Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na⁺‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na⁺‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Improvement of Tensile and Flexural Properties in Epoxy/Clay Nanocomposites Reinforced with Weave Glass Fiber Reel

The tensile strength, tensile modulus, flexural strength and flexural modulus properties were investigated on epoxy/clay nanocomposites to assess the influence of nanoclay. Mechanical properties were significantly increased due to an increase in clay content up to 5 wt%, and decreased with a further increase in clay content. Optimal improvement of properties was observed with increased clay content up to 5 wt%. Duo properties of the glass fiber were improved by clay addition due to the improved interface between the glass fiber and epoxy. SEM analysis was conducted on different fractured surfaces to study the mechanical behavior.     

Structure–properties relationships in clay nanocomposites based on PVDF/(ethylene–vinyl acetate) copolymer blends

The relationships between the microscopic structure and the macroscopic properties in two sets of clay nanocomposites based on polymer blends comprised of poly(vinylidene fluoride) (PVDF) and ethylene–vinyl acetate copolymer (EVAc) were examined. In nanocomposites based on a polymer blend matrix with high content of polar groups (VAc) the dispersion of polar nanoclay leads to significant enhancement in toughness and a substantial increase in viscosity. However, in nanocomposite blends based on a less polar matrix (i.e. with fewer VAc groups) it is the hydrophobic organoclay that leads to higher modulus and stronger viscoelasticity. The dispersion of nanoparticles and the mechanical response are discussed in terms of emulsifying efficiency of the clay particles in the immiscible polymer blend, an effect that largely depends on the localized interactions between the polymer groups and the clay surface modifier. The potential of nanoclays to serve as matrix sensitive structure-directing agents in tailor-made materials is demonstrated.     

Compressive behaviour of nanoclay modified aerospace grade epoxy polymer

Abstract

The effect of nanoclay on the compressive response of an aerospace grade epoxy polymer was studied. The resin was modified with montmorillonite clay type nanomer I.30, and compressive tests were performed on the optimised specimen geometry. A series of nanocomposite with 1–5 wt-% nanoclay content was fabricated using mechanical stirring and three-roll mill methods. The degree of dispersion of the clay nanoplatelets was examined using TEM. Static uniaxial compression tests were conducted. The compressive stress–strain curves showed that the presence of nanoclay improved the compressive strength and stiffness, promoted higher plastic hardening behaviour after yielding and enhanced the fracture toughness (area under σ–? curve) of the epoxy polymer. The fracture surfaces of the broken specimens were observed using SEM with the aim to identify critical failure mechanisms that contributed to the polymer toughening. Rule of mixtures, Halpin–Tsai and modified Halpin–Tsai models were employed to estimate the compressive modulus of the clay–epoxy nanocomposite system.     

黏土结构对聚氯乙烯/黏土复合材料性能的影响

用两种不同结构的黏土伊利石和海泡石作为填料填充到聚氯乙烯(PVC)树脂中,研究黏土结构对PVC性能的影响。结果表明:黏土的结构不同,对PVC的性能影响也存在明显差异。伊利石对提高PVC的拉伸强度优于海泡石;而海泡石对提高PVC的冲击强度优于伊利石。伊利石提高了PVC的弯曲强度,对弯曲模量的影响不大;而海泡石降低了PVC的弯曲强度,但明显加大了PVC的弯曲模量。海泡石对提高PVC的热变形温度优于伊利石。     

Effect of different types and loadings of modified nanoclay on mechanical properties and adhesion strength of EPDM-g-MAH/nylon 66 systems

