Barrier property and morphology of polypropylene/polyamide blend film

The barrier property of polypropylene (PP)/polyamide (PA) blend film produced by the extrusion casting film process was studied by investigating the effects of rheological properties of each components, compatibilizer content, screw rpm, and the absorbed moisture, and by performing morphological analysis and permeability modeling. The oxygen barrier property of blend film with ellipsoidal structure of PA dispersed phase was significantly improved by a factor of 5.4 with the addition of only 20 wt% PA, when compatibilizer was added by the content of 7 phr and the PP matrix resin and process condition was selected to induce lower viscosity ratio less than unity. Using Fricke’s model with the value of 19.6 of aspect ratio of the ellipsoid, the permeabilities of blend films as a function of PA content could be predicted and exhibited a good agreement with the experimental results. The absorbed moisture had a significant influence on the barrier property of the PP/PA blend system, suggesting that the hygroscopic PA resin should be incorporated with the high water barrier PP resin by the amount below about 20 wt% to minimize the deterioration of the barrier property in the humid atmosphere.     

制备HDPE/PA-6阻隔性共混合金工艺条件的研究

本文通过测试HDPE、PA 6的流变性能、共混合金的溶剂透过率和PCM,研究了制得阻隔性层状HDPE/PA 6共混合金工艺条件,如加工温度、剪切速率和混合时间等。结果表明:改变加工温度可以调节HDPE/PA 6共混组成粘度比,当PA 6与HDPE的粘度比较大时,能得到PA 6相呈层状分布结构的阻隔性共混合金;剪切作用有利于共混体系两相的分散,适当的剪切速率有利于使PA 6相形成层状结构。较高的剪切速率使PA 6相尺寸减,分散更均匀,但对提高共混物的阻隔性不利;较短的混合时间可以获得具有阻隔性的HDPE/PA 6共混合金体系     

The dynamics of montmorillonite clay dispersion and morphology development in immiscible ethylene-propylene rubber/polypropylene blends

The evolution of morphology during the melt compounding of polypropylene (PP), maleated ethylene-propylene rubber (EPR-g-MAn) and onium-ion exchanged montmorillonite clay (NR₄⁺-MM) is described. Irrespective of the ratio of components, clay partitions into the EPR-g-MAn phase exclusively, with significant amounts of mineral exfoliation occurring in the very early stages of compounding. These changes in filler distribution and dispersion are accompanied by reductions in the size of the dispersed PP phase, as the rate of droplet coalescence falls in response to an elevated EPR-g-MAn matrix viscosity. However, when NR₄⁺-MM is localized in a dispersed EPR-g-MAn phase, coalescence increases as a result of hindered particle break-up.     

增容剂含量对PP／EVOH共混物流变性能的影响

采用熔融共混法制备了聚丙烯／乙烯-乙烯醇共聚物（PP／EVOH）共混物,利用毛细管流变仪对共混物的流变行为进行了研究。结果表明：PP／EVOH共混物为假塑性流体,呈现出切力变稀的现象。马来酸酐接枝乙烯-辛烯共聚物（POE-g-MAH）的加入增大了PP／EVOH共混物的粘流活化能,说明共混物对温度的敏感性较强。     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of cross‐linked LLDPE/PP blend (LLDPE‐PP) as compatibilizer on morphology,crystallization behavior and mechanical property of LLDPE/PP blends

Moderate cross‐linked blend (LLDPE‐PP) of linear low‐density polyethylene (LLDPE) and polypropylene (PP) with benzoyl peroxide (BPO) were prepared by the reactive melt mixing in HAAKE mixer. Effect of LLDPE‐PP as compatibilizer on the morphology, crystallization behavior and mechanical properties of LLDPE/PP (87/13) blends were studied using scanning electron microscopy (SEM), polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and mechanical testing machines. The results showed that LLDPE‐PP not only improved the interfacial adhesion between the LLDPE and PP but also acted as selective nucleating agent for crystal modification of PP. In the blends, the sizes of LLDPE and PP spherulites became smaller, and their melting enthalpies reduced in the presence of LLDPE‐PP. Furthermore, the mechanical properties of LLDPE/PP blends were improved with the addition of LLDPE‐PP, and when the concentration of LLDPE‐PP was 2 phr, the ternary blend had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Laminar morphology of nylon/EIDPE blends: The formation and its barrier properties

