乙丙嵌段共聚物的X-射线衍射研究

用大角X-射线衍射(WAXD)方法对按嵌段聚合程序合成的聚丙烯(PP)和乙丙共聚物(EPR)的嵌段共聚物PP-EPR和PP-EPR-PP,以及相应的混合物进行对比研究.乙丙共聚物及其共混物均发现在2θ=20°处存在由EPR中PP链段引起的γ-晶型衍射峰.通过诠释X-射线衍射图,计算结晶度,微晶尺寸和晶格参数等表明,用δ-TiCl_3-Et_2AlCl催化剂获得了嵌段共聚物结构.     

WAXS studies on block copolymers of ethylene and propylene

Wide-angle X-ray scattering from presumed block copolymers of polypropylene (PP) and ethylene-propylene copolymer (EPR), i.e., PP-EPR and PP-EPR-PP, synthesized by sequential polymerization with δ-TiCl₃? Et₂AlCl, was examined and compared with WAXS of mechanical blends and chain-transfer mixtures of PP and EPR with comparable compositions. The peak at 2θ = 20° for both the copolymers and the mixtures was attributed to the γ modification of PP in EPR. A strong variation in the ratio of diffraction intensities I₀₄₀/I₁₁₀ of PP in block copolymers and mixtures was explained in terms of crystallite growth in different directions. Analysis of the patterns and calculation of crystallinity, crystallite size, and lattice parameters led to the conclusion that block structure existed in the prepared copolymers.     

Structure and properties of propylene-ethylene block copolymers and the corresponding blends

Structure and properties of presumed polypropylene(PP)-b-polyethylene(PE) block copolymers (PPPE) and the corresponding blends (PP/PE) have been investigated by wide-angle x-ray scattering (WAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), torsional pendulum apparatus, and other techniques measuring mechanical properties. Crystallinity, morphological structure, and mechanical properties of the block copolymers and blends vary with the PP and PE compositions. Compared with PP homopolymers and PP/PE blends, PP and PE segments in PP-PE block copolymers have a reduced crystallinity, especially PE segments. An additional peak at about ?40°C is observed in dynamic relaxation spectra; substantially different morphology is revealed; and mechanical properties are greatly improved for the sequentially copolymerized PP-PE block copolymers, indicating the existence of PP-PE block structure.     

Effect of maleic anhydride-grafted ethylene-propylene rubber on the mechanical, rheological and morphological properties of organoclay reinforced polyamide 6/polypropylene nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic modified montmorillonite (organoclay) were compatibilized with maleic anhydride-grafted ethylene-propylene rubber (EPRgMA). The blends were melt compounded in twin screw extruder followed by injection molding. The mechanical properties of PA6/PP nanocomposites were studied by tensile and flexural tests. The microstructure of the nanocomposite were assessed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The dynamic mechanical properties of the PA6/PP blend-based nanocomposites were analyzed by using a dynamic mechanical thermal analyzer (DMTA). The rheological properties were conducted from plate/plate rheometry via dynamic frequency sweep scans. The melt viscosity in a high shear rate region was performed by using a capillary rheometer. The strength and stiffness of the PA6/PP-based nanocomposites were improved significantly with the incorporation of EPRgMA. Adding EPRgMA to the PA6/PP blends resulted in a finer dispersion of the PP phase. TEM and XRD results revealed that the organoclay was dispersed more homogeneously in the presence of EPRgMA, however, mostly in the PA6 phase of the blends. DMTA results showed that EPRgMA worked as an effective compatibilizer. The storage (G′) and loss moduli (G″) assessed by plate/plate rheometry of PA6/PP blends increased with the incorporation of EPRgMA and organoclay. Furthermore, the apparent shear viscosity of the PA6/PP blend increased significantly for the EPRgMA compatibilized PA6/PP/organoclay nanocomposite. This was traced to the formation of an interphase between PA6 and PP (via PA6-g-EPR) and effective intercalation/exfoliation of the organoclay.     

Synthesis of polypropylene block copolymers from brominated styrene-terminated isotactic polypropylene

Isotactic polypropylene block copolymers, isotactic-polypropylene-block-poly (methyl methacrylate) (i-PP-b-PMMA) and isotactic-polypropylene-block-polystyrene (i-PP-b-PS), were prepared by atom transfer radical polymerization (ATRP) using a brominated styrene-terminated isotactic polypropylene macroinitiator synthesized from bromination of styrene-terminated isotactic polypropylene. The styrene-terminated isotactic polypropylene can be obtained by polymerization of propylene in the presence of styrene and hydrogen chain transfer agents using a rac-Me₂Si[2-methyl-4-(1-naphyl)Ind]₂ZrCl₂ as catalyst. The molecular weights of isotactic polypropylene block copolymers were controlled by altering the amount of hydrogen used in the polymerization of propylene and the amount of monomer used in the blocking reaction. The effect of i-PP-b-PS block copolymer on PP-PS blends and that of i-PP-b-PMMA block copolymer on PP-PMMA blends were studied by scanning electron microscopy.     