In this study, the effect of different levels and loadings of modified nanoclay (NC), nanoclay 1 CEC, 2 CEC and 4 CEC, cation exchange capacity on mechanical properties and adhesion strength of maleic anhydride grafted ethylene-propylene-diene terpolymer (EPDM-g-MAH)/nylon 66 systems were investigated. Fourier transform infrared (FTIR) data confirmed the reaction mechanism between maleic anhydride in the polymer backbone and the organomodifier of the nanoclay. Dynamic mechanical analysis (DMA) results showed that on increasing the levels of nanoclay modification, the storage modulus (Eʹ) increased as well as the glass transition temperature (T_g) was slightly shifted to lower temperature and the height of the damping property (tan δ) peaks decreased. The results revealed that the use of the three levels of modified clay with EPDM-g-MAH had significant effects on the tensile strength and elongation at break, especially at 5 parts per hundred rubber by weight (phr) filler content. Whereas in the case of lower nanoclay filler contents (i.e. 1 and 3 phr) the results clarified that they had little effect on tensile and elongation at break values. Pull-out adhesion tests showed that the adhesion force of NC 2 CEC nanocomposite was approximately twice that of the virgin polymer while the nanocomposite NC 4 CEC showed inferior adhesion values, especially at 5 phr filler content. Scanning electron microscopy (SEM) clarified that good wettability of elastomer took place, especially in case of NC 2 CEC which in turn led to an enhancement of the adhesion force between the elastomer and the nylon 66 cord.     

Multiscale micromechanical modeling of polymer/clay nanocomposites and the effective clay particle

Polymer/clay nanocomposites have been observed to exhibit enhanced mechanical properties at low weight fractions (W_c) of clay. Continuum-based composite modeling reveals that the enhanced properties are strongly dependent on particular features of the second-phase ‘particles’; in particular, the particle volume fraction (f_p), the particle aspect ratio (L/t), and the ratio of particle mechanical properties to those of the matrix. These important aspects of as-processed nanoclay composites require consistent and accurate definition. A multiscale modeling strategy is employed to account for the hierarchical morphology of the nanocomposite: at a lengthscale of thousands of microns, the structure is one of high aspect ratio particles within a matrix; at the lengthscale of microns, the clay particle structure is either (a) exfoliated clay sheets of nanometer level thickness or (b) stacks of parallel clay sheets separated from one another by interlayer galleries of nanometer level height, and the matrix, if semi-crystalline, consists of fine lamella, oriented with respect to the polymer/nanoclay interfaces. Here, quantitative structural parameters extracted from XRD patterns and TEM micrographs (the number of silicate sheets in a clay stack, N, and the silicate sheet layer spacing, d₍₀₀₁₎) are used to determine geometric features of the as-processed clay ‘particles’, including L/t and the ratio of f_p to W_c. These geometric features, together with estimates of silica lamina stiffness obtained from molecular dynamics simulations, provide a basis for modeling effective mechanical properties of the clay particle. In the case of the semi-crystalline matrices (e.g. nylon 6), the transcrystallization behavior induced by the nanoclay is taken into account by modeling a layer of matrix surrounding the particle to be highly textured and therefore mechanically anisotropic. Micromechanical models (numerical as well as analytical) based on the ‘effective clay particle’ were employed to calculate the overall elastic modulus of the amorphous and semi-crystalline polymer-clay nanocomposites and to compute their dependence on the matrix and clay properties as well as internal clay structural parameters. The proposed modeling technique captures the strong modulus enhancements observed in elastomer/clay nanocomposites as compared with the moderate enhancements observed in glassy and semi-crystalline polymer/clay nanocomposites. For the case where the matrix is semi-crystalline, the proposed approach captures the effect of transcrystallized matrix layers in terms of composite modulus enhancement, however, this effect is found to be surprisingly minor in comparison with the ‘composite’-level effects of stiff particles in a matrix. The elastic moduli for MXD6-clay and nylon 6-clay nanocomposites predicted by the micromechanical models are in excellent agreement with experimental data. When the nanocomposite experiences a morphological transition from intercalated to completely exfoliated, only a moderate increase in the overall composite modulus, as opposed to the expected abrupt jump, was predicted.     

