Synthesis and characterization of multiwalled carbon nanotube/polyurethane composites via surface modification multiwalled carbon nanotubes using silane coupling agent

Well‐dispersed multiwalled carbon nanotubes/polyurethane (MWCNTs/PU) composites were synthesized in situ polymerization based on treating MWCNTs with nitric acid and silane coupling agent. The morphology and degree of dispersion of the MWCNTs were studied using a high resolution transmission electron microscopy (HR‐TEM) and X‐ray powder diffraction (XRD). The result showed that MWCNTs could be dispersed still in the PU matrix well with the addition of 2 wt% MWCNTs. The thermal and mechanical properties of the composites were characterized by dynamic mechanical thermal analysis, thermogravimetric analysis, tensile, and impact testing. The result suggested that the glass transition temperature (T_g) of composites increased greatly with increasing MWCNTs content slightly, and the MWCNTs is also helpful to improve mechanical properties of composites. Furthermore, the composites have an excellent mechanical property with the addition of 0.5 wt% MWCNTs. The electrical property testing indicates that the MWCNTs can improve evidently the electrical properties of composites when adding 1 wt% MWCNTs to the PU matrix. The volume resistivity of composites reaches to an equilibrium value. POLYM. COMPOS., 33:1866–1873, 2012. © 2012 Society of Plastics Engineers     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

Miscibility,UV resistance,thermal degradation,and mechanical properties of PMMA/SAN blends and their composites with MWCNTs

Poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) (PMMA/SAN) blends, with varying concentrations, were prepared by melt‐mixing technique. The miscibility is ensured by fixing the acrylonitrile (AN) content of styrene acrylonitrile (SAN) as 25% by weight. The blends were transparent as well. The Fourier transform infrared spectroscopic (FTIR) studies did not reveal any specific interactions, supporting the well accepted ‘copolymer repulsion effect’ as the driving mechanism for miscibility. Addition of SAN increased the stability of PMMA towards ultraviolet (UV) radiations and thermal degradation. Incorporation of even 0.05% by weight of multi‐walled carbon nanotubes (MWCNTs) significantly improved the UV absorbance and thermal stability. Moreover, the composites exhibited good strength and modulus. However, at higher concentrations of MWCNTs (0.5 and 1% by weight) the thermo‐mechanical properties experienced deterioration, mainly due to the agglomeration of MWCNTs. It was observed that composites with 0.05% by weight of finely dispersed and well distributed MWCNTs provided excellent protection in most extreme climatic conditions. Thus, PMMA/SAN/MWCNTs composites can act as excellent light screens and may be useful, as cost‐effective UV absorbers, in the outdoor applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43628.     

Effect of carbon nanotube dispersion on electrochemical and mechanical characteristics of poly(methyl methacrylate)‐based gel polymer electrolytes

Polymer‐based electrolyte of lithium ion batteries and other devices have shortcomings of low ionic conductivity and inadequate mechanical strength. The study presents the preparation of polymethyl methacrylate (PMMA)‐based three‐layered nanocomposite gel polymer electrolytes (NCGPEs) having multiwalled carbon nanotubes (MWCNTs) dispersed in the middle layer of the composites and the effect of dispersoid quantities on the ionic, mechanical, and thermal characteristics of the electrolytes. The NCGPEs were synthesized by solution cast process with the various MWCNTs contents of 0.5, 1.0, 1.5, and 2.0 wt%. Morphology of the NCGPEs has been observed by scanning and transmission electron microscopes (SEMs). Interactions between the constituents of the composite and structural changes of the base polymer were investigated by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) techniques. The mechanical strength of the NCGPEs increases considerably owing to the dispersion of MWCNTs and the highest strength was found for the dispersion of 2.0 wt% of MWCNTs. The thermal stability of the nanocomposites was investigated by thermo‐gravimetric analysis (TGA). The chemical decomposition temperature of the nanocomposites increases considerably as compared to the gel polymer electrolyte. Ionic conductivity of the composite electrolyte increases with the increase in addition of MWCNTs and the maximum ionic conductivity (10⁻³ S cm⁻¹) of the nanocomposite has been found with the dispersion of 2.0 wt% MWCNTs among all the dispersoid. POLYM. COMPOS., 37:1936–1944, 2016. © 2015 Society of Plastics Engineers     