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     

增容聚苯乙烯共混物的研究进展

综述了增容聚苯乙烯与聚乙烯、聚丙烯、聚酰胺共混物的研究进展。不同共混物采用不同的增容剂,可使增容聚苯乙烯共混物改善分散相尺寸、界面相互作用与粘结,达到提高共混物的力学性能的目的。增容效果与增容剂的类型、用量和分子结构有关。     

The Influence of Copolymerization Condition on Rheology,Morphology and Thermal Behavior of Polypropylene Heterophasic Copolymers

In this work, the polypropylene impact copolymers were synthesized by a modified sequential polymerization process. The copolymerization of ethylene and propylene was carried out between two homopolymerization stages at two different pressures and temperatures and the rheology, morphology and thermal properties of reactor alloys were studied. It is found that the ethylene propylene rubber (EPR) content increased up to 32 wt% by increasing the copolymerization time to 20 min. At a fixed copolymerization time of 10 min, the addition of 50 ppm hydrogen (H₂), increased the EPR content from 9.7 to 12.8 wt%. By doubling H₂ concentration, no considerable change in EPR wt% was observed. It is found that the zero shear viscosity of the alloys is significantly under the influence of EPR wt%, not the molecular weight of matrix. The molecular weight of PP matrices determined by rheological data, mildly decreased from 463000 to 458000 g/mol by increasing the copolymerization time from 10 min to 15 min. At high copolymerization time/high H₂ concentration, a melting peak in the differential scanning calorimetry test around 165°C for isotactic PP and also an endothermic peak around 127°C for the block copolymer with long ethylene segments, is observed. The study of interfacial strength by theoretical emulsion models showed that 15 min copolymerization time is optimum considering EPR wt%.     

IMPROVED PROPERTIES OF METALLOCENE-CATALYZED LINEAR LOW-DENSITY POLYETHYLENE/POLYPROPYLENE BLENDS DURING ULTRASONIC EXTRUSION

Metallocene-catalyzed linear low-density polyethylene/polypropylene （mLLDPE/PP） blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends.     

Dynamic mechanical and gas transport properties of blends and random copolymers of bisphenol-A polycarbonate and tetramethyl bisphenol-A polycarbonate

Dynamic mechanical and gas transport properties for homogeneous homopolymer blends and random copolymers of bisphenol-A and tetramethyl bisphenol-A polycarbonates (PC-TMPC) were determined. The gas transport measurements were performed at 35°C for the gases He, H₂, O₂, Ar, N₂, CH₄, and CO₂. The results show that the copolymers have lower permeability, apparent diffusion, and solubility coefficients than the blends. Permeability coefficients for blends follow a semilogarithmic ideal mixing rule while copolymers exhibit negative deviations from this. Specific volume measurements show that the free volume available for gas transport is slightly larger in copolymers than in blends of the same composition. These apparently contradictory results may relate to the differences in local mode chain motions observed for the copolymer and blend series. The γ relaxation processes in PC and TMPC seem to operate independently in the blends (no intermolecular coupling) while there is clear evidence for intramolecular coupling in the copolymers. © 1992 John Wiley & Sons, Inc.     

Compatibilization efficiency of styrene–butadiene multiblock copolymers in PS/PP blends

The compatibilizing effect of di‐, tri‐, penta‐, and heptablock (two types) copolymers with styrene and butadiene blocks was studied in polystyrene/polypropylene (PS/PP) 4/1 blends. The structure of PS/PP blends with the addition of 5 or 10 wt % of a block copolymer (BC) was determined on several scale levels by means of transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS). The results of the structure analysis were correlated with measured stress‐transfer properties: elongation at break, impact, and tensile strength. Despite the fact that the molar mass of the PS blocks in all the BCs used was about 10,000, that is, below the critical value M^* (～18,000) necessary for the formation of entanglements of PS chains, all the BCs used were found to be good compatibilizers. According to TEM, a certain amount of a BC is localized at the interface in all the analyzed samples, and this results in a finer dispersion of the PP particles in the PS matrix, the effect being more pronounced with S‐B‐S triblock and S‐B‐S‐B‐S pentablock copolymers. The addition of these two BCs to the PS/PP blend also has the most pronounced effect on the improvement of mechanical properties of these blends. Hence, these two BCs can be assumed to be better compatibilizers for the PS/PP (4/1) blend than the S‐B diblock as well as both S‐B‐S‐B‐S‐B‐S and B‐S‐B‐S‐B‐S‐B heptablock copolymers. In both types of PS/PP/BC blends (5 or 10 wt % BC), the BC added was distributed between both the PS/PP interface and the PS phase, and, according to SAXS, it maintained a more or less ordered supermolecular structure of neat BCs. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 931–942, 2001     