PVC/MBS/无机物复合材料性能的研究

选择片状的滑石粉和针状的碱式硫酸镁晶须,将两者等质量比复合,与弹性体MBS一起加入到硬质PVC中,分别采用一步法和二步法制得了PVC/MBS/无机物的复合材料,研究了其力学性能、加工流变性能和耐热性能。结果表明,采用二步法改性时,在PVC中加入11phr母料时,复合材料的缺口冲击强度为纯PVC的3.1倍,同时弯曲模量不变;在相同配方下,二步法加工的最大扭矩和平衡扭矩均比一步法的小,且二步法加工可以延缓聚合物的热降解;无论采用一步法还是二步法加工,相同配方的复合材料的维卡软化温度均较纯PVC的有所提高。     

An improved technique for exfoliating and dispersing nanoclay particles into polymer matrices using supercritical carbon dioxide

An environmentally benign process, which uses supercritical carbon dioxide (sc-CO₂) as a processing aid, is developed in this work to help exfoliate and disperse nanoclay into the polymer matrices. The process relies on rapid expansion of the clay followed by direct injection into the extruder where the mixture is dispersed into the polymer melt. Results from the mechanical properties, rheological studies, and X-ray diffraction (XRD) show that this method represents a significant improvement relative to direct melt blending in single or twin-screw extruders or other methods using sc-CO₂. The greatest mechanical property response was a result of directly injecting pre-mixed sc-CO₂ and nanoclay into the polypropylene melt during extrusion. It was observed that for concentrations as high as 6.6 wt% (limited only by present process capabilities), XRD peaks were eliminated, suggesting a high degree of exfoliation. Mechanical properties such as modulus increased by as much as 54%. The terminal region of the dynamic mechanical spectrum was similar to that of the base polymer, contrary to what is frequently reported in the literature.     

PVC基木塑复合材料力学性能的研究

利用胺类改性剂M处理木粉,研究了改性剂M和力学性能改性剂丙烯腈-苯乙烯共聚(物AS)的用量对聚氯乙(烯PVC)基复合材料力学性能的影响。结果表明:随着改性剂M用量的增加,复合材料的拉伸强度、无缺口冲击强度、弯曲强度以及弯曲模量都呈先上升后下降的趋势,且当M用量略大于2%时达到最大值;随着AS用量的增加,复合材料的拉伸强度、弯曲强度及弯曲模量都呈逐渐上升的趋势,无缺口冲击强度呈逐渐下降的趋势到,8%时趋于平缓。     

Nanoclay filled soy‐based polyurethane foam

Polyurethane foam was fabricated from polymeric diphenylmethane diisocyanate (pMDI) and soy‐based polyol. Nanoclay Cloisite 30B was incorporated into the foam systems to improve their thermal stabilities and mechanical properties. Neat polyurethane was used as a control. Soy‐based polyurethane foams with 0.5–3 parts per hundred of polyols by weight (php) of nanoclay were prepared. The distribution of nanoclay in the composites was analyzed by X‐ray diffraction (XRD), and the morphology of the composites was analyzed through scanning electron microscopy (SEM). The thermal properties were evaluated through dynamic mechanical thermal analysis (DMTA). Compression and three‐point bending tests were conducted on the composites. The densities of nanoclay soy‐based polyurethane foams were higher than that of the neat soy‐based polyurethane foam. At a loading of 0.5 php nanoclay, the compressive, flexural strength, and modulus of the soy‐based polyurethane foam were increased by 98%, 26%, 22%, and 65%, respectively, as compared to those of the neat soy‐based polyurethane foam. The storage modulus of the soy‐based polyurethane foam was improved by the incorporation of nanoclay. The glass transition temperature of the foam was increased as the nanoclay loading was increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PVC／LPA6／LCP共混物的制备与性能研究

采用低熔点尼龙6（LPA6）／液晶高分子（LCP）复合物对PVC进行共混改性,研究了LPA6／LCP含量对PVC／LPA6／LcP共混物力学性能及维卡软化温度的影响。结果表明：加入质量分数为10％以下的LPA6／LCP,可明显提高共混物的弯曲强度及弯曲模量;加入质量分数为30％以下的LPA6／LcP,可明显提高共混物的...     