Nylon, owing to its excellent solvent-resistant properties, is blended with HDPE and used as a material for gasoline tanks. However, the effective diffusivity of gasoline intimately depends on the blend morphology. In this study, a model is proposed to describe the relationship between effective diffusivity and blend morphology. Via this model, the effects of Nylon concentration and the aspect ratio of the dispersed laminae on the barrier properties are investigated. Formation of the laminar morphology of the blend induced by processing is also studied through WATS analysis. These analyses are compared with experimental results. Moreover, the effect of rheological properties of components and compatibilizer on the morphology, as related to the barrier properties, is also studied.     

HDPE/EVOH高阻隔性材料的形态结构

采用层状分散形态共混技术制备了ＨＤＰＥ／ＥＶＯＨ高阻隔性材料，研究了增容剂的制备及其用量对材料形态结构的影响。结果表明采用ＥＶＯＨ／相容剂和ＨＤＰＥ、ＥＶＯＨ制备的母粒能明显改变材料的流变性能，当采用ＥＶＯＨ／增容剂为４／１的阻隔母粒，所得材料的结构为大而均匀的片状形态，具有优异的阻隔性。所得材料应在较小的剪切速率下加工成型，以利于ＥＶＯＨ形成较大的相区     

硅烷接枝交联LDPE、LLDPE及其共混物的结构研究

利用红外光谱、凝胶渗透色谱、热延伸试验、差示扫描量热法、扫描电子显微镜等方法研究了低密度聚乙烯（LDPE）、线型低密度聚乙烯（LLDPE）及其共混物的乙烯基硅烷接枝及交联产物的分子结构、熔融行为和形态。结果表明：硅烷接枝后,LDPE、LLDPE的重均摩尔质量小幅增加;硅烷接枝交联能力为：LLDPE〉LDPE／LLDPE共混物〉LDPE;接枝和交联使LDPE、LLDPE及其共混物的结晶度降低,晶粒变得不均匀;硅烷接枝和交联能增加LDPE／LLDPE共混物的相容性;交联结构提高了LDPE、LLDPE及其共混物的抗冲性。     

LLDPE/SEBS-g-MAH体系的等温结晶动力学

采用差示扫描量热法(DSC)研究了SEBS-g-MAH对LLDPE等温结晶行为的影响,并通过偏光显微镜(POM)观察了LLDPE及LLDPE/SEBS-g-MAH共混体系的结晶形态。结果表明,SEBS-g-MAH的加入阻碍了LLDPE分子链的规则排列,影响了链段在结晶扩散迁移规整排列的速度,使得结晶速率变慢,结晶活化能升高,对LLDPE晶体生长起了抑制作用,晶粒尺寸减小。用Avrami方程进行等温结晶动力学研究表明,LLDPE/SEBS-g-MAH共混体系的半结晶时间t1/2明显增大,Avrami指数n对结晶温度有依赖性,kn值随温度的升高而减小。利用Hoffman理论计算了球晶生长过程中晶核的折叠表面自由能σe为0.136 J.m-2,SEBS-g-MAH的加入使得σe增大了9.6%。     

Miscibility and morphology in blends of poly(l-lactic acid) and poly(vinyl acetate-co-vinyl alcohol)

Poly(vinyl acetate-co-vinyl alcohol) copolymers [P(VAc-co-VA)] were prepared by acidic hydrolysis of poly(vinyl acetate) (PVAc) at various reaction time, and the degree of hydrolysis was analyzed by ¹³C nuclear magnetic resonance spectroscopy (NMR). Blends of poly(l-lactic acid) (PLA) and P(VAc-co-VA) were prepared by a solvent casting method using chloroform as a co-solvent. The PLA/PVAc blends exhibited a single glass transition over the entire composition range, indicating that the blends were miscible systems. On the contrary, for the blends with even 10% hydrolyzed PVAc copolymer, the phase separation and double glass transition were observed. With increasing neat PVAc contents, the heat of fusion decreased and the melting peaks shifted to lower temperature. The interaction parameter indicated negative values for up to 10% hydrolyzed samples, but positive values at more than 20% hydrolyzed one. Small angle X-ray scattering analysis revealed that the long period and the amorphous layer thickness increased with PVAc composition, suggesting that a considerable amount of PVAc component located in the interlamellar region. Polarized optical microscopy showed that the texture of spherulites became rougher on increasing the PVAc content. In the case of P(VAc-co-VA) copolymer, the intensity of polarized light decreased significantly, indicating that P(VAc-co-VA) component seemed to be expelled out of the interfibrillar regions. Scanning electron microscopy analysis revealed that the significant phase separation occurred with increasing the degree of hydrolysis. In the case of 70/30 blend of PLA and P(VAc-co-VA) with 30 mol% vinyl alcohol, the P(VAc-co-VA) copolymer formed the regular domains with a size of about 10 μm.     

