Synthesis and properties of homogeneously dispersed polyamide 6/MWNTs nanocomposites via simultaneous in situ anionic ring‐opening polymerization and compatibilization

Toluene 2, 4‐diisocyanate (TDI) functionalized multiwalled carbon nanotubes (MWNTs‐NCO) were used to prepare monomer casting polyamide 6 (MCPA6)/MWNTs nanocomposites via in situ anionic ring‐opening polymerization (AROP). Isocyanate groups of MWNTs‐NCO could serve as AROP activators of ?‐caprolactam (CL) in the in situ polymerization. Fourier transform infrared (FTIR) showed that a graft copolymer of PA6 and MWNTs was formed in the in situ polymerization. MWNTs‐PA6 covalent bonds of the graft copolymer constituted a strong type of interfacial interaction in the nanocomposites and increased the compatibility of MWNTs and MCPA6 matrix. The nanocomposites were characterized for the morphology, mechanical, crystallization, and thermal properties through field emission transmission electron microscopy (FETEM), tensile testing, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). FETEM analysis showed that MWNTs were homogeneously dispersed in MCPA6 matrix. The initial tensile strengths and tensile modulus of the nanocomposite with 1.5 wt % loading of MWNTs were enhanced by about 16 and 13%, respectively, compared with the corresponding values for neat MCPA6. DSC analysis indicated that the crystallization temperature of the nanocomposites was increased by 8°C by adding 1.5 wt % MWNTs compared with pure MCPA6. Besides, it was found that the thermal stability of MCPA6 was improved by the addition of the MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

In situ synthesis of polyamide 6/MWNTs nanocomposites by anionic ring opening polymerization

In situ anionic ring opening polymerization is used to prepare monomer casting polyamide 6 (MCPA6)/carbon nanotubes (CNTs) nanocomposites, whereby water is used as auxiliary dispersing agent of hydroxyl functionalized multiwalled carbon nanotubes (MWNTs‐OH) and ε‐caprolactam (CL) monomer. The MWNTs‐OH were dispersed homogenously in MCPA6 matrix when being observed through transmission electron microcopy. The well dispersed MWNTs‐OH existed at the center of many radial texture phases in MCPA6 matrix. Polarizing microscope analysis showed that these radial texture phases were MCPA6 spherulitic crystallities. Differential scanning calorimetry analysis revealed that the crystallization temperature of the MCPA6/MWNTs‐OH nanocomposites had been improved by adding only 0.2 wt % MWNTs‐OH when compared with pure MCPA6. The influence of MWNTs‐OH on the thermal stability of MCPA6 under nitrogen and air environments was also investigated by thermal gravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl‐functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring‐opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A Kinetic Study on the Thermal Degradation of Multi‐Walled Carbon Nanotubes‐Reinforced Poly(propylene) Composites

Summary: The influence of the multi‐walled carbon nanotubes (MWNTs) content on the thermal degradation behavior of MWNTs‐reinforced poly(propylene) (PP) composites was investigated by using non‐isothermal thermogravimetric analysis (TGA). Kinetic parameters of degradation were evaluated by using the Flynn‐Wall‐Ozawa iso‐conversional method and the pseudo first‐order method. As a result, compared with pristine PP, MWNTs‐PP nanocomposites have lower peak temperatures of degradation, narrower degradation temperature ranges and a higher amount of residual weight at the end of the degradation, which is likely to be a result of specific interactions between complimentary functional groups. The values of the reaction order of MWNTs‐PP nanocomposites determined by the Kissinger method are close to 1 in the non‐isothermal degradation process. There is a good correlation between the E_a in region II and the peak temperature of degradation for the composites.

Activation energies for degradation of different contents of MWNTs‐filled PP nanocomposites as a function of conversion.     