The TiO2–Clay-LDPE Nanocomposite Packaging Films: Investigation on the Structure and Physicomechanical Properties

The role of nanoclays and TiO₂ nanoparticle loadings were investigated on low density polyethylene crystalline structure, in addition to studying packaging film properties such as barrier, thermal and mechanical properties. The polymer crystal study indicated for the orthorhombic crystal phase and about 20% lower degree of crystallinity for nanocomposites containing more than 2 wt.% TiO₂ nanoparticles. Based on the X-ray diffraction technique, the dispersion of nanoclays was improved to almost good degree of clay exfoliation with the company of 4 wt.% TiO₂ nanoparticles. In agreement with XRD results, the TEM morphological studies mainly suggest that TiO₂ has a helpful effect on nanoclay exfoliation. The increase in degradation temperature of nanocomposites may be attributed to the formation of inorganic char on polymer melt. The barrier properties of TiO₂/clay nanocomposite packaging films depend mainly on nanoclay loading with an unclear trend from TiO₂ nanoparticles. The increase in elastic modulus and the yield stress of nanocomposite films showed great effects on film mechanical properties by nanoclays.     

PVC/MBS/埃洛石纳米管复合材料的制备及其性能

采用熔融共混法制备了聚氯乙烯(PVC)/甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)/埃洛石纳米管(HNTs)三元复合材料,研究了HNTs对PVC/MBS共混体系力学性能、热性能和微观结构的影响。结果表明:HNTs与MBS可协同增韧PVC,使复合材料的强度和刚性得到改善,当HNTs的填充量为3 phr时,PVC/MBS(100/3)共混体系的冲击强度、拉伸强度、弯曲强度和弯曲模量分别提高了57.7%、12.1%、7.6%和45.9%;其冲击断面呈现韧性断裂特征;TEM观察结果发现,HNTs在PVC/MBS共混体系中具有良好的分散状态;热失重分析显示,HNTs对PVC/MBS共混体系热稳定性的提高能起到一定作用。     

Constitutive modeling of HDPE polymer/clay nanocomposite foams

A constitutive model for tensile behavior of high density polyethylene (HDPE)/clay nanocomposite foams was proposed. The elastic modulus of HDPE/clay nanocomposite was developed using micromechanics theory, and the modulus for foams was obtained by using representative volume element (RVE) concept. In order to describe the tensile behavior of the foams, a constitutive equation obtained from a viscoelastic model was proposed. The constitutive model was expressed in terms of microstructural properties of polymer, and physical properties of the foams. The effects of the material parameters and processing conditions on the foam morphologies and mechanical properties of HDPE/clay nanocomposite foams were investigated. Microcellular closed-cell nanocomposite foams were manufactured with HDPE, where the nanoclay loadings of 0.5, 1.0, and 2.0 wt% were used. The effect of clay loading and foaming conditions on the volume expansion ratio, elastic modulus, tensile strength, and elongation at break was investigated. Except for the elongation at break, the mechanical properties were improved with nanoclay loading. The tensile experimental data of the foams were compared with the prediction by the theoretical model. It was demonstrated that the tensile behaviors of HDPE/clay nanocomposite foams were well described by the constitutive model.     

The relationship between nano- and micro-structures and mechanical properties in PMMA-epoxy-nanoclay composites

Epoxy-aided dispersion of nanoclay particles in a glassy polymer, polymethylmethacrylate (PMMA), was studied using melt-blending technique. Organically treated nanoclay particles were dispersed in PMMA using mixtures of aromatic and aliphatic epoxies to yield three-phase composite materials, the mechanical properties of which were evaluated and compared with PMMA-nanoclay, epoxy-nanoclay, and PMMA-epoxy composite systems as function of nano- and micro-dispersed domains of phase separated epoxy and nanoparticles. Wide-angle-X-ray diffraction patterns and transmission electron microscope images revealed that the clay particles were in fully exfoliated state in the three-phase composites provided the ratio of epoxy to clay was 10. However, the dispersion of nanoclay to the scale of individual platelets was not achieved as exfoliated clay particles remained as aggregates inside phase separated epoxy domains of approximately 1 μm in diameter. Nevertheless, the values of tensile and impact strengths showed significant improvement over PMMA and PMMA-clay composites.     

