“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.

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.

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.

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.

PP/玻纤/EPDM-g-MAH复合材料性能研究

采用挤出熔融共混方法制备了马来酸酐接枝三元乙丙橡胶(EPDM-g-MAH)。研究了玻纤用量、EPDM-g-MAH用量对PP力学性能、热变形温度的影响。研究结果显示:在玻纤用量5~30份的区间内,随着玻纤用量的增加,PP/玻纤复合材料的冲击强度、拉伸强度、弯曲强度均逐渐增大,在玻纤用量30份时,缺口冲击强度为10.29 kJ/m^(2),约为纯PP的4.38倍,热变形温度呈上升趋势。而在EPDM-g-MAH用量为5~30份的范围内,随着EPDM-g-MAH添加量的增加,PP/玻纤/EPDM-g-MAH复合材料的缺口冲击强度先是上升,而后下降。在EPDM-g-MAH用量15份时,冲击强度最高,达到了13.38 kJ/m^(2),约是纯PP的5.69倍,热变形温度则呈下降趋势。

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.

A DYNAMIC MECHANICAL ANALYSIS STUDY OF THE TRANSITION BEHAVIOUR OF I-PP/EPDM BLENDS

The transition behaviour of the blends of isotactic polypropylene (i-PP) with ethylene-propylene terpolymer (EPDM) containing 42 wt% propylene was investigated by dynamic mechanical analysis technique (DMA). Owing to its high propylene content, EPDM is compatible with i-PP to some degree. The interaction between the two components was strengthened. As expected, for partially compatible system the glass transition temperature of i-PP in the blends shifted to lower temperature. It was found that there existed two transitions, αEPDM and βEPDM, for the EPDM used in this work. The former was considered to be the glass transition of the random chain segments of EPDM, while the latter the local motion of the long ethylene sequences in EPDM. The unusual transition behaviour of αEPDM in the blends was explained in terms of the greater thermal expansion of EPDM and the compatibility of the two components. On the other hand, the βEPDM changed with the composition of the blends in a regular manner.

PP/EPDM共混物断裂性能的研究

采用三元乙丙橡胶(EPDM)对共聚聚丙烯(PP)增韧改性。研究了共混物的力学性能和断裂性能,着重采用基本断裂功方法探讨了材料组成对共混体系断裂性能的影响。研究发现:随EPDM用量的增加,共混物的拉伸强度逐渐下降,冲击强度均较纯PP有一定程度的提高。不同组成的PP/EPDM共混物的we均高于纯PP,we值随EPDM用量的增加呈先增大后减小的趋势,且we主要受we,n变化的影响,同样βwp的变化主要受βnwp,n变化的影响。

硫酸钙晶须/PP/EPDM复合材料力学性能研究

采用对硫酸钙晶须进行表面处理和提高PP/EPDM基体树脂极性的方法制得具有良好界面层的硫酸钙晶须/PP/EPDM复合材料。力学性能测试结果表明,硫酸钙晶须可提高PP/EPDM基体的拉伸强度和弯曲强度,且通过控制各组分配比可制得韧性和刚度均衡的复合材料。

EPDM/PP热塑性动态硫化胶的进展

阐述了 EPDM/PP共混型热塑性动态硫化胶的发展历史、制备工艺、微观相态结构、性能、加工技术和应用领域。

PP/EPDM共混体系界面的研究

本文采用马来酸酐对三元乙丙橡胶（ＥＰＤＭ）进行熔融接枝改性，将改性后的ＥＰＤＭ与聚丙烯（ＰＰ）共混，对ＰＰ／ＥＰＤＭ和ＰＰ／ＥＰＤＭｇＭＡＨ两种共混体系的界面状况进行了对比。运用Ｈｕｇｇｉｎｓ参数（χ）、界面张力系数（γ１２）对界面状况进行了表征；运用扫描电镜（ＳＥＭ）和偏光显微镜对共混物的冲击断口形貌以及结晶情况进行了观察与分析；探讨了界面状况与共混物力学性能以及流变性能间的关系。

