The linear tearing properties of biaxially oriented PA6/MXD6 blending films

The main purpose of this work was to investigate the linear tearing properties of PA6/MXD6 films prepared by simultaneous biaxial stretching. The compatibility between PA6 and MXD6 and the thermal properties of the PA6/MXD6 composites were also investigated. The results showed that the tearing deviation of the blending films decreased from 100 to 3.8% when the MXD6 blend ratio increased from 0 to 25%, but the deviation increased when the MXD6 blend ratio continue to increase. It means that the PA6/MXD6 films with addition of 25 wt% MXD6 exhibited the best linear tearing properties. The differential scanning calorimetry results revealed that the addition of MXD6 reduced the melting temperature from 227.5 to 224.8°C and crystallization temperature of PA6 from 179.3 to 175°C due to the benzene ring structure of MXD6. The dynamic mechanical analysis results indicated that MXD6 exhibits favorable compatibility with PA6. In addition, it was found that the barrier properties of the biaxially oriented PA6/MXD6 films were extremely improved with the increase of MXD6 content.     

PA6/MXD6/黏土复合材料的流变行为研究

采用毛细管流变仪研究了聚己二酰间苯二甲胺(MXD6)及黏土的引入对聚酰胺6(PA6)流变性能的影响。结果表明:PA6、PA6/黏土、PA6/MXD6和PA6/MXD6/黏土复合材料均为假塑性流体;在220~240℃之间,PA6及其复合材料的非牛顿指数为0.50~0.85。另外,加入黏土使得PA6和PA6/MXD6的黏度上升,非牛顿指数和黏流活化能下降;而加入MXD6则使得PA6、PA6/黏土的黏度下降,非牛顿指数和黏流活化能上升。     

PA66、PA6改性MXD6共混物的定性定量分析

通过对进口样品MXD6/尼龙6(PA6)及MXD6/尼龙66(PA66)合金的分析,确立了合金中MXD6的定性、定量分析方法。     

Mechanical and oxygen barrier properties of organoclay-polyethylene nanocomposite films

An organically modified montmorillonite was compounded with ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) in a twin-screw extruder. The resulting organoclay-polyethylene nanocomposites were then blown into films. Tensile properties and oxygen permeability of these nanocomposite films were investigated to understand the effects of organoclay on different types of polyethylene. It was found that the clay enhancing effects are function of the matrix. The mechanical and oxygen barrier properties of clay/EVA systems increased with clay loading. Both the tensile modulus and oxygen barrier of EVA doubled at 5 wt% clay. Maleic anhydride grafted polyethylene (MAPE) usually is used as a compatibilizer for LDPE and HDPE-based nanocomposites. However, the MAPEs were found to weaken the oxygen barrier of the PEs, especially for HDPE. This is believed to be a result of less compactness caused by the large side groups and the increase in polarity of the MAPEs. Incorporating 5 wt% clay improves the oxygen barrier by 30% and the tensile modulus by 37% for the LDPE/MAPE system. Incorporation of clay does not enhance the properties of the HDPE-based systems, likely due to large domain structure and poor bonding. Halpin–Tsai equation and the tortuous path equation were used to model the tensile modulus and oxygen permeability of the clay/EVA nanocomposite films. POLYM. ENG. SCI., 47:1101–1107, 2007. © 2007 Society of Plastics Engineers     

Morphology,thermal, mechanical,and barrier properties of graphene oxide/poly(lactic acid) nanocomposite films