Cellulose acetate/multiwalled carbon nanotube nanocomposites with improved mechanical,thermal, and electrical properties

Cellulose acetate (CA)‐based nanocomposites with various contents of neat multiwalled carbon nanotube (MWCNT) or acid‐treated one (MWCNT‐COOH) are prepared via melt‐compounding method and investigated their morphology, thermal stability, mechanical, and electrical properties. SEM microphotographs reveal that MWCNT‐COOHs are dispersed uniformly in the CA matrix, compared with neat MWCNTs. FTIR spectra support that there exists a specific interaction between carboxyl groups of MWCNT‐COOHs and ester groups of CA, indicating good interfacial adhesion between MWCNT‐COOHs and CA matrix. Accordingly, thermal stability and dynamic mechanical properties of CA/MWCNT‐COOH nanocomposites were higher than those of CA/MWCNT composites. On the contrary, electrical volume resistivities of CA/MWCNT‐COOH nanocomposites are found to be somewhat higher than those of CA/MWCNT composites, which is because of the deterioration of graphene structures for MWCNT‐COOHs and the good dispersion of MWCNT‐COOHs in the CA matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Preparation,characterization, and thermal properties of poly (methyl methacrylate)/boron nitride composites by bulk polymerization

Poly (methyl methacrylate)/boron nitride (PMMA/BN) composites were prepared by dispersing BN particles into methyl methacrylate monomer phase by bulk polymerization method. BN particles modified with silane coupling agent, γ‐methacryloxypropyl trimethoxy silane, were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. Effects of modified BN particle content on thermal conductivity were investigated, and the experimental values were compared with those of theoretical and empirical models. With 16 wt% of BN particles, the thermal conductivity of the composite was 0.53 W/(m·K), 1.8 times higher than that of pure PMMA. The microstructures of the PMMA/BN composites were examined by scanning electron microscopy, energy‐dispersive X‐ray analysis, and transmission electron microscopy. Dynamic mechanical analysis and thermogravimetric analysis traces also corroborated the confinement of the polymer in an inorganic layer by exhibiting an increase in glass‐transition temperatures and weight loss temperatures in the thermogram. Mechanical properties and electrical insulation property of the PMMA/BN composites were also determined. These results showed that PMMA/BN composites may offer new technology and business opportunities. POLYM. COMPOS., 36:1675–1684, 2015. © 2014 Society of Plastics Engineers     

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (T_g) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in T_g. © 2018 Society of Chemical Industry     

Properties of PMMA/Carbon nanotubes nanocomposites prepared by “grafting through” method

A number of batch polymerizations were performed to study the effect of multi‐walled carbon nanotubes (MWCNTs) on the properties of PMMA/MWCNTs nanocomposites. To improve the dispersion of nanotubes in PMMA matrix, MWCNTs were functionalized with methacrylate groups via a four‐step modification process and the modified nanoparticles were used to synthesize the nanocomposites. The prepared samples were characterized by Raman spectroscopy, thermogravimetric analysis, dynamic mechanical thermal analysis, differential scanning calorimetry, gel permeation chromatography, UV–visible, and TEM techniques. According to the results, modified nanotubes improved thermal and mechanical properties better than the pristine MWCNTs. The main improvement in the mechanical and thermophysical properties was achieved for the nanocomposite containing 0.5 wt% of MWCNTs. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

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     

Polyester and multiwalled carbon nanotube composites: characterization,electrical conductivity and antibacterial activity