EPDM-g-SAN对EPDM/SAN共混体系形态及力学性能的影响

研究了接枝共聚物EPDM-g-SAN对EPDM/SAN共混体系的形态和力学性能的影响。扫描电镜和粒径统计分析发现,随着EPDM-g-SAN接枝共聚物的加入,共混体系EPDM分散相的粒径变小、粒径分布变窄,且共混物的缺口冲击强度明显提高,发生了脆韧转变;基体的塑性变形显著增加,表明接枝共聚物在不相容两相聚合物间起到了良好的增容作用。冲击断面扫描电镜分析证实了韧性增加的机理。

POE与EPDM对聚丙烯增韧改性研究

以茂金属聚烯烃弹性体(POE,乙烯-辛烯共聚物)和传统三元乙丙胶(EPDM)作为聚丙烯(PP)的增韧剂,比较研究了PP/POE及PP/EPDM共混物的加工性能及力学性能。研究结果表明,POE在加工性、增韧改性等方面比EPDM更具有优势。扫描电子显微镜(SEM)进一步探讨了共混物的形态结构与性能的关系。

EPDM/三元共聚尼龙高性能弹性体相容剂及共混工艺的研究

研究了相容剂及其用量和加工工艺对EPDM /三元共聚尼龙 (PA)共混体系物理性能的影响。结果表明 ,氯化聚乙烯 (CPE)是EPDM/PA共混体系性能优良且价廉易得的相容剂 ;CPE的最佳用量为PA的 1/2。SEM照片显示 ,EPDM与PA相容性差 ;二元体系EPDM/PA加入CPE后 ,分散相PA/CPE分散均匀 ,粒径细小。共混温度控制在 (16 0± 5 )℃为宜 ,PA与CPE共混时间控制在 15min为宜 ,EPDM与CPE/PA的混炼时间控制在 8min为宜。

HNBR/EPDM共混物结构与性能研究

分别采用过氧化物和硫给予体作交联剂 ,考察了不同共混比对氢化丁腈橡胶 (HNBR) /EPDM共混物性能的影响 ,并通过DSC和TEM分析了共混物的相容性 ,对两胶的共硫化也作了初步探讨。结果表明 ,两种硫化体系硫化的共混胶扯断伸长率保持率均在 60 %以上 ,都具有优异的耐热氧老化性能。随HNBR用量增大 ,共混物的定伸应力、拉伸强度和撕裂强度均提高 ,磨耗明显降低。HNBR和EPDM为不相容体系 ,但硫化仪曲线显示二者硫化速率接近 ,能较好地共硫化。

PP/EPDM/阻燃剂共混体系的力学性能与阻燃性能的研究

采用三元乙丙橡胶（ＥＰＤＭ）作增韧剂、十溴联苯醚（ＦＲ１０）和三氧化二锑（Ｓｂ２Ｏ３）的复合体系及红磷作阻燃剂，通过双螺杆挤出机与聚丙烯（ＰＰ）进行熔融挤出，研究了共混体系的组成与性能之间的关系。结果表明，通过选择适当的原材料和配比。

EPDM接枝马来酸酐增韧聚酰胺6的性能及冲击断面形态

研究了EPDM接枝马来酸酐 (EPDM g MAH)用量对聚酰胺 6(PA6)性能的影响及PA6/EPDM g MAH共混物的冲击断面形态。结果表明 :EPDM g MAH分散相颗粒与PA6基体能形成牢固的结合 ,对PA6具有显著的增韧改性作用 ;当PA6/EPDM g MAH的用量比为 90 /10时 ,共混物的综合性能最理想 ,其常温 (2 5℃ )及低温 (-2 0℃ )下的冲击强度分别比纯PA6增大 64 8%和 10 6 6% ,而且具有良好的挤出和注射成型加工性能。