To improve the physical and gas barrier properties of biodegradable poly(lactic acid) (PLA) film, two graphene nanosheets of highly functionalized graphene oxide (0.3 wt% to 0.7 wt%) and low-functionalized graphene oxide (0.5 wt%) were incorporated into PLA resin via solution blending method. Subsequently, we investigated the effects of material parameters such as loading level and degree of functionalization for the graphene nanosheets on the morphology and properties of the resultant nanocomposites. The highly functionalized graphene oxide (GO) caused more exfoliation and homogeneous dispersion in PLA matrix as well as more sustainable suspensions in THF, compared to low-functionalized graphene oxide (LFGO). When loaded with GO from 0.3 wt% to 0.7 wt%, the glass transition temperature, degree of crystallinity, tensile strength and modulus increased steadily. The GO gave rise to more pronounced effect in the thermal and mechanical reinforcement, relative to LFGO. In addition, the preparation of fairly transparent PLA-based nanocomposite film with noticeably improved barrier performance achieved only when incorporated with GO up to 0.7wt%. As a result, GO may be more compatible with hydrophilic PLA resin, compared to LFGO, resulting in more prominent enhancement of nanocomposites properties.     

Effect of uniaxial stretching on thermal,oxygen barrier,and mechanical properties of polyamide 6 and poly(m‐xylene adipamide) nanocomposite films

In this study, the effect of uniaxial stretching on the thermal, oxygen barrier and mechanical properties of aliphatic polyamide 6 (PA6) and aromatic Poly(m‐xylene adipamide) (MXD6) nylon films as well as their in‐situ polymerized nanocomposites with 4 wt% clay were studied. Cast films were prepared by extrusion process and rapidly cooled using an air knife. The precursor films were uniaxially stretched at 110°C with draw ratios varying from 1.5 to 5. DSC results showed that the cold crystallization temperature (T_cc) of the uniaxially stretched MXD6 and MXD6/clay films drastically shifted to the lower temperatures when draw ratio increased. The aromatic nylon films had lower oxygen permeability than those of the aliphatic films, due to more rigidity and chain packing. However, the oxygen permeability of the stretched films increased with draw ratio (DR) up to a critical value for each sample, while further stretching resulted in a reduction in the oxygen permeation. This phenomenon was related to the changes in free volume upon uniaxial stretching. The ability of different geometrical models to describe the experimental relative permeability data was investigated. The Bharadwaj model that took into account clay orientation was the most successful one to predict the oxygen barrier characteristics of the stretched nanocomposites at high draw ratios. The Young's modulus and tensile strength of the aliphatic and aromatic nylons increased with uniaxial deformation, while the flexibility and elongation at break of the former decreased with increasing DR. A larger increase in the Young's modulus of the uniaxially stretched nanocomposite films compared with the neat samples was observed and could be related to the improvement in the clay orientation as well as a better alignment of the crystalline phase due to incorporating the clay platelets in the polymer matrix. In contrast, the flexibility of the stretched MXD6 improved remarkably (ca., 25 times) compared with the precursor film (DR = 1) when the draw ratio increased to 1.5. This could be related to the effect of hot stretching on the enhancement of polymer chains relaxation and mobility at low draw ratios. POLYM. ENG. SCI., 55:1113–1127, 2015. © 2014 Society of Plastics Engineers     

Preparation and characterization of poly(propylene carbonate)/exfoliated graphite nanocomposite films with improved thermal stability,mechanical properties and barrier properties

Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 µm and a nanometer sized thickness of 30–50 nm were successfully prepared by thermal treatment at 1050 °C and subsequent ultrasonication for application as a filler to improve the physical properties of eco‐friendly poly(propylene carbonate) (PPC). A series of poly(propylene carbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives. © 2013 Society of Chemical Industry     

Physical and mechanical properties of nanocomposite barrier film containing encapsulated nanoclay

