Morphological effects on mechanical properties of polystyrene-polyvinylchloride blends

The morphological effects on mechanical properties of polystyrene/polyvinylchloride (PS/PVC) polymer blends were investigated through dynamic mechanical analyzer. Study reveals that the peaks of Tan δ curves of pure PVC and pure PS samples fall at temperatures 58.9 ± 0.2°C and 113.1 ± 0.1°C, respectively. Tan δ curves of 30, 50 and 70-wt% of PVC blends show two peaks indicating the immiscibility of PS/PVC blend. It has been observed that peak falling at lower temperature side shifts towards the higher temperature with the increase of PS concentration and the other one which falls at higher temperature side shifts towards lower temperature side with the increase of PVC concentration in PS/PVC blends. The variation in mechanical performance is attributed to the polymer domain interactions resulting from the different morphologies of various blend compositions.     

Synthesis and characterization of organic soluble polyaniline prepared by one-step emulsion polymerization

Emeraldine salt of polyaniline-dodecylbenzenesulfonic acid (PANI-DBSA) in organic solvents such as toluene and xylene was obtained by a direct one-step emulsion polymerization technique. When the molar ratio of DBSA to aniline monomer was 1.5:1, solubility and electrical property showed a maximum value. The solid contents of PANI-DBSA was 8 wt.% in toluene. The casting film of PANI-DBSA was obtained on glass or plastic substrate under ambient conditions. PANI solution can also be easily blended with polyurethane and polystyrene polymers in toluene. Better electrical performance (up to 5 S/cm), good light transmittance (up to 70% at 500 nm thickness), were obtained and more homogeneous morphology was observed for the casting film of PANI-DBSA prepared by the present method as compared with that prepared by the aqueous emulsion polymerization. The partially dispersed PANI-DBSA particles of 50–400 nm sizes in organic solvents such as toluene and xylene were observed and the crystalline nature of these powder samples was confirmed from the XRD patterns.     

Effects of atomic oxygen treatment on structures, morphologies and electrical properties of ZnO:Al films

ZnO:Al (ZAO) film has a potential application in providing spacecrafts the protection against atomic oxygen (AO) erosion. To advance the understanding of the AO resisting mechanisms and the relationships between the structures, morphologies and conductive properties of ZAO film, direct current magnetron sputtered ZAO films with different thicknesses were treated with AO in a ground-based simulation facility. The microstructure, surface chemical state, morphologies and electrical properties of pristine films and irradiated ones were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and Hall measurement. It is found that AO exposure produces novel, oriented recrystallization of the surface particles. It also increases the content of oxygen ions in fully oxidized stoichiometric surroundings on the surface, resulting in the decrease of the conductivity. As the thickness of ZAO film increases, the crystallinity, conductivity and resistance to AO erosion are all improved.     

A Study on the Morphology and Mechanical Properties of PVC/nano‐SiO2 Composites

Three methods were used to modify nano‐SiO₂ particles with various interfaces and interfacial interactions between the particles and Poly(vinyl chloride) (PVC) matrix. The experimental results show that direct surface treatment of nano‐SiO₂ particles with a silane coupling agent (KH‐550) is not effective for improving the mechanical properties of PVC/SiO₂ composites. Both ultrasonic oscillations and high energy vibromilling improve the interfacial interactions between SiO₂ particles and PVC matrix. With these methods, the aggregation of SiO₂ particles was inhibited and a good dispersion of SiO₂ particles in PVC matrix was obtained, which improved the mechanical properties of the PVC/SiO₂ composite. The mechanical properties of the PVC/SiO₂ composite with high energy vibromilling modified SiO₂ particles were remarkably improved. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic mechanical analysis (DMA), and theoretical calculations demonstrate these improvements.     

Effect of Clay Addition on the Properties of Carbon Nanotubes-Filled Immiscible Polyethylene/Polypropylene Blends

The effects of organically modified clay (OMC) incorporation on the microstructure and the electrical and mechanical properties of polypropylene (PP)/polyethylene (PE) blends filled with carbon nanotubes (CNT) were investigated. All blends were prepared by melt mixing in a batch mixer. The microstructures were characterized by scanning electron microscopy. In the OMC:CNT filled blends, the CNT were found to selectively localize within the PE phase, while the clay particles were observed in the PP phase. The electrical resistivity of OMC:CNT filled blends did not show any significant change as a result of the clay addition since it was localized in the CNT-free phase. On the other hand, the addition of clay degraded the blends' mechanical properties due to the poor adhesion between the OMC and the PP matrix.     

