Phase Morphology Of Blends Research Articles

Study on phase structure and evolution of PP/PEOc blends during heat preservation process under quiescent condition

The phase structure and evolution of polypropylene (PP)/poly(ethylene-1- octene) copolymer (PEOc) blends during heat preservation process under quiescent condition were studied using scanning electron microscopy (SEM). The structure parameters, such as the average area diameter dp, characteristic length L, and average characteristic length Lm, of the dispersed phase in PP/ PEOc blends were calculated by pattern analysis of SEM images. Moreover, the potential fractal behavior of the phase structure and morphology of polymer blends during the process was discussed. The histograms of P(L(t)/Lm) obtained at various time fell on a master curve, demonstrating the self-similar growth of the phase structure of the blends during heat preservation process.

One-step compatibilization of polyamide 6/ poly (ethylene-1-octene) blends with maleic anhydride and peroxide

Polyamide 6/poly(ethylene-1-octene) (POE) blends were prepared in the presence of both maleic anhydride and peroxide via melt blending. The intrinsic viscosity, mechanical properties, rheology, and phase morphology of blends were evaluated. Molau test was adopted to confirm the formation of a graft copolymer between PA 6 and POE, rheology property also indicated the graft reaction. The SEM analysis showed a significant reduction in particle size of seperation phase after one-step compatibilization. It provides a promising method to obtain toughened polyamide material.

Highly transparent thermoplastic elastomer from isotactic polypropylene and styrene/ethylene‐butylene/styrene triblock copolymer: Structure‐property correlations

AbstractPolypropylene (PP) is one of the most useful general purpose plastics. However, the poor transparency and brittleness of PP restricts its applications in the field of medical and personal care where silicone and polyvinyl chloride (PVC) are presently used. This work concentrates on developing highly transparent elastomeric PP blends and also thermoplastic elastomer by blending isotactic polypropylene (I‐PP) with styrene/ethylene‐butylene/styrene (SEBS) triblock copolymer. PP/SEBS blend derived from high melt flow index (MFI) PP and high MFI SEBS exhibit remarkable transparency (haze value as low as 6%) along with good percentage of elongation and processability. The reduction in difference of refractive index (RI) between PP and SEBS has been observed by blending SEBS with PP. The wide angle X‐ray diffraction studies show that there is significant reduction in the percentage crystallinity of PP by the addition of SEBS block copolymer. Temperature‐dependent polarized light microscopy studies reveal the reduction in spherulites size by the addition of SEBS block copolymer. Transmission electron micrographs show that the SEBS polymer forms a fine lamellar structure throughout the PP matrix with phase inversion at higher SEBS concentration. Development of phase morphology, crystalline morphology, and crystallinity in different blends has been analyzed and microstructure‐haze correlations have been developed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Influence of static and dynamic crosslinking techniques on the transport properties of ethylene propylene diene monomer rubber/poly (ethylene-co-vinyl acetate) blends

The transport characteristics of dynamically and statically cross-linked Ethylene Propylene Diene Monomer/poly (ethylene-co-vinyl acetate) (EPDM/EVA) blends have been examined in the temperature interval of 28–58 °C using benzene, toluene and xylene as probe molecules. The dynamically vulcanized blends exhibited enhanced properties on the sorption and diffusion features compared to the corresponding statically vulcanized blends. In both the cases, as the EVA content increased in the blends, the solvent uptake decreased. The experimental observations have been correlated with the phase morphology of the blends, using scanning electron micrographs. The crystallinity of the blends was studied using X-ray diffraction patterns. Among the three vulcanising systems, viz, sulphur, dicumyl peroxide (DCP), and a mixture consisting of sulphur and peroxide, employed for the matrix, the DCP cross linked system exhibited the lowest solvent uptake. The molar mass between cross links and the diffusion coefficients have been computed to complement the observed sorption behaviour.

