间规聚苯乙烯/等规聚丙烯/间规聚苯乙烯-b-聚(1-丁烯)共混体系相容性

间规聚苯乙烯(sPS)的改性主要是对其增韧改性,提高其力学性能.sPS的化学改性已有较多文献报道[1,2].     

Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers

The structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004     

用Z-N催化剂分段聚合制备PP/EPR共混物的结构和形态特征

用Ziegler-Natta(Z-N)催化剂MgCl2/TiCl4/BMF-AlEt3(BMF代表内给电子体9,9-二甲氧基甲基芴),采用分段聚合的方法制备了PP/EPR原位共混物,通过改变乙丙共聚的时间调节聚合物中乙烯的含量.使用核磁共振(13C-NMR)、凝胶渗透色谱(GPC)、示差扫描量热分析法(DSC)、动态力学分析(DMA)、扫描电子显微镜(SEM)和偏光显微镜(PLM)等研究了聚合物的结构和形态特征.研究发现,分段聚合制备的PP/EPR共混物是一种包括丙烯均聚物、乙丙无规和嵌段共聚物在内的多组分混合物.动态力学的结果显示混合物中聚丙烯与乙丙无规共聚物的玻璃化转变峰出现了内移现象,说明两者呈现部分相容性.扫描电镜的照片表明了聚丙烯基体与乙丙无规共聚物分散相之间的相界面模糊,两相之间的相容性较好.随着聚合物中乙烯含量的增加,分散相出现明显的塑性变形,同时,聚丙烯的结晶形态也发生明显的变化,球晶的尺寸逐渐变小,同时球晶变得不完善.     

Semicrystalline blends of polyethylene and isotactic polypropylene: Improving mechanical performance by enhancing the interfacial structure

The low‐temperature mechanical behavior of semicrystalline polymer blends is investigated. Isotactic polypropylene (iPP) is blended with both Zeigler–Natta polyethylene (PE) and metallocene PE. Transmission electron microscopy (TEM) on failed tensile bars reveals that the predominate failure mode in the Zeigler–Natta blend is interfacial, while that in the metallocene blend is failure of the iPP matrix. The observed change in failure mode is accompanied by a 40% increase in both tensile toughness and elongation at −10 °C. We argue that crystallite anchoring of interfacially entangled chains is responsible for this dramatic property improvement in the metallocene blend. The interfacial width between PE and iPP melts is approximately 40 Å, allowing significant interfacial entanglement in both blends. TEM micrographs illustrate that the segregation of low molecular weight amorphous material in the Zeigler–Natta blend reduces the number and quality of crystallite anchors as compared with the metallocene blend. The contribution of anchored interfacial structure was further explored by introducing a block copolymer at the PE/iPP interface in the metallocene blend. Small‐angle X‐ray scattering (SAXS) experiments show the block copolymer dilutes the number of crystalline anchors, decoupling the interface. Increasing the interfacial coverage of the block copolymer reduces the number of anchored interfacial chains. At 2% block copolymer loading, the low‐temperature failure mode of the metallocene blend changes from iPP failure to interfacial failure, reducing the blend toughness and elongation to that of the Zeigler–Natta blend. This work demonstrates that anchored interfacial entanglements are a critical factor in designing semicrystalline blends with improved low‐temperature properties. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 108–121, 2000     

Influence of Talc and SEBS-g-MA on PP/SEBS-g-MA/Talc Composites under Gamma Irradiation Sterilization Conditions

Among thermoplastics, polypropylene is outstanding with respect to its attractive combination of low cost, low weight, heat distortion temperature above 100°C, and extraordinary versatility in terms of properties and applications. With the appropriate modification, it is possible to improve the existing properties of the polypropylene, or even obtain the new ones. As a result of its originally superior properties, polypropylene is commonly used in medical purposes, where it has to undergo the process of sterilization beforehand. The sterilization of the polypropylene in medicine is most often being carried out with low dose of gamma irradiation, which can influence the changes of properties of both the polymeric matrix and modifiers. Therefore, the purpose of our research work was to determine the mechanical properties of unirradiated and gamma irradiated isotactic polypropylene (iPP) composites with talc filler and poly-(styrene-b-ethylene-co-butylene-b-styrene) block copolymer, grafted with maleic anhydride (SEBS-g-MA) as elastomeric modifier, as well as of corresponding binary blends. Unirradiated and gamma irradiated composites and blends were characterized by tensile measurements, measurements of notched impact strength and FTIR spectroscopy. The effects of composition and gamma irradiation on the properties of the iPP composites and blends are discussed, with emphasis on the study of the stabilizing effect of talc in irradiated iPP composites.     