Poly(butylene terephthalate) (PBT) composites containing multiwalled carbon nanotubes (MWCNTs) were prepared using a melt‐blending process and used to examine the effects on the composite structure and properties of replacing PBT with acrylic acid‐grafted PBT (PBT‐g‐AA). PBT‐g‐AA and multihydroxyl‐functionalized MWCNTs (MWCNTs‐OH) were used to improve the compatibility and dispersibility of the MWCNTs within the PBT matrix. The composites were characterized morphologically using transmission electron microscopy, and chemically using Fourier transform infrared, solid‐state ¹³C NMR and UV‐visible absorption spectroscopy. The antibacterial and electrical conductivity properties of the composites were also evaluated. MWCNTs or MWCNTs‐OH enhanced the antibacterial activity and electrical conductivity of the PBT/MWCNT or PBT‐g‐AA/MWCNTs‐OH composites. The functionalized PBT‐g‐AA/MWCNTs‐OH composites showed markedly enhanced antibacterial properties and electrical conductivity due to the formation of ester bonds from the condensation of the carboxylic acid groups of PBT‐g‐AA with the hydroxyl groups of MWCNTs‐OH. The optimal proportion of MWCNTs‐OH in the composites was 1 wt%; in excess of this amount, the compatibility between the organic and inorganic phases was compromised. Copyright © 2011 Society of Chemical Industry     

The role of a biobased epoxy monomer in the preparation of diglycidyl ether of bisphenol A/MWCNT composites

A biobased epoxy monomer (GA‐II) derived from gallic acid for multiwalls carbon nanotubes’ (MWCNTs) dispersion improvement is reported in this article. The aromatic group in its molecular structure made it to be absorbed onto the surface of MWCNTs via π‐π interactions and the GA‐II anchored MWCNT could be homogeneously dispersed in DGEBA matrix via sonication. That was proved by Raman and UV spectroscopy as well as scanning electron microscope. After curing reaction, the epoxy/MWCNT composites demonstrated enhanced mechanical properties, excellent thermal conductivity, and high electrical conductivity. With the addition of only 0.5 wt% GA‐II modified MWCNT, the tensile strength, tensile modulus, flexural strength, and flexural modulus of the composites were improved by 28%, 40%, 22%, and 16%, respectively. The thermal and electrical conductivities were also improved from 0.15 to 0.25 W/m K (67% increased) and from 0.7 × 10⁻¹⁴ to 0.24 × 10⁻⁴ S cm⁻¹ (10 orders increased). POLYM. COMPOS., 38:1640–1645, 2017. © 2015 Society of Plastics Engineers     

Multiwalled carbon nanotubes/polypyrrole/graphene/nonwoven fabric composites used as electrodes of electrochemical capacitor

The reduced graphene oxide/nonwoven fabric (rGO/NWF) composites have been fabricated through heating the NWF coated with the mixture of GO and HONH₂·HCl at 130°C, during which the GO is chemically reduced to rGO. Then the composites of polypyrrole (PPy)/rGO/NWF have been prepared through chemically polymerizing pyrrole vapor by using the FeCl₃·6H₂O adsorbed on rGO/NWF substrate as oxidant. Finally, multiwalled carbon nanotubes (MWCNTs) are used as conductive enhancer to modify PPy/rGO/NWF through dip‐dry process to obtain MWCNTs/PPy/rGO/NWF. The prepared composites have been characterized and their capacitive properties have been evaluated in 1.0M KCl electrolyte by using two‐electrode symmetric capacitor test. The results reveal that MWCNTs/PPy/rGO/NWF possesses a maximum specific capacitance (C_sc) of about 319 F g^?1 while PPy/rGO/NWF has a C_sc of about 277.8 F g^?1 at the scan rate of 1 mV s^?1 and that optimum MWCNTs/PPy/rGO/NWF retains 94.5% of initial C_sc after 1000 cycles at scan rate of 80 mV s^?1 which is higher than PPy/rGO/NWF (83.4%). Further analysis reveals that the addition of MWCNTs can increase the charger accumulation at the outer and inner of the composites, which is favorable to improve the stability and the rapid charge‐discharge capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41023.     