The role of nanoclay in the generation of poly(ethylene terephthalate) fibers with improved modulus and tenacity

The effect of nanoclay concentration on the molecular orientation and drawability of poly(ethylene terephthalate) PET was examined using thermal and vibrational spectroscopic analysis. Although drawability at 83 °C in hot air increased by the addition of nanoclay, the maximum draw ratio was independent of nanoclay concentration. The average molecular orientation of the PET chain was found to mimic the trend in mechanical property improvements. Both Young's modulus and tenacity (i.e. strength) showed the maximum improvement at a 1 wt% loading of clay, which was shown to coincide with the maximum amount of molecular orientation. Nanoclay was shown to intercalate with PET and enhanced amorphous orientation that led to modulus and strength improvements. However, at higher concentrations of nanoclay the presence of large agglomerates prevented efficient orientation to the fiber axis and acted as stress concentrators to aid in cavitation and failure during testing. Raman spectroscopy showed that the as-spun unfilled PET fibers possessed significantly more trans rotamer content of the ethylene glycol moiety than the nanocomposite fibers.     

Thermal and mechanical behavior evaluation of dental composites filled with irradiated montmorillonite

The effects of pre‐irradiation treatment (dose ranged from 25 to 50 kGy) of MMT (Montmorillonite) nanoclay added as filler (50 wt %) in experimental dental composites was studied; composites containing similar amounts of non‐irradiated MMT were also tested. The thermal stability of the resulting material was tested by thermogravimetric analysis ranging from 50 to 800 °C. Elastic modulus and flexural strength were determined by the three point bending test (n = 10). Data for elastic modulus was analyzed using two way ANOVA/Tukey's test. Data for flexural strength was analyzed using Kruskal–Wallis/Tukey's test. For all tests, the global significance level was 5%. The modifications in elastic modulus and flexural strength with applied dose were characterized. X‐ray diffraction analysis allows the depicting of intercalation phenomenon between base‐polymer and nanophase. The polymeric system modified with MMT nanoparticles showed higher thermal stability by delaying the thermal degradation, compared to the control group, and the radiation dose influenced this thermal behavior directly. However, the applied dose was not sufficient to improve the mechanical properties significantly, which is related to the interaction between MMT and polymeric matrix. The pre‐irradiation treatment of MMT nanoclay phase was useful for attaining efficient interaction between the two constitutive phases of the polymeric systems based bis‐GMA/TEGDMA [bisphenol A bis(2‐hydroxy‐3‐methacryloxypropyl)ether/triethyleneglycol dimethacrylate], modified with MMT nanoparticles, because the polymer component was not affected. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45063.     

纳米蒙脱土对PVC微发泡体系的影响

研究了纳米蒙脱土对PVC微发泡体系的力学性能和泡孔结构的影响。试验表明：纳米蒙脱土具有成核作用，当纳米蒙脱土用量为6份时。材料体内孔洞较多，且分布均匀。微孔达到最好状态，此时材料的冲击强度较好，热变形温度较高；当蒙脱土用量为8份时。界面有丝络状结构，蒙脱土与基体树脂之间的相容性较好，此时，材料的弯曲强度和拉伸强度较好；电镜试验验证了此结论。     

Morphology and properties of PVC/clay nanocomposites via in situ emulsion polymerization

PVC/Na⁺–montmorillonite (MMT) nanocomposites were prepared via a simple technique of emulsion polymerization at several different MMT clay concentrations. X‐ray diffraction and transmission electron microscopy studies revealed the formation of a mixture of intercalated and exfoliated nanostructure. Tensile testing results showed that the tensile modulus of the nanocomposites increased with the addition of clay, while the tensile strength decreased little. The notched impact strength of the nanocomposites was also improved. For systems containing clay in the range of 2.1 to 3.5 wt %, the impact strength was almost two times as large as that of pure PVC. However, those mechanical properties began to decrease with the continuously increasing amount of clay. The fracture surface of pure PVC and the nanocomposites was observed by scanning electron microscope. Thermal properties of the nanocomposites were found to increase as a result of clay incorporation. The glass transition temperatures of the PVC/clay nanocomposites were nearly identical to that of pure PVC. The Vicat softening points exhibited a progressively increasing trend with the clay content added. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 277–286, 2004