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1.
Tensile strength and morphology of blends of high‐density polyethylene (HDPE) and polypropylene (PP) obtained by oscillating packing injection molding were investigated via Universal Testing Machine, DSC, and SAXS. Tensile strength is greatly enhanced from 24.5 MPa to more than 90 MPa for pure HDPE and for blends with PP content less than 10 wt %. There exists a sharp decrease of tensile strength when PP content is more than 10 wt %. The shear‐induced morphologies with core in the center, oriented zone surrounding the core and skin layer are observed in the cross‐section areas of the samples. Interestingly, a sharp decrease of oriented zone is seen when PP content is more than 10 wt %, associated with the sharp decrease of tensile strength. DSC result shows double melting peaks with a high‐temperature melting peak that is not present in the endotherm obtained from the central core and obtained from the samples by static packing injection molding, which indicates the existence of shish‐kebab structure in the oriented zone. However, there is no difference of crystallinity between the samples by oscillating and by static packing injection molding. SAXS was used to analyze the complicated morphologies induced by shear stress, and results show that the crystal thickness could be greatly increased under shear stress. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 58–63, 2002 相似文献
2.
S. C. Gagieva T. A. Sukhova D. V. Savinov V. A. Optov N. M. Bravaya Y. M. Belokon' B. M. Bulychev 《应用聚合物科学杂志》2005,95(5):1040-1049
Three new titanium complexes bearing salicylidenimine ligands—bis[(salicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 1 ), bis[(3,5‐di‐tert‐butylsalicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 2 ), and bis[(3,5‐di‐tert‐butylsalicylidene)‐4‐trifluoromethyl‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 3 )—were synthesized. The catalytic activities of 1 – 3 for ethylene polymerization were studied with poly(methylaluminoxane) (MAO) as a cocatalyst. Complex 1 was inactive in ethylene polymerization. Complex 2 at a molar ratio of cocatalyst to pre catalyst of AlMAO/Ti = 400–1600 showed very high activity in ethylene polymerization comparable to that of the most efficient metallocene complexes and titanium compounds with phenoxy imine and indolide imine chelating ligands. It gave linear high‐molecular‐weight polyethylene [weight‐average molecular weight (Mw) ≥ 1,700,000. weight‐average molecular weight/number‐average molecular weight (Mw/Mn) = 4–5] with a melting point of 142°C. The ability of the 2 /MAO system to copolymerize ethylene with hexene‐1 in toluene was analyzed. No measurable incorporation of the comonomer was observed at 1:1 and 2:1 hexene‐1/ethylene molar ratios. However, the addition of hexene‐1 had a considerable stabilizing effect on the ethylene consumption rate and lowered the melting point of the resultant polymer to 132°C. The 2 /MAO system exhibited low activity for propylene polymerization in a medium of the liquid monomer. The polymer that formed was high‐molecular‐weight atactic polypropylene (Mw ～ 870,000, Mw/Mn = 9–10) showing elastomeric behavior. The activity of 3 /MAO in ethylene polymerization was approximately 70 times lower than that of the 2 /MAO system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1040–1049, 2005 相似文献
3.
The effects of two compatibilizing agents, polystyrene–poly(ethylene butylene)–polystyrene copolymer (SEBS) and SEBS‐grafted maleic anhydride (SEBS‐g‐MAH), on the morphology of binary and ternary blends of polyethylene, polypropylene, and polyamide 6,6 were investigated with scanning electron microscopy and melt rheology measurements. The addition of the compatibilizers led to finer dispersions of the particles of the minor component and a decrease in their size; this induced a significant change in the blend morphology. The rheological measurements confirmed the increased interaction between the blend components, especially with SEBS‐g‐MAH as the compatibilizer. New covalent bonds could be expected to form through an amine–anhydride reaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1976–1985, 2004 相似文献
4.