In situ polymerization of polyurethane‐silver nanocomposite foams with intact thermal stability,improved mechanical performance,and induced antimicrobial properties

Silver nanoparticle‐reinforced thermoplastic polyurethane (PU/AgNP) nanocomposite foams were prepared using in situ polymerization techniques in accordance with DOW chemicals’ industrial standards. The foams exhibited improved mechanical performance, induced antimicrobial properties, and intact stability when subjected to a thermal degradation treatment. Scanning electron microscopy (SEM) indicated a homogeneous dispersion of the silver nanoparticle (AgNP) within the polymeric matrix at low filler loadings and a cluster formation at higher loadings. SEM also indicated the agglomeration of the silver nanofiller particles as a result of the thermal degradation treatment, which caused them to lose their nanoscopic characteristics and act as ordinary silver metal. Molecular modeling techniques were used to explain these observations and confirmed the higher repulsive interactions between the polymer chains and the silver nanoparticles with the increase in the nanofiller content. Stress relaxation of the nanocomposites showed optimum mechanical performance and lowest hysteresis for the 0.1% AgNP nanocomposites due to the confinement of the PU chains between the large number of the nanoparticles. Incubation with 0.1% foam inhibited the growth of Klebseilla spp. and Escherichia coli and to some extent Staphylococcus spp. This is very interesting as the same nanocomposite loaded with 0.1% AgNp has also shown the best mechanical performance highlighting the strong action of this “unclustered” low concentration on both the material and biomedical sides. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43125.     

Synthetic Ni‐talc as filler for producing polyurethane nanocomposites

New synthetic Ni‐talc was used as filler in the synthesis of polyurethane (PU) nanocomposites by in situ polymerization and to emphasize the contribution of the new material compared with natural talc. Good dispersion of Ni‐talc was supported by homogeneous green coloration observed in the polymer matrix. X‐ray diffraction (XRD) analyses indicate the intercalation of polymeric matrix into the filler layers by the increase in d₀₀₁‐spacing value of the Ni‐talc for the nanocomposites when compared to the pristine filler. The nanocomposites obtained with synthetic talc showed an improvement in the crystallization temperature and in thermal stability when compared to pure PU and the composite obtained with natural talc. The young modulus of PU/talc materials containing both Ni‐talc and natural talc were slight higher than pure PU. As shown by scanning electron microscope (SEM), Ni‐talc fillers were well dispersed into the polymeric matrix probably due to the good compatibility of both phases filler/polymer mainly achieved by the filler OH interaction with the urethane group of the polymeric chain. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41854.     

Preparation and tribological properties of poly(methyl methacrylate)/styrene/MWNTs copolymer nanocomposites

Poly(methyl methacrylate)/styrene/multi‐walled carbon nanotubes (PMMA/PS/MWNTs) copolymer nanocomposites with different contents have been prepared successfully by means of in situ polymerization method. The structure and the microhardness of PMMA/PS/MWNTs copolymer nanocomposites were characterized. The tribological behaviors of the copolymer nanocomposites were investigated by a friction and wear tester under dry conditions. The relative humidity of the air was about 50% ± 10%. Comparing with pure PMMA/PS copolymer, the copolymer nanocomposites showed not only better wear resistance but also smaller friction coefficient. MWNTs could help the nanocomposites dramatically improve the wear resistance property. The mechanisms of the improvements on the tribological properties of the PMMA/PS/MWNTs copolymer nanocomposites were also discussed in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal degradation and flammability of nanocomposites composed of silica cross-linked to poly(methyl methacrylate)

The effect of polymer cross-linkages on thermal degradation of silica/poly (methyl methacrylate) (PMMA) nanocomposites is investigated using a single novel nanoparticle. Nanosilica surface treated with KH570, an organic surface treatment capable of free-radical polymerisation, was used to cross-link PMMA via an in situ method. Scanning electron microscopy was used to characterise nanosilica before use, while X-ray diffraction confirmed silica was well dispersed in PMMA. Thermogravimetric analysis (TGA) results showed that thermal degradation of silica cross-linked nanocomposites was significantly stabilised compared to PMMA, with a 30% reduction in the peak mass loss rate. Kinetic studies revealed the degradation of nanocomposites in this work abide by first-order kinetics, with an increase in the degradation activation energy of approximately 100?kJ?mol^?1. This is nearly double the improvement compared to conventional PMMA-silica nanocomposites in literature, showing dramatic enhancements to thermal stability. Analysis of high-temperature residuals from TGA tests suggest that cross-linked silica have increased char yields when compared with both PMMA and traditional silica nanocomposites. Cone Calorimetry results showed the materials in this work have reduced heat release rates compared to PMMA and traditional silica-PMMA nanocomposites.     