Mechanical,Water-swelling,and Morphological Properties of Water-swellable Thermoplastic Vulcanizates Based on Polyvinyl Chloride/Crosslinked Sodium Polyacrylate/Chlorinated Polyethylene Blends

A novel water-swellable rubber (WSR) was prepared by dynamically vulcanizing polyvinyl chloride (PVC)/chlorinated polyethylene (CPE) blends where a crosslinked poly(sodium acrylate) (CPNaAA) was used as a super water-absorbent resin and dispersed in the CPE rubber. The mechanical, water-swelling, and morphological properties were investigated. The results showed that the dynamically vulcanized PVC/CPNaAA/CPE blends exhibited obvious elastomeric behavior and could be considered as thermoplastic vulcanizates (TPVs). The PVC/CPNaAA/CPE TPVs showed strong water-swelling ability, with the water-swelling ratio of the PVC/CPNaAA/CPE TPV with 30/60/70 weight ratio reaching 2400% at 200 h immersion. Moreover, compared with the first water-swelling behavior, the second and third water-swelling behaviors of the TPVs showed significantly improved water-swelling ratio and a remarkable decrease of weight loss. Morphological study showed that the interface interaction between the CPNaAA and CPE was weak. The CPNaAA particles in the blends could be separated and even be pulled out from the matrix under tensile stress, leading to the formation of suspended CPNaAA particles on the fracture surface of PVC/CPNaAA/CPE TPVs. The surface of the dried TPVs was rough and significant cavities could be found. The dynamic mechanical properties were investigated and the TPVs showed the typical Payne effect.     

Stress whitening and yielding mechanism of rubber-modified PVC

Structure-property relationships were investigated for blends of grafted rubbery polymers with PVC. Increasing grafting levels as well as higher blending temperatures improved the dispersion of the graft copolymers in PVC, lowered the impact strength, and reduced stress whitening. Presuming a mechanistic connection between impact strength and stress whitening, the causes of whitening due to mechanical deformations were studied by a variety of methods. Electron microscopy of stress-whitened zones revealed a large number of cavities formed by rupture of rubber particles, which correlated with the extent of whitening. Density measurements and quantitative evaluations of the volume increase due to the cavities in the stress-whitened zones were in agreement and proved that crazing did not significantly contribute to either volume dilation or stress-whitening. Light scattering studies indicated the existence of reflecting planes oriented at an angle of 55 to 64° to the direction of the applied stress, depending on the particle size of the modifier in the blends. The orientation of the scattered light could not be attributed to the cavities in the rubber particles because of their smallness (< 0.5 μm). An explanation was finally found by transmission light microscopy at various resolving powers. It was demonstrated that the ruptured rubber particles were accumulated in bands which corresponded to shear bands in the PVC matrix. Thus it was concluded that the rubber particles improved the impact strength of PVC by initiating shear bands and not by generating crazes.     

CORRELATION AMONG MORPHOLOGY,INTERFACE, AND MECHANICAL PROPERTIES: EXPERIMENTAL STUDY

The effect of the disperse phase and the diffuse interface between phases on the tensile and impact strengths of polypropylene (PP)/poly(ethylene terephthalate) (PET) (75/20 by weight) blends compatibilized with maleic anhydride–grafted PP derivatives and on the tensile modulus of poly(vinyl chloride)/polystyrene (PVC/PS) nanoparticle blends compatibilized with polystyrene/poly(vinyl acetate) (PS/PVAc) block copolymers were investigated experimentally. The weight fraction of the diffuse interface between the PP and PET phases in the PP/PET blends was determined by modulated differential scanning calorimetry (MDSC). A correlation between the diffuse interface content and mechanical properties was found. With increasing diffuse interface weight fraction, the impact and tensile strengths of the PP/PET blends increased. There is a brittle-tough type transition in these PP/PET blends. With increasing diffuse interface content in the PVC/PS nanoparticle blends in which the particle size was fixed at about 100 nm, the tensile modulus also clearly increased.     

