Microstructure, morphology, crystallization and rheological behavior of impact polypropylene copolymer

Impact polypropylene copolymer (IPC), named polypropylene catalloy, not only possesses excellent impact property, but also presents good rigidity. Its superior performances result from the complicated composition and microstructure. In the present article, recent progress in the studies on microstructure, morphology, crystallization and rheological behavior of IPC is summarized, and findings of the authors and their collaborators are reported. In general, IPC is divided into three components, i.e., ethylene-propylene random copolymer (EPR), a series of different segment lengths ethylene-propylene copolymer (EbP) and propylene homopolymer. The reasonable macromolecular structures of EbP and a multilayered core-shell model of dispersed phase structure in IPC were proposed, in which the dispersed phase consists of an outer EbP shell, an inner EPR layer and an EbP core. It is found that the annealing at melt-state may lead to an abnormal phase inversion, and the phase inversion disappears when temperature cools down to room temperature. The cause of phase inversion is ascribed to the existence of EbP component, which results in the stronger activity of the dispersed phase. The crystalline structure and morphologic results confirm the formation of β-iPP in IPC. Furthermore, it is found that the ethylene content in IPC and cooling rate of the samples have an important influence on the formation of β-iPP. Based on the crystallization kinetics analyzed by Lauritzen-Hoffman theory, crystallization behavior of different IPC samples is discussed and it is proposed that the dilution effect of ethylene propylene copolymer has a more remarkable influence on surface nucleation than on crystal growth. In addition, annealing at high temperature can result in the changes of chain structure for IPC, and this instability is ascribed to the oxidative degradation and crosslink reaction mainly in iPP component.     

Effect of dispersed phase composition on morphological and mechanical properties of PET/EVA/PP ternary blends

Immiscible ternary blends of PET/EVA/PP (PET as the matrix and (PP/EVA) composition ratio = 1/1) were prepared by melt mixing. Scanning electron microscope results showed core‐shell type morphology for this ternary blend. Binary blends of PET/PP and PET/EVA were also prepared as control samples. Two grades of EVA with various viscosities, one higher and the other one lower than that of PP, were used to investigate the effect of components' viscosity on the droplet size of disperse phase. The effect of interfacial tension, elasticity, and viscosity on the disperse phase size of both binary and ternary blends was investigated. Variation of tensile modulus of both binary and ternary blends with dispersed phase content was also studied. Experimental results obtained for modulus of PET/EVA binary blends, showed no significant deviations from Takayanagi model, where considerable deviations were observed for PET/PP binary blends. Here, this model that has been originally proposed for binary blends was improved to become applicable for the prediction of the tensile modulus of ternary blends. The new modified model showed good agreement with the experimental data obtained in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 251–259, 2010     

Effect of nano‐polystyrene (nPS) on thermal,rheological, and mechanical properties of polypropylene (PP)

Polystyrene nanoparticles (nPS) in the range of 10–100 nm with spherical shape were synthesized by oil/water (o/w) microemulsion process. In this process ammonium persulfate (APS) as an initiator, sodium dodecyl sulphate as a surfactant and n‐pentanol as cosurfactant were used. Isolated nPS was characterized by FTIR and ¹H NMR spectroscopy. DSC studies of nPS showed higher T_g as compared to bulk PS. The effect of lower weight percentage (wt%) of nPS on the mechanical, rheological, and thermal properties of PP was investigated. The blends were prepared individually on brabender plastograph by incorporating nPS of ～60 nm with different wt% of loading (i.e., 0.10–0.5%). It was shown from the experimental results that thermal, rheological, and mechanical properties were increased as the polymer particles blended with PP. Blends with 0.25 wt% loading of nPS exhibit better properties compared with that of other wt% loadings. The improvements in properties were due to the close packing of PP chains as recorded by improvement in crystallinity of PP with the addition of nPS as shown by SEM. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of CaCO3 Filler Component on Solid State Decomposition Kinetic of PP/LDPE/CaCO3 Composites

