Influence of rubber content on mechanical,thermal, and morphological behavior of natural rubber toughened poly(lactic acid)–multiwalled carbon nanotube nanocomposites

The effects of natural rubber (NR) on the mechanical, thermal, and morphological properties of multiwalled carbon nanotube (CNT) reinforced poly(lactic acid) (PLA) nanocomposites prepared by melt blending were investigated. A PLA/NR blend and PLA/CNT nanocomposites were also produced for comparison. The tensile strength and Young's modulus of PLA/CNT nanocomposites improved significantly, whereas the impact strength decreased compared to neat PLA. The incorporation of NR into PLA/CNT significantly improved the impact strength and elongation at break of the nanocomposites, which showed approximately 200% and 850% increases at 20 wt % NR, respectively. However, the tensile strength and Young's modulus of PLA/NR/CNT nanocomposites decreased compared to PLA/CNT nanocomposites. The morphology analysis showed the homogeneous dispersion of NR particles in PLA/NR/CNT nanocomposites, while CNTs preferentially reside in the NR phase rather than the PLA matrix. In addition, the incorporation of NR into PLA/CNT lowered the thermal stability and glass‐transition temperature of the nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44344.     

The mechanisms and mechanics of the toughening of epoxy polymers modified with fullerene C60

This study examined the effect of fullerene C₆₀ on the mechanical properties of epoxy‐based polymer nanocomposites with different C₆₀ loadings. Mechanical testing shows that compared with neat epoxy, mechanical and toughening properties of composites are greatly improved. Young's modulus increased 6–20% by inducing 0.01–0.12 wt% of fullerene into the matrix resin. Furthermore, the toughness of the composite was improved up to about 200%. The toughening mechanism has been discussed. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Synthesis and mechanical properties of polybenzimidazole nanocomposites reinforced by vapor grown carbon nanofibers

Polybenzimidazole (PBI) nanocomposites containing 0.5–5 wt% vapor grown carbon nanofibers (VGNFs) were successfully synthesized by solvent evaporation method. Fracture morphology examination confirmed the uniform dispersion of VGNFs in the matrix. The mechanical properties of neat PBI and the nanocomposites were systematically measured by tensile test, dynamic mechanical analysis (DMA), hardness measurement, and friction test. Tensile tests revealed that Young's modulus increased by about 43.7% at 2 wt% VGNFs loading, and further modulus growth was observed at higher filler loadings. DMA studies showed that the nanocomposites have higher storage modulus than neat PBI in the temperature range of 30–350°C, holding storage modulus larger than 1.54 GPa below 300°C. Outstanding improvement of hardness was achieved for PBI upon incorporating 2 wt% of VGNFs. The results of friction test showed that coefficient of friction of PBI nanocomposites decreased with VGNFs content compared with neat PBI. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhanced mechanical properties of nanocomposites at low graphene content based on in situ ball milling

In this study, epoxy‐based nanocomposites with low content mechanically exfoliated graphene were successfully prepared via one‐step in situ ball milling method. The effect of graphene on mechanical properties of the nanocomposites was investigated. The results showed that samples with loadings less than 0.1% weight of mechanically exfoliated graphene increased by 160% in tensile strength and 65% in Young's modulus. The experimental value of Young's modulus was also compared with the predictions of the well‐established Halpin‐Tsai model. In addition, the adding of graphene did not decrease the impact strength of epoxy. The microstructural results showed that the as‐prepared graphenes were single‐ and few‐layer graphene sheets and preserved perfect structure. Thus enhancements of mechanical properties in the nanocomposites could be ascribed to the strong interfacial interaction between the stiff graphene nanosheets and the epoxy matrix. POLYM. COMPOS. 37:1190–1197, 2016. © 2014 Society of Plastics Engineers     

Simultaneously enhanced cryogenic mechanical behaviors of cyanate ester/epoxy resins by poly(ethylene oxide)‐co‐poly(propylene oxide)‐co‐poly(ethylene oxide) (PEO‐PPO‐PEO) block copolymer and clay