Enhanced Thermal Conductivity of Epoxy Composites with MWCNTs/AlN Hybrid Filler

To further improve the thermal conductivity of epoxy resin, the multi-walled carbon nanotube/aluminum nitride (MWCNTs/AlN) hybrid filler was employed to prepare thermal conductivity MWCNTs/AlN/epoxy composite by casting process, and the silane coupling reagent of γ-glycidoxy propyl trimethoxy silane(KH-560) was also used to functionalize the surface of MWCNTs and/or AlN. Results revealed that, the thermal conductivity of epoxy resin was improved remarkably with the addition of MWCNTs/AlN hybrid filler, a higher thermal conductivity of 1.04 W/mK could be achieved with 29 wt% MWCNTs/AlN hybrid filler (4 wt% MWCNTs +25 wt% AlN), about 5 times higher than that of native epoxy resin. And the epoxy composite with 29 wt% MWCNTs/AlN hybrid filler possessed better thermal conductivity and mechanical properties than those of single 5 wt% MWCNTs or 40 wt% AlN. The thermal decomposition temperature of MWCNTs/AlN/epoxy composite was increased with the addition of MWCNTs/AlN hybrid filler. For given filler loading, surface treatment of MWCNTs and/or AlN by KH-560 exhibited a positive effect on the thermal conductivity of epoxy composite.     

Evaluation of mechanical and thermal properties of tamarind seed filler reinforced vinyl ester composites

This article deals with the usage of tamarind seed filler (TSF) as reinforcement in vinyl ester (VE) composites. The composite plates have been fabricated by compression molding machine with TSFs of varying wt% from 5 to 50 as reinforcement material, and their properties such as tensile, flexural, impact, hardness, water absorption, heat deflection tests, and thermogravimetric analysis are studied. The mechanical properties of TSF reinforced VE composites are optimum at 15 wt% filler. The tensile strength and flexural strength of TSF‐VE composites are estimated to be around 34.1 and 121 MPa, respectively. The better impact strength of TSF‐VE composites is found to be 14.02 kJ/m², and barcol hardness can hold a value up to 42.33. Thermo gravimetric analysis and heat deflection test of TSF reinforced VE composite have improved the thermal stability. The fiber matrix interaction of the fractured mechanical testing specimen has been analyzed by scanning electron microscope. The TSF‐VE composites are used to fabricate the wheel hubcap of heavy‐duty buses, bus seat backrest cover, and silencer guard of the motorcycle. J. VINYL ADDIT. TECHNOL., 25:E114–E128, 2019. © 2019 Society of Plastics Engineers     

3D printing of copper particles and poly(methyl methacrylate) beads containing poly(lactic acid) composites for enhancing thermomechanical properties

Poly(lactic acid) (PLA) composite filaments with different copper (Cu) contents as high as 40 and 20 wt% of poly(methyl methacrylate) (PMMA) beads have been fabricated by twin-screw extruder for 3D printing. A fused-deposition modeling (FDM) 3D printing technology has been used to print the PLA composites containing hybrid fillers of Cu particles and PMMA beads. The morphology, mechanical, and thermal properties of the printed PLA composites were investigated. The tensile strength was slightly decreased, but storage modulus and thermal conductivity of PLA composites were significantly improved by adding Cu particles in the presence of PMMA beads. The PLA composites with hybrid fillers of 40 wt% of Cu particles and 20 wt% of PMMA beads resulted in thermal conductivity of 0.49 W m⁻¹ K⁻¹ which was three times higher than that of the bare PLA resin. The facilitation of the segregated network of high-thermally conductive Cu particles with the PMMA beads in PLA matrix provided thermally conductive pathways and resulted in a remarkable enhancement in thermal conductivity.     