Studies on the thermal stability and degradation kinetics of Pd/PC nanocomposites

Effect of heating rate, Pd content, and synthesis method on the thermal stability of the ex situ and in situ Palladium/polycarbonate (Pd/PC) nanocomposites was investigated. TEM images revealed discrete Pd nanoclusters of about 5 and 15 nm sizes for 1 and 2 vol % ex situ nanocomposites, respectively. However, agglomerated Pd nanoclusters were noticed in the in situ samples, irrespective of the Pd content. The ex situ Pd/PC nanocomposites showed high onset temperature (Ti) for thermal degradation of PC than the in situ and pure PC samples. Pd content and heating rates were found to have a positive influence on the Ti and Tm (temperature at the maximum degradation rate occurs) of the Pd/PC nanocomposites. Thermal degradation of the PC was found to follow the first‐order kinetics in the Pd/PC nanocomposites. The activation energies associated with the degradation were determined by using the Kissinger method. These activation energies are used to construct the Master decomposition curve (MDC) and weight–time–temperature (α–t–T) plots that describe the time‐temperature dependence of the PC pyrolysis in the Pd/PC nanocomposites. These constructed α–t–T plots were validated with the data from isothermal measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphology,thermal, and rheological behavior of nylon 11/multi‐walled carbon nanotube nanocomposites prepared by melt compounding

Nylon 11 (PA11) nanocomposites with different loadings of multi‐walled carbon nanotubes (MWNTs) were prepared by melt compounding. Scanning electron microscopy images on the fracture surfaces of the composites showed a uniform dispersion of MWNTs throughout the matrix. The presence of the MWNTs significantly improved the thermal stability and enhanced the storage modulus (G′) of the polymer matrix. Melt rheology studies showed that, compared with neat PA11, the incorporation of MWNT into the matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), and lower loss factor (tanδ). PA11 and its nanocomposites containing less than 1 wt% MWNTs showed similar frequency dependencies and reached a Newtonian plateau at low frequencies. For the nanocomposite with 2 wt% MWNTs, the regional network was destroyed and the orientation of the MWNTs during shearing exhibited a very strong shear thinning effect. The complex viscosities (|η*|) of the nanocomposites are larger than that of neat PA11 and decreased with increasing the temperature. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Synthesis and characterization of linear low‐density polyethylene/sepiolite nanocomposites

Linear low‐density polyethylene (LLDPE)/sepiolite nanocomposites were prepared by melt blending using unmodified and silane‐modified sepiolite. Two methods were used to modify sepiolite: modification before heat mixing (ex situ) and modification during heat mixing (in situ). The X‐ray diffraction results showed that the position of the main peak of sepiolite remained unchanged during modification step. Infrared spectra showed new peaks confirming the development of new bonds in modified sepiolite and nanocomposites. SEM micrographs revealed the presence of sepiolite fibers embedded in polymer matrix. Thermogravimetric analysis showed that nanocomposites exhibited higher onset degradation temperature than LLDPE. In addition, in situ modified sepiolite nanocomposites exhibited higher thermal stability than ex situ modified sepiolite nanocomposites. The ultimate tensile strength and modulus of the nanocomposites were improved; whereas elongation at break was reduced. The higher crystallization temperature of some nanocomposite formulations revealed a heterogeneous nucleation effect of sepiolite. This can be exploited for the shortening of cycle time during processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of chlorine‐containing flame‐retardant polyurethane nanocomposites via in situ polymerization

We have developed flame‐retardant polyurethanes (FRPUs) and polyurethane (PU) nanocomposites via in situ polymerization. Three series of thermoplastic elastomeric PUs were synthesized to investigate the effect of incorporating 3‐chloro‐1,2‐propanediol (CPD) and nanoclay on mechanical, thermal properties, and also resistance to burning. PU soft segments were based on poly(propylene glycol). Hard segments were based on either CPD or 1,4‐buthane diol (BDO) in combination with methyl phenyl di‐isocyanate named PU or FRPU, respectively. In the third series, CPD was used as chain extender also nanoclay (1% wt) and incorporated and named as flame‐retardant polyurethane nanocomposites (FRPUN). Mechanical properties and LOI of PUs and nanocomposites have been evaluated. Results showed that increasing the hard segment (chlorine content) leads to the increase in flame retardancy and burning time. Addition of nanoclay to CPD‐containing PUs leads to obtain self‐extinguish PUs using lower CPD contents, higher Young's modulus, and strength without any noticeable decrease in elongation at break. Investigation of the TGA results showed that copresence of nanoclay and chlorine structure in the PU backbone can change thermal degradation pattern and improve nanocomposite thermal stability. X‐ray diffraction and transmission electron microscopy studies confirmed that exfoliation and intercalation have been well done. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Amino‐functionalized multiple‐walled carbon nanotubes‐polyimide nanocomposite films fabricated by in situ polymerization