Cryogenic mechanical properties are important parameters for thermosetting resins used in cryogenic engineering areas. The hybrid nanocomposites were prepared by modification of a cyanate ester/epoxy/poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐PPO‐PEO) system with clay. It is demonstrated that the cryogenic tensile strength, Young's modulus, ductility (failure strain), and fracture resistance (impact strength) are simultaneously enhanced by the addition of PEO‐PPO‐PEO and clay. The results show that the tensile strength and Young's modulus at 77 K of the hybrid nanocomposite containing 5 wt% PEO‐PPO‐PEO and 3 wt% clay were enhanced by 31.0% and 14.6%, respectively. The ductility and impact resistance at both room temperature and 77K are all improved for the hybrid composites. The fracture surfaces of the neat BCE/EP and its nanocomposites were examined using scanning electron microscopy (SEM). Finally, the dependence of the coefficients of thermal expansion (CTE) on the clay and PEO‐PPO‐PEO contents was examined by thermal dilatometer. POLYM. COMPOS., 38:2237–2247, 2017. © 2015 Society of Plastics Engineers     

Synthesis and characterization of organically modified attapulgite/polyurethane nanocomposites

Polyurethane (PU) nanocomposites filled with attapulgite (ATT) nanorods were synthesized and characterized with thermal analysis, dynamic mechanical analysis (DMA), and mechanical testing. The formulations were based on 4,4′‐methylene bis(phenyl isocyanate) (MDI), polytetrahydrofuran, 1,4‐butanediol, and inorganic ATT premodified with MDI. The original and premodified ATT (ATT–OH and ATT–MDI) nanorods were characterized with thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The analysis revealed that 17 wt % MDI was grafted/adsorbed onto the surface of ATT as a result of the modification. Pristine PU and ATT–MDI/PU nanocomposites were characterized with scanning electron microscopy, differential scanning calorimetry, and TGA. The mechanical tests and DMA showed an increase in the storage modulus and Young's modulus with increasing ATT–MDI content. The crystallinity of the hard and soft segments and thermal stability showed enhancements over those of the neat resin. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reinforcement effect of nanodiamond on properties of epoxy matrix

Epoxy/nanocrystalline diamond nanocomposites composites were prepared by dispersing ultrasonically, 0.4, 0.7, 1.0, and 4.0 wt% acid‐treated nanocrystalline diamond (NCD) powder in epoxy matrix. Fourier infrared spectroscopy was utilized to study the moieties attached to the nanodiamond particles. The trace elements present in NCD powder before and after acid treatment were analyzed by ion beam techniques. Thermomechanical properties of the nanocomposites showed that incorporation of low content (0.4 wt%) of nanodiamond powder into epoxy matrix enhanced the storage modulus, loss modulus, and hardness by ∼68, ∼55, and ∼86%, respectively, over neat epoxy. By increasing the concentration of modified NCD to 0.7 wt% resulted in lower values of hardness and thermomechanical properties but still remain higher than neat epoxy. An increasing trend in properties was again observed at 4 wt% concentration of modified nanofiller. The glass transition temperature was up shifted to ∼110°C over neat epoxy. The mechanisms responsible for enhanced properties of epoxy matrix are also discussed in detail. POLYM. COMPOS., 34:811–818, 2013. © 2013 Society of Plastics Engineers     

