Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity....Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity.In order to evaluate the mechanism on recovery of the orientation,we processed the molding under the condition of different thermal compressive strains with modified hot-rolling machine.The stability of the molding's conductivity after rolling was studied under the action of alternated loading.The disoriented behavior of the microstructures during rolling was observed by SEM and 2 D-WAXD,and the degree of orientation of CNT was calculated.The conductivity of the sample was measured using a standard two-terminal DC resistor.The results showed that the deformation resistance in the rolling direction was greater than that in the transverse deformation under the action of large thermal compressive strain.The samples would mainly deform in the transverse direction and not elongate in the direction of the rolling,which could speed up the recovery of the orientation structure and reduce the anisotropy of the conductivity.The recovery speed of the orientation was related to the level of the thermal compressive strain.After the hotrolling processing,the stability of the sample's conductivity under the alternating load was improved because of the effect induced by polymer strengthening.展开更多
The phase morphology and thermal behavior of various isotactic polypropylene （PP）/linear low density polyethylene （LLDPE） blends were investigated with aid of scanning electron microscopy （SEM） and differential ...The phase morphology and thermal behavior of various isotactic polypropylene （PP）/linear low density polyethylene （LLDPE） blends were investigated with aid of scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）, respectively. The effect of barrel （melt） temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that： first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.展开更多
Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has bee...Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.展开更多
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 injecti...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.展开更多
To improve the slab quality, a kind of non-sinusoidal oscillation technique of mold driven by elliptic gears was developed. The waveform functions of non-sinusoidal oscillation were determined, and the calculation met...To improve the slab quality, a kind of non-sinusoidal oscillation technique of mold driven by elliptic gears was developed. The waveform functions of non-sinusoidal oscillation were determined, and the calculation method and curves of technological parameters for non-sinusoidal oscillation were given. At the case of waveform deviation factor a equal to 0.31 and oscillation amplitude h equal to ±2.7 mm, the relationship between oscillation frequency and casting speed is determined, and the technological parameters for non-sinusoidal oscillation are calculated. The testing results of industrial application indicated that this technique could not only improve the Slab surface quality, but also reduce the steel breakout.展开更多
Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed. The working princi...Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed. The working principle of the non-sinusoidal oscillator was analyzed and the model of the oscillator was validated via simulation software.Then,taking advantage of resonance technology,the hinging force and moment were calculated. The results showed that the hinging force and driving moment reduced,which was useful in reducing the impact of the hinge and prolonging the service life of the bearing. Besides,the best initial spring pressure was 0. 9 times the mold gravity,which improved the oscillation system stability and reduced the load fluctuation and servomotor driving power.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51373048 and U1604253)
文摘Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity.In order to evaluate the mechanism on recovery of the orientation,we processed the molding under the condition of different thermal compressive strains with modified hot-rolling machine.The stability of the molding's conductivity after rolling was studied under the action of alternated loading.The disoriented behavior of the microstructures during rolling was observed by SEM and 2 D-WAXD,and the degree of orientation of CNT was calculated.The conductivity of the sample was measured using a standard two-terminal DC resistor.The results showed that the deformation resistance in the rolling direction was greater than that in the transverse deformation under the action of large thermal compressive strain.The samples would mainly deform in the transverse direction and not elongate in the direction of the rolling,which could speed up the recovery of the orientation structure and reduce the anisotropy of the conductivity.The recovery speed of the orientation was related to the level of the thermal compressive strain.After the hotrolling processing,the stability of the sample's conductivity under the alternating load was improved because of the effect induced by polymer strengthening.
基金supported by the National Natural Science Foundation of China(Nos.50533050,20874064 and 50873063)
文摘The phase morphology and thermal behavior of various isotactic polypropylene （PP）/linear low density polyethylene （LLDPE） blends were investigated with aid of scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）, respectively. The effect of barrel （melt） temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that： first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.
基金National Basic Research Program of China (Grant No. 2004CB719802)Hi-Tech Research and Development Program of China (Grant No. 2006AA03Z113)
文摘Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.
基金This work was supported by the National Natural Science Foundation of China (Nos. 20404008, 50533050, 50373030 and 20490220). This work is subsidized by the Special Funds for Major State Basic Research Projects of China (No. 2003CB615600) by Ministry of Education of China as a key project (No. 104154).
文摘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.
基金Item Sponsored by National Natural Science Foundation of China(51275446)National Natural Science Foundation of China and Baosteel Group Co.,Ltd.(U1260203)Natural Science Foundation of Hebei Province of China(E2012203080)
文摘To improve the slab quality, a kind of non-sinusoidal oscillation technique of mold driven by elliptic gears was developed. The waveform functions of non-sinusoidal oscillation were determined, and the calculation method and curves of technological parameters for non-sinusoidal oscillation were given. At the case of waveform deviation factor a equal to 0.31 and oscillation amplitude h equal to ±2.7 mm, the relationship between oscillation frequency and casting speed is determined, and the technological parameters for non-sinusoidal oscillation are calculated. The testing results of industrial application indicated that this technique could not only improve the Slab surface quality, but also reduce the steel breakout.
基金financially supported by the National Natural Science Foundation of China(51275446, 61503323 )National Natural Science Foundation of China and Baosteel Group Co.,Ltd.(U1260203)Natural Science Foundation of Hebe Province of China(E2016203492)
文摘Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed. The working principle of the non-sinusoidal oscillator was analyzed and the model of the oscillator was validated via simulation software.Then,taking advantage of resonance technology,the hinging force and moment were calculated. The results showed that the hinging force and driving moment reduced,which was useful in reducing the impact of the hinge and prolonging the service life of the bearing. Besides,the best initial spring pressure was 0. 9 times the mold gravity,which improved the oscillation system stability and reduced the load fluctuation and servomotor driving power.