Youhua Hu Chenze Qi Weiming Liu Baoyi Wang Houtian Zheng Xudong Sun Xiaoming Zheng 《应用聚合物科学杂志》2003,90(6):1507-1514
The free‐volume properties of high‐impact polystyrene (HIPS)/polypropylene (PP) and HIPS/high‐density polyethylene (HDPE) blends were investigated by means of positron annihilation lifetime spectroscopy (PALS). The measured results show that the free‐volume holes in the semicrystalline polymers, such as PP and HDPE, were not large enough to accommodate the branched chains and the end groups of the macromolecular chains in HIPS to produce favorable interactions between the semicrystalline polymers and the HIPS polymer in these blends; thus immiscible blends were formed. The weak interaction between two dissimilar polymer molecules only took place in the regions between two amorphous phases. In addition, the observed negative deviations of the longest lifetime intensity and the free‐volume fraction were attributed to the influence of the interfacial polarization during PALS measurement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1507–1514, 2003 相似文献
5.
The crystallization and morphology of very‐low‐density polyethylene (VLDPE) and ultra‐low‐density polyethylene (ULDPE) blends with isotactic polypropylene (PP) were studied by differential scanning calorimetry (DSC) and hot‐stage optical microscopy (HSOM) with polarized light. In particular, the isothermal crystallization of PP in molten PE was investigated. A polypropylene homopolymer was melt‐blended with six types of VLDPEs and ULDPEs, with variations in branch content and length and in molecular weight. All the blends contained 20% PP by mass. It was found that the crystallization temperatures of PP and PE changed in the blends, and the crystallization of PP was affected by branch length and content and by the molecular weight of the PE, indicating a certain degree of miscibility between PP and PE. The isothermal crystallization rate of PP decreased in the blends; in particular, the crystallization rate of PP was slower in the ULDPE with lower MFI, suggesting that crystallization of PP was hindered by PE and that its rate was regulated by the viscosity of ULDPE. HSOM images showed that a portion of the PP crystallized from molten PE, although phase separation was obvious, providing additional information on the miscible behavior between PP and VLDPEs (or ULDPEs). Furthermore, the miscible level between the PP and the ULDPEs was higher than that between the PP and the VLDPEs because the degree of change in the crystallization behavior of the PP and PE was greater in the PP–ULDPE blends. This was possibly a result of the higher branch content in the ULDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1179–1189, 2003 相似文献
6.
An experimental study on crystal structure and morphology of isotactic polypropylene (iPP) subjected to vibration was carried out on a laboratory apparatus. Crystallite size, crystal structure, and crystallinity of iPP under vibration or nonvibration were investigated through differential scanning calorimeter (DSC), wide angle X‐ray diffraction (WAXD), and polarized optical microscopy (POM). The results reveal that at high cooling rate, the crystallinity of samples under vibration decreases, and at low cooling rate it remains constant because of chain relaxation. On the other hand, the sizes of the iPP spherulites under vibration decrease as compared with those without vibration. Taking the relaxation of the iPP chain into consideration, we believe that the influence of vibration conditions on the main α‐form of the iPP crystal is rather complex. An obvious increase of β‐form content in the crystal phase results from the imposition of vibration. The results indicate that the content of β‐iPP is dependent on vibration amplitude and time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2187–2195, 2004 相似文献
7.
The electrical conductivities of various polyolefins filled with a high‐structure carbon black (CB) were studied. Typical percolation behaviors were observed in all of the materials studied. At a critical CB content, which defined the percolation threshold, CB formed conductivity pathways, and resistivity fell sharply from a value characteristic of an insulator into the range of 10–100 Ω cm. The dependence of the percolation threshold on the matrix viscosity was understood in terms of competing effects on CB dispersion during blending and CB flocculation during compression molding. For the conditions used in this study, polypropylene with a melt flow index of about 50 was optimum. Flocculation in the quiescent melt was studied directly by atomic force microscopy. Conductivity pathways formed over time by CB agglomeration. The temperature dependence of the percolation time was described by an Arrhenius relationship. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1799–1805, 2005 相似文献
8.
