“Cutting effect” of organoclay platelets in compatibilizing immiscible polypropylene/polystyrene blends

In this work, polypropylene (PP)/polystyrene (PS) blends with different organoclay concentrations were prepared via melt compounding. Differing from the results of previous reports, the organoclay platelets are mostly located in the dispersed PS phase instead of the interface. The dimensions of the dispersed PS droplets are greatly reduced and apparent compatibilization effect still exists, which cannot be explained by the traditional compatibilization mechanism. A novel compatibilization mecha- nism, "cutting" to apparently compatibilize the immiscible PP/PS blends was proposed. The organoclay platelets tend to form a special "knife-like structure" in the PS domain under the shear stress of the continuous PP phase during compounding. The "clay knife" can split the dispersed PS domain apart and lead to the dramatic reduction of the dispersed domain size.

FRACTAL CHARACTER OF PHASE MORPHOLOGY OF HIGH IMPACT POLYSTYRENE/POLY(cis-BUTADIENE) RUBBER BLENDS

Evolution and fractal character of the phase morphology of high impact polystyrene/poly（cis-butadiene） rubber （HIPS/PcBR） blends during melting and mixing were investigated using scanning electron microscopy （SEM）. The characteristic length L was defined as the size of particles of the dispersed phase in blends. Different fractal dimensions, Df and Din, were introduced to study the distribution width of phase dimensions in the dimensionless region and the uniformity of the spatial distribution of particles, respectively. The results showed that the average characteristic length Lm and Df increase as the volume fraction of the dispersed phase increases, when the volume fraction of the dispersed phase is lower than 50%. In other words, the size of particles increases and their distribution in the dimensionless region becomes more uniform. Meanwhile, the uniformity of the spatial distribution becomes more perfect as the volume fraction increases. At a certain composition, Lm decreases in the initial stage of the mixing and levels off in the late stage. In the initial stage, Df becomes large rapidly with the process of blending, which means that the distribution of L in the dimensionless region becomes more uniform. Meanwhile, the spatial distribution tends to be ideal rapidly in the early stage and fluctuates in a definite range in the late stage of the mixing.

Rheology-morphology relationship in polystyrene/poly(methyl methacrylate) blends

The relationship between rheological properties and morphology of immiscible polystyrene(PS)/poly(methyl methacrylate)(PMMA) blends was studied.The blends were prepared using a twin screw extruder.A single screw extruder equipped with a slit die was used to perform shear flow measurements of PS/PMMA blends.Morphological examinations were conducted on the cryogenically fractured and extracted samples by scanning electron microscopy.The results show that the melt viscosity of PS/PMMA blend decreases with increasing shear stress,which is attributed to not only the disentanglement of macromolecules but also the reduction in the domain size and the resultant increase of the interfacial area.The power-law index of the blend melt is lower than any of its component melt,suggesting that deformation and breakup of the dispersed phase increase the dependence of the melt viscosity on the shear stress.The blend whose domain size decreases at a faster rate with increasing shear stress,exhibits a strong shear rate dependence on the melt viscosity.The comparison of the morphologies of samples before and after the slit section of the die indicates that the morphology of the blend has a quick response to shear flow,the coalescence of the dispersed drops is predominant for blends at low shear rates.

CROSSLINKING AND COMPATIBILIZATION IN BLENDS OF POLYSTYRENE AND POLYETHYLENE

This paper investigated the influences of butadiene rubber (BR) and dicumyl peroxide (DCP) on thermal and rheological behaviour, morphology and mechanical properties of PS/LLDPE/SBS blend. Addition of DCP alone was found to decrease the mechanical properties of PS/LLDPE/SBS blend due to the decomposition of PS. When BR was added together with DCP, it is found that the co-crosslinking of BR, SBS and PE takes place, and the decomposition of PS is reduced simultaneously because of the consumption of the free radicals in the crosslinking process. Synergism was thus realised which resulted in the improvement of the ductility of blend.

SPATIAL HIERARCHY AND INTERFACIAL STRUCTURE IN INJECTION-MOLDED BARS OF POLYPROPYLENE-BASED BLENDS AND COMPOSITES

The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene （PP） based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion, a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars.