In this study, the effect of addition Calcium carbonate (CaCO₃) filler component on solid state thermal decomposition procedures of Polypropylene-Low Density Polyethylene (PP-LDPE; 90/10 wt%) blends involving different amounts (5, 10, 20 wt%) Calcium carbonate (CaCO₃) was investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. An integral composite procedure involving the integral iso-conversional methods such as the Tang (TM), the Kissinger-Akahira-Sunose method (KAS), the Flynn-Wall-Ozawa (FWO), an integral method such as Coats-Redfern (CR) and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. The Iso-conversional methods indicated that the thermal decomposition reaction should conform to single reaction model. The results of the integral composite procedures of TG data at various heating rates suggested that thermal processes of PP-LDPE-CaCO₃ composites involving different amounts of CaCO₃ filler component (5, 10, 20 wt%) followed a single step with approximate activation energies of 226.7, 248.9, and 252.0 kJ.mol^{? 1} according to the FWO method, respectively and those of 231.3, 240.1 and 243.0 kJ mol^{? 1} at 5°C min^{? 1} according to the Coats-Redfern method, the reaction mechanisms of all the composites was described from the master plots methods and are P_n model for composite C-1, R_n model for composites C-2 and C-3, respectively. It was found that the thermal stability, activation energy and thermal decomposition process changed by the increasing CaCO₃ filler weight in composite structure.     

SEP对PP/PS共混物的增容作用

研究了苯乙烯 -乙烯 /丙烯二嵌段共聚物 (SEP)对聚丙烯 /聚苯乙烯 (PP/PS)共混物的形态和力学性能的影响。结果表明 ,SEP在PP/PS共混物中作为增容剂 ,降低了分散相的聚结 ,减小了分散相的平均粒子尺寸 ,大大改变了共混物的形态 ,提高了共混物的力学性能 ,对PP/PS( 2 0 /80 )共混物的增容作用较为显著     

Correlation between rheological behavior and structure of multi-component polymer systems

Rheological measurement has been an effective method to characterize the structure and properties for multiphase/multi-component polymers, owing to its sensitivity to the structure change of hetero- geneous systems. In this article, recent progress in the studies on the morphology/structure and rheological properties of heterogeneous systems is summarized, mainly reporting the findings of the authors and their collaborators, involving the correlation between the morphology and viscoelastic relaxation of LCST-type polymer blends, the microstructure and linear/nonlinear viscoelastic behavior of block copolymers, time scaling of shear-induced crystallization and rheological response of poly- olefins, and the relationship between the structure/properties and rheological behavior of filled polymer blends. It is suggested that a thorough understanding of the characteristic rheological response to the morphology/structure evolution of multiphase/multi-component polymers facilitates researchers’ op- timizing the morphology/structure and ultimate mechanical properties of polymer materials.     

Mechanical and Rheological Behavior of Unvulcanized and Dynamically Vulcanized i-PP/EPDM Blends

The mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. It is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.     

共混改性ACS合金的性能形态与流变性研究

利用增容原理,以α－甲基苯乙烯,丙烯酸酯为单容改性单体,与苯乙烯,丙烯腈乳液共聚,所得共聚物与氯化聚乙烯共混得ＡＣＳ合金,研究了以α－甲基苯乙烯,丙烯酸乙酯用量对ＡＣＳ合金力学性能,流变性的影响,同时考察了树脂的微观结构与形态。     

Effect of sacrificial bond on molecular dynamics and rheological behavior of hybrid butadiene-styrene-vinylpyridine rubber vulcanizates with reversible sacrificial network

Due to the improvement of strength and toughness at the same time, construction of reversible sacrificial bond network has attracted extensive attention to realize the high performance and functionalization of rubber materials. However, the research on the viscoelastic behavior of vulcanized rubber with reversible sacrificial bond network lags behind seriously. In this work relaxation kinetics, linear rheological behavior and nonlinear rheological behavior of hybrid crosslinked butadiene-styrene-vinylpyridine rubber (VPR) with reversible Zn²⁺-pyridine coordination bond were investigated in detail. It was found that, the tensile results under small strain were more conducive to reflect the contribution of sacrificial bond after sequential tensile-recovery process than those under large strain. Although sacrificial bond could affect both G' and G" at low temperature, the contribution of it to G" was more prominent. When the temperature was higher than the dissociation temperature of Zn²⁺-pyridine coordination bond, the sacrificial bond could only affect G", which was due to the fact that the pyridine group was equivalent to the graft on VPR backbone and acted as dangling chain. In addition, the destruction and reconstruction of coordination bond was the dominant factor in modulus recovery.     

