Compatibilized iPP/aPS blends: The effect of the viscosity ratio of the components on the blends morphology

More than 25 PP/PS/SEP blends, where PP is isotactic polypropylene, PS is atactic polystyrene, and SEP is poly(styrene‐block‐ethylene‐co‐propylene), were prepared. The main objective of this study was to investigate the influence of PP/PS viscosity ratio, λ_TM, on the blends' morphology. It was shown that λ_TM strongly influenced not only the overall morphology of the blends, but also the morphology of SEP, which exhibited as many as five different types of structure when blended with PP and/or PS. SEP was found an efficient compatibilizer of PP/PS blends as it decreased the average particle size in all studied systems. An interesting “by‐product” of this work was the discovery of a brand‐new type of polymer morphology, which was called morel structure. The characteristic feature of the morel structure was PS matrix compartmentalized by SEP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2236–2249, 2006     

Fluctuation-assisted nucleation in the phase separation/crystallization of iPP/OBC blends

This work mainly focused on the nucleation behavior in iPP/OBC (isotactic polypropylene/polyolefin block copolymers) blends with two distinct OBCs. The influence of composition and molecular structure of the OBC component on the crystallization kinetics of the blends was investigated systematically with the aim to better understand the interplay between the two coupled phase transitions in the blends: macrophase separation and crystallization. The isothermal crystallization kinetics showed component and composition dependence in iPP/OBC blends. All the blends in the studied range have enhanced nucleation ability of iPP than the pure iPP under identical conditions. Furthermore, the distinct macrophase separation morphology resulting from the different compatibility between the various OBCs and iPP caused remarkable diversity between the blends: the nuclei density is qualitatively higher (or the nucleation rate is qualitatively faster) in the more compatible blends, and this enhancement of nucleation can be depressed by imposing a macrophase separation process before crystallization. The crystal nuclei from the phase separated matrix were preferentially formed at the interface of the phase domains, and then grew toward and into the iPP-rich phase. It is postulated that the increased nuclei density and/or nucleation rate followed the fluctuation-assisted nucleation mechanism: the enhanced concentration fluctuation at the interfacial area created by the spinodal decomposition played an important role in the nucleation behavior of iPP/OBC blends. The decreased interface areas with increased domain sizes after deeper phase separation, coupled with a more depressed concentration fluctuation, are responsible for lower nuclei density after long time annealing for phase separation.     

The influence of HOCP oligomer on the crystallization and morphology of iPP/HDPE blends

Summary Ternary mixtures of isotactic polypropylene (iPP), high density polyethylene (HDPE) and hydrogenated oligo(cyclopentadiene) (HOCP) commercial products were prepared by melt mixing. The crystallization behaviour of iPP/HDPE and (iPP/HDPE)/HOCP systems were compared. It was shown that the ternary system separated in two binary systems. The presence of HOCP modified the morphology of iPP and HDPE phases. The polyolefins nucleation and crystal growth rates decreased due to the diluent effect of the oligomer. HDPE showed higher compatibility with HOCP than iPP.     

Investigation of morphology formation in SBS block copolymer/homopolystyrene blends

Polymer blends comprising a polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) block copolymer and atactic homopolystyrene (hPS) were investigated using injection molded and solution cast samples. The morphology of the materials was studied by means of transmission electron microscopy (TEM) and scanning force microscopy (SFM). Dynamic mechanical analysis (DMA) was used to characterize the phase behavior and the morphology formation of the block copolymer as well as of the SBS/hPS blends. The glass transition temperatures seem to strongly depend on the homogeneity of the corresponding phases. A distinct difference was found between the morphologies of the blends prepared by different methods. While the SBS block copolymer always shows a lamellar morphology in injection molded or as‐cast samples, the injection molded blends show a disturbance in the morphology consisting of alternating layers. In contrast, in the case of as‐cast samples, added hPS forms polystyrene domains dispersed in a matrix of the pure block copolymer. Regarding the change in the glass transition temperature, in the effective volume and in the interfacial volume obtained from DMA curves, the morphology formation of the injection molded samples (pure SBS block copolymer and the corresponding blends) was investigated. Two different structural models for the blends are proposed. Polym. Eng. Sci. 44:1534–1542, 2004. © 2004 Society of Plastics Engineers.     