This article describes results obtained with a process developed for rolling and drawing simultaneously polymer profiles in the solid state. Solid‐state roll drawing has the advantage of being continuous, which allows relatively high production rates and the generation of high deformation ratios with some degree of biaxial orientation. The roll‐drawing process allows the extent of biaxial orientation to be controlled by the adjustment of the tension and compression loads applied to the polymers, in particular semicrystalline thermoplastics. Some experimental results obtained with a four‐station roll‐drawing apparatus are presented, particularly on high‐density polyethylene (HDPE) and polypropylene. The effect of process parameters, such as the gap between the rolls and tension, are discussed. Aspects discussed also include relaxation; structure development in terms of orientation and crystallinity as a function of draw ratio (λ); λ as a function of process parameters; and finally, mechanical and thermal properties as a function of λ. Moduli as high as 25 GPa in the longitudinal direction and about 4 GPa in the transverse direction were obtained with successively rolled, initially thick, HDPE profiles. © 2006 Government of Canada. Exclusive worldwide publication right in the article have been transferred to Wiley Periodicals, Inc. J Appl Polym Sci 102: 3391–3399, 2006 相似文献
9.
Imidovanadium complexes with cyclopentadienyl (Cp) ligands—(Cp)V(?NC6H4Me‐4)Cl2 (1), (Cp)V(?NtBu)Cl2 (2), and (tBuCp)V(?NtBu)Cl2 (3; tBuCp = tert‐butylcyclopentadienyl)—were synthesized through the reaction of imidovanadium trichloride with (trimethylsilyl)cyclopentadiene derivatives. The molecular structure of 3 was determined by X‐ray crystallography. The monocyclopentadienyl complex 1 exhibited moderate activity in combination with methylaluminoxane [MAO; 10.3 kg of polyethylene (mol of V)?1 h?1 atm?1], whereas similar complexes with bulky tBu groups, 2 and 3, were less active. (2‐Methyl‐8‐quinolinolato)imidovanadium complexes, V(?NR)(O ?N)Cl2 (R = C6H3iPr2‐2,6 (4) or n‐hexyl (5), O ?N = 2‐methyl‐8‐quinolinolato), were obtained from the reaction of imidovanadium trichloride with 2‐methyl‐8‐quinolinol. Upon activation with modified MAO, complex 4 showed moderate activities for the polymerization of ethylene at room temperature. The complex 5/MAO system also exhibited moderate activity at 0°C. The polyethylenes obtained by these complexes had considerably high melting points, which indicated the formation of linear polyethylene. Moreover, the 5/dried MAO system showed propylene polymerization activities and produced polymers with considerably high molecular weights and narrow molecular weight distributions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1008–1015, 2005 相似文献
10.
This study was concerned with the structural features and mechanical properties of polypropylene (PP)/low‐density polyethylene (LDPE) blends, which after compounding were modified by the free‐radical grafting of itaconic acid (IA) to produce [PP/LDPE]‐g‐IA in the course of reactive extrusion. To analyze the structural features of the [PP/LDPE]‐g‐IA systems, differential scanning calorimetry and relaxation spectrometry techniques were used. The data were indicative of the incompatibility of PP and LDPE in the [PP/LDPE]‐g‐IA systems on the level of crystalline phases; however, favorable interactions were observed within the amorphous phases of the polymers. Because of these interactions, the crystallization temperature of PP increased by 5–11°C, and that of LDPE increased by 1.3–2.7°C. The rapprochement of their glass‐transition temperatures was observed. The single β‐relaxation peak for the [PP/LDPE]‐g‐IA systems showed that compatibility on the level of structural units was responsible for β relaxation in the homopolymers used. Variations in the ratios of the polymers in the [PP/LDPE]‐g‐IA systems led to both nonadditive and complex changes in the viscoelastic properties as well as mechanical characteristics for the composites. Additions of up to 5 wt % PP strengthened the [PP/LDPE]‐g‐IA blended systems between the glass‐transition temperatures of LDPE and PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1746–1754, 2006 相似文献
11.
The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004 相似文献
12.