Structure and properties of starch nanocrystal‐reinforced soy protein plastics

Pea starch nanocrystals (StNs) were incorporated into a soy protein isolate (SPI) matrix to produce a class of full‐biodegradable nanocomposites. The StN with low loading level (2 wt%) showed a predominant reinforcing function, resulting in an enhancement in strength and Young's modulus. This was attributed to uniform dispersion of StN in the amorphous region of the SPI matrix, as well as maintaining stress of the rigid StN and transfer of stress mediated by interfacial interaction between the active StN surface and the SPI matrix. As a result, the nanocomposite containing 2 wt% StN had the maximum strength and Young's modulus in all the materials. With an increase in StN content, the number and the size of StN domains simultaneously increased due to a strong self‐aggregation tendency of StN. It lowered the effective active StN surface for interaction with the SPI matrix and destroyed the ordered structure in the SPI matrix, resulting in a gradual decrease of strength and Young's modulus. The introduction of relatively hydrophilic StN did not cause an obvious decrease of water resistance for any of the nanocomposites. The water uptake behavior of all the nanocomposites similar to that of neat SPI material was attributed mainly to the strong interfacial interaction between the StN filler and the SPI matrix. POLYM. COMPOS., 2009. Published by the 2008 Society of Plastics Engineers     

Effect of ethylene‐1‐butene copolymer on tensile properties and toughness of polypropylene/mica/organoclay hybrid nanocomposites

In this study, polypropylene (PP) was reinforced using 1 wt% organically modified‐grafted mica (OMGM) and various levels of Cloisite15A (C15A), 0–3 wt%. For OMGM preparation, polypropylene graft maleic anhydride (PP‐g‐MAH) was grafted onto diacetone acryl amid modified mica. The results showed the highest impact strength enhancement of 68% and Young's modulus of 12% for hybrid nanocomposite containing 1 wt% OMGM and 0.5 wt% C15A when compared to neat PP. In order to considerably improve the impact strength of PP with advantage of elastic modulus enhancement, PP was melt blended with above‐mentioned amounts of OMGM and C15A and different contents of ethylene‐1‐butene copolymer (EBR), 0–10 wt%. The dispersion of low‐ and high‐aspect ratio layered silicate tactoids and EBR nanoparticles in the polymer matrix was studied using transmission electron microscopy. The effect of EBR level on the crystallization behavior, tensile properties, impact strength, and fracture toughness of the resultant toughened hybrid nanocomposite was investigated. The presence of EBR nanoparticles did not show any sufficient effect on the melting and crystallization temperatures of the toughened PP and hybrid nanocomposites. However, the impact results indicated that the addition of EBR to neat PP remarkably increased the toughness while sharply decreased its Young's modulus. The incorporation of 7 wt% EBR in the hybrid nanocomposite containing 1 wt% OMGM and 0.5 wt% C15A considerably enhanced impact strength 119% and 30% in comparison to neat PP and its hybrid nanocomposite, respectively. Additionally, the incorporation of EBR nanoparticle in the presence of the silicate layered nanoparticles prevented significant decreasing in Young's modulus of the matrix. J. VINYL ADDIT. TECHNOL., 25:117–126, 2019. © 2018 Society of Plastics Engineers     

Effect of graphene and CNT reinforcement on mechanical and thermomechanical behavior of epoxy—A comparative study

Graphene‐nanoplateles (Gr) and multiwalled carbon nanotubes (CNTs) reinforced epoxy based composites were fabricated using ultrasonication, a strong tool for effective dispersion of Gr/CNTs in epoxy. The effect of individual addition of two different nanofillers (Gr and CNT) in epoxy matrix, for a range of nanofiller content (0.1–1 wt %), has been investigated in this study. This study compares mechanical and thermomechanical behavior of Gr and CNT reinforced epoxy. Gr reinforcement offers higher improvement in strength, Young's modulus, and hardness than CNT, at ≤0.2 wt %. However, mode‐I fracture toughness shows different trend. The maximum improvement in fracture toughness observed for epoxy‐Gr composite was 102% (with 0.3 wt % loading of Gr) and the same for epoxy‐CNT composite was 152% (with 0.5 wt % loading of CNT). Thorough microstructural studies are performed to evaluate dispersion, strengthening, and toughening mechanisms, active with different nanofillers. The results obtained from all the studies are thoroughly analyzed to comprehend the effect of nanofillers, individually, on the performance of the composites in structural applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46101.     