A Study on Compatibility and Properties of POE/PS/SEBS Ternary Blends

Ethylene‐α‐olefin copolymer (POE)/polystyrene (PS)/poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) blends were prepared via melt blending in a co‐rotating twin‐screw extruder. The effects of SEBS copolymer on the morphology and rheological and mechanical properties of the blends were studied. Scanning electron microscopy (SEM) photos showed that the addition of SEBS copolymer resulted in finer dispersion of PS particles in the POE matrix and better interfacial adhesion between POE and PS compared with POE/PS blends, which exhibited a very coarse morphology due to the immiscibility between them. Interestingly, the tensile strength increased from 12.5 MPa for neat POE to 23.5 MPa for the POE/PS/SEBS (60/10/30) blend, whereas the tensile strengths of POE/PS (85.7/14.3) blend and POE/SEBS (66.7/33.3) blend were only 10.5 and 16.5 MPa, respectively. This indicates that both SEBS copolymer and PS have a synergistic reinforcing effect on POE. Dynamic mechanical thermal analysis (DMTA) and dynamic rheological property measurement also revealed that there existed some interactions between POE and SEBS as well as between SEBS and PS. DMTA results also showed that the storage modulus of POE increased when PS and SEBS were incorporated, especially at high temperature, which means that the service temperature of POE was improved.     

The Effects of Different Processing Methods on the Morphology and Properties of PP/EPDM/Nano-CaCO3 Ternary Blend

The effects of different processing methods (direct extrusion, two-step extrusion or lateral injection extrusion) on the morphology of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/calcium carbonate nanoparticles (nano-CaCO₃) ternary blend were investigated, including the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles, by means of scanning electron microscopy (SEM). The results showed that the processing methods had a significant influence on the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles. In the lateral injection extruded blends, it was amazingly observed that the EPDM particles encapsulated the PP phase tightly, and the dimension of EPDM particles was remarkably decreased. It was also found that the content of nano-CaCO₃ particles in the matrix of the lateral injection extruded blends was less than that of the two-step extruded blend, and that of the direct extruded blend was most. The properties of the ternary blend, including dynamic mechanical properties, rheological properties, and crystallization, were characterized in order to confirm the variety of morphologies caused by the different processing methods. The differences in the crystallization temperature, elastic modulus, and glass transition temperature of the blends prepared by different methods well agreed with the variation of their morphology.     

Electrical Properties of Isotactic Polypropylene/Multiwalled Carbon Nanotubes Composites Prepared by Vibration Injection Molding

To study the effect of vibration field on the electrical conductivity properties of nanocomposites, isotactic polypropylene (iPP)/multiwalled carbon nanotubes (MWCNT) composites were prepared by conventional injection molding and vibration injection molding. Results showed that the electrical conductivity of iPP/MWCNT composites was significantly promoted by vibration injection molding. Vibration injection molded samples had a percolation threshold of about 2.7 wt% compared with the threshold of about 4.5 wt% for conventional injection molded samples. The effects of test locations and vibration frequency on the electrical conductivity of composites were investigated. The samples exhibited an inhomogeneity along the injection direction. The electrical conductivity of the samples was different at different test locations and increased with increasing vibration frequency. Polarized light microscopy (PLM) results indicated that vibration injection molding can induce MWCNT aggregates to be stretched and oriented along the flow direction, which could form conductive networks and greatly enhance the electrical conductivity of iPP/MWCNT composites.     

Morphology-property relationships in polycarbonate-based blends. I. Modulus

The tensile, dynamic mechanical and morphological properties of PC/HDPE, PC/LDPE and PC/PS blends have been investigated with the intent of clarifying the major factors governing the modulus of these essentially incompatible blends. Scanning electron microscopy shows that all of the PC/HDPE, PC/LDPE and PC/PS blends have a domain structure whose morphology is strongly dependent on the concentration of the dispersed phase; when the dispersed phase concentration is less than 15%, the domains are mostly of spherical shape, while above 20% agglomeration takes place to form rodlike structures. Dynamic mechanical data shows there is essentially no adhesion at the PC-HDPE and PC-LDPE boundaries, while there is appreciable adhesion at the PC-PS interface. The existence of an intermixed zone was postulated to explain this interfacial adhesion. Morphological and thermal analysis results also indicate that both the HDPE and LDPE inclusions are loosely sitting in the holes in the PC matrix while the PS inclusions are compactly embedded in the PC matrix. These differences in boundary nature give marked effects on the tensile properties including the modulus. For the modulus, PC/HDPE and PC/LDPE blend systems can be regarded to be mechanically equivalent to a PC matrix alone with holes in it when the dispersed phase concentration is lower than 15%, while in the case of PC/PS blends the PS inclusions contribute substantially to the sample's overall modulus.     