For the preparation of high‐quality polymeric carbon nanocomposites, it is required that carbon nanotubes are fully compatible with matrix polymers. For this purpose, amino‐functionalized multiple‐walled carbon nanotubes (a‐MWNTs) were synthesized. The a‐MWNTs/polyimide nanocomposite films were prepared through in situ polymerization. According to the spectroscopic characterizations, the a‐MWNTs were homogeneously dispersed in the nanocomposite films as the acid‐functionalized MWNTs. The mechanical properties of the polyimide composite were also studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

High performance epoxy resin nanocomposites containing both organic montmorillonite and castor oil-polyurethane

Summary Epoxy resin/polyurethane interpenetrating polymer network nanocomposites with various contents of organophilic montmorillonite (oM-EP/PU nanocomposites) were prepared by a sequential polymeric technique and an in situ intercalation method. X-ray diffraction(XRD), and transmission electronic microscopy(TEM) analysis showed that organophilic montmorillonite (oMMT) disperses uniformly in epoxy resin/polyurethane interpenetrating networks(IPNs), and the intercalated or exfoliated microstructures of oMMT are formed. Differential scanning calorimetry(DSC) test proved that oMMT promotes the compatibility of EP phase and PU phase, and glass transition temperature(T_g) of oM-EP/PU nanocomposites improves with increasing oMMT content. Mechanical properties tests and thermal gravity analysis (TGA) indicated that oMMT and the IPNs of EP and PU exhibit synergistic effect on improving mechanical and thermal properties of pure EP. The mechanism of toughing and reinforcing of oM-EP/PU nanocomposites was further discussed by scanning electronic microscope(SEM).     

Synthesis,characterization, and thermal aging behavior of HCl‐doped polyaniline/TRGO nanocomposites

In this article polyaniline (PANI) nanocomposites containing thermally reduced graphene oxide (TRGO) were synthesized and characterized before and after thermal aging. The nanocomposites were prepared through in situ oxidative polymerization of aniline in the presence of TRGO nanoplatelets. FTIR and Raman spectroscopies, XRD, FESEM, and electrical conductivity measurements were used to characterize synthesized materials. PANI/TRGO nanocomposites showed considerably higher electrical conductivity when compared to pure PANI, which was associated with the higher electrical conductivity of TRGO and increased crystallinity of PANI in the presence of TRGO. Pure PANI and PANI/TRGO nanocomposites were thermally aged at 70, 80, 90, and 100 °C. The results showed that the characteristic time of thermal aging process is higher for PANI/TRGO nanocomposites and increases with TRGO loading, which indicates better stability of conductivity during thermal aging process. On the other hand, the characteristic time of thermal aging reduced with aging temperature and a fast decrease was observed from 80 to 90 °C. Improved resistance over thermal aging can be attributed to the barrier effect of TRGO nanoplatelets to the dopant molecules, which retards conductivity degradation in the thermal aging process. Furthermore, TRGO increases PANI crystallinity and it can also prevent crystallinity reduction during thermal aging process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44635.     

Effect of clay platelet dispersion as affected by the manufacturing techniques on thermal and mechanical properties of PMMA‐clay nanocomposites

In this work, the properties of Poly(methyl methacrylate) (PMMA)‐clay nanocomposites prepared by three different manufacturing techniques viz., solution mixing, melt mixing, and in‐situ bulk polymerization in presence of clay were studied. Morphological analysis revealed that the extent of intercalation and dispersion of the nanoclay were relatively higher in the in‐situ polymerized nanocomposites than those of solution and melt blended nanocomposites. Differential Scanning Calorimetric study indicated maximum increment in T_g of the PMMA in the in‐situ polymerized PMMA‐clay nanocomposites. Thermo gravimetric analysis showed improved thermal stability of PMMA in all the nanocomposites and the maximum improvement was for in‐situ polymerized nanocomposites. The storage moduli of all the nanocomposites were higher than the pure PMMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal degradation kinetics of polyimide nanocomposites from different carbon nanofillers: Applicability of different theoretical models