Covalent addition of diethyltoluenediamines onto carbon nanotubes for composite application

Diethyltoluenediamines (DETDA) was grafted to single‐walled carbon nanotubes (SWNTs) through diazonium‐based addition for improving dispersion and interfacial bonding in SWNT/epoxy nanocomposites. Characterization results of Fourier Transformed Infrared spectroscopy and Raman spectroscopy validated covalent bonding between DETDA and carbon nanotubes. The degree of functionalization was about 4% based on thermo‐gravimetric analysis. Interfacial bonding strength was computed in the presence of chemical bonding and the computation results indicated that the interfacial shear strength in the presence of functionalized carbon nanotubes was significantly enhanced. The experimental test revealed that the tensile strength of nanocomposites was enhanced about 23% and Young's modulus about 25%, with 0.5 wt% loading of functionalized‐nanotubes. These considerable improvements further verified the load‐transfer enhancement in the functionalized‐SWNTs/epoxy nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Preparation of epoxy composites with CTAB‐modified BN and MWCNTs

In this study, multi‐walled carbon nanotubes (MWCNTs) and boron nitride (BN) were functionalized with cetyltrimethylammonium bromide (CTAB) at both pH 5.5 and pH 11. These MWCNT‐CTAB and BN‐CTAB particles used to prepare the composites were dispersed in a bisphenol A (DGEBA)‐type epoxy resin (ER) system at room temperature. The TGA analysis showed that the BN composite can significantly improve the thermal stability of neat ER at temperatures above 400 °C. The curing degrees of the nanocomposites were calculated to be approximately the same values as neat ER using the Beer–Lambert law from FTIR spectra. The best electrical conductivity of the composites obtained was 3.10 × 10⁻³ S/cm for ER/MWCNT‐CTAB (pH 5.5). The surface hardness, Young's modulus, and tensile strength of the composites were examined. The surface hardness values of the ER/MWCNT‐CTAB composites were higher than those of the other composites. The composite morphology was characterized using X‐ray diffraction (XRD) and scanning electron microscopy (SEM). POLYM. COMPOS., 37:3423–3432, 2016. © 2015 Society of Plastics Engineers     

Epoxy composites based on inexpensive char filler obtained from plastic waste and natural resources

In this study, plastic [polyethylene terephthalate (PET)] waste was recycled as raw material for the preparation of diglycidyl ether of bisphenol A‐type epoxy composite materials. The other inexpensive fillers used to prepare the composites were wood shavings char and pine cone char (PCC), obtained from natural resources. The thermogravimetric analysis showed that plastic waste char (PWC) and PCC can significantly improve the thermal stability of neat epoxy resin at temperatures above 300°C. The best thermal and electrical conductivity results were obtained with PWC. The residual weight of the composite with 30 wt% PWC was 69%. Surface hardness, Young's modulus, and tensile strength of the composites were higher than those with a pure epoxy polymer matrix. The composite morphology was characterized by X‐ray diffraction and scanning electron microscopy. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Structure and properties of polypropylene‐wrapped carbon nanotubes composite

By means of in situ graft method, polypropylene (PP)‐wrapped carbon nanotubes (CNTs) composite were prepared. Infrared spectroscopy (IR) results showed that there was covalent linkage between PP and CNTs via maleic anhydride (MAH) grafting. Owing to the uniform dispersion of CNTs and covalent adhesion between PP and CNTs, the tensile strength of PP‐wrapped CNTs composite was higher than that for neat PP by 110%, and a 74% increase as compared to the CNTs/PP (with the same CNTs content) composite. The further test showed a strong mechanical behavior with up to 113% increase in Young's modulus of the neat PP. Based on the uniform dispersion of CNTs, the electrical conductivity of PP‐wrapped CNTs composite increased sharply by up to seven orders of magnitude with 4 wt % CNT fillers. As a result, the volume resistivity was decreased with increase in the CNT content that could be governed in a percolation‐like power law with a relatively low percolation threshold. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fabrication and characterization of functionally graded nanoclay/glass fiber/epoxy hybrid nanocomposite laminates