A study on the DC-electrical and thermal conductivities of epoxy/ZnO composites doped with carbon black

Thermo-electrical characterizations of hybrid polymer composites, made of epoxy matrix filled with various zinc oxide (ZnO) concentrations (0, 4.9, 9.9, 14.9, and 19.9 wt%), and reinforced with conductive carbon black (CB) nanoparticles (0.1 wt%), have been investigated as a function of ZnO concentration and temperature. Both the measured DC-electrical and thermal conductivities showed ZnO concentration and temperature dependencies. Increasing the temperature and filler concentrations were reflected in a negative temperature coefficient of resistivity and enhancement of the electrical conductivity as well. The observed increase in the DC conductivity and decrease in the determined activation energy were explained based on the concept of existing paths and connections between the ZnO particles and the conductive CB nanoparticles. Alteration of ZnO concentration with a fixed content of CB nanoparticles and/or temperature was found to be crucial in the thermal conductivity behavior. The addition of CB nanoparticles to the epoxy/ZnO matrix was found to enhance the electrical conduction resulting from the electronic and impurity contributions. Also, the thermal conductivity enhancement was mostly attributed to the heat transferred by phonons and electrons hopping to higher energy levels throughout the thermal processes. Scanning electron microscopy and energy-dispersive spectroscopy were used to observe the morphology and elements’ distribution in the composites. The observed thermal conductivity behavior was found to correlate well with that of the DC-electrical conductivity as a function of the ZnO content. The overall enhancements in both the measured DC- and thermal conductivities of the prepared hybrid composites are mainly produced through mutual interactions between the filling conductive particles and also from electrons tunneling in the composite's bulk as well.     

Electrically conducting film of silver sub-micron particles as mechanical and electrical interfaces for transfer printed micro- and nano-pillar devices

In this paper we report a novel application of electrically conductive film (ECF) of Ag sub-micron particles that includes both isotropic and anisotropic film technologies in providing simultaneous electrical contact and mechanical anchor between fracture transfer-printed (1-D) single crystal semiconductor micro- and nano-pillars and a carrier substrate. We assembled silver sub-micron particles (AgSP) monolayers with varying particle diameters and investigated their optical and electrical characteristics prior to their incorporation into thermoplastic polymers. It was found that transfer-printing of the Si micropillar arrays, into electrically conductive thermoplastic receiver substrates, made of films of AgSP/PMMA blends atop metallic substrates could be effectively achieved to yield electrically interfaced 1-D Si micropillar arrays with retention of their orientation and integrity according to the SEM images. The carrier substrate can potentially be reused to generate additional Si micropillar arrays that can be similarly harvested.     

Melt-Processed,Electrically Conductive Ternary Polymer Blends Containing Polyaniline

Conductive binary and ternary blends containing polyaniline (PANI) were developed through melt blending. The investigation of the binary blends focused on their morphology in light of the interactions between their components and on the resulting electrical conductivity. Similar solubility parameters of PANI and a constituting polymer lead to a fine PANI particle segregated dispersion within that polymer and to the formation of conducting paths at low PANI contents. In ternary blends consisting of PANI and two immiscible polymers, the PANI preferentially locates in one of the phases due to increased interactions between PANI and the preferred polymer. This concentration magnification effect leads to increased electrical conductivity at lower PANI nominal contents. The electrical conductivity of a ternary blend is mainly determined by the effective PANI content in the preferred phase, by the level of PANI fracturing in this phase, and by the details of the conductive network structure created in the co-continuous structure blend.     

