Shear yield behavior of calcium carbonate–filled polypropylene

The rheological properties of calcium carbonate-filled polypropylene has been examined using a Rheometrics dynamic analyzer RDAII. The study included a steady shear test, a transient stress growth test, and a dynamic oscillatory shear flow. Yield behavior was observed in all kinds of rheological tests for highly filled compounds when the volume loading exceeded a critical value at about 20%. The empirical Cox-Merz rule, which is usually applicable to an unfilled polymer, was found to be invalid for highly filled compounds. The modified Cox-Merz rule, in which the apparent viscosity versus the shear rate is equal to the complex viscosity versus the frequency-amplitude in the nonlinear region, was found to be valid only for highly filled compounds. The viscosity and the apparent yield values appear to increase with increasing volume loading of filler particles. The surface treatment of fillers, which presumably reduces the interaction between filler particles and the extent of agglomeration, results in major viscosity reductions and decreases in apparent yield values. The yield values determined from various tests are not the same. The results are interpreted in terms of a system forming a filler network due to weak inter-particle forces. The yield stress resulting from the breakdown and recovery of the network is thus dependent on the characteristic time of the individual test.     

The deformation behavior of polypropylene film under high strain rates

The relationship between stress and strain for polypropylene film was studied under strain rates from 0.13 to 5.21 s^?1 in order to study the deformation behavior of film under higher strain rates than previous studies. Uniform thickness was obtained in the strain rates from 2.08 to 5.21 s^?1 at 435 K, or from 2.08 to 3.13 s^?1 at 437 K. The temperature rise of film due to the generation of heat from plastic strain influenced the relationship between stress and strain, in particular, at high strain rates and low temperature. Material constants for the constitutive equation of film were determined using the measurements from 2.08 to 5.21 s^?1 at 435 K and from 2.08 to 3.13 s^?1 at 437 K. Film thicknesses during and after transverse direction stretching were successfully predicted by applying the material constants obtained. The authors concluded that the material constants should be determined by applying the stretching conditions, under which there is little or no effect from heat generation and under which film can be stretched uniformly in thickness. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Aging of air-corona-treated polypropylene film

X-ray photoelectron spectroscopy (ESCA), wettability measurements, and an ink adhesion test were used to characterize changes in the surface properties of air-corona-treated polypropylene (PP) films upon aging under a variety of storage conditions. No changes in ESCA O/C atomic ratios as a function of aging were observed for corona-treated PP films. The wettability data indicated a slight decrease in wettability upon aging. Aging did not affect ink adhesion for the particular PP and ink studied. The responses obtained were independent of the various film storage conditions employed. The slight decrease in wettability observed upon aging was attributed to reorientation of oxidized functionalities within the surface region.     

聚丙烯中挥发性有机物释放行为的研究

采用自动吹扫捕集-气相色谱-质谱联用法研究了聚丙烯(PP)中挥发性有机物(VOC)的种类、含量以及加热温度、加热时间对VOC释放行为的影响。结果表明:不同牌号的PP在一定温度下可释放出多达50余种VOC,其中绝大部分是长碳链的烷烃;加热温度对PP中VOC的释放有显著影响;在不同温度下,不同牌号PP的总挥发性有机物(TVOC)的释放量不同;TVOC释放量随加热时间的增加而缓慢增加,直至趋于稳定。     

Kinetic parameters in polypropylene degradation from DTA traces

A novel and relatively simple procedure is described for the estimation of kinetic parameters in pyrolyses from DTA traces. The expressions derived are tested by utilizing data from experimental thermograms. Calculated values of parameters agree well with reported values.     

Pullout behavior of polypropylene fibers from cementitious matrix

A comprehensive experimental investigation was performed to understand the pullout behavior of polypropylene fibers from a cementitious matrix. The effect of embedded length on the pullout characteristics, the development of the interfacial bond with age of curing of matrix and the effect of exposure to degrading environments, like seawater and salt water, on the interfacial bond between the fibers and cementitious matrix were studied. The aim of these experiments was to understand the properties of fiber/matrix interface, which are of primary significance in predicting the overall behavior of fiber-reinforced cement-based composites. Polypropylene fibers have a weak bond with cementitious matrix because of smooth surface of fibers, which does not allow for sufficient friction to develop between the two. In this study a new method to improve the frictional bond by means of mechanical indentations of fibers was also proposed. The bonding performance was characterized by means of pullout tests of the plain and modified fibers from a cementitious matrix. An optimum level of fiber modification for maximization of bond efficiency was determined experimentally.     