EFFECT OF COMPATIBILITY ON PHASE MORPHOLOGY AND ORIENTATION OF ISOTACTIC POLYPROPYLENE （IPP） BLENDS OBTAINED BY DYNAMIC PACKING INJECTION MOLDING

The effect of compatibility on phase morphology and orientation of isotactic polypropylene （iPP） blends under shear stress was investigated via dynamic packing injection molding （DPIM）. The compatibility of iPP blended with other polymers, namely, atactic polypropylene （aPP）, octane-ethylene copolymer （POE）, ethylene-propylene-diene rubber （EPDM） and poly（ethylene-co-vinyl acetate） （EVA）, have first been studied using dynamic mechanical analysis （DMA）. These blends were subjected to DPIM, which relies on the application of shear stress fields to the melt/solid interfaces during the packing stage by means of hydraulically actuated pistons. The phase morphology, orientation and mechanical properties of the injection-molded samples were characterized by SEM, 2D WAXS and Instron. For incompatible iPP/EVA blends, a much elongated and deformed EVA particles and a higher degree of iPP chain orientation were observed under the effect of shear. However, for compatible iPP/aPP blends, a less deformed and elongated aPP particles and less oriented iPP chains were deduced. It can be concluded that the compatibility between the components decreases the deformation and orientation in the polymer blends. This is most likely due to the hindering effect, resulting from the molecular entanglement and interaction in the compatible system.     

Phase morphology of iPP/aPS/SEP blends

Supermolecular structure and phase morphology of the ternary isotactic polypropylene/atactic polystyrene/poly(styrene-b-ethylene-co-propylene) (iPP/aPS/SEP) compression molded blends with 100/0, 90/10, 70/30, and 50/50 iPP/aPS weight ratios and with different amounts of added SEP compatibilizer were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). SEP significantly reduced the size of dispersed aPS particles that enabled better spherulitization in the iPP matrix. Furthermore, iPP spherulites in ternary blends with 90/10 iPP/aPS weight ratio became larger in comparison with the pure iPP. TEM revealed that the SEP formed continuous interface layer around the dispersed aPS particles even when only 2.5 wt.% of SEP was added. Particle size distribution was distinctly bimodal. When the SEP content was increased to 10 wt.%, joining together smaller and bigger aPS and SEP particles formed dispersed aggregates. Additionally, both amorphous components (aPS and SEP) influenced crystallization process of iPP matrix and so modified, to some extent, its final supermolecular structure. SEP compatibilizer did not significantly affect crystallite orientation. The increase of crystallite sizes, which was more affected by the addition of aPS than by the addition of SEP, seemed to be influenced by the solidification effect rather than by the phase morphology of the blends.     

Evolution of phase morphology of high impact polypropylene particles upon thermal treatment

Solvent fractionation and differential scanning calorimetry (DSC) results show that high impact polypropylene (hiPP) produced by a multistage polymerization process consists of PP homopolymer, amorphous ethylene-propylene random copolymer (EPR), and semicrystalline ethylene-propylene copolymer. For the original hiPP particles obtained right after polymerization, direct transmission electron microscopy (TEM) observation reveals a fairly homogeneous morphology of the ethylene-propylene copolymer (EP) phase regions inside, while the polyethylene-rich interfacial layer observed between the EP region and the iPP matrix supports that EP copolymers form on the subglobule surface of the original iPP particles. Compared with that in original hiPP particles, the dispersed EP domains in pellets have much smaller average size and relatively uniform size distribution, indicating homogenization of the EP domains in the hiPP by melt-compounding. Upon heat-treatment, phase reorganization occurs in hiPP, and the dispersed EP domains can form a multiple-layered core-shell structure, comprising a polyethylene-rich core, an EPR intermediate layer and an outer shell formed by EP block copolymer, which accounts to some extent for the good toughness-rigidity balance of the material. The results indicate that to establish the optimum phase structure and desired properties for hiPP, both the architecture of original hiPP particles and subsequent melt-processing conditions should be carefully modulated.     

Compatibilizing effect of polyarylate-polystyrene block copolymer in polyarylate/polystyrene blends

The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc.     