In this work, hardness, tensile, impact, bearing strength and water absorption tests were performed to study the mechanical properties of stepwise graded and non-graded hybrid nanocomposites. Three different stepwise graded nanocomposites and one non-graded (homogeneous) nanocomposite with the same geometry and total nanoclay content of 10 wt% were designed and prepared. Moreover, one neat glass fiber laminate was manufactured. The results of the tests indicated that addition of the graded and non-graded nanoclay improves hardness over neat glass fiber reinforcement. The maximum increase in hardness of about 53% over neat specimen is obtained for specimens that have the highest weight percentage (2 wt%) of the clay nanoparticles on its surface (S-specimen and the side of F-specimen that reinforced with 2 wt% nanoclay). The gradation process results in an increase in hardness of about 11% compared with non-graded (homogeneous) specimen. In addition, an improvement of 11.9% in strain-to-failure is achieved with specimen having greatest amount of nanoclay in the middle over neat glass fiber/epoxy composite. The other nanoclay-filled glass fiber composites have strain-to-failure close to neat glass fiber/epoxy. The addition of nanoclay reinforcement has insignificant effect on ultimate tensile strength, tensile modulus, water absorption, bearing strength and impact strength compared with neat glass fiber/epoxy.     

Study of morphological and mechanical performance of amine‐cured glassy epoxy–clay nanocomposites

The effect of three different alkylammonium‐modified montmorillonite on morphological and mechanical properties of glassy epoxy‐amine nanocomposites is reported. Small amounts of clays <10 phr (part per hundred of resin) were used in each system of nanocomposite. The morphology of the prepared nanocomposites was performed by means of X‐ray diffraction and transmission electron microscopy. Differential scanning calorimetry (DSC) was used to investigate the glass transition temperatures (T_g). Mechanical properties were based on tensile characteristics (Young's modulus), impact strength, and fracture toughness. The measured moduli were compared to theoretical predictions. Scanning electron microscopy was used to study the morphological structure of the fracture surfaces of impacted specimens. It was found that at a low content of 2 phr (1.2 wt %) of nanoclays, the impact strength and the fracture toughness were improved by 77 and 90% respectively, comparatively to the neat epoxy, whereas DSC revealed a reduction of the T_g of nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate)‐hyperbranched polymer–nanoclay nanocomposites

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were investigated. According to the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride‐alt‐1‐octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan‐δ curve, specific toughness, and strain‐at‐break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay‐based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Alignment and properties of carbon nanotube buckypaper/liquid crystalline polymer composites

Carbon nanotubes (CNTs) have been recognized as a potential superior reinforcement for high‐performance, multifunctional composites. However, non‐uniform CNT dispersion within the polymer matrix, the lack of adequate adhesion between the constituents of the composites, and lack of nanotube alignment have hindered significant improvements in composite performance. In this study, we present the development of a layer‐by‐layer assembly method to produce high mechanical performance and electrical conductivity CNT‐reinforced liquid crystalline polymer (LCP) composites using CNT sheets or buckypaper (BP) and self‐reinforcing polyphenylene resin, Parmax. The Parmax/BP composite morphology, X‐ray diffraction, mechanical, thermal, and electrical properties have been investigated. SEM observations and X‐ray diffraction demonstrate alignment of the CNTs due to flow‐induced orientational ordering of LCP chains. The tensile strength and Young's modulus of the Parmax/BP nanocomposites with 6.23 wt % multi‐walled carbon nanotube content were 390 MPa and 33 GPa, respectively, which were substantially improved when compared to the neat LCP. Noticeable improvements in the thermal stability and glass transition temperature with increasing CNT content due to the restriction in chain mobility imposed by the CNTs was demonstrated. Moreover, the electrical conductivity of the composites increased sharply to 100.23 S/cm (from approximately 10^?13 S/cm) with the addition of CNT BP. These results suggest that the developed approach would be an effective method to fabricate high‐performance, multifunctional CNT/LCP nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008