Azobis (isobutyronitrile) as an initiator. The products with different addition of methyl methacrylate (MMA) were pressed into slices to prepare specimens for electrical conductivity testing. It was found that the MWCNT‐PMMA nanocomposites demonstrate excellent electrical conductivity. To investigate the microsphere morphology and the colloidal surfactant of MWCNTs in MWCNT‐PMMA composites, samples were submitted to scanning electron microscopy and transmission electron microscopy. The thermogravimetric analysis of the prepared composites confirmed that MWCNTs as a thermal stabilizer for PMMA, which could have a wide range of potential applications, such as in catalysts, sensors, environmental remediation, and energy storage. Two series of poly(lactic acid) (PLA) based biocomposites with different MMA additions and MWCNT‐PMMA composites contents were prepared with twin‐screw extruding and injection molding. The results show the mechanical properties changed a little with the MMA and MWCNT‐PMMA composites contents increasing, which suggested the well compatibility between MWCNT‐PMMA composites and PLA. POLYM. COMPOS., 37:503–511, 2016. © 2014 Society of Plastics Engineers     

A one‐pot method to prepare transparent poly(methyl methacrylate)/montmorillonite nanocomposites using imidazolium‐based ionic liquids

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by a new one‐pot technique, where the hydrophilic Na‐MMT layers were decorated with hydrophobic 1‐dodecyl‐3‐methylimidazolium hexafluorophosphate (C₁₂mimPF₆) ionic liquid in situ during melt blending with PMMA and intercalation of polymer chains took place subsequently. The in situ modification and intercalation of Na‐MMT were confirmed using X‐ray diffraction and transmission electron microscopy. The combination of the compatible C₁₂mimPF₆ with PMMA and the good dispersion of MMT layers at the nanoscale rendered the resultant PMMA/MMT nanocomposites with improved optical transparency, thermal stability and mechanical properties. Copyright © 2012 Society of Chemical Industry     

Influence of aminosilane‐functionalized carbon nanotubes on the rheometric,mechanical, electrical and thermal degradation properties of epoxidized natural rubber nanocomposites

We describe the preparation, characterization and physical properties of multiwalled carbon nanotube (MWCNT)‐filled epoxidized natural rubber (ENR) composites. To ensure better dispersion in the elastomer matrix, the MWCNTs were initially subjected to aminopropyltriethoxysilane (APS) treatment to bind amine functional groups (?NH₂) on the nanotube surface. Successful grafting of APS on the MWCNT surface through Si–O–C linkages was confirmed using Fourier transform infrared spectroscopy. Grafting of APS on the MWCNT surface was further corroborated using elemental analysis. ENR nanocomposites with various filler loadings were prepared by melt compounding to generate pristine and APS‐modified MWCNT‐filled elastomeric systems. Furthermore, we determined the effects of various filler loadings on the rheometric, mechanical, electrical and thermal degradation properties of the resultant composite materials. Rheometric cure characterization revealed that the torque difference increased with pristine MWCNT loading compared to the gum system, and this effect was more pronounced when silane‐functionalized MWCNTs were loaded, indicating that this effect was due to an increase in polymer–carbon nanotube interactions in the MWCNT‐loaded materials. Loading of silane‐functionalized MWCNTs in the ENR matrix resulted in a significant improvement in the mechanical, electrical and thermal degradation properties of the composite materials, when compared to gum or pristine MWCNT‐loaded materials.© 2013 Society of Chemical Industry     

Properties and degradation behavior of surface functionalized MWCNT/poly(L‐lactide‐co‐ε‐caprolactone) biodegradable nanocomposites