聚丙烯与聚酯-聚醚多嵌段共聚物共混的研究

聚丙烯和聚酯-聚醚多嵌段共聚物的熔融共混物是微多相分散体系,其力学性能和软链段的结构有关。DSC和偏光显微镜图分别表明共混物中聚丙烯结晶度以及球晶尺寸随聚酯-聚醚的混入量而变小。聚丙烯和少量聚酯-聚醚多嵌段共聚物共混,可改进聚丙烯的流变性,吸湿性和染色性。     

Synthesis and characterization of polyethylene‐g‐polystyrene as the compatibilizer for polypropylene/ Polystyrene blends

Polyethylene‐g‐polystyrene (PE‐g‐PS) was synthesized as a compatibilizer for polypropylene/polystyrene­(PP/PS) blends by the living radical polymerization of styrene with polyethylene‐co‐glycidylmethacrylate (PE‐co‐GMA). The compatibilizer effect of PE‐g‐PS on the morphology and thermal properties of PP/PS blends was investigated. The crystalline temperature of PP in PP/PS blends decreased with increasing PE‐g‐PS contents. Morphologies of PP/PE‐g‐PS/PS blends showed much better dispersion of each domain for higher PE‐g‐PS contents. The molecular weight of PS segment in PP/PE‐g‐PS/PS blend was increased by addition of styrene monomer during the post melt blending process where post living radical polymerization reaction proceeded. Copyright © 2003 John Wiley & Sons, Ltd.     

Compatabilization of polystyrene/polypropylene blends by styrene–butadiene block copolymers with differing polystyrene block lengths

Compatibilization of polystyrene/polypropylene (PS/PP) blends, by use of a series of butadiene–styrene block copolymers was studied by means of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The compatibilizers used differ in molar mass and the number of blocks. It was shown that the ability of a block copolymer (BC) to participate in the formation of an interfacial layer (and hence in compatibilization) is closely associated with the molar mass of styrene blocks. If the styrene blocks are long enough to form entanglements with the styrene homopolymer in the melt, then the BC is trapped inside this phase of the PS/PP blends, and its migration to the PS/PP interface is difficult. In this case, the BC does not participate in the formation of the interfacial layer nor, consequently, in the compatibilization process. On the other hand, the BC's with the molar mass of the PS blocks below the critical value are proved to be localized at the PS/PP interface. This preferable entrapping of some styrene–butadiene BC's in the PS phase of the PS/PP blend is, of course, connected to the differing miscibility of the BC blocks with corresponding components of this blend. Although the styrene block is chemically identical to the styrene homopolymer in the blend, the butadiene block is similar to the PP phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1647–1656, 1999     

Preparation and properties of PP/PC/POE blends

In order to develop PP (polypropylene)‐based blends with balanced toughness and rigidity, the poly‐blends of PP/PC (polycarbonate)/POE (ethylene–octene copolymer) were prepared by applying styrene–ethylene–propylene–styrene (SEPS) as the macromolecular compatibilizer. The compatibilizing effect was studied in terms of the mechanical, morphologies and thermal properties, and the compatibilized PP‐based blends presented remarkable improvement in impact toughness and balanced tensile strength due to the formed special morphology structure. Additionally, by preparing the pre‐blend of PC/SEPS, the melt viscosity of the PP matrix can match that of the dispersed phase PC and POE, which led to a further improvement in the mechanical property of the blends. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of Propylene Diblock Copolymers via Metallocene and Borane Chemistry

An isotactic chain end unsaturated polypropylene was prepared by the homogeneous metallocene catalyst Et(Ind)₂ZrCl₂ with MAO. Herein, the chain end unsaturated polypropylene proceeded the hydroboration reaction to prepare borane‐containing polypropylene. The borane‐containing polypropylene could be transformed to hydroxyl‐terminated polypropylene, PPOH. And then the polypropylene‐nylon 6 diblock copolymer, PP‐b‐NY6, was synthesized from telechelic PPOH by converting this prepolymer with toluene diisocyanate and using the resulting materials as macroactivators for anionic caprolactam polymerization. Meanwhile, this investigation used borane‐containing polypropylene and oxygen to produce free radicals at the chain end on the polypropylene. Experimental results indicate that the free radical is an effective initiator for the polymerization of methyl methacrylate to produce diblock PP‐b‐PMMA. The block copolymers are characterized by IR, NMR, and DSC analyses. The diblock copolymer is a good compatibilizer for polymer blends.     

