Cure Characteristics and Mechanical Properties of Natural Rubber–Layered Clay Nanocomposites

The effect of interlayer distance of nanoclay on mechanical properties, cure characteristics, and swelling resistance of natural rubber (NR) in varying clay proportion were studied. X-ray diffraction results of nanocomposite with 10 phr of nanoclay showed the formation of an intercalated structure. The rate of vulcanization and maximum torque value of the nanocomposite are higher than the gum compound. Nanocomposites with clay having higher interlayer distance shows superior mechanical properties. Mechanical properties gradually increase with increase in clay loading up to 10 phr. A 50% increase in tensile strength and about 150% increase in modulus at 300% elongation were observed for the nanocomposite with 10 phr clay loading. Better barrier properties offered by the nanocomposites due to the presence of tortous path was confirmed by the Nielson's model.     

Constitutive modeling for intercalated PMMA/clay nanocomposite foams

A constitutive model for tensile behavior of PMMA/clay nanocomposite foams was developed in this study. The elastic modulus of the nanocomposites is affected by the form of clays embedded in the polymer matrix. The reinforcing effect by intercalation of the clays and the detrimental effect by clay agglomeration were considered for the determination of the elastic modulus of the nanocomposites. A viscoelastic model was adapted for the tensile behavior of the material. The developed constitutive equation is expressed in terms of clay morphology and material properties. The aspect ratio of clays and the expansion of clay layer spacing in the intercalated clay clusters were proved to play a vital role in the reinforcing mechanism. For the verification of the constitutive model, Poly(methyl‐methacrylate) (PMMA)/clay nanocomposite foams were manufactured by batch process method and their uniaxial tensile test results were compared with theoretical predictions. Compared with the experimental results, the proposed constitutive equation showed agreement with the experimental test results. POLYM. ENG. SCI. 46:1787–1796, 2006. © 2006 Society of Plastics Engineers.     

Nanoclay reinforced bio-based elastomers: Synthesis and characterization

A new bio-based elastomer synthesized from soybean oil was filled with nanoclay to generate an elastic nanocomposite. A solubility parameter study was used to select the organoclay for poly(acrylated oleic methyl ester) (AOME). Effects of the nanoclay on the macroscopic and microscopic properties were explored. The morphology varies from fully exfoliated to intercalated structure with different types of clay and clay concentrations. Mechanical properties are significantly improved by the addition of organoclays. The elongation at break increases as well as the tensile strength. A decrease in the crosslink density of this elastic nanocomposite, measured by swelling test, indicates that the clay hinders chemical crosslinking and also confirms the formation of physical crosslinks. Percolation studies show the improvement of the network structure by nanoclays. The onset of the thermal decomposition was hindered by the loading of the nanoclay. Clay effects on biodegradability were studied as well.     

Mechanical response and rheological properties of polycarbonate layered‐silicate nanocomposites

The effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties of intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, the linear dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. The 3.5 and 5 wt% clay nanocomposites exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared to the pure PC and the 1.5 wt% clay nanocomposite. Thermal degradation of PC resulted from the melt compounding of organo‐modified nanoclays was evident from the reduction in the glass transition temperature and molecular weight of the PC nanocomposites. These nanocomposites also exhibited a significant decrease in the extent of tensile elongation and ductility with respect to the nanoclay incorporation. A concomitant decrease in the rheological properties at high frequencies was also observed, and was consistent with the lowering of the molecular weight of PC, particularly near or above the percolation threshold of nanoclay. These nanocomposites, nevertheless, exhibited elastic‐plastic deformation in compression, regardless of nanoclay content. Polym. Eng. Sci. 44:825–837, 2004. © 2004 Society of Plastics Engineers.     