In this research, poly(L ‐lactide‐co‐ε‐caprolactone) (PLACL) reinforced with well‐dispersed multiwalled carbon nanotubes (MWCNTs) nanocomposites were prepared by oxidization and functionalization of the MWCNT surfaces using oligomeric L ‐lactide (LA) and ε‐caprolactone (CL). It is found that the surface functionalization can effectively improve the dispersion and adhesion of MWCNTs in PLACL. The surface functionalization will have a significant effect on the physical, thermomechanical, and degradation properties of MWCNT/PLACL composites. The tensile modulus, yield stress, tensile strength, and elongation at break of composite increased 49%, 60%, 70%, and 94%, respectively, when the concentration of functionalized MWCNTs in composite is 2 wt %. The in vitro degradation rate of nanocomposites in phosphate buffer solution increased about 100%. The glass transition temperature (T_g) of composites was decreased when the concentration of functionalized MWCNTs is 0.5 wt %. With further increasing the concentration of functionalized MWCNTs, the T_g was increased. The degradation kinetics of nanocomposites can be engineered and functionalized by varying the contents of pristine or functionalized MWCNTs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Towards transparent PMMA/SiO2 nanocomposites with promising scratch‐resistance by manipulation of SiO2 aggregation followed by in situ polymerization

Poly(methyl methacrylate) grafted silica (SiO₂‐g‐PMMA) was synthesized via in situ suspension polymerization. To achieve better uniform dispersion, hexadecyltrimethylammonium bromide (CTAB) was introduced into xylene to manipulate SiO₂ aggregation. SiO₂‐g‐PMMA or SiO₂ was incorporated into PMMA matrix by in situ polymerization to prepare PMMA‐based nanocomposites. The effect of CTAB amount, in the range 0–35 wt %, on the modification was evaluated by DLS, TGA, and FTIR. Furthermore, morphology, optical, mechanical, and thermal properties of PMMA nanocomposites was characterized by SEM, UV–vis, DMA, and TGA. Owing to surface functionalization, SiO₂‐g‐PMMA exhibited far more excellent compatibility and dispersion in matrix compared with SiO₂. Surface hardness and thermal properties of nanocomposites were enhanced significantly under the premise in high transparency. It is expected that transparent nanocomposites with promising scratch‐resistance could have wide applications, such as airplane shielding window and daily furniture. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44612.     

Microwave assisted functionalization of carboxylated‐multiwalled carbon nanotubes with 5‐aminoisophthalic acid and its application for the preparation of chiral poly(ester‐imide)/CNT nanocomposites

This article presents the results of investigation into surface modification of carboxylated‐multiwalled carbon nanotubes (MWCNT)s by 5‐aminoisophthalic acid under microwave irradiation as a fast, safe, and simple method. The different contents of functionalized MWCNTs (5, 10, 15 wt%) were effectively dispersed in an aromatic polymer through ultrasonic irradiation to prepare MWCNT reinforced polymer nanocomposites (NC)s. The chiral poly(ester‐imide) (PEI) was prepared by a direct polycondensation of chiral diacid with 4,4′‐thiobis(2‐tert‐butyl‐5‐methylphenol). The effect of the presence of MWCNTs on morphological and thermal properties of the NCs was investigated by X‐ray diffraction, FT‐IR spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy, and field emission scanning electron microscopy. According to TGA data, the PEI/MWCNT NCs showed a much better thermal stability than pristine polymer. The microstructure study of the NCs indicated the compatibility of functionalized MWCNTs with PEI and uniform distribution of them in the polymer matrices. POLYM. COMPOS., 37:835–843, 2016. © 2014 Society of Plastics Engineers     

Synergistic effect of dual nanofillers (MWCNT and Ni–Al LDH) on the electrical and thermal characteristics of polystyrene nanocomposites

The advantage of using 3D hybrid filler containing carboxylic acid functionalized multiwalled carbon nanotubes (c‐MWCNTs) and sodium dodecyl sulfate modified Ni–Al layered double hydroxide (sN‐LDH) over c‐MWCNTs and sN‐LDHs acting alone was investigated. PS/c‐MWCNT composites proved to be good for improvement of properties, but not to an appreciable level, especially in case of electrical conductivity, flame retardancy, rheology, and water vapor permeability. Hence, a combination of 0.3 wt % of c‐MWCNT and 3 wt % of sN‐LDH was optimized as additives to assist in the full expression of the filler traits in the nanocomposite and to obtain a versatile nanocomposite with properties specific to both the fillers. This approach slightly decreases the dispersion challenge faced with handling high loadings of CNT and also the intrinsic limitations specific to the individual fillers (i.e., inertness of CNTs and low conductivity of LDHs). Moreover, the anion/anionic repulsion of organically modified CNT/LDH facilitates effective dispersion of the additive opposing adhesion. FTIR and Raman spectroscopy provided evidence for incorporation and proper dispersion of the additives in the polymer matrix, with XRD and TEM confirming a well‐dispersed morphology of the nanocomposites. In this work, focus is made on the improvement of thermal stability, flame retardancy, melt rheology, hardness, electrical conductivity, and water vapor permeability of PS/0.3 wt % c‐MWCNT/3 wt % sN‐LDH nanocomposites over PS/0.3 wt % c‐MWCNT, making use of the synergistic effect of c‐MWCNT coupled with sN‐LDH on polystyrene. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46513.     