The Effect of OMMT on the Morphology and Mechanical Properties of PVC/ABS Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene-styrene (ABS) blends containing organically modified montmorillonite (OMMT) were prepared using a twin-screw extruder followed by injection molding. The OMMT dispersion was evaluated by X-ray diffraction and transmission electron microscopy. The clay was preferentially situated in the PVC phase and across the interfaces of PVC/ABS. The effect of the addition of OMMT on the morphology and mechanical properties was also evaluated. Scanning electron microscopy revealed a large reduction in domain size when OMMT was used. The mechanical properties were studied through tensile and impact tests. The yield stress increased when an appropriate amount of OMMT was used without impairing the impact strength.     

Nanoclay and Cu Nanoparticles Loaded Polyethylene Nanocomposites for Natural Gas Transfer Applications

High density polyethylene nanocomposites loaded with a reinforcing filler (Cloisite 20A as a modified nanoclay) and an electrically conductive filler (Cu nanoparticles) were prepared by a melt blending method. The morphological, mechanical, thermal, and electrical properties of the prepared nanocomposites were investigated to evaluate their performances as appropriate materials for production of reinforced conductive polymeric pipes to be used in natural gas distribution and transportation pipelines. A random and uniform dispersion of both nanoparticles in the polyethylene matrix, with a nanoclay intercalated morphology, was observed by scanning electron microscopy and X-ray diffraction techniques. The results revealed ca. 117, 13 and 21% increases in the Young’s modulus, tensile strength and yield stress of the polyethylene matrix by adding 3 wt.% of Cloisite 20A into it. For the similar conditions, however, more than a 71% decrease was observed for the elongation at break. Thermal analysis demonstrated that the melting points of the nanocomposites were increased by incorporating both fillers and the crystallinity of polyethylene chains was decreased by incorporating Cloisite 20A and then slightly increased by adding Cu nanoparticles. Moreover, the results revealed the creation of conductivity inside the non-conductive polyethylene matrix due to the presence of the conductive Cu nanoparticles.     

Effect of Compression Pressure on the Ethylene Propylene Diene Terpolymer (EPDM)/Acrylonitrile Butadiene Copolymer (NBR) Rubber Blends Filled with Different Types of Carbon Black

Blends of ethylene-propylene diene terpolymer/acrylonitrile butadiene copolymer (EPDM/NBR) loaded with different types [(N326-HAF) and (N774-SRF)] and ratios of carbon black (CB) fillers were prepared. The mechanical properties of the EPDM/NBR rubber blends unloaded and loaded with different ratios of CB were investigated. Among the blends, the one with 75% EPDM and 25% NBR, both loaded and unloaded with CB, were found to exhibit the highest tensile strength and elongation at break. The observed changes in the mechanical properties of the blends were correlated to the morphology as observed by scanning electron microscopy. The changes of the electrical resistivity of the rubber blend composites during compression were investigated. The experimental results were explained from the position that an external pressure induces either an increase or decrease of the resistivity of the blend composites according to whether annihilation or creation of effective conductive paths occurs, respectively.     

Mobilization of tungsten dust by electric forces and its bearing on tritiated particles in the ITER tokamak

Experimental investigations on the electric field strength required to overcome the adhesion forces of micron size tungsten metallic dust as well as silver and aluminum oxide in powdery form deposited on a conductive surface are presented. The results reveal a strong influence of particulate surface properties on the detachment threshold, especially for tungsten particles which exhibit a thin surface oxide layer that screens their electrical conductivity. Such tungsten particles makes possible that electrostatic self-charging occurs when tritiated because of their dielectric properties even if there are deposited on a conductive grounded surface.     

Improving the Barrier Properties of Poly(Lactic Acid) by Blending with Poly(Ethylene-Co-Vinyl Alcohol)

Poly(lactic acid) (PLA)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared via melt blending to improve the barrier properties of PLA. The phase morphologies and final properties (rheological behavior, thermal and dynamical-mechanical features, barrier properties, and mechanical behaviors) of the blends were investigated as a function of the EVOH content. The results indicated that hydroxyl groups of EVOH promoted the degradation of PLA, and thus affected the viscosities and morphologies of the resulting blends. The intrinsic viscosities of PLA in the blends decreased with the content of EVOH. The PLA and EVOH presented typical phase-separated morphologies, with a relatively small domain size of the EVOH phase. The EVOH enhanced the cold-crystallization behavior of PLA. The barrier properties to water vapor and oxygen increased linearly with increasing EVOH content.