Bulk and surface mechanical properties of clay modified HDPE used in liner applications

High‐density polyethylene (HDPE)/clay nanocomposites were prepared by melt blending process. The HDPE was mixed with different organoclays and polyethylene‐grafted‐maleic anhydride was used as a compatibiliser. A masterbatch procedure was used to obtain final organoclays concentrations of 1, 2.5 and 5 wt%. The effects of various types of nanoclays and their concentrations on morphological, thermal and mechanical properties of nanocomposites were investigated. Surface mechanical properties such as instrumented nanohardness, modulus of elasticity and creep were also measured using a nanoindentation technique. Young's, storage and loss moduli, were found to be higher than that of the neat polymer at low loading (2.5 wt%) for clay Cloisite 15A and at higher loading (5 wt%) for clay Nanomer 1.44P. The ultimate strength and the toughness decreased slightly compared to pure HDPE. The differential scanning calorimetry analysis revealed that the peak temperature of the nanocomposites increased with increased clay content while the crystallinity decreased. Also, dynamic mechanical analysis revealed the storage and loss moduli are enhanced by addition of nanoclay. Both mechanical and thermal properties of HDPE/Nanomer 1.44P nanocomposite showed interesting trends. All properties first dropped when 1 wt% of the clay was added. Thereafter, a gradual increase or decrease then followed as the loading of Nanomer was increased. These trends were observed for all mechanical properties. The results obtained from nanoindentation tests for surface mechanical properties also showed similar trend to that of bulk measurements. Based on these measurements a nanoclay additive for a liner grade HDPE was selected. © 2011 Canadian Society for Chemical Engineering     

改性大洋黏土填充聚乙烯的力学性能研究

为确定大洋黏土的实际应用效果,对北太平洋东部的大洋黏土沉积物进行悬浮扩散提纯、硅烷偶联剂干法改性后,设计了一系列高密度聚乙烯填充实验,利用冲片机制备相应的聚乙烯复合材料进行拉伸实验,结果表明:复合材料的拉伸强度和断裂伸长率随着黏土用量的增加呈现完全相反的变化趋势,填充效果较好的黏土用量约为2%,双辊混炼的效果略胜于单螺杆挤出;同时,添加相容剂和抗氧剂对于改善复合材料力学性能的意义不大。     

High density polyethylene foams. III. Tensile properties

The room temperature tensile properties of closed‐cell polyethylene foams have been investigated. High density polyethylene (HDPE) foams of four different molecular weight were used to study the effect of molecular weight and foam density on mechanical properties during tension and at the break point. It was found that increasing the molecular weight changes the tensile behavior of polyethylene foams from brittle to ductile fractures. For brittle foams, the break strength follows a square power‐law model and the break strain is independent of the volume fraction of the voids. For ductile foams, the normalized yield strength also follows a square power‐law relation with normalized density, the yield strain is similar to the value of the solid polymer and remains constant for all void volume fractions, and the break strain increases with HDPE molecular weight. Finally, the toughness of the foams was found to increase with normalized density and HDPE molecular weight. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2130–2138, 2003     

HDPE及增韧HDPE的力学性能与测试条件的关系

于23℃时,研究了拉伸、弯曲速度及试样缺口剩余宽度对高密度聚乙烯(HDPE)、HDPE/弹性体、HDPE/E型增韧母料(E-TMB)的拉伸、弯曲及冲击强度等力学性能的影响。结果表明,所研究的测试条件对这三种材料力学性能影响的程度不同:对于这三种材料,均是拉伸速度对拉伸屈服应力、弹性模量影响的程度较小,对断裂伸长率影响的程度较大,弯曲速度对弯曲弹性模量、弯曲强度影响的程度较大;三种材料中,拉伸速度对断裂伸长率影响程度最大的是HDPE/弹性体,最小的是HDPE/E-TMB,弯曲速度对弯曲弹性模量、弯曲强度影响程度最大的是HDPE/E-TMB,最小的是HDPE/弹性体;随外力作用速度增大性能并非匀速变化,对不同的材料、不同的性能有相应的敏感区;试样缺口剩余宽度对HDPE/E-TMB的悬臂梁缺口冲击强度影响程度较大,而且缺口剩余宽度由7.8mm增加到8.0mm是影响的敏感区,对HDPE、HDPE/弹性体的影响的程度很小。     