Phase separation induced morphology evolution andcorresponding impact fracture behavior of iPP/PEOc blends

In this study, the influence of phase separation on impact toughness of isotactic polypropylene (iPP)/poly(ethylene‐co‐octene) (PEOc) blends was investigated. For the typical toughened polymeric system, three iPP/PEOc compositions (80/20, 70/30, and 60/40) were selected. When the polymeric blends were annealed at 200°C, the coarsening of phase domains was more prominent for the blend containing higher content of PEOc, and the scale of its morphological evolution was increased as well. The impact test showed that the impact strength variation trend as a function of annealing time was closely related to morphological evolution. It was believed that the sharpening of phase boundary and coarsening of phase domains were responsible for the depression of impact toughness, and the probable fracture mode alteration from shear banding to crazing and voiding. Structure evolution induced by phase separation showed an important effect on impact toughness, and it was also affected by the environmental conditions. Proper temperature was required to catch the tough‐brittle transition induced by phase separation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of processing conditions on the phase morphology of PC/ABS polymer blends

The phase morphology of PC/ABS blends can be significantly affected by its processing conditions. Blends prepared in a mixing chamber at different conditions show a strong influence of mixing time and temperature on its morphology. The blend morphology changes from a well-dispersed PC phase surrounded by the ABS matrix phase to a cocontinuous morphology with increase in the mixing time. Higher blending temperatures promote changes in the PC/ABS morphology, probably due to thermal degradation. The rotor speed has not shown much influence on the blend phase morphology. The cocontinuous phase morphology of the PC/ABS blends obtained after mixing for 10 min was shown to be unstable as detected by the heat treatment. A melt annealing for a few minutes showed a significant change in the morphology. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1605–1613, 1998     

Thermoplastic elastomers from iPP/EPR blends: Crystallization and phase structure development

The phase morphology and structure of thermoplastic elastomers obtained from isotactic polypropylene (iPP) and ethylene—propylene random copolymer (EPR) blends by means of the dynamic curing of EPR rubbery component carried out during its melt mixing with iPP in a Banbury mixer at 180°C were investigated. Samples obtained by compression molding and by using isothermal crystallization conditions of the iPP phase were analyzed by means of differential scanning calorimetry, of optical, scanning, and transmission electron microscopy, and of wide-angle and small-angle X-ray diffraction. The influence of cooling below the melting point and of EPR molecular structure on the kinetic and thermodynamic parameters related to crystallization process of the iPP phase was also studied. It was found that the process of dynamic curing of the EPR component dramatically affects the development of the phase morphology and structure in the material. As a matter of fact, the blend containing the uncured EPR is characterized by the presence of iPP domains randomly distributed in the EPR rubbery matrix, whereas in the blend containing the cured EPR the iPP phase becomes the continuous phase crystallizing in a structure that resembles a cobweb tending to surround the EPR cured particles; moreover such an iPP cobweb appears to be contituted by row structures of stacked lamellae. It was found that the addition of EPR phase interferes dramatically with the crystallization process of the iPP, thus inducing drastic modification in its intrinsic morphology (size, neatness, regularity of spherulites, inner structure of spherulites, etc.). Such interference was found to be comparatively stronger when the iPP phase crystallizes in presence of cured EPR. The elastic behavior of the thermoplastic elastomer material was accounted for by applying the “leaf spring model” to the morphology and structure of the iPP phase crystallized in presence of cured EPR. © 1994 John Wiley & Sons, Inc.     

Extrusion coating performances of iPP/LDPE blends

The performance of iPP/LDPE blends in an extrusion coating process was investigated in the terms of coating width and draw‐down ability. It is well known that iPP alone is not proper because of lower draw‐down ability with severe draw resonance in elongational flow. To obtain higher draw‐down ability, iPP was blended with LDPE. Additionally, iPPs having different molecular weight distribution (MWD) were used in this study to find out the effect of MWD of iPP on neck‐in and draw‐down ability. It was observed that iPP/LDPE blend with narrower MWD exhibits narrower coating width and higher draw‐down ability. Neck‐in and draw‐down ability were correlated with shear and elongational properties obtained by several rheological measurements. From this study, the major rheological parameters affecting extrusion performance in iPP/LDPE blends could be assessed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

SBS/CPE共混物辐射效应研究

研究了不同辐照剂量下苯乙烯-丁二烯-苯乙烯嵌段聚合物（SBS）／氯化聚乙烯（CPE）共混物的动态流变性能及力学性能。结果表明：随着辐照剂量的增大，共混物的粘流活化能降低，温度敏感性减弱；共混物拉伸强度和断裂伸长率下降，凝胶含量增加。     