Electrical conductivity behavior of epoxy matrix nanocomposites with simultaneous dispersion of carbon nanotubes and clays

In this work, nanocomposites with simultaneous dispersion of multiwalled carbon nanotubes (MWCNT) and montmorillonite clays in an epoxy matrix were prepared by in situ polymerization. A high energy sonication was employed as the dispersion method, without the aid of solvents in the process. The simultaneous dispersion of clays with carbon nanotubes (CNT) in different polymeric matrices has shown a synergic potential of increasing mechanical properties and electrical conductivity. Two different montmorillonite clays were used: a natural (MMT‐Na⁺) and an organoclay (MMT‐30B). The nanocomposites had their electrical conductivity (σ) and dielectric constant (ε_r) measured by impedance spectroscopy. The sharp increase in electrical conductivity was found between 0.10 and 0.25 wt% of the MWCNTs. Transmission electron microscopy (TEM) of the samples showed a lower tendency of MWCNT segregation on the MMT‐30B clay surface, which is connected to intercalation/exfoliation in the matrix, that generates less free volume available for MWCNTs in the epoxy matrix. Data from electrical measurement showed that simultaneously adding organoclay reduces the electrical conduction in the nanocomposite. Moreover, conductivity and permittivity dispersion in low frequency suggest agglomeration of nanotubes surrounding the natural clay (MMT‐Na⁺) particles, which is confirmed by TEM. POLYM. COMPOS., 37:1603–1611, 2016. © 2014 Society of Plastics Engineers     

Siloxane Core-Modified Organo Soluble Novel Polyimide/Multi-walled Carbon Nanotube Nanocomposites

Siloxane core-modified polyimides (PI)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were designed and developed. The confinement of segmental motion of the PI chain due to high dispersion uniformity of the MWCNTs caused the increment in the glass transition temperature (T _g ) and remarkable elevated thermal stability. All the PIs could afford better solubility with high dielectric constants of 3.5–5.9 and low water absorptions of 0.42–0.68%. These PIs emitted a strong blue fluorescent at 380 nm, assigning the structural confirmation of PI matrix. Heterogeneous morphology of MWCNT/PI nanocomposites was evidenced by SEM and TEM images, resulted from the incorporation of MWCNT.     

Electrical and mechanical tuning of 3D printed photopolymer–MWCNT nanocomposites through in situ dispersion

An electric field-assisted in situ dispersion of multiwall carbon nanotubes (MWCNTs) in polymer nanocomposites, fabricated through stereolithography three-dimensional (3D) printing technique, was demonstrated. The introduction of MWCNTs increased the elasticity modulus of the polymer resin by 77%. Furthermore, the use of an electric field for in situ MWCNT dispersion helped improving the average elongation at break of the samples with MWCNTs by 32%. The electric field also increased the ultimate tensile strength of the MWCNT reinforced nanocomposites by 42%. An increase of over 20% in the ultimate tensile strength of in situ dispersed MWCNT nanocomposites over the pure polymer material was observed. Finally, it was demonstrated that the magnitude and direction of the electrical conductivity of MWCNT nanocomposites can be engineered through the application of in situ electric fields during 3D printing. An increase of 50% in the electrical conductivity was observed when MWCNTs were introduced, while the application of the electric field further improved the electrical conductivity by 26%. The presented results demonstrated the feasibility of tuning both electrical and mechanical properties of MWCNT reinforced polymer nanocomposites using in situ electrical field-assisted 3D printing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47600.