A study of LLDPE functionalized through ultraviolet irradiation and interfacial interaction of PA66/functionalized LLDPE blends

Some oxygen‐containing groups, such as C? O? C, C? OH, C?O, C(?O)O, and C(?O)OH, were introduced onto linear low‐density polyethylene (LLDPE) chains during ultraviolet irradiation under air, without adding any monomers and auxiliaries and without environmental pollution. After ultraviolet irradiation, the molecular weight of LLDPE decreased and its distribution became wider. The melting temperature and crystallinity of irradiated LLDPE decreased with irradiation time. The copolymer LLDPE‐g‐PA66 was formed by reaction between oxygen‐containing groups of irradiated LLDPE and amine or carboxyl end groups and amide linkage of polyamide 66 (PA66) during preparation of PA66/irradiated LLDPE blends. Compared with PA66/LLDPE blend, the mechanical properties of PA66/irradiated LLDPE blends were improved greatly because of the improved interface interaction and dispersion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

LLDPE/纳米ZnO复合材料的制备与性能研究

将改性纳米ZnO与线型低密度聚乙烯(LLDPE)熔融共混、制备了LLDPE/纳米ZnO复合材料。通过SEM观察纳米ZnO粒子在LLDPE基体中的分散情况;研究了复合材料的力学性能及维卡软化点。结果表明:改性纳米ZnO的加入可提高LLDPE的力学性能和维卡软化点。其中,复合材料的拉伸强度、断裂伸长率、冲击强度、弯曲强度的最大值分别比LLDPE提高了17.00%、13.42%、9.90%、7.04%。     

Elongational creep experiments - A new method for investigations of morphology development in polymer blends

This work is focused on the changes of phase structure in polystyrene/polyethylene blends with up to 15 wt.% of dispersed phase during elongational experiments in creep. In the first part, features of the experiments at constant stress with a special attention to morphology development in polymer blends are discussed. In the second part of the paper the deformation behavior of the dispersed droplets in dependence on applied stress and total strain is studied. It was found that with increasing the initial particle size the formation of homogeneously deformed long fibrils is preferred during the elongation. A maximum deformability of the droplets was observed, which cannot be increased by applying higher stresses, although the affine deformation of the droplets was not reached.     

A facile route for preparing stable co-continuous morphology of LLDPE/PA6 blends with low PA6 content

A facile method is employed to prepare a series of LLDPE/PA6 blends with co-continuous morphology with low PA6 content via reactive extrusion. In these blends, co-continuous morphology is obtained by introducing graft copolymers with both high and low molecular weight trunk chains to the interface simultaneously. Maleic anhydride functionalized polybutadine (PB-g-MAH, and MAH content = 10 wt%) is first melt grafted onto the LLDPE backbones with dicumyl peroxide (DCP) as an initiator. Part of PB-g-MAH is grafted onto LLDPE to form LLDPE-g-PB-g-MAH copolymer. During reactive extrusion, in-situ formed Copolymer II (polybutadiene-graft-polyamide, PB-g-PA6) with a low molecular weight trunk chain (PB) is obtained from the reaction between the maleic anhydride group of free or non-grafted PB-g-MAH and the amino group on PA6 molecules; while Copolymer I (LLDPE-g-PB-g-PA6) is obtained via the reaction between the maleic anhydride group of the grafted PB-g-MAH (i.e., LLDPE-g-PB-g-MAH) and the amino group of PA6. Copolymer I with a high molecular weight trunk chain, LLDPE, should strengthen the interface and favor stress transfer, enabling the deformation of PA6; and Copolymer II (PB-g-PA6) with a low molecular weight trunk chain, PB, facilitates the formation of a flat interface between LLDPE and PA6, thus promoting an elongated PA6 phase. Therefore, co-continuous morphology of LLDPE/PA6 blend is successfully prepared with only 25 wt% PA6 by controlling suitable amounts of Copolymers I and II in the blend.     