Implications of LDPE Branching and Mw on Thermal and Mechanical Properties of PP/LDPE Blends

Summary: The influences of short chain branching (SCB) and molecular (M_w) weight of low density polyethylene (LDPE) on the solid state properties of polypropylene (PP)-LDPE blends were investigated by mechanical and thermal techniques. DSC analysis of all blends exhibit a double melting peak at all compositions studied thus suggesting that both PP and LDPE crystals exist separately in the solid state. It was found that the SCB and Mw of LDPE influenced the modulus and ultimate tensile strength of the blends. However, elongation at break seems to be independent of the molecular characteristics of the pure homopolymer especially at PP blend composition greater than 50%. LDPE with high SCB showed broader melting peaks. Addition of a small amount of a low Mw LDPE (10%) resulted in a higher elongation at break than a high Mw LDPE. There is likely a correlation between the presence of a new peak in the thermograms of PP-rich blends and the observed poor elongation at break.     

Effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene compatibilizer on the recycled polypropylene and recycled high‐impact polystyrene blends

The recycled polypropylene/recycled high‐impact polystyrene (R‐PP/R‐HIPS) blends were melt extruded by twin‐screw extruder and produced by injection molding machine. The effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene copolymer (SEPS) used as compatibilizer on the mechanical properties, morphology, melt flow index, equilibrium torque, and glass transition temperature (T_g) of the blends were investigated. It was found that the notch impact strength and the elongation at break of the R‐PP/R‐HIPS blends with the addition of 10 wt% SEPS were 6.46 kJ/m² and 31.96%, which were significantly improved by 162.46% and 57.06%, respectively, than that of the uncompatibilized blends. Moreover, the addition of SEPS had a negligible effect on the tensile strength of the R‐PP/R‐HIPS blends. Additionally, the morphology of the blends demonstrated improved distribution and decreased size of the dispersed R‐HIPS phase with increasing the SEPS content. The increase of the melt flow index and the equilibrium torque indicated that the viscosity of the blends increased when the SEPS was incorporated into the R‐PP/R‐HIPS blends. The dynamic mechanical properties test showed that when the content of SEPS was 10 wt%, the difference of T_g decreased from 91.72°C to 81.51°C. The results obtained by differential scanning calorimetry were similar to those measured by dynamic mechanical properties, indicating an improved compatibility of the blends with the addition of SEPS.     

ABA triblock copolymers with a ring‐opening metathesis polymerization/macromolecular chain‐transfer agent approach

Block copolymers containing polystyrene and polycyclooctene were synthesized with a ring‐opening metathesis polymerization/chain‐transfer approach. Polystyrene, containing appropriately placed olefins, was prepared by anionic polymerization and served as a macromolecular chain‐transfer agent for the ring‐opening metathesis polymerization of cyclooctene. These unsaturated polymers were subsequently converted to the corresponding saturated triblock copolymers with a simple heterogeneous catalytic hydrogenation step. The molecular and morphological characterization of the block copolymers was consistent with the absence of significant branching in the central polycyclooctene and polyethylene blocks [high melting temperatures (114–127 °C) and levels of crystallinity (17–42%)]. A dramatic improvement in both the long‐range order and the mechanical properties of a microphase‐separated, symmetric polystyrene–polycyclooctene–polystyrene block copolymer sample was observed after fractionation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 361–373, 2007     

Preparation and characterization of spherical PP/PB alloys with MgCl2-supported Ziegler-Natta catalyst

Polypropylene（PP）/polybutene-1（PB） alloys within reactor were prepared by MgCl₂-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology.First,propylene homo-polymerizations were carried out to form isotactic polypropylene（iPP） particles containing active catalyst.Then,butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles.Finally,iPP/PB alloys with spherical shape and adjustable PB content were synthesized.The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed.The composition and physical properties of the PP alloys were characterized by FT-IR,¹³C-NMR,SEM,DSC and XRD.It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly（butene-co -propylene） random copolymers and poly（butene-block-propylene） block copolymers.SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly.The incorporation of PB upon the PP matrix affects the properties of final products greatly.