Effects of polyoxyethylene nonylphenol on dynamic mechanical properties and crystallization of polypropylene

Polypropylene (PP) was blended with polyoxyethylene nonylphenol (PN) in a twin-screw extruder and injection moulded. The dynamic mechanical properties of PP/PN blends were characterized by dynamic mechanical analyser (DMA). The glass transition temperature (T_g) of PP showed a slight decrease with incorporation of PN. Differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM) were employed to investigate the effects of PN on crystallization of PP. In a study of nonisothermal crystallization of PP and PP/PN blends, crystallization parameter analysis showed the addition of PN reduced the peak temperature of crystallization. β-form crystals of PP coexisted with α-form crystals in PP/PN blends, and oriented on the surface layer of injection moulded bar as revealed by WAXD. The degree of orientation was determined using Hermans orientation function. The thermal stability of β-form crystals was evaluated using high temperature WAXD and POM.     

Effects of silver nanoparticles on the dynamic crystallization and physical properties of syndiotactic polypropylene

The effects of silver (Ag) nanoparticles on the physical properties of syndiotactic PP (sPP) were investigated concentrating on the isothermal melt crystallization behavior under shear. sPP with 5 wt % Ag nanoparticles presented higher crystallization temperature (T_c) and heat of crystallization (ΔH_c) than pure sPP. At 90°C, the Ag nanoparticles had little effect on the induction time of crystallization but a little increased the half‐time (t_1/2) for the crystallization. At 100°C, however, the induction time was decreased with increasing the Ag content and the t_1/2 was decreased up to the Ag content of 0.5 wt %. DSC melting endotherms exhibited double melting peaks when crystallized at 90°C under shear but a single melting peak when crystallized at 100°C. The WAXD patterns exhibited that the presence of Ag nanoparticles did not produce any change in the crystal structure of sPP. The tensile strength of sPP is little changed up to the Ag content of 0.1 wt % but it was decreased with further addition. In addition, the introduction of less than 0.1 wt % Ag increased the elongation at break, but further addition decreased it abruptly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of addition of sepiolite on the mechanical properties of glass fiber reinforced polypropylene

Short glass fiber reinforced polypropylene is one of the composites with the widest range of applications in the plastics industry. The partial replacement of the glass fibers by sepiolite, brings forth a hybrid composite with better mechanical properties and, as a result, enhanced compatibility and better interfacial adhesion as a consequence of the surface properties of the sepiolite. The results obtained are also interesting from a practical point of view, as they allow for considerable reductions in the costs of the formulation.     

A contribution to the study of the polymer-filler interface in polyester and surface treated sepiolite composites

The acetalation and esterification of the sepiolites with different acids and aldehydes have been carried out in order to study the interface phenomena through their technological properties. Also, a complete study of the characterization of all the organic minerals obtained has been done. It must be pointed out the strengthening effect which is produced when some of the organic minerals obtained are present in polyester compounds.     

The effect of addition of high-density polyethylene on the crystallization and mechanical properties of polypropylene and glass-fiber-reinforced polypropylene

High-density polyethylene up to about 30% by weight was melt-mixed with polypropylene and short-glass-fiber-reinforced polypropylene. The presence of high-density polyethylene and glass fibers in the polypropylene matrix affects its crystallization characteristics, which were studied with the help of differential scanning calorimetry. The blend and composite samples have a large number of polypropylene domains apparently due to an abundance of surface nuclei; as a result, the tensile strength, tensile modulus, and toughness are enhanced. The temperature dependence of shear modulus and logarithmic decrement indicate that high-density polyethylene can have plasticizing effect below the glass transition temperature of polypropylene. The scanning electron micrographs of fractured ends show the presence of dispersed domains in the composite samples.     

Effect of surface coverage of silane treated CaCO3 on the tensile properties of polypropylene composites

Polypropylene (PP) composites were prepared with a constant volume fraction of a CaCO₃ filler, which was treated with eight trialkoxy functional silane coupling agents and the routinely used stearic acid, as comparison, The tensile properties of the composites were determined as a function of surface coverage and the chemical composition of the coupling agent. Significant differences were detected in the effect of the silane coupling agents on the tensile properties of the composites studied. They could be classified into groups of reactive, nonreactive and inactive compounds, in accordance with an earlier study. Moreover, tensile properties proved to be very sensitive to surface treatment. Reactive coupling leads to a maximum in tensile strength, while the use of nonreactive agents decreases strength rapidly with increasing surface coverage. The rate of strength decrease slows down above the concentration necessary for the formation of a monolayer coverage. Treatment influences deformability accordingly, it decreases on reactive coupling, while agents with a surfactant effect increase elongation. Amino functional silanes show a strong reactive coupling effect. A trialkoxy derivative of stearic acid, (3-stearyloxy-propyl-triethoxy-silane), synthesized the first time in our laboratory, has an outstanding surfactant effect; its use increases both the elongation and the tensile strength of the composites. Both characteristics exceed the corresponding properties of the reference composite containing the filler treated with stearic acid.     