Reaction-induced microphase separation in epoxy resin containing polystyrene-block-poly(ethylene oxide) alternating multiblock copolymer

Polystyrene-block-poly(ethylene oxide) alternating multiblock copolymer (PS-alt-PEO) was synthesized with the combination of atom transfer radical polymerization (ATRP) and Huisgen 1,3-dipolar cycloaddition (i.e., click chemistry). The copolymer has been characterized by means of Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The PS-alt-PEO alternating multiblock copolymer was incorporated into epoxy resin to investigate the behavior of reaction-induced microphase separation, which has been compared to the case of the thermosets containing PS-b-PEO diblock copolymer. The morphology of epoxy thermosets containing PS-alt-PEO alternating multiblock copolymer were investigated by means of atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS) and the nanostructures were detected in all the thermosetting blends investigated. In marked contrast to the case of the thermosets containing PS-b-PEO diblock copolymer, the thermosets containing PS-alt-PEO multiblock copolymer displayed disordered nanostructures, which have been interpreted on the basis of the restriction of the alternating multiblock topology of the block on the formation of the nanostructures via reaction-induced microphase separation.     

Structure-property relationships in a reactively coupled ductile matrix/brittle dispersed phase blend

Blends of t-butylaminoethyl methacrylate grafted polyethylene (PE-g-tBAEMA) with methyl methacrylate-methacrylic acid copolymer (PMMA-MAA) and polymethyl methacrylate (PMMA) were prepared in a Banbury type batch mixer. The effects of component proportions and processing conditions on the melt flow index, morphology, impact, and tensile properties of the resulting polymer blends were investigated. The interfacial chemical reaction was studied using Fourier transform infrared (FTIR) technique. It was observed that the melt index of the blends was reduced with increasing melt processing temperature and mixing time, indicating the formation of PE-g-PMMA block copolymer. New IR bands at 1554, 1628, 1800, and 1019 cm^?1 were observed only for PE-g-tBAEMA/PMMA-MAA, the reactive blends, but not for PE-g-tBAEMA/PMMA, the nonreactive blend. These IR bands were attributed to the amide, carboxylate anion and methacrylimide formation resulting from the chemical reaction between the secondary amine on the PE-g-tBAEMA/PMMA moiety and the carboxylic acid on PMMA-MAA segment. The morphology of the blends in various compositions was examined using scanning electron microscopy (SEM) and related to their mechanical properties. All of the blends have a domain structure whose morphology is strongly dependent on the concentration of the dispersed phase. Furthermore, the PE-g-tBAEMA/PMMA-MAA reactive blends were shown to have much finer morphology than the corresponding nonreactive blends. For the reactive polymer blends consisting of brittle particles dispersed in the ductile matrices, the PE-g-tBAEMA/PMMA-MAA, impact and tensile result higher than predicted by the additivity rule were observed. The toughening of polyethylene by PMMA was explained by a “cold-drawing” mechanism. The Young's modulus of the blends and the extent of interfacial adhesion were analyzed with Takayanagi and Sato-Furukawa's theories. © 1993 John Wiley & Sons, Inc.     

Annealing induced microstructure and fracture resistance changes in isotactic polypropylene/ethylene‐octene copolymer blends with and without β‐phase nucleating agent

Previous work showed that annealing induced the great improvement of fracture resistance of β‐iPP, relating to the decreased number of chain segments in the amorphous region. To further prove the rationality of this observation, in this work, the ethylene‐octene copolymer (POE) toughened isotactic polypropylene (iPP) blends with or without β‐phase nucleating agent (β‐NA) were adopted and the changes of microstructure and fracture resistance during the annealing process were further investigated comparatively. The results showed that, whether for the α‐phase crystalline structure (non‐nucleated) or for the β‐phase crystalline structure (β‐NA nucleated) in iPP matrix, annealing can induce the dramatic improvement of fracture resistance at a certain annealing temperature (120–140 °C for β‐NA nucleated blends whereas 120–150 °C for non‐nucleated blends). Especially, non‐nucleated blends exhibit more apparent variations in fracture resistance compared with β‐NA nucleated blends during the annealing process. The phase morphology of elastomer, supermolecular structure of matrix, the crystalline structure including the degree of crystallinity and the relative content of β‐phase, and the relaxation of chain segments were investigated to explore the toughening mechanism of the samples after being annealed. It was proposed that, even if the content of elastomer is very few, the excellent fracture resistance can be easily achieved through adjusting the numbers of chain segments in the amorphous phase by annealing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Phase morphology and mechanical properties of iPP/SEP blends