十八烷基缩水甘油醚的合成及其增容尼龙6/高密度聚乙烯共混体系的研究

利用十八醇和环氧氯丙烷反应合成了十八烷基缩水甘油醚(OGE),并将其作为熔融共混方法中的增容剂,制备了尼龙6(PA6)/高密度聚乙烯(HDPE)共混材料。研究了OGE用量对共混物的热性能、结晶行为、形态结构、力学性能及吸水性的影响。结果表明,OGE促进了HDPE在PA6基体中的分散,在保持共混材料吸水率的同时,有效改善了共混物的力学性能,与未加入增容剂的PA6/HDPE共混物相比,OGE含量为2.9%(m/m)时,共混材料的缺口冲击强度、拉伸模量、断裂伸长率、弯曲强度分别提高了12%、33%、95%、6%,拉伸强度基本保持不变,而弯曲模量下降了8%。     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Foaming conditions of high density polyethylene–natural rubber blends

Abstract

Foams made from high density polyethylene (HDPE) and natural rubber (NR) blends, using azodicarbonamide as a chemical blowing agent, have been investigated to establish a relationship between the structure and physical properties. The blends of HDPE, NR, epolene wax, chemical blowing agent, and necessary ingredients were prepared on a two roll mill. Subsequently, foamed structures of the blends were obtained by a single stage compression moulding. Results indicate that foaming process variables, i.e. heating time, blowing agent loading, ratio of HDPE/NR, crosslinking agent loading, and ratio of HDPE/NR at a fixed crosslinking agent loading, affect the physical properties of the foams. Attempts were made to relate such properties as foam density, hardness, tensile strength, elongation at break, tear strength, flexural strength, elastic modulus, and gel content to the foam structure. The foam structure was investigated using optical microscopy, in terms of the average cell size and its distribution.     

Ethylene–octene copolymer (engage)–clay nanocomposites: Preparation and characterization

In this work, preparation and properties of nanoclay modified by organic amine (octadecyl amine, a primary amine) and Engage (ethylene–octene copolymer)–clay nanocomposites are reported. The clay and rubber nanocomposites have been characterized with the help of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The X‐ray results suggest that the intergallery spacing of pristine clay increases with the incorporation of the amine. The XRD peak observed in the range of 3–10° for the modified clay also disappears in the rubber nanocomposites at low loading. TEM photographs show exfoliation of the clays in the range of 10–30 nm in Engage. In the FTIR spectra of the nanocomposite, there are common peaks for the virgin rubber as well as those for the clay. Excellent improvement in mechanical properties, like tensile strength, elongation at break, and modulus, is observed on incorporation of the nanoclay in Engage. The storage modulus increases, tan δ peak decreases, and the glass transition temperature is shifted to higher temperature. The results could be explained with the help of morphology, dispersion of the nanofiller, and its interaction with the rubber. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 603–610, 2006     

Nanoindentation and morphological studies on nylon 66 nanocomposites. I. Effect of clay loading

Nanoindentation technique has been used to investigate the mechanical properties of exfoliated nylon 66 (PA66)/clay nanocomposites in present study. The hardness, elastic modulus and creep behavior of the nanocomposites have been evaluated as a function of clay concentration. It indicates that incorporation of clay nanofiller enhances the hardness and elastic modulus of the matrix. The elastic modulus data calculated from indentation load-displacement experiments are comparable with those obtained from dynamic mechanical analysis and the tensile tests. However, the creep behavior of the nanocomposites shows an unexpected increasing trend as the clay loading increases (up to 5 wt%). The lowered creep resistance with increasing clay content is mainly due to the decrease of crystal size and degree of crystallinity as a result of clay addition into PA66 matrix, as evidenced by optical microscopy and X-ray diffraction. At lower clay concentration (here ≤5 wt%), morphological changes due to addition of clay plays the dominant role in creep behavior compared with the reinforcement effect from nanoclay.     