Transparency of recycled polypropylene film

Turbidity of quenched polypropylene films was measured as a function of the film thickness and number of times film was recycled. Turbidity τ is defined by τ = (1/d) ln (I_o/I_t), where I_o and I_t are the intensity of the incident and transmitted lights, respectively, and d is the thickness of the sample. We assume here that most of the attenuation of light is due to scattering from superstructure in the film, such as spherulites, since no characteristic absorption bands are present in the wavelength region studied in this work. Turbidity varied sigmoidally with film thickness. It remained constant when the film thickness was lower than ca. 400 μm and then increased with film thickness and reached a plateau around 800 μm. When the film preparation was repeated, turbidity increased exponentially with the number of recycles. The spherulite size, however, was an invariant against the number of recycles and was dependent upon film thickness. The variation of turbidity with film thickness and the number of recycles is discussed.     

Studies on biaxial stretching of polypropylene film. IX. Melting behavior of biaxially stretched film in one step

Melting temperature of a film biaxially stretched in one step in air at 152 or 140°C increases with increase of vA, whereas heat of fusion and density decrease with increase of vA, where vA is the degree of stretching in area. The rapid decrease in density occurs for vA > 10. Extrapolation of the plot of the density versus vA^?1/2 gives a value of 0.870 g/cm³ at infinite vA, which has been reported as the amorphous density of isotactic polypropylene by Farrow. This is so because the fine structure of the film becomes more and more amorphous with further stretching and reaches completely amorphous state at infinite vA. The temperature of stretching has a strong effect on the thermal behavior of a film; a low stretching temperature (140°C) brings about lower melting temperature, heat of fusion, and density. Crystallinity after melt press has not so large an effect on the melting behavior as the stretching temperature. Melting temperature and the shape of the thermogram also depend on the heating rate. There is an appropriate heating rate depending on vA which gives the minimum melting temperature. With stretched samples, a small side peak or a shoulder appears at a relatively low temperature in the thermogram when a high heating rate is used.     

Effects of structural parameters on water film properties of transpiring wall reactor

Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone.     

聚丙烯薄膜与铜箔的粘接

通过聚丙烯薄膜和铜箔的表面处理和胶粘剂的选择,对它们的粘接进行了研究,经胶接接头的剥离强度和耐溶剂性能测试,筛选出粘接强度高、耐溶剂性能良好粘接接头,结果铜箔和聚丙烯薄膜的最高的剥离强度可达到14N/cm,与不经任何处理的空白试样相比,增加近7倍。     

High-performance polypropylene film prepared from reactor powders having different characteristics

Ultra-high molecular weight isotactic polypropylene (UHMW-iPP) reactor powders have been successfully ultra drawn below melting temperature (T_m) by a combination of calendar rolling and tensile drawing techniques. Two UHMW-iPP reactor powders having different MWs were synthesized by using the same Ziegler-Natta catalyst system at 70 °C in hexane. The resultant tensile properties increased with increasing draw ratio, due to orientation-crystallization during tensile draw, which was indicated by DSC and WAXD measurements. The film drawn under optimum conditions exhibited the maximum tensile modulus of ∼25 GPa, independent of sample MW, corresponding to 70% of the ultimate modulus of iPP crystal. However, the higher maximum tensile strength of ∼1.0 GPa was achieved for the reactor powder having the higher MW, which is three times as high as those of commercial high-strength iPP tapes. Such a fact that high performances have been achieved by processing from reactor powder state below T_m implies that crystallization with less entanglement occurs during polymerization. When drawability and resultant properties were compared among different iPP reactor powders prepared under different conditions, it was clarified that they were predominantly affected by not only MW but also by the reactor powder morphology, especially surface smoothness.     

Pressure-volume-temperature behavior of polypropylene

The pressure-volume-temperature behavior for both solid and molten polypropylene was determined for pressures up to 618 atmospheres. These data were measured with a newly developed compressibility device capable of obtaining precise and accurate data. Compressibilities calculated from the experimental data compared favorably to the limited existing literature data. Constants were determined for the Spencer-Gilmore polymer equation of state for both the solid and molten material.     