An optothermomechanical (OTM) device was designed and constructed for fiber characterization with a double‐beam interference microscope. This device enabled us to correlate both the mechanical properties and the thermal properties with the optical properties of fibers. The OTM device consisted of three parts, which were used for the drawing (stress–strain), cooling, and heating of the fibers. The designed OTM device (cooling and heating) was attached to the Pluta microscope for the determination of the optical properties of high‐density polyethylene (PE) fibers at different temperatures (0–50°C). Also, this OTM device (drawing and heating), connected to the Pluta microscope, was used to study the influence of the temperature (10–50°C) and draw ratio (1–7) simultaneously on the optical properties of polypropylene (PP) fibers. Microinterferograms were provided for illustration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 647–658, 2005 相似文献
13.
Four polyolefin in‐reactor alloys with different compositions and structures were prepared by sequential polymerization. All the alloys were fractionated into five fractions: a random copolymer of ethylene and propylene (25°C fraction), an ethylene–propylene segmented copolymer (90°C fraction), an ethylene homopolymer (110°C fraction), an ethylene–propylene block copolymer (120°C fraction), and a propylene homopolymer plus a minor ethylene homopolymer of high molecular weight (>120°C fraction). The effect of the structure on the morphology and spherulitic growth kinetics of the polypropylene (PP) component in the alloys was investigated. The polyolefin alloys containing a suitable block copolymer fraction and a larger amount of PP had a more homogeneous morphology, and the crystalline particles were smaller. Quenching the polyolefin alloys led to smaller crystallites and a more homogeneous morphology as well. Isothermal crystallization was carried out above the melting temperature of polyethylene, and the growth of PP spherulites was monitored with polarized optical microscopy with a hot stage. The alloys with higher propylene contents exhibited a faster spherulitic growth rate. The fold surface free energy was derived, and it was found that a large amount of block copolymer fractions and random copolymer fractions could reduce the fold surface free energy. The structure of the alloys also affected the crystallization regime of PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 632–638, 2005 相似文献
14.
The aim of this study is the creation of an empirical model that can be used to predict the viscosity of a semicrystalline polymer melt for polymer process control. We have developed an empirical viscosity equation from both analysis and experimentation that takes into consideration the effect of temperature on both the flow behavior and the consistency index in the power law. The analysis is based on previously published literature, whereas the experimental data have been obtained from both the literature and laboratory investigations. The coefficients of the empirical model for low‐density polyethylene and polypropylene have been obtained from the experimental data derived from capillary rheometer measurements in the laboratory. This empirical model is able to produce results matching the experimental data with remarkable accuracy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3045–3057, 2003 相似文献
15.
S. Yamaguchi Y. W. Leong T. Tsujii M. Mizoguchi U. S. Ishiaku H. Hamada 《应用聚合物科学杂志》2005,98(1):294-301
A previous study has shown that the adhesion between the film and substrate of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate was evident with the increases in barrel temperature and injection holding pressure. In this second part of the research work, the crystallinity at the interfacial region (i.e., region between the film and the injected substrate) was extensively studied using FTIR imaging, polarized light microscopy, and DSC in an attempt to determine the level of influence that crystallinity has on the interface and bulk mechanical properties. Consequently, a more thorough and clearer picture of the influence of the inserted film on the interfacial crystallinity and subsequently the substrate mechanical properties, such as peel strength and impact strength, has been revealed. The initial proposition that crystallinity could enhance film–substrate interfacial bonding has been confirmed, judging from the higher peel strength with increasing crystallinity at the interfacial region. Nevertheless, the change in crystallinity was not only confined to the interfacial region. With the film acting as heat‐transfer inhibitor between the injected resin and the mold wall, the total crystal structure of the substrate was substantially altered, which subsequently affected the bulk mechanical properties. The lower impact strength of film‐insert injection‐molded samples compared to that of samples without film inserts provided evidence of how the film could impart inferior properties to the substrate. The difference in cooling rate between the substrate and film might also cause other defects such as warpage and/or residual stress build‐up within the product. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 294–301, 2005 相似文献
16.