The effects of the addition of diblock copolymer poly(styrene‐b‐ethylene‐co‐propylene) (SEP) to isotactic polypropylene (iPP) on the morphology and mechanical properties were investigated. Phase morphologies of iPP/SEP blends up to a 70/30 weight ratio, prepared in Brabender Plasticoder, were studied with optical microscopy, scanning electron microscopy, transmission electron microscopy, and wide‐angle X‐ray diffraction. The addition of 2.5 wt % SEP caused a nucleation effect (by decreasing the crystallite and spherulite size) and randomization of the crystallites. With further SEP addition, the crystallite and spherulite size increased because of prolonged solidification and crystallization and achieved the maximum in the 80/20 iPP/SEP blend. This maximum was a result of the appearance of β spherulites and the presence of mixed α spherulites in the 80/20 iPP/SEP blend. Dispersed SEP particles were irregular and elongated clusters consisting of oval and spherical core–shell microdomains or SEP micelles. SEP clusters accommodated their shapes to interlamellar and interspherulitic regions, which enabled a well‐developed spherulitization even in the 70/30 iPP/SEP blend. The addition of SEP decreased the yield stress, elongation at yield, and Young's modulus but significantly improved the notched impact strength with respect to the strength of pure iPP at room temperature. Some theoretical models for the determination of Young's modulus of iPP/SEP blends were applied for a comparison with the experimental results. The experimental line was closest to the Takayanagi series model. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 566–580, 2001     

Morphology, crystallization behavior and properties of impact-modified polypropylene copolymer with or without sodium benzoate as a nucleating agent

 The morphology, crystallization behavior, and properties of an impact-modified polypropylene (PP) copolymer with or without sodium benzoate were investigated. The contents of ethylene–propylene rubber (EPR) in the reactor-made PP copolymer is about 15 wt%. For comparison, blends of PP and EPR containing the same EPR composition were prepared by melt-mixing. Morphological studies by scanning probe microscopy indicated that the impact-modified copolymer consists of three different phases, i.e., polyethylene, PP, and EPR phases, which is considerably different from the morphology of the conventional PP/EPR blend of the corresponding composition. The impact-modified PP copolymer exhibited a higher crystallization rate in terms of the lower crystallization half-time and thus higher thermal and mechanical properties, such as impact strength and hardness, than the PP/EPR blend did. The addition of sodium benzoate as a nucleating agent to the copolymer increased the crystallization rate and the mechanical properties. Received: 4 June 2001 Accepted: 31 October 2001     

接枝共聚物EPR-g-PS作PS/EPDM共混体系增容剂的探讨

使用了由大分子单体共聚合制备的以乙丙橡胶(EPR)为主干、聚苯乙烯(PS)为支链的接枝共聚物EPR-g-PS作为PS/EPDM共混体系的增容剂。实验结果表明,共混体系的组成、增容剂加入量以及增容剂分子结构对共混体系冲击强度有很大影响。将这些因素与相差显微镜及扫描电镜研究所揭示的共混物形态的变化相联系,对此类接校共聚物作为不相容体系增容剂的机理作了探讨。     

Morphology evolution and location of ethylene–propylene copolymer in annealed polyethylene/polypropylene blends

Binary blends of linear low density polyethylene (PE) and polypropylene (PP), and ternary blends of PE, PP, and EP copolymer (EPR) were prepared in a finely mixed state. In all blends the ratio of PP to PE was 85/15. In some of the blends, the PE component was labeled with a fluorescent dye; in other blends, the EPR component was labeled. These blends were investigated by laser scanning confocal fluorescence microscopy [LCFM] as a function of annealing time as well as EPR compatibilizer content. In this way we were able to follow the evolution of sample morphology and the location of the EPR in the blends. The presence of EPR in the blends retards the growth of droplets of the dispersed PE phase. When EPR was added in amounts up to 5 wt %, it tended to cover the PE droplets in patches rather than form a true core-shell structure. In the LCFM images, the EPR/PP interface appeared sharper than the EPR/PE interface. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 979–991, 1997     