马来酸酐(MAH)表面改性纳米碳酸钙粉体的制备及表面性能

通过在两相法制备纳米碳酸钙的过程中添加一定量的马来酸酐(MAH)的方法，在纳米碳酸钙的表面引入羧基、羟基、双键等活性基团对纳米碳酸钙进行表面改性，并通过调节马来酸酐的用量，有效地控制纳米碳酸钙的极性和表面能。接触角实验结果表明，当马来酸酐的加入量为2%时可以获得界面性能最理想的改性纳米碳酸钙。还在此基础上提出了马来酸酐(MAH)对纳米碳酸钙进行表面改性的过程机理，并以SEM，ATR-FTIR和TGA等手段对上述过程机理进行了验证。     

Novel synthesis of nano‐calcium carbonate (CaCO3)/polystyrene (PS) core–shell nanoparticles by atomized microemulsion technique and its effect on properties of polypropylene (PP) composites

Calcium carbonate (CaCO₃)/polystyrene (PS) nanoparticles (<100 nm) with core–shell structure were synthesized by atomized microemulsion technique. The polymer chains were anchored onto the surface of nano‐CaCO₃ through triethoxyvinyl silane (TEVS) as a coupling agent. Ammonium persulfate (APS), sodium dodecyl sulfate (SDS) and n‐pentanol were used as initiator, surfactant, and cosurfactant, respectively. Polymerization mechanism of core–shell latex particles was discussed. Encapsulation of nano‐CaCO₃ by PS was confirmed by using transmission electron microscope (TEM). Grafting percentage of core–shell particles was investigated by Thermogravimetric Analyzer (TGA). Nano‐CaCO₃/PS core–shell particles were characterized by Fourier transform infrared (FTIR) spectrophotometer and differential scanning calorimeter (DSC). The results of FTIR revealed existence of a strong interaction at the interface of nano‐CaCO₃ particle and PS, which implies that the polymer chains were successfully grafted onto the surface of nano‐CaCO₃ particle through the link of the coupling agent. In addition, TGA and DSC results indicated an enhancement of thermal stability of core–shell materials compared with the pure nano‐PS. Nano‐CaCO₃/PS particles were blended with polypropylene (PP) matrix on Brabender Plastograph by melt process with different wt% of loading (i.e. 0.1–1 wt%). The interfacial adhesion between nano‐CaCO₃ particles and PP matrix was significantly improved when the nano‐CaCO3 particles were grafted with PS, which led to increased thermal, rheological, and mechanical properties of (nano‐CaCO₃/PS)/PP composites. Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed a perfect dispersion of the nano‐CaCO₃ particles in PP matrix. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of Cr and Mn ions on the structure and magnetic properties of GaFeO3: Role of the substitution site

Effect of substitution of Cr and Mn in the Fe and Ga sites of GaFeO₃ on the structural parameters and magnetic properties has been investigated by preparing GaFe_1−xCr_x(Mn_x)O₃ and Ga_1−xCr_x(Mn_x)FeO₃ starting with appropriate oxide precursors. It is shown that, starting with Cr or Mn substituted Ga₂O₃, one obtains Ga_1−xCr_x(Mn_x)FeO₃, while reaction of Cr or Mn substituted α-Fe₂O₃ with Ga₂O₃ yields GaFe_1−xCr_x(Mn_x)O₃. The structural parameters and magnetic properties vary significantly with the substitution site of Cr showing a large decrease in the unit cell parameters as well as the T_C and other magnetic properties when the substitution is at the octahedral Fe (1, 2) site. Substitution of Cr at the octahedral Ga2 site results in marginal changes. Substitution of Mn in the Ga and Fe sites also show differences although the changes themselves are much smaller. First-principles calculations confirm such site-specificity and show how Cr substitution affects the properties differently when substituted at the Ga2 and Fe1 sites.     