Waterborne poly(styrene‐co‐butyl acrylate) was prepared via miniemulsion polymerization in which nanoclay (Cloisite® 30B, modified natural MMT) in different concentrations was encapsulated. Scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy confirmed the encapsulation and intercalated‐exfoliated structure of Cloisite® 30B within poly(styrene‐co‐butyl acrylate). The effect of nanoclay content on water vapor permeability, water uptake, oxygen permeability, thermal, and mechanical properties of thin films containing 1.5, 2.56, 3.5, and 5.3 wt % encapsulated Cloisite® 30B in poly(styrene‐co‐butyl acrylate) was investigated. The presence of encapsulated Cloisite® 30B within the polymer matrix improved tensile strength, Young's modulus, and toughness of the nanocomposites depending on the nanoclay content. Water vapor transmission rate, oxygen barrier properties, and thermal stability were also improved. The results indicated that the incorporation of Cloisite® 30B in the form of encapsulated platelets improved physicomechanical properties of the nanoclay‐polymer composite barrier films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructure and mechanical properties of Mo/DLC nanocomposite films

Mo-doped diamond-like carbon (Mo/DLC) films were deposited on stainless steel and Si wafer substrates via unbalanced magnetron sputtering of molybdenum combined with inductively coupled radio frequency (RF) plasma chemical vapor deposition of CH₄/Ar. The effects of Mo doping and sputtering current on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), and nano-indentation. It was found that Mo doping led to increase in the content of sp² carbon, and hence decreased the hardness and elastic modulus of Mo/DLC films as compared with that of DLC films. The content of Mo in the films increased with the increasing sputtering current, and most of Mo reacted with C atoms to form MoC nanocrystallites at a higher sputtering current. Moreover, the Mo-doped DLC films had greatly decreased internal stress and increased adhesion to the substrate than the DLC film, which could be closely related to the unique nanocomposite structure of the Mo-doped films. Namely, the Mo/DLC film was composed of MoC nanoparticles embedded in the cross-linked amorphous carbon matrix, and such a kind of nanostructure was beneficial to retaining the loss of hardness and elastic modulus.     

Small strain mechanical properties of latex-based acrylic nanocomposite films

A waterborne latex-based technique has been used to prepare acrylic films with laponite contents up to about 25 vol%. The laponite was attached to the surfaces of the latex particles, giving a cellular arrangement of laponite-rich regions at high laponite contents. Two regimes of reinforcement were observed, depending on whether T was above or below T_g, reinforcement at T > T_g being significantly greater than predicted by micromechanical models. Modulated differential scanning calorimetry and dynamic mechanical analysis showed part of the organic content of the films not to contribute to the glass transition. This “rigid amorphous fraction” (RAF) was argued to correspond to intercalated regions of the matrix. However, the RAF alone was insufficient to account for the observed increases in stiffness at T > T_g. The mechanical response is therefore discussed in terms of a four-phase model, in which intercalated laponite stacks are embedded in a matrix with reduced mobility, forming a foam-like structure, in turn embedded in a matrix with the properties of the bulk polymer.     

Bio-based engineered nanocomposite foam with enhanced mechanical and thermal barrier properties

Bio-based polyurethane (PU) foams were developed from bio-polyol (castor oil-based) in the presence of selective catalyst, surfactant, and blowing agent. Bentonite nanoclay (NC) was incorporated into the bio-polyol mixture as nano-reinforcement, while, triethyl phosphate was used as flame-retardant agent. After fabrication, these bioengineered foam nano-composites were studied for microstructural, mechanical and thermal characterizations. Fourier transform infrared spectroscopy analysis indicated the presence of characteristic functionalities within biopolyol segments, which was influenced by reactant activity within the polyurethane (PU) foams. Scanning electron microscopy revealed the cellular morphology of the foam. Thermogravimetric analysis enabled the study of foam decomposition behavior for different sample compositions. Incorporation of NC into pristine foam was found to delay the onset degradation temperature. Flammability studies depicted significant enhancement of flame retardancy with incorporation of NC up to a certain loading level. Compression tests demonstrated that significant improvement of compressive strength properties of foams could be achieved by incorporating bentonite nanoclay, owing to nucleation effect of nanoclay and corresponding enhanced structural integrity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47063.     