Influence of chalk and its surface treatment on crystallization of filled polypropylene

Isotactic polypropylene has been shown to crystallize from the melt spherulitically at intermediate undercoolings (100–130°C) in the presence of a high amount (40 wt %) of chalk (calcium carbonate). Linear growth rate is not remarkably affected by the presence of a filler. Both nonisothermal and isothermal crystallization DSC experiments indicate that chalk acts as a weak nucleant. Introduction of liquid [oligomer of ethylene oxide (OEO), M_w = 300] at polymer–filler interface lowers the nucleating activity of chalk. Analysis of crystallization kinetics in Avrami coordinates, followed by dimensional-analysis correction for the case of nonintegral values of exponents, indicates that the amount of extra “chalk nuclei” is approximately constant in the range of 100–130°C while the amount of OEO-modified “chalk nuclei” decreases with the increase of the crystallization temperature. Comparison of the melting endotherms indicates that filled melt-crystallized material contains higher fraction of lower melting crystallites than unfilled polypropylene. This fraction is also higher in the case of polypropylene filled with unmodified chalk. Nucleating activity of chalk has been shown to depend upon its crystal structure (calcite or aragonite), surface topography, and aggregation.     

高流动抗冲PP的结晶特性及结晶动力学

采用X射线衍射仪、差示扫描量热仪和偏光显微镜研究了5种高流动抗冲聚丙烯(PP)树脂的结晶特性和结晶动力学。结果发现：国产试样的结晶度与晶粒尺寸明显不同于进口试样;在等温结晶条件下。总结晶速率常数和总结晶速率随结晶温度的增加而下降,而结晶半值期增加;在所研究的温度范围内。所有试样的Avrami指数基本为2～3的非整数;在133℃以下,5^#试样的球晶生长速率明显高于其他试样,但在相同结晶温度时,国产试样的总结晶速率大于进口试样。5种试样在抗冲击性能上的差异归因于它们在结晶特性和结晶动力学方面的不同。     

Melt rheological studies of polypropylene filled with coconut water treated and untreated fly ash

The melt rheology of polypropylene (PP) filled with fly ash (FA) before and after treatment with coconut water (CW) was studied for different concentration of the filler. The fly ash after coconut water treatment clearly showed additional peaks in the infrared (IR) spectra corresponding to the hydroxyl and carbonyl groups indicating good adsorption of CW on FA. The X‐ray diffraction of melt compounded PP filled with CW‐treated (CWT) FA showed large reduction of the main silica peak of FA and considerable broadening of Mullite and hematite peaks suggesting formation of fine particles by this treatment. Scanning electron microscopy (SEM) confirmed the drastic reduction of particle size in these composites. The melt rheological studies for these composites indicated considerable increase in viscosity at low filler loading for CW treated FA. The concentration dependence of melt viscosity did not follow any of the theoretical equations suggested in literature. Although, the behavior was similar to nanoparticle‐filled polymers, there were some differences especially above the critical concentration of 4.5% by volume. The frequency dependence of storage and loss modulus indicated crossover point clearly, which was greatly affected by CW treatment. The Cole–Cole plots of real and imaginary part of melt viscosity brought out the broad distribution of relaxation time for the CW treated FA. The CW treated FA melt compounded with PP gave rise to nanocomposites with uniform dispersion. However, above 4.5% by volume, there appears to be agglomerate formation along with a thin interfacial layer, which assists the melt flow even at high filler loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43900.     

The impact of polypropylene‐graft‐maleic anhydride on the crystallization and dynamic mechanical properties of isotactic polypropylene

Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to identify the mechanisms that lead to differences in the mechanical behavior of formulations of polypropylene blended with maleated polypropylene (MAPP) copolymers. MAPP lowered the melting temperature of PP indicating that less stable crystals were formed possibly because of cocrystallization of PP and MAPP. Crystallization kinetics revealed that copolymers do not change the rate of crystal growth, but may retard nucleation leading to a more spherulitic morphology. The dynamic storage modulus slightly increased in the glassy region with the small addition amounts of MAPP, while mechanical dampening systematically decreased with MAPP addition. An analysis of the viscoelastic behavior did not reveal any real differences in molecular coupling around the β‐transition of PP with the addition of the MAPP copolymer. At low addition levels, MAPP does not appear to have a significant impact on the viscoelastic properties of the polymer blend. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