Effect of the method used for crystal structure formation on the rheological behavior of organocyclotetrasiloxane in the plastically crystalline state

The rheological properties of cis-cyclotetrasiloxane, cis-[PhSi(O)(OSiMe₃)]₄, in the plastically crystalline state were investigated. The yield stress and non-Newtonian character of the flow indicates that cis-[PhSi(O)(OSiMe₃)]₄ is a viscoplastic material with respect to its rheological behavior. The conditions of crystal structure formation determine the rheological properties of organocyclotetrasiloxane in the mesophase. The temperature and stress during capillary flow were shown to affect the size and orientation of crystallites formed upon cooling of extrudates.     

St / AA共聚物的组成对碳酸钙结晶及形貌影响的研究

在聚苯乙烯-丙烯酸两亲共聚物(简称PAS)溶液中制备CaCO₃，用XRD、FTIR和SEM等研究随着PAS的亲水AA和亲油St单元组成的变化所引起的聚合物分子链段、溶解性质和胶束空间构象等的改变对CaCO₃晶型和形貌的影响。结果显示：随着亲水性AA单元组成的提高，可以由AA链段的晶面匹配成核调控碳酸钙为方解石纳米晶，并因PAS在水溶液中溶解性不同，形成了多种碳酸钙形貌的聚集体；当St和AA的物质的量比为3∶1时，合成出类珍珠岩层碳酸钙结构。根据PAS的结构性质和在水溶液中的溶解行为初步探讨了类珍珠岩层碳酸钙的形成机理，认为是PAS基质模板和羧酸根对钙的键合作用形成这一特殊形貌碳酸钙。     

High-pressure structural behavior of GdAlO3 and GdFeO3 perovskites

The orthorhombic perovskites, GdAlO₃ and GdFeO₃, have been studied using single-crystal X-ray diffraction up to 8.52 and 8.13 GPa, respectively, in a diamond anvil cell at 298 K. The evolution of the structures of GdAlO₃ and GdFeO₃ involves compression of both the GdO₁₂ and the octahedral (AlO₆ and FeO₆) sites. The compression of the GdO₁₂ site is anisotropic in both perovskites, with the four longest Gd-O distances compressing more than the eight shorter Gd-O bond lengths, resulting in a decrease in the distortion of GdO₁₂ with pressure. In GdAlO₃, the GdO₁₂ site is less compressible than the AlO₆ site, resulting in an increase of both the interoctahedral Al-O1-Al and Al-O2-Al angles with increasing pressure. Thus GdAlO₃ perovskite becomes less distorted with increasing pressure. In GdFeO₃, the GdO₁₂ site displays a similar compressibility as the FeO₆ site, with little change in the Fe-O2-Fe angle with pressure but an increase of the Fe-O1-Fe tilting angle. Thus GdFeO₃ perovskite becomes less distorted with increasing pressure, but the change is not as pronounced as GdAlO₃. The high-pressure behavior of GdAlO₃ and GdFeO₃ is similar to orthorhombic YAlO₃ perovskite but contrasts with orthorhombic CaSnO₃, which becomes more distorted with increasing pressure.     

高活性耐硫MoO3改性NiO-Al2O3催化剂用于焦炉煤气甲烷化

采用双水解共沉淀法结合浸渍法合成了系列的MoO₃改性的xMoO₃/NiO-Al₂O₃催化剂(x%为MoO₃的质量分数),利用固定床装置对催化剂的甲烷化反应活性和耐硫性能进行评价,并对失活前后催化剂进行详细表征。结果表明,随着MoO₃含量的升高MoO₃改性后的催化剂甲烷化活性有所下降,但MoO₃的掺杂显著提升了催化剂的耐硫性能。催化剂低温甲烷化活性降低的原因在于MoO₃负载量的增加降低了催化剂的活性比表面积,但MoO₃的引入也为硫化物提供了一个竞争吸附位点,进而延缓了活性位点的硫中毒过程。当 MoO₃负载量(质量分数)为 12.5% 时,12.5MoO₃/NiO-Al₂O₃催化剂在 143 mg·m^-3 H₂S/H₂气氛下运行时间长达7 h,远高于其他催化剂。12.5MoO₃/NiO-Al₂O₃催化剂吸收硫的量(质量分数)达到0.71%,是NiO-Al₂O₃催化剂硫吸附量的1.48倍。XPS表征进一步发现12.5MoO₃/NiO-Al₂O₃催化剂表面生成的MoS₂最多,这说明在此负载量下Mo优先吸附了更多的硫而保护了活性位点。此外,MoO₃负载量为12.5%时,MoO₃在催化剂表面接近单层分散阀值,当竞争吸附发生时,为硫化物提供更多的吸附位点。     