Morphological Aspects of In-Situ Compatiblized Binary Polymer Blends With Variable Viscosity Ratios of Components

The in-situ compatiblized binary polymer blend polypropylene(PP)/polystyrene(PS)/ anhydrous aluminum chloride(AlCl3) was selected as a model system of a reactive polymer blend to investigate the effect of viscosity ratio of components at a constant shear rate on the phase morphological behavior in in-situ compatibilized systems. The results showed that the well-known interfacial compatibilization effect was related to variations of viscosity ratios of components in the reactive PP/PS blends with different contents of AlCl3 catalyst. The phase morphology evolution of the in-situ compatiblized reactive blend was determined by both the interfacial compatibilization and the variation of the viscosity ratio of components under the fixed mixing conditions, which showed characteristics obviously different from and much more complex than those in binary polymer blends generally compatiblized by added compatiblizers. The results implied that the variation of the viscosity ratio of components should be checked carefully and taken into account if necessary, when the phase morphology of binary polymer blends is investigated, especially in complex in-situ compatiblized reactive polymer blends.

Silicone Rubber Compatibilized Syndiotactic Polystyrene and Thermotropic Liquid Crystalline Polymer (Vectra A950) Blend

Blends of syndiotactic polystyrene (s-PS), thermotropic liquid crystalline polymer (Vectra A-950), and silicone rubber with two different loading levels, have been prepared through melt processing in internal mixer at 285°C. Silicone rubber was used as a compatibilizer for this blend system. The effect of silicon rubber on crystalline, dynamic mechanical, rhelogical, thermal properties, and phase morphology of the (s-PS/TLCP) blend has been investigated in details. With the addition of compatibilizer the viscosity of the blend system increased to an order of magnitude. Dynamic mechanical analysis (DMTA) and differential scanning calorimetry (DSC) results showed that the glass transition temperature (Tg) of the blend, in presence of silicone rubber, shifted towards lower temperature region. From FTIR analysis it is evident that the ‘C=O’ stretching frequency has shifted towards lower side. SEM analysis suggested that, the TLCP domain size is reduced in ternary blend in comparison to binary blend system.

Shear-induced change of phase morphology and tensile property in injection-molded bars of high-density polyethylene/polyoxymethylene blends

It is feasible to control the phase morphology and phase inversion for immiscible polymer blends to manipulate their properties. In this work, the blend of high-density polyethylene (HDPE)/polyoxymethylene (POM) was used as an example, to demonstrate the effect of shear on the phase morphology and resultant mechanical properties in immiscible polymer blends. To do so, a well defined “in-process morphology control” process during injection molding was conducted. That was: after making the blends via melt mixing, the injection-molded bars were prepared via a so-called dynamic packing injection molding equipment to impose a prolonged shearing on the melts during the solidification stage. Phase morphologies and crystal structures of the blends were estimated mainly through scanning electron microscopy, differential scanning calorimetry and 2D wide-angle X-ray scattering, respectively. For in-process morphology controlled samples, co-continuous structures, especially subinclusions inside another continuous phase induced by shear, were observed when the HDPE content was between 30 wt% and 50 wt%, leading to much early occurrence of phase inversion and also the lowest degree of orientation for both HDPE and POM. However, for samples obtained via conventional injection molding, a droplet morphology was always observed with HDPE dispersed in POM as the content of HDPE was up to 30 wt%, but with POM dispersed in HDPE as the content of HDPE was 50 wt%. The performances of injection-molded bars were mainly respect to the phase morphologies for samples obtained via conventional injection molding in which tensile properties continuously decreased with increasing of HDPE content up to 30 wt% and then increased with further increasing of HDPE content. For the in-process morphology controlled samples, the tensile properties depended not only on the phase morphology, but more importantly on the degree of orientation. One observed only a slight decrease of tensile property as the content of HDPE was less than 15 wt%, while an abrupt decrease when the content of HDPE was between 30 wt% and 50 wt%, probably due to the lowest degree of orientation in this composition range.