阳离子染料可染丙纶的结晶特性和形态结构研究

将自制可染剂通过与聚丙烯共混纺丝生产的阳离子染料可染丙纶进行 X射线衍射分析和SEM观察研究。结果表明 :可染丙纶的晶粒尺寸 ( L110 )越大 ,其染色性能越好 ;可染剂与聚丙烯有一定的相容性 ,并且能均匀分散在聚丙烯中 ,使纤维上染率达到 90 %以上。     

The role of crystallization kinetics in the development of the structure and properties of polypropylene filaments

The processing, structure, and properties of filaments melt spun from three polypropylenes with similar rheology but substantially different crystallization kinetics were studied. The crystallization kinetics of the homopolymer was increased by the addition of a nucleating agent, whereas slower crystallization kinetics was obtained through a small amount of random copolymerization with ethylene. The relative crystallization kinetics of these three polymers was examined under quiescent conditions using differential scanning calorimetry. The technique of on-line diameter and birefringence measurement was used to show the characteristics of the on-line crystallization of the different resins. It was found that changing the quiescent crystallization kinetics by either the addition of a nucleating agent or through copolymerization with ethylene can produce profound effects on the structure and properties of polypropylene as-spun filaments when they are spun under relatively low stress and low takeup velocity conditions. Higher takeup velocities and spinline stresses reduce the effect of differences in quiescent crystallization due to the influence of on-line stress-induced (molecular orientation-enhanced) crystallization. © 1993 John Wiley & Sons, Inc.     

成核剂对聚丙烯力学性能与结晶行为的影响

研究了两种类型的成核剂对国产共聚聚丙烯的结晶形态以及拉伸强度、冲击强度的影响。结果表明:加入TMB-5型成核剂,聚丙烯的冲击强度有一定程度改善,w(TMB-5)为0.1%时,改性聚丙烯的缺口冲击强度达到最大;TMX-2型成核剂可改善聚丙烯的拉伸性能,但抗冲击性能降低较大;TMB-5型成核剂可显著地改变聚丙烯的结晶行为,诱导聚丙烯在结晶过程中主要形成β晶;TMX-2型成核剂可诱导聚丙烯在结晶过程中主要生成α晶,与纯PP相比,α晶的形成能力增强。     

Morphology,crystallization and melting properties of isotactic polypropylene blended with lignin

The influence of lignin (L) on the thermal properties and kinetics of crystallization of isotactic polypropylene (PP) is reported in this article. PP blends containing 5 and 15 wt % of L were prepared by mixing the components in a screw mixer. An increase of the thermal degradation temperature of the blends was observed as a function of L content. The crystallization and thermal behavior of the pure PP and of the PP/L blends were analyzed by differential scanning calorimetry (DSC). Isothermal crystallization kinetics were described by means of the Avrami equation, which suggests a three‐dimensional growth of crystalline units, developed by heterogeneous nucleation. The isothermal growth rate of PP spherulites was studied using a polarizing optical microscope. The enhancement of PP crystallization rate for the PP/L blends was observed and ascribed to the nucleating action of lignin particles. Non‐isothermal crystallization kinetics were applied, according to the results elaborated by Ziabicki and the method modified by Jeziorny. The kinetic crystallizability of the PP is not influenced by the L present in the blend. In the presence of L, PP can simultaneously crystallize in both the α and β crystalline forms, and the ratio between the α and β forms was determined by X‐ray diffraction analysis. Two melting peaks relative to the two crystalline form of PP were observed for the PP/L blends, for all isothermal crystallization temperatures investigated by means of DSC. The equilibrium melting temperature for α‐form of pure PP was obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1435–1442, 2004     

Effect of silane‐grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

Talc‐filled polypropylene (PP) composites coupled with silane‐grafted polypropylene (PP‐g‐Si) were prepared. Effect of PP‐g‐Si on the mechanical properties, crystallization, and melting behavior of PP composites was investigated. Compared with the uncoupled composites, the mechanical properties of Talc/PP composites coupled with a small amount of PP‐g‐Si were increased to some extent. Meanwhile, PP‐g‐Si can promote crystallization rate and increase crystallization temperature of PP in the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2974–2977, 2000     

Oriented crystallization and mechanical properties of polypropylene nucleated on fibrillated polytetrafluoroethylene scaffolds

