Analysis of phase morphology and dynamics of immiscible PP/PA1010 blends and its partial-miscible blends during melt mixing from SEM patterns

The formation and evolution of the phase morphology of polypropylene (PP) with Nylon1010 (PA1010) blends before and after adding the compatibilizer, polypropylene grafted maleic anhydride (PP-g-MAH), during melt mixing are investigated by the pattern analysis of scanning electron microscope (SEM). The average particle diameter DP_AV, characteristic length Λ and the average characteristic length Λm are calculated to discuss the melt mixing process. It is proved, by the figure-estimation theory, that the distribution of Λ is log-normal distribution. Furthermore, the phase morphology during melt mixing is discussed in depth by the parameters of the log-normal distribution. The results demonstrate that the structure of the dispersed phase during melt mixing evolves with dynamical self-similarity through the competition of break-up and coalescence of dispersed phase. A fractal dimension, based on the probability density of the character length, is calculated in this study. The results show that the fractal dimension is an effective parameter to characterize the melt mixing process of polymer blends.     

Morphological and fractal studies of polypropylene/poly(ethene‐1‐octene) blends during melt mixing using scanning electron microscopy

BACKGROUND: Polymer blending creates new materials with enhanced mechanical, chemical or optical properties, with the exact properties being determined by the type of morphology and the phase dimension of the blend. In order to control blend properties, morphology development during processing needs to be understood. The formation and evolution of polypropylene/poly(ethylene‐1‐octene) (PP/POE) blend morphology during blending are qualitatively represented by a series of time‐dependent scanning electron microscopy (SEM) patterns. The area diameter and its distribution of dispersed phase domains are discussed in detail. In order to characterize the formation and evolution of phase morphology quantitatively, two fractal dimensions, D_s and D_d, and their corresponding scaling functions are introduced to analyze the SEM patterns. RESULTS: The evolution of the area diameter indicates that the major reduction in phase domain size occurs during the initial stage of melt mixing, and the domain sizes show an increasing trend due to coalescence with increasing mixing times. The distribution in dispersed phase dimension obeys a log‐normal distribution, and the two fractal dimensions are effective to describe the phase morphology: D_s for dispersed phase dimension and D_d for the distribution in it. CONCLUSIONS: The fractal dimensions D_s and D_d can be used quantitatively to characterize the evolutional self‐similarity of phase morphology and the competition of breakup and coalescence of dispersed phase domains. It is shown that the fractal dimensions and scaling laws are useful to describe the phase morphology development at various mixing times to a certain extent. Copyright © 2007 Society of Chemical Industry     

Phase Morphology and Miscibility of iPP/PcBR Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR) blends were prepared by melt mixing. Phase morphology of the blends was investigated by scanning electronic microscopy (SEM). It was found that the dispersed phase spread in continuous phase in a form of spherical particles. The size of the dispersed phase increased as its content increased. The phase-inversion region was the composition of 50/50 and 40/60 vol% in the blends. In the phase-inversion region, a double continuous phase was formed. The glass transition temperatures (T _g ) of iPP, PcBR and blends were analyzed by dynamic mechanical analysis (DMA). The blend compositions exhibited two distinct glass transition temperatures corresponding to the iPP-rich and PcBR-rich phases, respectively. The approach of these two peaks with increasing PcBR content indicated partial miscibility between the iPP and PcBR, which was verified by the equilibrium melting point depression of blends.     

Phase morphology development of polypropylene/ethylene-octene copolymer blends: effects of blend composition and processing conditions

Summary Blends of polypropylene (PP)/ethylene-octene copolymer (EOC) was studied. The influences of blend composition and processing conditions on phase morphology development of the blends were investigated by scanning electron microscopy (SEM) in detail. The minor composition formed the dispersed phase and the major composition formed the continuous phase, and the blends formed interpenetrating co-continuous morphology just at the intermediate concentration. The effect of concentration on phase coarsening was explained by the increase of dispersed phase coalescence with dispersed phase concentration’s increase. Phase coarsening and phase fine dispersing were studied. The effect of mixing time on phase morphology development of the blends was investigated, the PP/EOC (80/20) blends has already formed a well-established droplet/matrix morphology after 1.5 min of mixing, and the similar blends phase morphology persisted until 11 min of mixing. The most prominent phenomenon is that the dispersed phase domain deformed from spherical droplet to elliptical droplet, even fibrillar or sheet morphology as the rotor speed increased. The increase of shear rate and elasticity ratio was applied to interpret this phenomenon.     

