Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer (LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving a slit die in open air. The morphology, structu...Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer (LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving a slit die in open air. The morphology, structure and mechanical properties of the resulting strands were studied as a function of LCP content and draw ratio. It was found that the thermal and mechanical properties of the matrix phase did not change dramatically with the amount of LCP and draw ratio, but the orientation of LCP phase could be increased with draw ratio. The mechanical properties of the strands could be improved by moderately drawing the melts. Wide angle X-ray diffraction suggested that the improvement in tensile strength of the strands was due to the resultant fibrillation of LCP phase and enhanced molecular orientation. Morphological observation indicated that excessive drawing of the strands could lead to the break down of the microfibrils of LCP and thus resulted in the decrease of mechanical strength.展开更多
The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (...The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.展开更多
The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene- styrene(ABS)over a composition range of 30-70 wt% using a styrene-maleic anhydride(SMA)copolymer as the com...The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene- styrene(ABS)over a composition range of 30-70 wt% using a styrene-maleic anhydride(SMA)copolymer as the compatibilizing agent with a constant content(5phr)was investigated.The results of the scanning electron microscope (SEM)observation revealed that compared with the binary blends of nylon 6 and ABS,the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of ny...展开更多
As a long-term project aimed at developing super polyolefin blends, in this paper we summarize our work on themechanical reinforcement and phase morphology of polyolefin blends achieved by dynamic packing injection mo...As a long-term project aimed at developing super polyolefin blends, in this paper we summarize our work on themechanical reinforcement and phase morphology of polyolefin blends achieved by dynamic packing injection molding(DPIM). The main feature of this technology is that the specimen is forced to move repeatedly in the model by two pistonsthat move reversibly with the same frequency during cooling, which results in preferential orientation of the dispersed phaseas well as the matrix. The typical morphology of samples obtained via DPIM is a shear-induced morphology with a core inthe center, an oriented zone surrounding the core and a skin layer in the cross-section areas. Shear-induced phase dissolutionat a higher shear rate but phase separation at low shear rates is evident from AFM examination of LLDPE/PP (50/50) blends.The super polyolefin blends having high modulus (1.9-2.2 GPa), high tensile strength (100-120 MPa) and high impactstrength (6 times as that of pure HDPE) have been prepared by controlling the phase separation, molecular orientation andcrystal morphology.展开更多
Bi 0.5 Sb 1.5 Te 3/polyaniline composites were prepared by mechanical blending and in situ polymerization, and their transport properties were measured. It was found that for the composites with 1%, 3%, 5% and 7% poly...Bi 0.5 Sb 1.5 Te 3/polyaniline composites were prepared by mechanical blending and in situ polymerization, and their transport properties were measured. It was found that for the composites with 1%, 3%, 5% and 7% polyaniline (mass fraction) respectively, which were prepared by mechanical blending, the power factors decrease by about 30%, 50%, 55% and 65% compared with the Bi 0.5 Sb 1.5 Te 3 samples, which is mainly due to the remarkable decreases of the electrical conductivity. The electrical conductivity and power factor of the composites samples with 7% polyaniline prepared by in situ polymerization are higher by about 65% and 60%, respectively, than that of the corresponding samples prepared by mechanical blending.展开更多
以过氧化二异丙苯 (DCP)为引发剂 ,甲基丙烯酸缩水甘油酯 (GMA)为活性单体 ,高抗冲苯乙烯(HIPS)通过熔融接枝制得了功能化的高抗冲聚苯乙烯接枝物 (HIPS g GMA)。用红外光谱和电子能谱对其结构进行了表征。HIPS g GMA的红外谱图 ,证明GM...以过氧化二异丙苯 (DCP)为引发剂 ,甲基丙烯酸缩水甘油酯 (GMA)为活性单体 ,高抗冲苯乙烯(HIPS)通过熔融接枝制得了功能化的高抗冲聚苯乙烯接枝物 (HIPS g GMA)。用红外光谱和电子能谱对其结构进行了表征。HIPS g GMA的红外谱图 ,证明GMA已经接枝到HIPS上。电子能谱分析也提供了相似的结论。研究了单体浓度和DCP用量对产物接枝率的影响 ,并用化学滴定方法测定了接枝物的接枝率。用DSC、SEM、WAXD、DMA等研究了PBT/HIPS和PBT/HIPS g GMA的结晶、形态结构、动态力学性能及力学性能随组成的变化。SEM及DMA分析表明增容后体系的相容性得到改善 ,力学性能有较大提高。展开更多
文摘Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer (LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving a slit die in open air. The morphology, structure and mechanical properties of the resulting strands were studied as a function of LCP content and draw ratio. It was found that the thermal and mechanical properties of the matrix phase did not change dramatically with the amount of LCP and draw ratio, but the orientation of LCP phase could be increased with draw ratio. The mechanical properties of the strands could be improved by moderately drawing the melts. Wide angle X-ray diffraction suggested that the improvement in tensile strength of the strands was due to the resultant fibrillation of LCP phase and enhanced molecular orientation. Morphological observation indicated that excessive drawing of the strands could lead to the break down of the microfibrils of LCP and thus resulted in the decrease of mechanical strength.