It is known that friction deposited polytetrafluoroethylene (PTFE) layers are able to nucleate crystallization of thin films of isotactic polypropylene (iPP). In order to investigate the influence of PTFE on the crystallization behavior and morphology of iPP in bulk, PTFE‐particles of two different sizes in various concentrations were melt‐blended with iPP and subsequently processed by injection molding. For one size of particles, high resolution scanning electron microscopy (HR‐SEM) showed the presence of a PTFE scaffold consisting of highly fibrillated PTFE particles. With X‐ray diffraction (WAXD) pole‐figures, it was evidenced that, after melting and recrystallization of the iPP matrix, a strongly oriented crystallization of iPP on this PTFE scaffold takes place (quiescent crystallization conditions). With WAXD it was also shown that under processing conditions, PTFE acts as a nucleating agent for iPP and that PTFE strongly enhances the formation of processing induced morphologies. Impact and tensile performance of the mixtures were measured. Both the strain energy release rate (G_I) and the E‐modulus were found to increase upon introducing PTFE in iPP. POLYM. ENG. SCI., 45:458–468, 2005. © 2005 Society of Plastics Engineers.     

The effect of elastomeric nano-particles on the mechanical properties and crystallization behavior of polypropylene

Generally, toughness of polypropylene (PP) is an issue which has been investigated for many years to search for improvements. A traditional approach is to blend with rubber particles to enhance the toughness of PP yet modulus of PP decreases accordingly. Recently, we have achieved a good balance of toughness and stiffness of PP via blending PP with a small amount of elastomeric nano-particles (ENP). Based on our measurements, mechanical properties of the blends studied both the toughness of PP at room temperature and at −20 °C show substantial increase. On the other hand, the stiffness of the PP blends retains or even possesses a slight enhancement. One of the reasons for this improvement is due to the fact that the ENP is not only a toughening modifier but also a nucleation agent for the PP. The nucleation density of the blends increases, while the crystallization kinetics of the blends becomes faster compared with the pure PP samples.     

降解PP/EPDM共混物的结晶性能研究

采用过氧化二异丙苯(DCP)降解聚丙烯(PP),熔融法制备了降解PP与三元乙丙橡胶(EPDM)共混物,采用差示扫描量热分析(DSC)及广角X射线衍射(WAXD)研究了降解PP/EPDM共混物的结晶行为,结果发现PP降解后β-PP晶型(300)消失 ;降解PP/EPDM共混物的非等温结晶过程是由成核控制的,并伴有明显的快速初级结晶和缓慢的次级结晶过程,降解PP以均相成核的三维球晶方式生长.     

Effects of nucleating agents on crystallization behavior and mechanical properties of high-fluid polypropylene

The effects of organic aluminum phosphate (NA-21) and rare earth organic coordination compounds (WBG), serving as ??, ?? nucleating agents, on crystallization and mechanical properties of high-fluid polypropylene (PP) have been investigated. As determined by differential scanning calorimetry, the isothermal crystallization temperature of PP increased from 126.5 to 137.7?°C and 133.6?°C with NA-21 and WBG, respectively. The two endothermal melting peaks of PP blending with WBG indicated the transformation of ??-crystal. The wide-angle X-ray diffraction pattern and melting behavior of PP blending with WBG testified that a high proportion of ??-crystal, which was more than 70%, was induced, while the crystal-phase of PP modified with NA-21 had little change. The mechanical properties of nucleated PP were tested by tensile testing machine and izod pendulum impact tester. A dramatic increment of impact strength, as high as 191%, was obtained for PP with the introduction of WBG, comparing to 132% by NA-21 addition. The impact fracture surfaces were observed by scanning electron microscope; the resistance of crack growth of nucleated PP was better than that of pure PP. Although flexural strength of PP improved in both scenarios, the influence of nucleators on yield strength of PP differed. Yield strength of PP increased by 8.5% when using 0.2?wt% NA-21, but decreased by 6% when using WBG at the same content. Therefore, WBG, a novel ??-nucleator, played an essential role in enhancing impact strength of PP.     

Cell structure and dynamic properties of injection molded polypropylene foams

The cell structure and properties of branched and linear polypropylene (PP) foams containing organically modified nanoclay and maleic anhydride grafted polypropylene (PPMA) have been thoroughly investigated. X-ray diffraction (XRD) and melt rheometry were used to identify the structure and linear viscoelastic properties of the nanocomposites, as well as the effectiveness of two different compatibilizers. These nanocomposites were used in injection molding to investigate their foamability and the influence of experimental conditions such as chemical foaming agent concentration, shot size, back pressure, injection speed, as well as melt temperature and different injection methods on the resulting cell structure of the foams. Quite different results were obtained with the linear and the branched PP. While the foamability of the branched PP was intrinsically good, that of the linear one could largely be improved by modifying its rheological properties and favoring nucleation through the addition of nanoclay. The effect of cell structure on the dynamic mechanical properties of the foams was also investigated using dynamic mechanical analysis (DMA). POLYM. ENG. SCI., 47:1070–1081, 2007. © 2007 Society of Plastics Engineers