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing and melt-mixing

A novel phenolic rigid organic filler (named KD) with a high melting point was dispersed in an isotactic polypropylene (iPP) matrix by solution-mixing and/or melt-mixing. A series of KD/iPP blends was prepared with or without addition of maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer. Influences of MAPP and mixing methods on the filler dispersion were studied using polaried optical microscope (POM), scanning electron microscope (SEM) and tensile test. The filler particles are always inclined to form large irregular aggregates in the iPP matrix due to their significant differences in polarity and solubility in solvent. However, an iPP/MAPP/KD (PMK) blend containing filler particles with a quasi-spherical shape (~97.8 nm in diameter) and narrow particle size distribution (polydispersity index= 1.076) was successfully prepared by incorporating MAPP to reduce the interfacial tension and surface free energy between the dispersion phase and the continuous phase, and adopting a spray-drying method after solution-mixing to suppress the increase of the size of the dispersed phase during the removal of solvent.     

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 d _p , characteristic length L, and average characteristic length L _m , 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)/L _m ) 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.     

Morphological development of polypropylene in immiscible blends with cellulose acetate butyrate

Isotactic polypropylenes (iPP) with different melt flow indexes were melt blended with cellulose acetate butyrate (CAB) and then prepared into microspheres or nanofibers following a novel process of producing well dispersed CAB/iPP immiscible blends and subsequent removal of the CAB matrix. The morphologies of iPP microspheres were investigated by a scanning electron microscopy, and the dimensions of iPP microspheres were evaluated. The melt viscosities of iPP, CAB, and CAB/iPP blends were measured by using a capillary rheometer. The influences of the viscosity, viscosity ratio, and composition ratio of iPP/CAB on the morphology formation of iPP in CAB matrix were studied.     

Morphology, phase structure and thermal behaviour of films of isotactic polypropylene/hydrogenated oligocyclopentadiene blends: 1. Extruded isotropic films

The effect of hydrogenated oligocyclopentadiene (HOCP) on the structure and morphology of isotropic isotactic polypropylene (iPP) films obtained by melt extrusion has been studied using wide-angle X-ray scattering, thermal analysis and electron microscopy. It was found that the addition of HOCP causes the formation of the smectic phase of iPP at temperatures where bulk iPP crystallizes only in the monoclinic form. The amount of smectic phase present in the blend is dependent on the blend composition. The spherulitic morphology of iPP is completely modified by the presence of HOCP. For blends containing up to 10% HOCP, the iPP spherulite dimensions are drastically reduced. In the case of blends of higher HOCP content, the film crystallinity is reduced, no spherulites are visible and the film surface appears smoother.     

Nylon 6/ethylene propylene rubber (EPM) blends: Phase morphology development during processing and comparison with literature data

The morphology of immiscible blends of nylon 6 and ethylene propylene rubber blends (EPM) was studied. The blends were prepared by melt blending in a twin‐screw miniextruder and a Haake Rheocord mixer. The influence of the blend ratio, time of mixing, rotation speed of the rotors, mixing temperature, and quenching of the extruded melt at low temperature on the phase morphology of the blends was quantitatively analyzed. The morphology was examined by scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain‐size measurements. The morphology of the blends indicated that the EPM phase was preferentially dispersed as domains in the continuous nylon matrix up to 40 wt % of its concentration. A cocontinuous morphology was observed at 50 and 60 wt % EPM content followed by a phase inversion beyond 60 wt % of EPM where the nylon phase was dispersed as domains in the continuous EPM phase. The size, shape, and distribution of the domains were evaluated by image analysis as a function of the blend composition. The effect of the time of mixing on the phase morphology was studied up to 20 min for the 30/70 EPM/nylon blend. The most significant domain breakup was observed within the first 3 min of mixing followed by a leveling off up to 15 min. This may be associated with the equilibrium between the domain breakup and coalescence. The influence of rotor speed on the morphology was insignificant at a high rotor speed although a significant effect was observed by changing the rotor speed from 9 to 20 rpm. The influence of high‐temperature annealing, repeated cycles of extrusion, the molecular weight of the nylon matrix, and the nature of the mixer type (twin‐screw miniextruder versus Haake Rheocord mixer) on the morphology was also investigated in detail. The experimental results were compared with literature data. Finally, the extent of interface adhesion in these blends was analyzed by examination of the fracture‐surface morphology. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1405–1429, 1999     