The phase inversion and morphology of nylon 1010/polypropylene blends

Noncompatibilized and compatibilized blends of nylon 1010/PP blends having five different viscosity ratios were prepared by melt extrusion. Glycidyl methacrylate-grafted-polypro-pylene (PP-g-GMA) was used as the compatibilizer to enbance the adhesion between the two polymers and to stabilize the blend morphology. The effect of the viscosity ratio on the morphology of nylon 1010/polypropylene blends was investigated, with primary attention to the phase-inversion behavior and the average particle size of the dispersed phase. The relationship between the mechanical properties and the phase-inversion composition was investigated as well. Investigation of the morphology of the blends by microscopy indicated that the smaller the viscosity ratio (ηpp/ηpa) the smaller was the polypropylene concentration at which the phase inversion took place and polypropylene became the continuous phase. The compatibilizer induced a sharp reduction of particle size, but did not have a major effect on the phase-inversion point. An improvement in the mechanical properties was found when nylon 1010 provided the matrix phase. © 1996 John Wiley & Sons, Inc.     

Study of PS/SBS/nano-CaCO3 blends

Abstract

The effect of SBS and nano-CaCO₃ on the mechanical properties of PS blends was studied, and their morphologies were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Izod impact strengths of notched samples of PS/SBS/CaCO₃ blends with nanometre particles of nano-CaCO₃ and SBS are higher than those of PS and PS/SBS blends with the same content of SBS, and the tensile strengths are higher than those of PS/SBS blends. The inclusion of nano-CaCO₃ within the dispersed phase of SBS enlarges the volume of the domains of SBS, which increases the toughness of the ternary blends (PS/SBS/CaCO₃). The mass ratio of SBS/CaCO ₃ plays an important role in the properties of the ternary blends because it affects the concentration of SBS in these blends, the dispersion of nano-CaCO₃ and the morphology of the ternary blends.     

iPP/HDPE blends: Interactions at lower HDPE contents

Mechanical and rheological properties of blends of polypropylene (PP) and linear polyethylene (PE) were studied, with particular attention to the effects of aging of such mixtures. These two olefin polymers are basically incompatible. In PP-rich blends, addition of highdensity PE (HDPE) causes only a slight decrease in tensile properties and impact resistance of injection-molded specimens. In all cases, annealed specimens have higher moduli and lower impact strength than as-molded products. While none of these changes are very drastic, the addition of small amounts of HDPE was observed to result in a serious decrease of gate-region impact resistance of thin-walled moldings. Blends with 10–20% HDPE exhibited an unexpected interaction in tensile, thermal, and melt-flow properties as well as in crystallization behavior. © 1995 John Wiley & Sons, Inc.     

Structure and properties of new reversibly crosslinked iPP/LDPE blends

Reversibly crosslinked blends of isotactic polypropylene and low density polyethylene (iPP/LDPE) were prepared in the presence of crosslinking agents using reactive extrusion. The structure and properties of the modified blends were investigated by means of wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and macro- and micro-mechanical measurements. The crystallinity of the modified samples (LDPE, iPP, and their blends) does not seem to be so much affected by the crosslinking process. Results show that the microhardness of the iPP/LDPE blends notably increases with the iPP content. The micromechanical properties of the modified blends only improve slightly as a consequence of the crosslinking process. In the iPP samples, and also in the iPP/LDPE blends, this process gives rise to the appearance of new, crystalline ethylenic chains, as evidenced by the calorimetric measurements. Furthermore, the impact strength of the modified materials is improved as compared with that of the original ones, while some of the crosslinked blends show a ductile fracture behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystalline morphology of isotactic polypropylene (iPP) in injection molded poly(ethylene terephthalate) (PET)/iPP microfibrillar blends

The poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) in situ microfibrillar blends have been prepared through a “slit die extrusion-hot stretch-quenching” process, in which PET assumes microfibrils with 0.5-15 μm in diameter depending on the hot stretching ratios (HSR, the area of the transverse section of the die to the area of the transverse section of the extrudate). The injection molded specimens of virgin iPP and the PET/iPP blends were prepared by conventional injection molding (CIM) and by shear controlled orientation injection molding (SCORIM), respectively. The effect of shear stress and PET phase with different shape on superstructures and their distribution of injection molded microfibrillar samples were investigated by means of small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). The shear (or elongational) flow during CIM and SCORIM can induce oriented lamellae (i.e. kebabs induced by shish). The shish-kebab structure appears not only in the skin and intermediated layers of CIM samples, but also in the whole region of SCORIM samples. For the neat iPP samples, a more “stretched” shish-kebab structure with higher orientation degree can be obtained in the interior region (intermediate and core layers) by the SCORIM method; moreover, the SCORIM can result in the growth of β-form crystal both in intermediate layer and in core layer, which only appears in intermediate layer of the neat iPP samples obtained by CIM. For the PET/iPP blends, interestingly, the addition of microfibrils as well as their aspect ratios can affect the orientation degree of kebabs only in the intermediate layers, and the addition of microfibrils with a low aspect ratio can bring out a considerable increase in the orientation degree of kebabs along the flow direction. However, for the SCORIM, the addition of microfibrils seems to be a minor effect on the orientation degree of kebabs, and it tends to hamper the formation of a more “stretched” shish-kebab structure and suppresses the growth of β-form crystal distinctly. Furthermore, It appears from experiment that γ-form crystals can grow successfully in this oriented iPP melt with the synergistic effect of shear and pressure only when the growth of β crystals can be restrained by some factors, such as the PET dispersed phase and thermal conditions (cooling rate).     

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.     

Study on the compatibility of BR/CR/SBS blends by using small amounts of SBS

The structures and properties of BR/CR/SBS blends were studied by using optical, electron microscopy, FTIR methods, etc. Results showed that the addition of a small amount of SBS to the thermodynamically immiscible blends BR/CR could significantly promote fine and homogeneous dispersion of the system, increase crosslink density of vulcanizates and tensile strength, and decrease loss of tan δ of the blends. IR spectra also demonstrated the stronger interaction between SBS and BR, CR. The theoretical prediction of compatibilizing activity of SBS in the BR/CR blends is in excellent agreement with experimental results. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 215–220, 1999     

Extrusion of polyethylene/polypropylene blends with microfibrillar‐phase morphology

Extrusion of immiscible polymers under special conditions can lead to creation of microfibrillar‐phase morphology, ensuring significant increase of mechanical properties of polymer profiles. Polyethylene/polypropylene blend extrudates with microfibrillar‐phase morphology (polypropylene microfibrils reinforcing polyethylene matrix phase) were prepared through continuous extrusion with semihyperbolic‐converging die enabling elongation and orientation of microfibrils in flow direction. Structure of extruded profiles was examined using electron microscopy and wide‐angle X‐ray scattering. Tensile tests proved that extrudates with microfibrillar‐phase morphology show significantly higher mechanical properties than the conventional extrudates. The presented concept offers possibility of replacing the existing expensive multi‐component medical devices with fully polymeric tools. POLYM. COMPOS., 31:1427–1433, 2010. © 2009 Society of Plastics Engineers     

氟橡胶/环氧丙烯酸酯橡胶共混物的双连续相形态和性能(英文)

采用双螺杆挤出机,通过熔融共混法制备了氟橡胶(FKM)/环氧丙烯酸酯橡胶(EACM)共混物.用透射电镜和动态机械热分析仪研究了FKM/EACM共混物的形态、热力学性能和动态机械性能,探讨了共混比对其力学性能的影响.透射电镜研究结果显示,FKM/EACM共混物在共混比范围内呈现出完美的两相连续结构形态,共混体系的相畴尺寸随着EACM用量的不同而改变,当FKM/EACM(质量比)为80/20时,EACM在FKM的基质中形成最完善的网络结构;同时两相产生了协同效应,FKM/EACM共混物的拉伸强度和撕裂强度达到最大值.     

The effect of matrix toughness and dispersed elastomer phase on the brittle-ductile transition in PP/HDPE/SBS blends

In this paper the sbrittle-ductile transition of polypropylene, high density polyethylene, and a styrene-butadiene-styrene triblock copolymer (PP/HDPE/SBS) ternary blends is investigated for fixed compositions and prepared under various conditions. The morphology of the SBS dispersed phase particles and impact strength of the PP ternary blends is closely related to the processing conditions. There is a sharp Brittle-Ductile transition for the ternary blends when interparticle distance T becomes less than the critical interparticle distance T_c. Both the impact strength in general and more specifically, T_c depend upon the toughness of the PP/HDPE composite matrix.     

高温贮存稳定的SBS/沥青共混物的制备

在沥青生研究中引入动态硫化概念,制得了力学性能优良、高温贮存稳定的ＳＢＳ／沥青共混物。