Microscopic morphology of blends between a new “all-acrylate” radial block copolymer and a rosin ester resin for pressure sensitive adhesives

With the goal of developing new pressure sensitive adhesive systems, the miscibility and the phase morphology of blends between novel symmetric four-arm star “all-acrylate” block copolymers synthesized by atom transfer radical polymerization (ATRP) and a rosin ester resin tackifier was studied with a combined differential scanning calorimetry (DSC) and atomic force microscopy (AFM) approach. Copolymer–resin compositions with increasing resin content in the blend were studied. The DSC results show good miscibility for compositions lower than 60 wt%, with a single glass transition at a temperature between those of the two pure compounds. The AFM results indicate that the initial two-phase morphology typical of the block copolymer matrix is preserved up to 60 wt% of resin. Above that value, a third phase, attributed to aggregates of the pure resin, is observed. Upon ageing, the homogeneous systems (e.g., blends with 40 wt% of resin) undergo a slow migration of the tackifying resin towards the surface of the sample, which can be understood in terms of surface free energy considerations. This eventually leads to the formation of a layer of pure resin at the surface.

The use of dynamic mechanical thermal analysis technique for determining an uneven distribution of precipitated silica in CPE/NR blends

Precipitated silica is generally used as non-black reinforcing filler for light colored products. Compared with carbon black, the use of silica is subject to many problems, particularly poor silica dispersion and distribution. In silica filled CPE/NR blends, the uneven distribution of silica in each phase of the blend occurs mainly due to strong filler–polymer interaction between silanol groups on the silica surfaces and chlorine atoms on the CPE backbone. In order to investigate the uneven filler distribution in polymer blends, changes in damping behavior could be used to calculate the amount of silica localizing in each phase of the blends. The results reveal that, with small loading of silica, an even silica distribution is observed due to the counter-balancing effects of relatively low viscosity of the NR phase and strong silica–CPE interaction. As silica loading increases, the effect of strong silica–CPE interaction becomes dominant, leading to preferential migration of silica to the CPE phase. The uneven silica distribution at high silica loading is found to be reduced by addition of silane coupling agents. The effect of 3-thiocyanatopropyl triethoxy silane (Si-264) is more pronounced than bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) due to the superior wettability and, hence, the silanol deactivation efficiency. The determination of uneven silica distribution by dynamic mechanical properties is in good agreement with the phase morphology of blends.

THE EFFECT OF BLENDING SEQUENCE ON PHASE MORPHOLOGY OF NYLON 6/ABS/SMA BLENDS

The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene-styrene (ABS) over a composition range of 30-70 wt% using a styrene-maleic anhydride (SMA) copolymer as the compatibilizing agent with a constant content (5phr) was investigated. The results of the scanning electron microscope (SEM) observation revealed that compared with the binary blends of nylon 6 and ABS, the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of nylon 6 when ABS was blended with the preblended nylon 6/SMA blend, while the co-continuous structures could be observed over a considerably narrower composition range when nylon 6 was blended with the pre-blended ABS/SMA blend. An examination through dynamic mechanical analysis (DMA) tests confirmed the results obtained with SEM. It is found that near the phase inversion region a remarkable change in the dynamic storage modulus (G′) and the loss tangent (tanδ) appears. Moreover, the influence of blending sequence on the size of dispersed particles has been probed for uncompatibilized and compatibilized blends of nylon 6 and ABS over a wide range of compositions below or beyond the phase inversion points. For the blends of ABS dispersed in a nylon 6 matrix, little discernible effects of blending sequence on particle size could be observed. Furthermore, there exists a significant difference in morphologies of the blends prepared by nylon 6 particles dispersing in a ABS matrix in cases of different blending sequences used. Some possible factors responsible for the above asymmetric behaviors have been proposed.

Design of Blends with an Extremely Low Viscosity Ratio between the Dispersed and Continuous Phases. Dependence of the Dispersed Phase Size on the Processing Parameters

AbstractSummary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components.