聚苯乙烯／顺丁橡胶合金相结构的X光小角散射研究

采用X光小角散射法研究了聚苯乙烯/顺丁橡胶合金体系的相结构及相容性。用Debye-Bueche光散射理论的结构参数，如相关距离ac．平均弦长l、旋转半径Rg和积分不变量Q等表征了合金中分散相的尺度及其分布在连续相中的均匀性，用扫描电子显微镜(SEM)定量测定了合金中分散相尺寸的大小和尺寸分布。结果表明：上述各光散射结构参数均可以在纳米尺度范围内表征合金体系的相结构，积分不变量Q可以表征合金体系相结构的均匀性。聚苯乙烯(PS)/颐丁橡胶(PB)合金是典型的不相容体系，无论PB还是PS处于稀相时均不呈现分子分散。     

Time evolution of phase structure and corresponding mechanical properties of iPP/PEOc blends in the late-stage phase separation and crystallization

A typical toughened polymeric alloy system, isotactic polypropylene (iPP)/poly(ethylene-co-octene) (PEOc) blend, was selected in this study to investigate the influence of phase separation and crystallization on the final mechanical properties of the polyolefin blend. The time dependence of the morphology evolution of this iPP/PEOc blend with different compositions was annealed at both 200 and 170 °C and investigated with scanning electron microscopy (SEM) and phase contrast optical microscopy (PCOM). It was found that under the above two phase separation temperatures, the domain size of iPP80/PEOc-20 (PEOc-20) increases only slightly, while the structure evolution of iPP60/PEOc-40 (PEOc-40) is quite prominent. The tensile tests revealed that the mechanical properties of PEOc-20, including break strength and elongation at break decrease only in a very small amount, while those of PEOc-40 are depressed obviously with phase separation time. The decrease of interphase and a sharper boundary resulting from domain coarsening during the late-stage phase separation are responsible for the poor tensile properties. It is believed that the composition, the annealing time and the processing temperatures all contribute to the morphology evolution and the consequent mechanical properties of iPP/PEOc blends, furthermore, the crystallization procedure is another crucial factor influencing the ultimate mechanical properties of the investigated blends.     

In situ fibrillation of isotactic polypropylene in ethylene-vinyl acetate: Toward enhanced rheological and mechanical properties

In situ microfibrillar reinforced composites with ethylene-vinyl acetate (EVA) as matrix and isotactic polypropylene (iPP) as dispersed fibrils were successfully fabricated by multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs). Four types of EVA with different apparent viscosity were utilized to study the influence of viscosity ratio on the morphology and mechanical properties of EVA/iPP in situ microfibrillar blends. The scanning electron micrographs revealed that the dividing–multiplying processes in LMEs could effectively transform the morphology of iPP phase into microfibrils and the morphology of iPP microfibrils strongly depended on the viscosity ratio. Higher viscosity ratio was favorable for formation of finer microfibrils with narrower diameter distribution. The morphology development of iPP with different viscosity ratio greatly affected the rheological and mechanical properties of EVA/iPP blends. The dynamic rheological results shown that the iPP microfibrils were helpful to increase the storage modulus and loss modulus. The tensile test indicated that the mechanical properties of EVA/iPP blends were controlled by the morphology of iPP phase and the polarity of EVA matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47557.     

Tensile properties in the oriented blends of high-density polyethylene and isotactic polypropylene obtained by dynamic packing injection molding

In this article, tensile properties have been discussed in terms of phase morphology, crystallinity and molecular orientation in the HDPE/iPP blends, prepared via dynamic packing injection molding, with aid of scanning electron microscopy (SEM), differential scanning calorimetry (DSC) as well as two dimensional X-ray scattering (2D WAXS). For the un-oriented blends, the tensile properties (tensile strength and modulus) are mainly dominated by the phase morphology and interfacial adhesion related to the influenced crystallization between HDPE and iPP component. A maximum in tensile strength and modulus is found at iPP content in the range of 70-80 v/v%. As for the oriented blends, however, the presence of dispersed phase in the blends, independent of phase morphology and crystallinity, always makes tensile properties to be deteriorated through reducing molecular orientation of matrix. It is molecular orientation of matrix that determines the tensile properties of oriented blends. In the blends with HDPE as matrix, steep decreasing of tensile properties is related to the rapid reducing of molecular orientation of HDPE, whereas in the blends with iPP as a major component, slight decreasing of molecular orientation of iPP results in slight reducing of tensile properties. Other factors, such as interfacial properties and phase morphology, seem to be little contribution to the modulus and tensile strength.     