In this study, the nanocomposites of polyimide (PI) with the nanofillers multiwalled carbon nanotube (MWCNT) and carbon nanofiber (CNF) were prepared by in situ polymerization technique. The thermal stability of the nanocomposites were investigated and discussed with respect to nanofillers type, concentration, and their functionality within the PI matrix. It is observed that there are 16 and 18 °C increment in thermal degradation temperature with the addition of 3 wt % MWCNT and CNF within the PI matrix, respectively. The thermal degradation kinetics of the nanocomposites were studied by Kissinger–Akahira–Sunose method, Flynn–Wall–Ozawa method, and Kim–Park method. The results show that these models are well fitted with the experimental data. It is found that the calculated activation energy increases with the increase in nanofillers loading and PI/CNF nanocomposites exhibit higher activation energy compared to PI/MWCNT composites at their similar loading. Moreover, the effect of nanofillers type and loading on the glass transition temperature of nanocomposites were also investigated in details. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45862.     

Synthesis and characterization of polyimide/multi‐walled carbon nanotube nanocomposites

Polyimide/multi‐walled carbon nanotube (PI‐MWNT) nanocomposites were fabricated by an in situ polymerization process. Chemical compatibility between the PI matrix and MWNTs is achieved by pretreatment of the carbon nanotubes in a mixture of sulfuric acid and nitric acid. The dispersion of MWNTs in the PI matrix was found to be enhanced significantly after acid modification. The glass transition (T_g) and decomposition (T_d) temperature of PI‐MWNT nanocomposites were improved as the MWNT content increased from 0.5 to 15 wt%. The storage modulus of the PI/MWNT nanocomposites is nine times higher than that of pristine PI at room temperature. The tensile strength of PI doubles when 7 wt% MWNTs is added. The dielectric constant of the PI‐MWNT nanocomposites increased from 3.5 to 80 (1 kHz) as the MWNT content increased to 15 wt%. The present study demonstrates that enhanced mechanical properties can be obtained through a simple in‐situ polymerization process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical and thermal properties of functionalized multiwalled carbon nanotubes and multiwalled carbon nanotube–polyurethane composites

Multiwalled carbon nanotube (MWNT)–polyurethane (PU) composites were obtained by an in situ polycondensation approach. The effects of the number of functional groups on the dispersion and mechanical properties were investigated. The results showed that the functionalized MWNTs had more advantages for improving the dispersion and stability in water and N,N′‐dimethylformamide. The tensile strength and elongation at break of the composites exhibited obvious increases with the addition of MWNT contents below 1 wt % and then decreases with additions above 1 wt %. The maximum values of the tensile strength and elongation at break increased by 900 and 741%, respectively, at a 1 wt % loading of MWNTs. Differential scanning calorimetry measurements indicated that the addition of MWNTs resulted in an alteration of the glass‐transition temperature of the soft‐segment phase of MWNT–PU. Additionally, new peaks near 54°C were observed with differential scanning calorimetry because of the microphase‐separation structures and alteration of the segment molecular weights of the hard segment and soft segment of PU with the addition of MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of CNT‐polyurethane nanocomposites using ester‐based polyols with different molecular structure: Mechanical,thermal, and electrical properties

Polyurethanes (PUs) were prepared by in situ polymerization of three diisocyanate with three synthesized low cost ester‐based polyols. The effect of diisocyanate type, diol structure, and molar ratio of diisocyanate to polyol on the mechanical properties was examined and the optimum chemical structure was introduced regarding the superior mechanical properties. Also, in presence of well dispersed hydroxylated multiwalled carbon nanotubes (CNT), PU/CNT nanocomposites were synthesized and fully characterized. The results showed that PU synthesized based on 1,4‐butane diol (BDO) has the best mechanical properties and thermal stability. Also, the PU samples synthesized from 1,6‐hexamethylene diisocyanate (HDI) were more profitable than aromatic diisocyanate structures due to higher crystallinity and microstructure packing. The nanocomposite sample containing 1.5% CNT was the optimum composition for the maximum tensile strength and electrical conductivity. This result was related to the uniform dispersion and bonding of CNTs to PU chains at this composition, while aggregates were formed at higher concentration of CNTs which increased the defects and reduced the uniformity of the structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44567.