NMR study of the nanomorphology in thin films of polymer blends used in organic PV devices: MDMO‐PPV/PCBM

AbstractThe disclosure of the nanomorphology of thin films in organic solar cells, prepared from blends of conjugated polymers and PCBM, is of key importance for a better understanding of the occurring photovoltaic (PV) mechanisms. Hereto solid‐state NMR relaxometry has been evaluated as a complementary technique to traditional microscopic techniques like atomic force microscopy and transmission electron microscopy. It is demonstrated that proton wide‐line solid‐state NMR relaxometry is a useful and innovative tool to study the phase morphology of blends used in semi‐conducting polymer based PV devices. Attention is focused on the influence of the blend composition and casting conditions on the resulting phase morphology. Two different casting techniques, i.e. spincoating and Doctor Blading, were compared. To demonstrate the applicability of NMR relaxometry in this field, MDMO‐PPV/PCBM blends where used, since these are known for their significant phase separation behavior in combination with toluene as solvent. In films prepared from blends in toluene with a PCBM content ≥70 wt %, a fraction of the PCBM is phase separated into crystalline domains, whereas the remaining part remains homogeneously mixed with the MDMO‐PPV. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 138–145, 2008

Real‐time ultrasonic monitoring of the injection‐molding process

AbstractIn this study, a noninvasive and nondestructive ultrasonic technique has been used to monitor the polymer injection‐molding process in an attempt to establish a fundamental understanding of the processing/morphology/ultrasonic signal relationships. The ultrasonic technique not only can provide information on solidification affected by various temperatures and pressures but also can reflect the evolution of the crystal morphology and phase morphology of polymer blends. In addition, the periodic vibration of the dynamic‐packing injection‐molding process, in which the melt is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part, can also be monitored with the ultrasonic velocity and attenuation. Our results indicate that the ultrasonic technique is sensitive and promising for the real‐time monitoring of the injection‐molding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate)/polycarbonate blends—Mixing time effect

This work examined the mixing time effect on the thermal properties and phase morphology of melt-mixed blends of poly(trimethylene terephthalate) (PTT) with polycarbonate (PC). Differential scanning calorimetry (DSC) results indicated that the short time-mixed blends are miscible to a limited extent, with the PTT/PC-75/25 blend exhibiting the most miscibility. With increasing mixing time, the miscibility of the blends was enhanced, owing mostly to the occurrence of a transesterification reaction. The crystallization ability of PTT was hindered in the blends, and was further depressed with the increase in the mixing time. The PTT/PC-50/50 blend was inferred to possess the highest extent of transesterification after extended mixing. As revealed from thermogravimetry (TGA) analyses, the thermal stability of the blends declined as the mixing time increased; the blend with a higher PC content showed a higher degradation temperature. The original two-phased morphology was observed by scanning electron microscopy (SEM) to evolve to one homogeneous phase with increasing the mixing time for PTT/PC-75/25 and PTT/PC-50/50 blends. The PTT/PC-25/75 blend showed a higher resistance to developing the homogeneous phase morphology with mixing time, indicating less vulnerability to the transesterification reaction. The polarized light microscopy (PLM) results showed that the PTT spherulites became smaller or disappeared in the blends with increase in the mixing time.

Phase behavior and crystallization in blends of a low molecular weight polyethylene- block-poly(ethylene oxide) diblock copolymer and poly(hydroxyether of bisphenol A)

The phase behavior, morphology and crystallization in blends of a low-molecular-weight ( M n = 1400) double-crystalline polyethylene- block-poly(ethylene oxide) (PE-PEO) diblock copolymer with poly(hydroxyether of bisphenol A) (PH) were investigated by differential scanning calorimetry, transmission electron microscopy and small-angle X-ray scattering. The symmetric PE-PEO diblock copolymer consists of a PH-miscible PEO block and a PH-immiscible PE block. However, PH only exhibits partial miscibility with the PEO block of the copolymer in the PH/PE-PEO blends; both macrophase and microphase separations took place. There existed two macrophases in the PH/PE-PEO blends, i.e., a PH-rich phase and a PE-PEO copolymer-rich phase. The PE block of the copolymer in the blends exhibited fractionated crystallization behavior by homogeneous nucleation. There appeared three crystallization exotherms related to the crystallization of the PE block within three different microenvironments in the PH/PE-PEO blends.