Temporal evolution of phase morphology of polypropylene/poly(ethylene octene) elastomer binary polymer blends by phase contrast microscope

Blend films of polypropylene/poly(ethylene‐octane) at various mixing times are prepared by freezing‐microtome. The temporal evolution of their phase morphologies is investigated by phase contrast microscope (PCM). The digital image analysis, which contains the analysis in both real and wave‐number space, is introduced to deal with the PCM graphs. The characteristic length, L in real space, the average domain spacing, and the average chord lengths in wave‐number space, are used to express the domain sizes of two phases. The temporal evolution of phase morphology reaches the dynamic equilibrium between breakup and coalescences of domains at the late stage of mixing. In addition, two different fractal dimensions are defined to discuss the symmetry of the distribution of dispersed phase domains and the distribution uniformity: D_f for the symmetry and D_c for the uniformity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

PO／PS合金的相态结构与力学性能

以氢化ＳＢＳ（ＳＥＢＳ）为增容剂的聚烯烃／聚苯乙烯（ＰＯ／ＰＳ）合金，与聚烯烃相比具有更好的力学性能，尤其是抗冲击强度随机容剂的增加而大幅度提高，应用ＴＥＭ，ＳＥＭ、ＤＳＣ、偏光显微技术对一系列合金相形态，相容程度及分散相颗粒尺的考察研究发现，合金中分散相多数呈卵石状，随ＳＥＢＳ含量增加，分散相粒径显著变小，而合金抗冲击强度增大，分散相形态结构。颗粒尺寸与材料力学性能密切相联。     

Minor‐phase particles evolution in a polyethylene/ethylene–propylene copolymer (80/20) blend across mixing: Breakup and coalescence

On the basis of an online sampling microscopy method, the morphological evolution of a metallocene polyethylene/metallocene ethylene–propylene copolymer system (80/20 vol %) across various mixing regimes was investigated and treated statistically. The size distributions of the minor‐phase metallocene ethylene–propylene (mEP) droplets were described with principles of irreversible thermodynamics. Such an approach allowed us to find two superimposed statistical ensembles involving primary (broken) and secondary (coalesced) mEP particles. The mean size and relative number of both broken and coalesced mEP particles were calculated. The evolution of these characteristics across melt mixing, static coalescence, and flow‐driven coalescence was analyzed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3421–3431, 2013     

Effect of dynamic cross-linking on mixing torque behavior and tensile yield behavior of isotactic polypropylene (iPP) / ethylene-propylene diene rubber (EPDM) /nitrile rubber (NBR) elastomeric blends

The mixing torque behavior of ter blends of isotactic-polypropylene (iPP) with ethylene-propylene diene rubber (EPDM)/Nitrile rubber (NBR) was studied with the help of Rheometer using resole type phenolic resin as a cross-linking agents. Systematic changes with varying blend composition were observed in stress-strain behavior in the yield region viz., width of yield peak, work of yield, yield stress and yield strain. Analysis of yield stress data was made on the basis of various mathematical expressions of first power and two-thirds power laws of blend composition dependence and the porosity model. It led to consistent result from the expressions about the variation of stress concentration effect in both uncross-linked and cross-linked blend systems. With the aid of scanning electron microscopy (SEM) shapes and sizes of dispersed elastomer phase (EPDM / NBR) domains at varying blend compositions were studied.     

Dynamic mechanical, thermal, physico-mechanical and morphological properties of LLDPE/EMA blends

The effect of blend composition on the morphology, dynamic mechanical properties, thermal and physico-mechanical properties of linear low density polyethylene (LLDPE)/ ethylene-co-methyl acrylate (EMA) blends were studied. The blend showed both dispersed and continuous phase morphology that depends on the blend composition. A co-continuous structure is formed for blends containing 50 wt% of EMA. Dynamic mechanical studies showed that flexibility of the blend enhanced with the expansion of the amorphous region as EMA content increased. However, two separate melting temperature peak observed in differential scanning calorimetry (DSC) analysis indicate that the blends are immiscible in crystalline region of the two polymers. X-ray diffraction (XRD) studies showed that crystallinity of blends decreases with increase in EMA content and negative deviation of tensile strength from the mixing rule indicates the poor interfacial adhesion between the two components. FTIR spectroscopy established the lack of chemical interaction between LLDPE and EMA, which support the SEM, DSC, DMA and XRD observations. Parallel-Voids model has been applied to characterize phase morphology of these blends.     