文摘The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.
基金This work was supported by the National Science Funds for GuiZhou Province Science Projects(No.GY-2005-3036)the Special Funds for Major State Basic Research Projects(No.2005CB623802).
文摘The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene- styrene(ABS)over a composition range of 30-70 wt% using a styrene-maleic anhydride(SMA)copolymer as the compatibilizing agent with a constant content(5phr)was investigated.The results of the scanning electron microscope (SEM)observation revealed that compared with the binary blends of nylon 6 and ABS,the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of ny...
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29992535) and the China National Distinguished Young Investigator Fund.
文摘As a long-term project aimed at developing super polyolefin blends, in this paper we summarize our work on themechanical reinforcement and phase morphology of polyolefin blends achieved by dynamic packing injection molding(DPIM). The main feature of this technology is that the specimen is forced to move repeatedly in the model by two pistonsthat move reversibly with the same frequency during cooling, which results in preferential orientation of the dispersed phaseas well as the matrix. The typical morphology of samples obtained via DPIM is a shear-induced morphology with a core inthe center, an oriented zone surrounding the core and a skin layer in the cross-section areas. Shear-induced phase dissolutionat a higher shear rate but phase separation at low shear rates is evident from AFM examination of LLDPE/PP (50/50) blends.The super polyolefin blends having high modulus (1.9-2.2 GPa), high tensile strength (100-120 MPa) and high impactstrength (6 times as that of pure HDPE) have been prepared by controlling the phase separation, molecular orientation andcrystal morphology.
文摘Bi 0.5 Sb 1.5 Te 3/polyaniline composites were prepared by mechanical blending and in situ polymerization, and their transport properties were measured. It was found that for the composites with 1%, 3%, 5% and 7% polyaniline (mass fraction) respectively, which were prepared by mechanical blending, the power factors decrease by about 30%, 50%, 55% and 65% compared with the Bi 0.5 Sb 1.5 Te 3 samples, which is mainly due to the remarkable decreases of the electrical conductivity. The electrical conductivity and power factor of the composites samples with 7% polyaniline prepared by in situ polymerization are higher by about 65% and 60%, respectively, than that of the corresponding samples prepared by mechanical blending.
文摘以过氧化二异丙苯 (DCP)为引发剂 ,甲基丙烯酸缩水甘油酯 (GMA)为活性单体 ,高抗冲苯乙烯(HIPS)通过熔融接枝制得了功能化的高抗冲聚苯乙烯接枝物 (HIPS g GMA)。用红外光谱和电子能谱对其结构进行了表征。HIPS g GMA的红外谱图 ,证明GMA已经接枝到HIPS上。电子能谱分析也提供了相似的结论。研究了单体浓度和DCP用量对产物接枝率的影响 ,并用化学滴定方法测定了接枝物的接枝率。用DSC、SEM、WAXD、DMA等研究了PBT/HIPS和PBT/HIPS g GMA的结晶、形态结构、动态力学性能及力学性能随组成的变化。SEM及DMA分析表明增容后体系的相容性得到改善 ,力学性能有较大提高。