New polyurea MWCNTs nanocomposite films with enhanced mechanical properties

Polyurea nanocomposites represent a promising option in the development of advanced materials for applications that require high mechanical resistance. This article describes an optimized synthetic route for obtaining polyurea nanocomposites with enhanced mechanical properties by employing epoxy‐functionalized multiwalled carbon nanotubes (MWCNTs) as reinforcing agent. The experimental measurements revealed that these functionalized nanofillers have a positive effect on the properties of the composite only until they reach a certain concentration; therefore, the optimal composition was reported (the samples containing 0.2 weight % functionalized MWCNTs). The functionalization of the MWCNTs was confirmed through RAMAN, X‐ray photoelectron spectroscopy, scanning electron microscopy and thermogravimetric analysis, while the polyurea nanocomposites obtained have been characterized by thermal (differential scanning calorimetry and TGA) and mechanical (dynamic mechanical analysis and tensile tests) analyses. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45061.     

Rheological,mechanical, optical,and transport properties of blown films of polyamide 6/residual monomer/montmorillonite nanocomposites

Exfoliated nanocomposites of polyamide 6 (PA6) with residual monomer and an organically treated montmorillonite (3 and 5 wt %) were produced by twin‐screw extrusion. The composites had their steady state, dynamic, and transient rheological properties measured by parallel‐plates rheometry; their exfoliation level was characterized by wide angle X‐rays diffraction (WAXD) and transmission electron microscopy (TEM). The characterization showed as follows: (i) the nanoclay's lamellas were well dispersed and distributed thru the PA6, (ii) the postpolymerization of the residual monomer produced more branched chains than linear ones in the pure PA6, (iii) the nanoclay's lamellas acted as entanglement points in the nanocomposites, and (iv) the molecular weight of the PA6 in the nanocomposites decreased. Blown films of the nanocomposites were produced by single screw extrusion; the die pressure during the film blowing of the nanocomposites strongly decreased. The tensile mechanical properties of the blown films were also measured. Along the machine direction (MD), the best mechanical properties were obtained with the 5 wt % nanocomposite, whereas along the transverse direction (TD), the 3 wt % nanocomposite had the best behavior. The glass transition temperature (T_g) of the blown films was measured by dynamic mechanical thermal analyses (DMTA). The 5 wt % nanocomposite had the highest T_g of all the films. The optical properties were measured by spectrophotometry; the nanoclay decreased the films' haze, but the level of transmittance was not affected. The water vapor and oxygen permeability rates of the nanocomposites films were found to be lower than in the pure PA6 blown film as a result of a tortuosity effect. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

MXD6/PA6/EPT共混物力学性能与形态结构研究

以马来酸酐接枝三元乙丙热塑性弹性体(EPT-g-MAH)为反应性增容剂,通过熔融共混方法制得聚(间二甲苯己二酰二胺)/聚酰胺6/三元乙丙热塑性弹性体(MXD6/PA6/EPT)共混物。利用电子万能试验机、记忆式冲击试验机、动态热机械分析仪(DMA)和扫描电子显微镜(SEM)等研究了MXD6/PA6/EPT共混物的力学性能、动态力学性能以及形态结构。结果表明:引入EPT-g-MAH后,MXD6/PA6/EPT共混物的储能模量降低,MXD6的β转变峰增强,但共混体系的力学状态没有发生根本改变;EPT-g-MAH的引入增强了EPT与MXD6两相界面的相互作用,分散相EPT尺寸明显减小,共混体系的相容性得到有效改善,并且共混物呈现出韧性断裂行为,其中当EPT-g-MAH含量为3.6%时,MXD6/PA6/EPT共混物的冲击强度较纯MXD6提高了7.61倍。     

EVOH nanocomposite films with enhanced barrier properties under high humidity conditions