Investigation on the morphology and tensile behavior of β‐nucleated isotactic polypropylene with different stereo‐defect distribution

Large amount of work has been published on the tacticity‐properties relationship of isotactic polypropylene (iPP). However, the stereo‐defect distribution dependence of morphology and mechanical properties of β‐nucleated iPP (β‐iPP) is still not clear. In this study, two different iPP resins (PP‐A and PP‐B) with similar average isotacticity but different uniformities of stereo‐defect distribution were selected, their β‐iPP injection molding specimens were prepared, and the morphology evolution and tensile behaviors were studied by means of differential scanning calorimetry (DSC), 2D wide‐angle X‐ray diffraction (2D‐WAXD) and scanning electron microscope (SEM). DSC results showed that with the same concentration of β‐nucleating agent (0.3 wt % WBG‐II), PP‐B with more uniform stereo‐defect distribution exhibited more amount of β‐phase than that of PP‐A with less uniform stereo‐defect distribution, indicating that PP‐B is more favorable for the formation of β‐phase. SEM results showed that PP‐B formed more amount of β‐crystals with relatively high structural perfection, while in PP‐A a mixed morphology of α‐ and β‐phase with obviously higher amount of structural imperfection emerges. The results of room‐temperature tensile test indicated that the yield peak width of PP‐B was obviously wider, and the elongation at break of PP‐B was higher than that of PP‐A, showing a better ductile of PP‐B. The morphology evolution results of SEM, 2D‐WAXD and DSC suggest that, a combination of lamellar deformation and amorphous deformation occurred in PP‐A, while only amorphous deformation mainly took place in PP‐B, which was thought to be the reason for the different tensile behaviors of the samples. In the production of β‐PP products via injection molding, the uniformity of stereo‐defect distribution was found to be an important factor. PP with more uniform distribution of stereo‐defect favors the formation of large amount of β‐phase with high perfection, which exhibit superior ductile property. The related mechanism was discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40027.     

Morphology and mechanical properties of polypropylene/poly (propylene-1-octene) in-reactor alloys prepared by Metallocene/Ziegler–Natta hybrid catalyst

A series of isotactic polypropylene/poly(propylene-1-octene) (iPP/PPOc) in-reactor alloys were synthesized by a one-step polymerization process, using Metallocene/Ziegler–Natta hybrid catalyst. The alloys were characterized by FT-IR, DSC, optical microscopy and SEM. The results suggested that the spherical morphology was maintained during one-step polymerization process, which provided a potential application for one-step polyolefin in-reactor alloys. A characteristic “shell–core” structure of the nascent alloy particles was observed for the first time. This phenomenon may be due to the difference between the homopolymerization and copolymerization rate at different active centers. It was also found that the majority of the elastomers in the matrix were homogeneously distributed in the alloys. The introduction of the relatively long 1-octene branches could effectively reduce the crystal size and the crystallinity of the obtained iPP/PPOc alloys and made it possible to vary their rigidity and elasticity in a wide range. The crystallization kinetics of the alloys with pure iPP was also investigated. With the increase of elastomer content, an increase of nucleation density (the nuclei number per unit area) and the decrease of crystal perfection could be clearly observed. In comparison with pure PP, the overall crystallization rates and the growth rates of the spherulites of the alloys decreased obviously. These results indicated that the growth rate of the spherulites was the decisive step for the overall crystallization rate in this case, which can be explained on the basis of dilution effect and obstruction effect on the mobility of PP chains in the propylene–octene copolymer. Investigation of the mechanical properties indicated that notched Izod impact strength of iPP/PPOc alloys have obviously increased in comparison with that of pure iPP. The improvement of impact strength can be mainly attributed to the increase of random copolymer content. Based on the understanding of microstructure and phase morphology, the correlation between morphological structure and mechanical properties has been established.