Synthesis of β-myrcene-based macroporous nanocomposite foams: Altering the morphological and mechanical properties by using organo-modified nanoclay

Organo-modified nanoclay incorporated high internal phase emulsions (HIPEs) were successfully used for the preparation of macroporous nanocomposite foams. Due to the aim of obtaining mechanically improved foams, HIPEs were prepared by using a monomer mixture composed of β-myrcene and ethylene glycol dimethacrylate. Accordingly, two groups of macroporous nanocomposite foams were synthesized depending on the nanoclay type. The morphological analysis demonstrated that the pore openness of the resulting nanocomposites were significantly improved due to the decrease in the average cavity size and increase in the interconnected pore size. In terms of mechanical properties, it was found that filling 1 wt% of nanoclay which is surface modified by hydrogenated tallow lead to a 33% of increment in the compression modulus, as compared to the neat foam. However, loading 5 wt% of nanoclay having octadecylamine and aminopropyltriethoxysilane surface groups caused only 11% of increment in the compression modulus, as compared to the neat foam.     

Effect of the extensional flow on the properties of oriented nanocomposite films for twist wrapping

In this study, we examined the mechanical behavior of nanocomposite films based on polyethylene (PE) and pristine PE films. The films were prepared by film blowing and were then cold‐drawn at low temperature. The experimental results show that cold drawing significantly enhanced the orientation; with increasing draw ratio (DR), the elastic modulus and tensile strength of the PE films strongly increased, particularly in the presence of the organoclay. To obtain polymeric films suitable for twist wrapping, the films must be sufficiently stiff so that no shrinkage or elastic recovery occur during or after twisting. The elongation at break and the yield strain sharply decreased with orientation, mainly in films upon drawing. According to the mechanical behavior, the twist angle increased with increasing DR and, particularly, with the addition of nanoclay, probably because of the applied DR, which reduced the nanoparticle size and, as a consequence, hindered the applied torsional elastic recovery. Therefore, the nanocomposite film with a higher DR was particularly suitable for twist‐wrapping applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Synthesis and characterization of poly(vinyl alcohol): Cloisite® 20A nanocomposites

Polymeric nanocomposite materials are very important materials because of their promised applications. However, many of their fundamental physical, mechanical, and chemical behaviors have not been quantified. Depending on the interface forces between polymer and clay, different configurations of polymer–clay nanocomposites exist: intercalated, flocculated, and exfoliated nanocomposites. In this paper, a study on the first two configurations is presented. Poly(vinyl alcohol) (PVA)–Cloisite^® 20A was chosen for the intercalated system and PVA–Cloisite^® 10A was chosen for the flocculated one. In both cases, the phyllosilicate clays used were organically modified by tallow‐triethanol‐ammonium ion. The morphology of the two systems was investigated by using X‐ray diffraction and nanoscanning electron microscopy. Although both confirmed the intercalation between PVA and 20A nanoclay, they confirmed the nonintercalation between PVA and 10A nanoclay. Another confirmation of the intercalation phenomena in PVA and 20A nanoclay was obtained from differential scanning calorimetry, which showed an increase in crystallinity upon intercalation. A main focus for the intercalated system was to study the effect of the nanoparticle's loading on the mechanical properties. Intercalation markedly affected both Young's modulus and the extent of elongation of the PVA–Cloisite^® 20A nanocomposite. Young's modulus and tensile stress increased with the loading of the clay up to 2 wt%. For higher loading, opposite results were reported due to the agglomeration of nanoparticles and as a consequence of the formation of microvoids. J. VINYL ADDIT. TECHNOL., 23:181–187, 2017. © 2015 Society of Plastics Engineers     