Effect of synthesis parameters in polyaniline: influence on yield and thermal behavior

Summary Influence of chemical polymerization conditions on the yield and thermal behavior of PANI doped Dodecylbenzensulfonic (DBS) was studied by means of a 2⁴ factorial experimental design. These conditions included temperature, concentration of dopant, concentration of oxidant and stirring rate. It was found that the thermogravimetric behavior was not sensitive to any of the conditions tested. By contrast, the yield was dependent on three of the variables studied. For 10 mmol of aniline, the maximum yield was obtained when temperature, concentration of dopant, concentration of oxidant and stirring rate were 25 °C, 27 mmol, 11.5 mmol and 500 rpm, respectively. The most important effects on the yield are the main effect of oxidant (APS), the interaction dopant concentration-stirring rate and the three-factor interaction effect of dopant concentration-oxidant concentration-stirring rate. The prediction equation is: Mass PANI (g) = 1,5920 + 0,0477 DBS + 0,3496 APS + 0,1080 rpm + 0,0533 DBS*APS + 0,2504 DBS*rpm + 0,0959 APS*rpm + 0,2333 DBS*APS*rpm     

Drawing behavior of polyblend fibers from polypropylene and liquid crystal polymers

Polyblend fibers were made from mixtures of polypropylene (PP) and thermotropic liquid crystal polymers (LCPs). The as-spun fibers were drawn to produce the oriented structure for the PP matrix. The LCPs were found to exist in thin and long fibrils in the as-spun fibers; after drawing, they were split into short fragments. From a simplified model whereby a single LCP fibril is embedded in a PP matrix fiber, it was calculated out that the length of the LCP fibril in the drawn fiber is directly proportional to the fibril diameter and tenacity, and is reversely proportional to the compressional stress on the fibril and the friction coefficient between the fibril and the surrounding matrix. With regard to the drawing conditions, it was found that a long length of the LCP fibrils can be preserved by increasing the drawing temperature, or by reducing the draw rate. The effect of two-stage drawing on the LCP phase morphology was also studied in the present work. © 1994 John Wiley & Sons, Inc.     

Structure of blown film from blends of polyethylene and high melt strength polypropylene

The structure of blown film processed from linear low density polyethylene blended with up to 30 wt[percnt] of a high melt strength polypropylene (hmsPP) was examined using primarily atomic force microscopy and wide angle X-ray scattering. The study focused on two polyethylene resins with the same density: a conventional Ziegler-Natta catalyzed linear low density polyethylene (znPE) and a blend of a Ziegler-Natta catalyzed and a metallocene catalyzed linear low density polyethylene (zn/mPE). Parallel characterization was performed on blown film of the hmsPP and blown film of each of the polyethylene resins. In films of the blends, the hmsPP was well-dispersed in the polyethylene matrix as elongated domains. In the domains, the hmsPP crystallized as planar row-nucleated structures with the long axis of the lamellae perpendicular to the extrusion direction. Row-nucleated hmsPP lamellae provided a template for epitaxial crystallization of polyethylene lamellae. The 42° angle of the lattice match imparted a characteristic herringbone texture to the polyethylene. Blending with hmsPP increased the tensile modulus and strength of polyethylene film without significantly affecting the ultimate elongation.     

Orientation and crystallinity in film casting of polypropylene

In the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422     

The structural evolution and lithiation behavior of vacuum-deposited Si film with high reversible capacity

The silicon film (6 μm) was prepared by vacuum deposition method on a surface modified copper foil as anode for lithium-ion batteries with high capacity and long cycle life. The modified copper foil has a rough and pyramid-like surface which helps the deposited Si film to connect toughly. The deposited hill-like Si is favorable to reduce the mechanical stress coming from the volume expansion and shrinkage of active materials during lithiation and de-lithiation. Moreover, the Si film exists mostly in an amorphous state. After cycling, partial amorphous phase transforms into the polycrystalline Si grains, forming a combination of amorphous and crystalline structure. Cyclic voltammograms (CVs) and electrochemical impedance spectra (EIS) research indicate that the vacuum-deposited thick Si film has a good reversibility of lithiation/de-lithiation. As a consequence, the thick Si film exhibits an excellent cycling performance with high reversible capacity.     

Determination of effective capacitance and film thickness from constant-phase-element parameters

Two different mathematical formulas for estimating effective capacitance from Constant-Phase-Element (CPE) parameters, taken from the literature, are associated unambiguously with either surface or normal time-constant distributions. Application to different systems are used to illustrate the importance of using the correct formula that corresponds to a given type of distribution. Experiments and simulations are used to show that the effective capacitance obtained for a normal distribution yields correct values for the film thickness under conditions where the local resistivity does not vary significantly. When the local resistivity varies considerably over the thickness of a film, the experimental frequency range may preclude observation of the capacitance contribution of a portion of the film, resulting in under prediction of the film thickness.