Miscibility and morphology of poly(ethylhexylacrylate)/liquid crystal blends prepared under different conditions

AbstractA comparative study of the phase diagrams and morphology of blends of poly(2‐ethylhexylacrylate) and low molecular weight liquid crystals (LCs) prepared under different conditions is presented. Two LCs are used; one is the 4‐cyano‐4′‐n‐pentyl‐biphenyl and the other is the eutectic mixture of cyanoparaphenylenes known as E7. Two series of blends are prepared under different conditions. The first series is obtained by the polymerization induced phase separation (PIPS) process under UV‐curing starting from a monomeric mixture, while the second series is prepared by a combination of the solvent induced phase separation and the thermally induced phase separation process starting from a mixture containing a commercial polymer with known molecular weight. Using gel permeation chromatography, it is found that the polymer molecular weight of the UV‐cured systems decreases with the concentration of LC in the precursor mixture. The experimentally obtained phase diagrams of these two series of systems show a miscibility shift at the composition where the molar mass of the polymer in the PIPS/UV blend exceeds that of the commercial polymer. Data are rationalized in terms of the Flory‐Huggins theory of isotropic mixing and the Maier‐Saupe theory of nematic order. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 18–27, 2007

Study on Energy Ratio Model for Phase Morphology of Immiscible Polymer Blends

The formulas of polymer melt velocity, shearing rate, and shearing stress in simple shearing flow under the vibration force field were established. Based on the concept of an energy ratio model, the rate of energy dissipation and the energy ratio for blending systems are expressed theoretically. The calculated and analytical results of both the dynamic flow field and energy ratio show that with the increasing of vibration strength the fluctuating shearing force field exerted on polymer melt and the negative pressure diffusion behavior of instantaneous impulse strengthen. The energy consumption for phase inversion of immiscible polymer blends under the vibration force field is less than that of steady state. The parameter controllability of the vibration force field provides a more effective method for realizing phase inversion of immiscible polymer blends.

ＰＬＡ／ＰＣＬポリマーブレンドの相構造制御と破壊特性

Phase morphology of blends of biodegradable polymers, PLA and PCL, was controlled by introducing an additive, LTI, to improve the mechanical properties of the mixture. Fracture properties such as the J-integral at initiation Jin, and the total fracture energy Jf, of PLA/PCL blends with different LTI contents were evaluated, and were compared to assess the effect of LTI content on these properties. Both Jin and Jf values were dramatically improved by LTI addition. Fracture surfaces were also examined using SEM to characterize the effect of LTI addition on the fracture mechanism. It was confirmed that the size of PCL spherulites became smaller due to the activation of LTI as a surface-active agent. As a result, void formation was inhibited, and plastic deformation to be larger, resulting the improvement of fracture properties.

Characterization of elastomeric blends by atomic force microscopy

AbstractThe bulk mechanical properties of a blend of elastomers are found to depend on the micro and nano scale morphology of the phases of the materials in the blend. In this study, we examine the phase morphology of blends of incompatible elastomers using Atomic Force Microscopy (AFM). Specifically, nanoindentation and Tapping Mode AFM (TMAFM) imaging techniques are used as experimental tools for mapping the composition of unfilled elastomeric blends. Depending on the composition of the blend, either co‐continuous or discontinuous domain/matrix morphology is observed. To identify the different components in bromobutyl (BIIR)/natural rubber (NR) blends, nanoscale indentation measurements were made on the observed phase‐separated regions. Results from force mode AFM and mechanical measurements of bulk NR and BIIR are used to assist in the interpretation of the TMAFM results for the BIIR/NR blends. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 492–503, 2006

Clay locked phase morphology in the PPS/PA66/clay blends during compounding in an internal mixer

In this communication, we will demonstrate, by using poly( p-phenylene sulfide) (PPS)/polyamide66 (PA66) blends as an example, the clay can not only affect the phase morphology in immiscible polymer blends, but also frozen in the phase inversion. By adjusting the processing method, an inversed phase, where the minor component PA66 forms the continue phase and the major component PPS forms the dispersed phase, is observed for the first time. This is explained as due to the locking effects of clay layers on the phase development. The result is interesting and also very important, which provides a new way to control the phase morphology and phase inversion in immiscible polymer blends by using clay.