高活性耐硫MoO3改性NiO-Al2O3催化剂用于焦炉煤气甲烷化

采用双水解共沉淀法结合浸渍法合成了系列的MoO₃改性的xMoO₃/NiO-Al₂O₃催化剂(x%为MoO₃的质量分数),利用固定床装置对催化剂的甲烷化反应活性和耐硫性能进行评价,并对失活前后催化剂进行详细表征。结果表明,随着MoO₃含量的升高MoO₃改性后的催化剂甲烷化活性有所下降,但MoO₃的掺杂显著提升了催化剂的耐硫性能。催化剂低温甲烷化活性降低的原因在于MoO₃负载量的增加降低了催化剂的活性比表面积,但MoO₃的引入也为硫化物提供了一个竞争吸附位点,进而延缓了活性位点的硫中毒过程。当MoO₃负载量(质量分数)为12.5%时,12.5MoO₃/NiO-Al₂O₃催化剂在143 mg·m^-3 H₂S/H₂气氛下运行时间长达7 h,远高于其他催化剂。12.5MoO₃/NiO-Al₂O₃催化剂吸收硫的量(质量分数)达到0.71%,是NiO-Al₂O₃催化剂硫吸附量的1.48倍。XPS表征进一步发现12.5MoO₃/NiO-Al₂O₃催化剂表面生成的MoS₂最多,这说明在此负载量下Mo优先吸附了更多的硫而保护了活性位点。此外,MoO₃负载量为12.5%时,MoO₃在催化剂表面接近单层分散阀值,当竞争吸附发生时,为硫化物提供更多的吸附位点。     

A study on properties and morphological structure of ferrocene-filled PVC

The crystallization, special interaction, rheological behavior, and mechanical properties of PVC/ferrocene blends were studied through WAXD, FTIR, XPS, capillary rheometry, and mechanical property tests. The experimental results showed that the tensile strength of PVC/ferrocene (100/10) amounts to 82 MPa, 1.3 times as high as that of PVC. In the presence of a small amount of ferrocene, the processability of PVC is also improved. Crystallization of ferrocene in the blend is inhibited. The FTIR characteristic peaks of ferrocene shift or disappear. A new peak appears in the C1s XPS spectra and the Cl (2p) XPS spectra of PVC/ferrocene blends, and most of the ferrocene in the blends cannot be extracted by solvent alcohol, indicating the existence of some intermolecular interactions between PVC and ferrocene which cause the mechanical strength of the blends to increase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2828–2834, 1999     

Effect of sulfuric and phosphoric acid pretreatments on enzymatic hydrolysis of corn stover

The pretreatment of corn stover with H₂SO₄ and H₃PO₄ was investigated. Pretreatments were carried out from 30 to 120 min in a batch reactor at 121°C, with acid concentrations ranging from 0 to 2% (w/v) at a solid concentration of 5% (w/v). Pretreated corn stover was washed with distilled water until the filtrate was adjusted to pH 7.0, followed by surfactant swelling of the cellulosic fraction in a 0–10% (w/v) solution of Tween-80 at room temperature for 12 h. The dilute acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digetibility. Hemicellulose recovery was 62–90%, and enzymatic digestibility of the cellulose that remained in the solid was >80% with 2% (w/v) acid. In all cases studied, the performance of H₂SO₄ pretreatment (hemicellulose recovery and cellulose digestibility) was significantly better than obtained with H₃PO₄. Enzymatic hydrolysis was more effective using surfactant than without it, producing 10–20% more sugar. Furthermore, digestibility was investigated as a function of hemicellulose removal. It was found that digestibility was more directly related to hemicellulose removal than to delignification.