Constitutive modeling for mechanical behavior of PMMA microcellular foams

Constitutive equations for nonlinear tensile behavior of PMMA foams were studied. Five viscoelastic models composed of elastic and viscous components were accounted for the modeling of the constitutive equations. The developed constitutive equations are expressed in terms of material properties and foam properties such as strain, strain rate, elastic modulus, relative density of foam, and relaxation time constant. It was found that the stress-strain behaviors by Generalized Maxwell model, Three Element model and Burgers model could be described by the constitutive equation obtained from the Maxwell model. For the verification of the constitutive model, poly(methyl methacrylate) (PMMA) microcellular foams were manufactured using batch process method, and then uniaxial tensile tests were performed. The stress-strain curves by experiment were compared with the theoretical results by the constitutive equation. It was demonstrated that nonlinear tensile stress-strain behaviors of PMMA foams were well described by the constitutive equation.     

Morphological,mechanical, tribological,and thermal expansion properties of organoclay reinforced polyethylene composites

The morphological, mechanical, thermal, and tribological properties of high‐density polyethylene (HDPE) composites reinforced with organo‐modified nanoclay (3 and 6 wt%) were studied. A commercial maleic anhydride‐based polymeric compatibilizer (PEgMA) was used to improve the adhesion between the polyethylene and clay. Transmission electron microscopy (TEM) characterization of composites revealed that nanoclay exists mainly in a multilayered structure in the HDPE matrix. Mechanical testing of composites showed that Young's modulus and tensile strength increased with nanoclay content. Coefficients of the linear thermal expansion (CLTE) of HDPE–PEgMA–clay composites were slightly lower in the flow direction than those of HDPE–PEgMA. The tribological properties were measured in dry conditions against a steel counterface. The friction coefficient of the matrix was decreased by the addition of clay. Electron microscopic results suggested that the wear mechanism for HDPE and HDPE composites was mainly adhesive. Clay agglomerates were observed on the worn surfaces of the composites, which may partly explain decreased friction. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Experimental and theoretical studies on the mechanical and structural changes imposed by the variation of clay loading on poly(vinyl alcohol)/cloisite® 93A nanocomposites

Polymer nanocomposites (PNC) structures are promising materials due to their novel properties. However, many of their characteristic physical, mechanical, and chemical behavior have not been quantified. Depending on the interface interactions between polymeric chains and clay sheets, various classes of polymer/clay nanocomposite exist: Intercalated, flocculated and exfoliated nanocomposites. In this work, we present an experimental study of poly(vinyl alcohol) (PVA)‐cloisite® 93A followed by a classical molecular dynamic (MD) simulations. The structural properties of the system were studied using X‐ray diffraction (XRD), nanoscanning electron microscopy (NSEM). Both revealed intercalation between PVA chains and cloisite® 93A nanoclay. Another evidence of the intercalation between PVA and cloisite® 93A nanoclay was realized from the differential scanning calorimetry (DSC) which confirmed as surge in crystallinity upon intercalation. A main focus for the intercalated structure was to investigate the impact of nanofillers content on the mechanical performance. Intercalation significantly influenced both Young's modulus and the % of elongation of PVA/cloisite® 93A blends. Young's modulus and tensile stress were raised with the content of the filler content up to 3 wt%. For higher content, opposite observations are addressed owing to the formation of aggregates of nanofillers and as consequence construction of microvoids. From the MD simulations, the intercalation has been shown by the increase of the d‐spacing with the clay loading. By calculating the density profile, it has been demonstrated that in case of low clay loading, the cloisite® 93A has its nitrogen groups on the clay surface and the long tails form layers. For the high loading of clay, nitrogen and carbon groups are together on the surface. Young modulus calculated theoretically follows the same experimental trend where an increase of the values has been observed with a clay loading up to 3 wt%, followed by a decrease of the values for higher clay loading. J. VINYL ADDIT. TECHNOL., 25:172–181, 2019. © 2018 Society of Plastics Engineers