TIME-DEPENDENT MORPHOLOGY OF POLYETHYLENE-POLYPROPYLENE BLENDS

The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.

A METHOD TO QUANTIFY CRAZING DEFORMATION BY TENSILE TESTS FOR POLYSTYRENE/POLYOLEFIN ELASTOMER IMMISCIBLE BLENDS

A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, increased with the content of POE. SEM micrographs showed the poor compatibility between PS and POE. In simple tensile tests, it is very easy to achieve the ratio of crazing deformation, i.e. K by measuring the size changes of samples. The K values decreased with increasing the content of POE, and the deformations of PS/POE blends were dominated by crazing. The plots of the change of volume （△V） against longitudinal variation （△I） showed a linear relationship, and the slope of lines decreased with the content of POE. Measuring samples at the tensile velocities of 5 mm/min, 50 mm/min, and 500 mm/min respectively, the K values kept unchanged for each PS/POE blends.

Study of Spherulite Growth Rate and Morphology of Polypropylenebased Blends by Image Processing Technology

The method for measuring the spherulite growth rate and studying the morphology of polypropylene - based blends by image processing technology is described. The main advantages of this method, as compared to existing techniques, are: better reliability; reproducibility; ease of manipulation. Such an approach provides a means of measuring the rate of spherulite growth. In this study, isotactic polypropylene (PP), polystyrene (PS)/PP, and polybutylene terephthalate (PBT)/PP have been studied. The results show that the technology of image analysis is very useful in the study of the kinetics of crystallization of polymer.

Morphology and Thermal Behavior of Polypropylene/Easily Hydrodegraded Polyester Blend Fibers

Ultrafine polypropylene fibers are prepared frompolypropylene/easily hydro - degraded polyester （PP/EHDPET） blend fibers, in which file EHDPET compo-nent is degradable by treating with NaOH - H2O solu-tion. We investigated the morphology of PP/EHDPETblend fibers before and after stretching and alkalinehydrolysis. Then thermal behavior of the blend has alsobeen studied.

STUDY ON THE MORPHOLOGY OF POLYVINYL CHLORIDE/POLYSTYRENE BLENDS BY ELECTRON MICROPROBE ANALYSIS

The morphology of polyvinyl chloride/polystyrene (PVC/PS) blend samples with different mass ratios, prepared by means of solution casting and melt mixing, have been successfully examined by electron microprobe analysis (EMP). This experiment was performed in a scanning electron microscope attached to an energy dispersive X-ray analyzer. Differential scanning calorimetry was also used to investigate the phase separation of the blends. The results show that PVC and PS are incompatible and the blends have sea-islands phase structures. Blends prepared via melt mixing have finer phase-dispersion than those prepared via solution casting.

Temperature Effect on the Conformation Transition of Ultra-high Molecular Weight Polyethylene/Polypropylene Blends Undergoing Continuous Volume Extensional Flow:A Mesoscopic Simulation

Due to the multiformity and complexity of chain conformation under external flow and the challenge of systematically investigating the transient conformation and dynamic evolution process of polymer chains at the molecular level by means of present experimental techniques,a universal description of both chain conformation and dynamics with respect to continuous volume extensional flow(CVEF)is still absent.Taking into account the temperature effect,we performed dissipative particle dynamics(DPD)simulations with the particles corresponding to the repeat units of polymers over a wide temperature range and analyzed the correlation with the conformational properties of ultra-high molecular weight polyethylene/polypropylene(UHMWPE/PP)blend in response to the CVEF.With time evolution,the polymer chains become highly oriented parallel to the flow direction instead of the initial random coiling and self-aggregation.It is found that a high temperature is necessary for more substantial compactness to take place than low temperature.The low-k plateau and low-k peak in structure factor S(k)curves suggest a low degree of conformational diversity and a high degree of chain stretching.It is also concluded that the intra-molecular C-C bond interaction is the main driving force for the dynamics process of the chain conformations undergoing CVEF,where the motion of the alkyl chains is seriously restricted owing to the increase in bond interaction potential,resulting in a reduction of the difference in diffusion rates among alkyl chains.