A new kind of rosin‐type nucleating agent for polypropylene (PP), the cocrystal of dehydroabietic acid, potassium dehydroabietate, and sodium dehydroabietate, was prepared, and the effects of the nucleating agents on the mechanical and crystallization properties of PP were also studied. The results of differential scanning calorimetry and X‐ray diffraction proved that the cocrystal of dehydroabietic acid and compound alkali dehydroabietate was formed rather than a simple blend of dehydroabietic acid and single alkali dehydroabietate. When it was added to PP, the size of the PP spherulite decreased; the mechanical properties, crystallization temperature, and transparency of PP were substantially improved. Thus, the cocrystal of dehydroabietic acid, potassium dehydroabietate, and sodium dehydroabietate acted as a more effective nucleating agent for PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2137–2141, 2003 相似文献
17.
The hot stretching of thick, extruded sheets at high temperatures is a very important process in the production of finished biaxially oriented polypropylene (BOPP) films with special inner structures. Through a simulation of hot stretching in the machine direction (MD) of the processing of BOPP films, it was found that at high temperatures, the stretching ratio greatly influenced the obtained crystalline structure, as observed by differential scanning calorimetry (DSC). Also, in MD hot stretching, the crystallinity increased by an average of 20%. Wide‐angle X‐ray diffraction patterns of extruded sheet samples with and without stretching confirmed the structural changes shown by DSC, and the results proved that β‐crystal modification did not occur during the MD hot‐stretching process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 686–690, 2003 相似文献
18.
The modification of the polarity and adhesive properties of linear low‐density polyethylene, low‐density polyethylene, and isotactic polypropylene through blending with paraffin wax (Fischer–Tropsch synthesis), grafted by maleic anhydride, was investigated. Maleic anhydride grafted paraffin wax significantly increased the polar component of the total surface free energy of polyolefins. Modified polyolefins also had significantly higher adhesion to the polar substrate, a crosslinked, epoxy‐based resin. The conservation of the good mechanical properties of the blends was observed up to 10 wt % wax, except for isotactic polypropylene blends, for which there was a reduction in the stress and strain at break at wax concentrations higher than 5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3069–3074, 2006 相似文献
19.
The thermal behavior including melting and crystallization behavior and morphological and rheological properties of the blends based on an isotactic polypropylene and a novel maleated elastomeric ethylene copolymer were investigated in this work. The addition of an elastomer to polypropylene (PP) was found not to change the PP crystalline structure significantly when cooled quickly from the melt. On recrystallization at a lower cooling rate, the elastomer promotes the formation of β?pseudohexagonal PP in PP‐rich blends. In elastomer‐rich compositions, heterogeneous nucleation is hindered and homogeneous nucleation takes place. These phenomena are revealed by morphology observation: that, with increasing of the elastomer content, the system undergoes PP continuous, dual‐phase continuity and PP‐dispersed morphologies. The blend viscosity at a low shear rate range increases continuously with increasing elastomer content and shows positive deviations from the additivity rule. In the terminal zone, the dynamic storage modulus of the blends shows positive deviation from the simple mixing rule and the maximum deviation lies in the composition range of dual‐phase continuity which could be caused by a large increase in the interfacial tension. The Cox–Merz rule does not hold for the blends because of the two‐phase heterogeneous structure and its variation in steady and oscillatory shear flow. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3430–3439, 2002 相似文献
20.
The morphologies of the fracture surface under impact and flexural testing of Mg(OH)2/Polypropylene (PP) composites and their modified composites were investigated by scanning electron microscopy. Experimental results indicated that addition of functionalized polypropylene (FPP) and acrylic acid (AA) and the formation of in situ FPP changed the fracture morphologies of Mg(OH)2/PP composites. We believe that addition of these modifiers improved the interfacial interaction and enhanced the interface adhesion between the particle and the matrix in Mg(OH)2/PP composites. The degree of improvement was more significant in Mg(OH)2/PP composites modified by the formation of in situ FPP. At low Mg(OH)2 content, 2 phr AA exhibited a marked effect, but at high Mg(OH)2 content, 4 phr AA afforded good effect. Due to the improved interface adhesion by interface interactions the fracture mechanism transformed from interface debonded fracture into a matrix fracture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2148–2159, 2003 相似文献