Preparation and properties of multi‐walled carbon nanotubes/carbon fiber/epoxy composites

Multi‐walled carbon nanotubes/carbon fiber (MWCNTs/CF) hybrid fillers are employed to prepare MWCNTs/CF/epoxy composites. Results reveal that a great improvement of the thermal conductivities of the epoxy composites with the addition of MWCNTs/CF hybrid fillers, and the thermal conductivity of the MWCNTs/CF/epoxy composites is 1.426 W/mK with 8 vol% treated MWCNTs/CF hybrid fillers (5 vol% MWCNTs + 3 vol% CF). Both the flexural and impact strength of the MWCNTs/CF/epoxy composites are increased firstly, but decreased with the excessive addition of MWCNTs. The flexural and impact strength of the MWCNTs/epoxy composites are optimal with 2 vol% MWCNTs. For a given MWCNTs/CF hybrid fillers loading, the surface treatment of MWCNTs/CF hybrid fillers can further increase the thermal conductivities and mechanical properties of the MWCNTs/CF/epoxy composites. POLYM. COMPOS., 35:2150–2153, 2014. © 2014 Society of Plastics Engineers     

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     

Enhancing electrical properties of MWCNTs in immiscible blends of poly(methyl methacrylate) and styrene‐acrylonitrile copolymer by selective localization

Multiwalled carbon nanotubes (MWCNTs) were introduced into poly(methyl methacrylate) (PMMA) and styrene‐acrylonitrile copolymer (SAN) blends by melt mixing in an asymmetric miniature mixer (APAM). A composition of 70 wt% of PMMA and 30 wt% of SAN was mixed to create a co‐continuous morphology. Transmission electron microscopy images of ultra‐microtomed samples (70 nm in thickness) showed selective localization of MWCNTs inside the percolated SAN phase. The occurrence of the double percolation phenomenon resulted in lower electrical percolation thresholds of PMMA/SAN/MWCNT blends molded at high temperatures. Dielectric spectroscopy indicated a higher electrical permittivity for samples that were compression molded at 260°C. Due to the higher affinity of MWCNTs to SAN, there was a migration of MWCNTs into the SAN phase during the melt processing. Conductivity measurements revealed a significant decrease in electrical percolation threshold (0.4 wt%) for PMMA70/SAN30 blends compared with MWCNT‐filled SAN and MWCNT‐filled PMMA (ca. 0.8 wt%). POLYM. COMPOS., 37:1523–1530, 2016. © 2014 Society of Plastics Engineers     

Structures and properties of injection‐molded biodegradable poly(lactic acid) nanocomposites prepared with untreated and treated multiwalled carbon nanotubes

Structural, mechanical, thermal, and electrical properties of low‐loaded (0?1.5 wt%), untreated, and treated (with heat and nitric acid) multiwalled carbon nanotubes (MWCNTs)/poly (lactic acid) (PLA) nanocomposites have been studied. Among all synthesized composites, acid‐treated 1.0 wt% MWCNTs reinforced PLA shows superior tensile strength and modulus to those shown by other samples. All nanocomposites including the pure PLA exhibit the orthorhombic β‐form crystalline structure with low degree of crystallization, as demonstrated by X‐ray diffraction study. Differential scanning calorimetry (DSC) of injection molded samples, respectively, reveals an enhancement of PLA crystallinity by 8% and 14% for untreated and treated nanotubes, relating to the observed improvement in mechanical properties. Nanocomposites show double melting behavior when crystallized nonisothermally by DSC, whilst the pure PLA shows single melting character. Thermogravimetric analysis discloses that the MWCNTs‐loaded sample degraded faster than PLA. Surface resistivity of the nanocomposites is found to be dropped drastically by a factor of 10¹³ with a low loading of MWCNTs (1.5 wt%). A detailed discussion and correlation of the observed structures and properties are presented in this study. POLYM. ENG. SCI., 54:317–326, 2014. © 2013 Society of Plastics Engineers