电子束辐照和氢氧化铝对LLDPE/EVA共混物凝胶含量和力学性能的影响

研究了电子束辐照剂量和氢氧化铝(ATH)的含量对线性低密度聚乙烯(LLDPE)/乙烯-醋酸乙烯酯(EVA)共混物凝胶含量和力学性能的影响。辐照剂量是影响LLDPE/EVA/ATH阻燃体系凝胶含量的主要因素,而ATH对其凝胶含量的影响较小。随着ATH含量的增加,LLDPE/EVA共混物的拉伸强度逐步增加,断裂伸长率迅速下降。所有阻燃体系的拉伸强度均是随着辐照剂量的增加而逐步增大,但辐照剂量对这些阻燃体系的断裂伸长率的影响却比较复杂。     

Crystallization and morphology of ultrathin films of homopolymers and polymer blends

Ultrathin films of thicknesses below 100 nm are now considered in different areas of applications. Their behavior in term of kinetics of crystallization is very different from that of bulk samples due to the film confinement in two-dimensions, and their morphologies are unique. In this review, recent advances in the crystallization of ultrathin films of homopolymers and miscible polymer blends will be described, with an emphasis on morphologies and, in the case of blends, on mixtures made of two crystalline polymers.     

HDPE／UHMWPA层状分散合金的亚微形态,流变性能及体系相容性研究

本文研究了HDPE/UHMWPA共混体系的相容性及各组分的流变性能,据此选取了制备层状分散合金的工艺参数,获得了具有各种层状分散相态的共混物。研究结果表明:在低剪切及分散相粘度大于连续相粘度时,分散相易被层化;体系相容性和外剪切场对层状平板的尺寸及形状有明显的影响。     

Morphologies of miscible PCL/PVC blends confined in ultrathin films

Morphologies of ultrathin films (10–60 nm) of miscible poly(ε-caprolactone)/poly(vinyl chloride) (PCL/PVC) blends have been investigated under isothermal crystallization conditions by real time atomic force microscopy, and electron diffraction techniques. It was found that the morphology and growth rate of PCL/PVC blends strongly depend on the blend composition, crystallization temperature and film thickness. At a film thickness of 30 nm, the truncated lozenge-shape morphology of pure PCL crystals, found when the growth rate is slow, bent with increasing PVC content to form S-shaped or inverted S-shaped crystals, the curvature increasing by lowering the crystallization temperature. Electron diffraction patterns reveal that these crystals are flat-on single crystals with the PCL molecular chains (c axis) in the blends slightly tilted with respect to the lamella normal, while the b direction of the crystal lattice, corresponding to the fast growing direction of the growth front, follows a S line. Upon decreasing the film thickness (<30 nm), the S-shaped or inverted S-shaped crystals transform into four-branch dendritic lamellae.     

水辅助注塑PP/EVOH共混物制品的相形态与阻渗性能

选择3种不同黏度的聚丙烯(PP)与聚乙烯醇(EVOH)共混制备质量比为90/10的共混物,并采用水辅助注塑(WAIM)将这3种共混物成型为中空制品。从WAIM制品靠近浇口(1^#)和末端(2^#)两个位置取出样品,通过扫描电镜观察样品壁厚上3个位置的相形态,并测试所取样品的甲苯渗透率。借助WAIM中高压水作用下模腔内熔体的流场对样品中3个位置的相形态进行了分析。对WAIM的高黏度比共混物制品2^#样品,在外表层和内表层分散相呈粗纤维状,芯层主要呈液滴状,其阻渗性能与相应的WAIM PP样品比有适度提高(约2.4倍);对WAIM的2种低黏度比共混物制品2^#样品,外表层和内表层分散相呈细纤维状,芯层呈粗长纤维状,其阻渗性能与相应的WAIM PP样品比提高幅度较大(其中对黏度比最小的共混物达9.8倍)。1^#位置所取3种WAIM PP/EVOH样品中分散相纤维的平均直径比2^#位置的大,导致1^#位置所取样品的阻渗性能比2^#位置的低。