To improve the oxygen and water vapor barrier properties of ethylene vinyl alcohol, EVOH/EFG nanocomposite films under high humidity conditions, we successfully prepared highly exfoliated graphite (EFG) containing a monolayer or a few layers of graphene via rapid heating treatment and ultrasonication as confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), elemental analysis (EA), and nitrogen adsorption–desorption analysis. Six different EVOH/EFG nanocomposite films containing as‐prepared EFG were prepared via a solvent blend method and their physical and barrier properties at different relative humidities were investigated as a function of EFG content. Depending on the EFG content, oxygen transmission rate (OTR) decreased from 3.7 to 0.1 cc/m²/day at dry condition, and the difference in OTR between dry condition and humid condition decreased from 6.5 to 2.3 cc/m²/day. Barrier properties of the EVOH/EFG nanocomposite films were strongly dependent on their chemical structure and morphology. Crystallinity, tortuous path length, and hydrophobicity of EVOH/EFG nanocomposite films were enhanced by the addition of EFG. However, the thermal stability and glass transition temperature of the nanocomposite films were not improved by incorporation of EFG due to the weak interaction between EVOH and EFG. To maximize the performance of EVOH/EFG nanocomposite films, the compatibility of the polymer matrix and fillers needs to be improved. POLYM. COMPOS., 35:644–654, 2014. © 2013 Society of Plastics Engineers     

Preparation and properties of PET/PA6 copolymer/montmorillonite hybrid nanocomposite

From in situ polycondensation, a poly(ethylene terephthalate)/Polyamide 6 copolymer/montmorillonite nanocomposite was prepared, after the treatment of montmorillonite (MMT) with a water soluble polymer. The resulting nanocomposites were characterized by X‐ray diffraction (XRD), differential scanning calorimeter (DSC), nuclear magnetic resonance (NMR), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The results of DSC, ¹H NMR, and DMA proved that the nanocomposite synthesized was PET/PA6 copolymer/MMT nanocomposite, not the PET/PA6 blend/MMT nanocomposite. The results of XRD and TEM proved that the dispersion of MMT was improved observably after the introduction of PA6 molecular chain into PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2512–2517, 2006     

Rheological properties of thermoresponsive nanocomposite hydrogels

Highly elastic and robust nanocomposite hydrogels based on N‐isopropylacrylamide (NIPAM) and cationic (3‐acrylamidopropyl) trimethylammonium chloride (AMPTMA) were synthesized by photopolymerization. Nanoscopic clay, laponite XLS, was added in the gels during the synthesis. The effect of a hydrophobic salt, lithium bis(trifluoromethane) sulfonimide (LiNTf₂), and clay content on the viscoelastic properties, swelling ratio, and stiffness of the nanocomposite hydrogels were investigated as a function of temperature. Synthetic clay served as a multifunctional cross‐linker, producing hydrogels with enhanced elastic properties. Anionic NTf₂ binds to the cationic comonomer units and significantly affected the viscoelasticity and thermal properties. DSC measurements showed that the volume phase transition temperature and its enthalpy changed with the clay content and with introducing the cationic comonomer (AMPTMA) in the PNIPAM network. With the addition of either laponite XLS or the comonomer and 5 mM solution of LiNTf₂, a fourfold and fivefold increase in elastic modulus was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With increasing the temperature from 20 to 45°C for the copolymer gel with 10% AMPTMA in 5 mM LiNTf₂, the elastic modulus grew 15 times larger. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43123.     

Influence of clay modification process in PA6-layered silicate nanocomposite properties

The melt intercalation method was employed to prepare layered silicate polyamide 6 nanocomposites. Low cost bentonite clay was purified and modified with octadecylamine using different experimental conditions in order to improve efficiency in the modification step. Nanocomposites properties as a function of clay nature, solid content during the modification process and the excess of surfactant in the organophilic clay were analysed. Small Angle X-Ray Diffraction (SAXD) and Transmission Electron Microscopy (TEM) gave a qualitative picture of the microstructure and a correlation to mechanical properties has been established. Thermogravimetric Analysis was used to investigate the surfactant location in the organophilic layer silicates by the identification of the observed thermal degradation transitions. Surfactant excess was found to be one of the crucial parameters to be taken into account.