Crystallization and Crystalline Structure of Syndiotactic Polypropylene and Syndiotactic-Poly(1-Butene) Blend

The crystallization and crystalline structure of syndiotactic-polypropylene (sPP) and syndiotactic-poly(1-butene) (sPB) blend containing 10 (Bl-10), 25 (Bl-25), 50 (Bl-50), 75 (Bl-75), and 90 (Bl-90) wt% of sPB, have been investigated by means of differential scanning calorimetry (DSC), FT-IR, and wide-angle X-ray diffraction (WAXD) analyses. The melt-crystallization behavior of the blend samples was studied by DSC on the cooling process at constant rates. Bl-50, Bl-75, and Bl-90 showed lower crystallization temperatures than the neat sPP. sPP in Bl-75 showed the lowest crystallization rate among the blend samples. Bl-90 showed a two-phase molten state, and sPP in Bl-90 crystallized via two-stepprocess. Time evolution of FT-IR spectroscopy at room temperature detected conformational transformation of the sPP polymer chain in the blend samples of Bl-50 and Bl-75. The absorption peaks intensity in the FT-IR spectra derived from the helical conformations in the crystalline phase decreased, and the planar zigzag conformations in the amorphous and mesophase phases decreased over the crystallization time. The time evolution of the WAXD profile of Bl-90 indicated that sPP in the blend accelerated the crystallization of sPB. The crystallized Bl-10, Bl-25, and Bl-50 samples showed diffraction peaks in WAXD profiles and melting endothermic peak in DSC profiles derived from only the sPP crystal. The crystallinity and melting temperature of sPP in the crystallized Bl-10, Bl-25, and Bl-50 samples were almost independent of the sPB content. Both the crystalline structure of sPP and sPB were detected in Bl-75 and Bl-90. Bl-75 showed the lowest crystallinity and melting temperature of sPP among the blend samples.

The Crystallization Behavior of L-Poly(lactic acid)/Polypropylene Blends:The Acceleration for Both L-Poly(lactic acid)and Polypropylene

For a polymer/polymer dismissible blend with two crystallizable components,the crystallization behavior of different components and the reciprocal influences between different crystals are interesting and important,but did not investigate in detail.In this study,the L-poly(lactic acid)/polypropylene(PLLA/PP)blends with different weight ratios were prepared by melt mixing and the crystallization behavior of the blends were investigated.Results showed that the crystalline structures of PLLA and PP were not altered by the composition.For the crystallization of PLLA,both the diffusion of chain segments and crystallization rate were enhanced under the existence of PP crystals.For the crystallization of PP,its crystallization rate was depressed under the existence of amorphous PLLA molecular chains.When the PP crystallized from the existence of PLLA crystals,although the diffusion rate of PP was reduced by PLLA crystals,the nucleation positions were obviously enhanced,which accelerated the formation of PP crystals.This investigation would supply more basic data for the application of PLLA/PP blend.

植物纤维增强混凝土力学性能试验研究

以剑麻纤维、黄麻纤维和竹纤维为增强体,研究了植物纤维对混凝土的抗压、抗折等力学性能的增强效果,以及植物纤维的长度、掺入量和纤维分布对增强效果的影响,并与聚丙烯纤维增强效果进行对比分析。试验证明:植物纤维对混凝土抗压强度的影响可忽略不计,但对混凝土抗折强度产生重要影响。剑麻纤维(长度20 mm,体积分数1.5%)、竹纤维(长度10 mm,体积分数1.0%)和黄麻纤维(长度10 mm,体积分数1.5%)增强效果均较好,竹纤维增强效果优于其他两种植物纤维。植物纤维混掺增强效果优于单一植物纤维增强效果,总体积分数1.5%的“剑麻纤维—黄麻纤维—竹纤维”混掺增强效果最好。

聚丙烯的亲水改性与性能研究

本文在概述聚丙烯改性技术的基础上,针对聚丙烯亲水性差的问题,采用共混改性技术制备亲水聚丙烯样品,并测试改性、未改性样品力学性能和亲水表征。经研究发现,共混改性亲水PP与未改性PP力学性能基本一致。亲水PP接触角、滴水观察、分散实验均优于未改性PP。根据实验结果表明,采用共混改性亲水聚丙烯亲水性能良好。