CRYSTALLIZATION OF BLENDS OF AN ASYMMETRIC POLY（OXYETHYLENE）-b-POLY（OXYBUTYLENE） BLOCK COPOLYMER WITH POLY（OXYBUTYLENE）

An oxyethylene/oxybutylene block copolymer with asymmetric volume fraction (E115B103) was blended with oxybutylene homopolymer (Bh) at different volume fractions of the block (φE). Crystallization behavior of the blends was studied and was compared with that of the blends from a symmetric block copolymer (E114B56). It was found that the crystallization temperature of E115B103/B28 blend is lower than that of the blends from symmetric block copolymer. For the blend with φE= 0.30 breakout crystallization with an Avrami exponent n ≈ 3.0 is observed. At φE = 0.22 the blend exhibits a variable crystallization behavior: confined crystallization with n ≈ 1.0 at lower crystallization temperatures but breakout crystallization at high crystallization temperatures. For the blend with φE = 0.14 and sphere morphology confined crystallization occurs at all crystallization temperatures studied. When compared with the blends from symmetric block copolymer, confined crystallization occurs more easily in the E115B103/B28 blends. The SAXS results agree with the isothermal crystallization kinetics. Deformation of the confined crystalline block is observed in the blend with φE = 0.14 and mixed lamellar and cylinder morphologies in the blend with φE = 0.22.     

The synergistic effects of β-nucleating agent and ethylene–octene copolymer on toughening isotactic polypropylene

The mechanical properties of isotactic polypropylene (iPP) and ethylene–octene copolymer (POE) blends with or without β-nucleating agent (β-NA) were systematically studied. Results demonstrated that, after β-NA and POE were separately added, the impact strength of injection molded iPP samples increased. β-NA and POE were also found to have a synergistic toughening effect on iPP matrix, and the effect was significant. When the contents were 0.05 wt% β-NA and 10 wt% POE, the impact strength reached the maximum, i.e., almost 15 times that of neat iPP. SEM further revealed that POE in skin and core layers existed as long and narrow strips along the flow direction and throughout crystals. The tensile strength did not deteriorate because of the special phase morphology and tight interfacial interaction between POE phase and matrix. WAXD and DSC revealed that POE addition had negligible influence on crystal form, and a considerable number of β crystals was generated by adding β-NA. SEM results also confirmed a critical β-NA content. When β-NA content was lower than the critical value, perfect β sphaerocrystals were generated. When β-NA was higher, “bundle-like” crystal structures formed. Perfect β sphaerocrystals were more efficient for dissipating energy because of the looser stacking pattern, thus showing better toughness.     

The orientation of the dispersed phase and crystals in an injection-molded impact polypropylene copolymer

The orientation of the dispersed phase and crystals in the injection-molded bar of an impact polypropylene copolymer (IPC) containing isotactic polypropylene (iPP), ethylene-propylene rubber (EPR) and a β-nucleating agent (β-NA) were studied simultaneously. In the IPC, iPP and EPR act as the matrix and dispersed phase, respectively. The EPR is amorphous and the iPP is crystallizable in α- and β-crystalline forms in the presence of the β-NA. The orientation and orientation distribution for both of the EPR phase and the iPP crystals, as well as the crystallization behavior of iPP, were investigated by two-dimensional wide-angle X-ray diffraction (2D-WAXD), two-dimensional small-angle X-ray scattering (2D-SAXS), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The results of the experiment show that orientation exists for both the EPR phase and the iPP crystals. But their orientation distribution manifests an opposite tendency. The EPR phase was observed to be highly oriented in the core layer but the orientation of the iPP crystals was weakened gradually from skin to core. The difference in the orientation behavior between the EPR phase and the iPP crystals reflects the distinct response of the micrometer-scale EPR particles and nanometer-scale iPP chains upon the flow field and temperature gradient in the mold. The diffraction geometry of the β-crystals has also been discussed in detail. The observations in this study may shed light on the study in the structure and property relationship for the IPC injection-molded products.     

iPS－b－iPP共聚物对iPS／iPP共混物的性能和形态影响的研究

报道了苯乙烯－丙烯等规嵌段共聚物（ｉＰＳ－ｂ－ｉＰＰ）增溶作用及ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ三组分共混体系微观形态和力学性能的研究结果。ｉＰＳ－ｂ－ｉＰＰ的加入明显地改善了ｉＰＳ／ｉＰＰ二组分共混物的力学性能;共聚物含量超过１５％时,三组分共混物的抗冲击强度超过ＮＩＰＳ的抗冲击强度,并具有较高的耐热性。ＳＥＭ结果表明,ｉＰＳ－ｂ－ｉＰＰ在ｉＰＳ／ｉＰＰ共混中起到了相分散和相间“偶联”作用,并降低了共混体系的微相尺寸和增加相间相互作用或粘附性。ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ共混合金具有高的软化温度和刚性。