废旧家电回收塑料的改性研究

使用回收洗衣机外壳塑料为主要原料,加入回收电视机外壳塑料进行共混改性,研究回收电视机外壳塑料加入量对共混料熔体流动速率(MFR)、拉伸性能、冲击性能的影响,确定最佳配料比。结果表明:回收洗衣机外壳塑料主要成分为聚丙烯(PP)、回收电视机外壳塑料主要成分为ABS树脂,二者相容性好,加工性能优异。加入回收电视机外壳塑料,可以提高回收洗衣机外壳塑料的强度和韧性。最佳配料比为回收电视机外壳塑料加入量为25%,此时共混料的MFR为0.17 g/10 min、抗拉强度达到25.71 MPa,断裂伸长率达到27.8%,冲击强度为18.94 kJ/m^(2)。

Control of surface morphology of polypropylene/polystyrene blend pellets prepared by diffusion and subsequent polymerization of styrene in isotactic polypropylene pellets

Inhibitor hydroquinone （HQ） was added to the reaction system to prepare polypropylene/polystyrene （PPIPS） blend pellets without PS on the surface during diffusion and subsequent polymerization of styrene in isotactic polypropylene pellets. The effects of the amount of HQ on diametrical distribution of PS, surface morphology of the pellets and phase morphology inside the blend pellets were investigated. 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

聚丙烯及聚苯乙烯催化共热解的产物分布规律

将聚丙烯与聚苯乙烯等质量混合物在小型固定流化床内进行催化共热解,选用废FCC催化剂,分析了温度、催化剂比例、载气流速(停留时间)对热解产物分布及组成的影响。在480~560℃下进行实验,将水蒸气作为载气,催化剂与反应物的比例为2:6、载气流速为0.5~2.0 mL水/min。液体与气体产物组成分别采用气相色谱质谱联用(GC⁃MS)及气相色谱(GC)进行分析。结果表明,催化共热解产物主要由油、气及积碳组成,三者的最高收率分别为75.65%、15.77%及5.55%。温度与催化剂比例的提高促进了裂解反应的发生,而随着停留时间的增加,发生二次反应数量增加,例如聚合、环化及异构化等。共热解油以芳烃为主,收率可达到69.16%,烷烃及烯烃含量较低,热解气以C_(1)~C_(4)为主,其中,与烷烃相比,烯烃总收率较高,可达到62.87%。在所有气态烃中,丙烯的含量最大,其值为37.83%。

微发泡聚丙烯共混改性研究进展

综述了微发泡聚丙烯(PP)制备中常用的化学发泡剂和物理发泡剂,以及近几年有关微发泡PP共混改性用无机填料和有机填料对其发泡性能和力学性能的影响。经共混改性的微发泡PP泡孔直径为1~100μm,泡孔密度达1×10^(10)个/cm^(3)。分析了微发泡PP的发展现状及应用前景,以进一步促进新产品开发。

温度对聚甲醛/聚丙烯共混物流变性能及界面张力的影响

使用旋转流变仪测试聚甲醛(POM)及聚丙烯(PP)的稳态流变性能,研究温度为190~210℃、剪切速率(γ)为10^(-3)~10^(0)s^(-1)条件下PP和POM的剪切黏度(η)及黏流活化能(△E_(η))随γ及温度的变化规律;制备POM/PP共混物,采用DDR-IFR法研究190~210℃下POM/PP共混物的界面张力随温度的变化规律。结果表明:PP与POM熔体的η均随着的提高呈现出下降的趋势,符合非牛顿流体中假塑性流体的流变规律;在相同γ下,PP熔体的η随温度上升而降低的现象较为明显;PP和POM的△E_(η)均随γ的增大而降低,并且呈现出良好的线性变化关系,相比POM,PP的△E_(η)随γ的变化较为明显;在温度为190~210℃,POM/PP共混物的界面张力随温度的上升而降低,并且呈现良好的线性变化关系,线性相关系数为-0.49 mN/(m·℃)。