Conductive polyvinylidene fluoride（PVDF）matrix composites filled with graphited fiber（GF）or carbon fiber（CF）were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polym...Conductive polyvinylidene fluoride（PVDF）matrix composites filled with graphited fiber（GF）or carbon fiber（CF）were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polymer matrix were studied by scanning electron microscope（SEM）and optical microscope（OM）observations,respectively. The differences in the positive temperature coefficient（PTC）effects of the composites were mainly attributed to inter-fiber contact ability.The elimination of the negative temperature coefficient（NTC）effect for CF/PVDF composite was because of an increase in the viscosity of the polymer matrix.With the same filler content,CF could be more effective,to eliminate the NTC effect when compared with GF.Addition of 2%CF（mass fraction）in the PVDF composite with 7%GF（mass fraction）could effectively eliminate the NTC phenomenon of the composite.展开更多
正温度系数(Positive temperature coefficient, PTC)材料是一种电阻随温度变化的热控功能材料,然而,传统的PTC材料由于高室温电阻率以及负温度系数效应而限制了其在电子设备热控领域的应用。本文基于石蜡/乙烯–醋酸乙烯酯共聚物混合基...正温度系数(Positive temperature coefficient, PTC)材料是一种电阻随温度变化的热控功能材料,然而,传统的PTC材料由于高室温电阻率以及负温度系数效应而限制了其在电子设备热控领域的应用。本文基于石蜡/乙烯–醋酸乙烯酯共聚物混合基体,利用多壁碳纳米管和炭黑杂化填料的协同效应制备得到具有室温居里点、低室温电阻率和优异电阻正温度效应的新型PTC材料。研究了基体配比、填料含量对室温电阻率和PTC性能的影响,并采用羧甲基纤维素对其负温度系数效应现象进行改善。此外,对新型PTC材料的自适应热控性能进行了研究和分析。研究发现:与普通的电阻加热器相比,PTC加热器具有自适应控温能力,并且在没有任何外部控制系统的条件下可以将被控设备的温度控制在正常工作温度范围内。展开更多
The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stag...The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stage, PAS particles in the crystal region of PE are expelled to the amorphous region; in the second stage, PAS particles aggregate due to small surface areas and PE chains are adjusted continuously, which makes the crystal region complete; PAS particles are separated from each other and the total energy increases in the third stage. During the whole dispersing process, PAS particles are more stable in the amorphous region than in the crystal region. All the simulation results are in good agreement with the experimental results.展开更多
文摘为提高聚乙烯/炭黑导电复合材料的PTC性能,将高分子PTC复合材料热处理一定时间后,再分别通过淬火、慢火、空气冷却等方式进行处理,室温放置一定时间后进行电气性能测试.结果表明:慢火处理比淬火和空气冷却处理更能降低样品的电阻;在低于基体熔融温度下处理,可以使样品电阻降低;而在高于熔融温度下处理时,可以使电阻增大,但却缩短了样品的动作时间.在170℃加热后的样品经淬火冷却后,其动作时间缩短为28 s.
基金the National Natural Science Foundation of China(Nos.20771030 and 20671025).
文摘Conductive polyvinylidene fluoride（PVDF）matrix composites filled with graphited fiber（GF）or carbon fiber（CF）were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polymer matrix were studied by scanning electron microscope（SEM）and optical microscope（OM）observations,respectively. The differences in the positive temperature coefficient（PTC）effects of the composites were mainly attributed to inter-fiber contact ability.The elimination of the negative temperature coefficient（NTC）effect for CF/PVDF composite was because of an increase in the viscosity of the polymer matrix.With the same filler content,CF could be more effective,to eliminate the NTC effect when compared with GF.Addition of 2%CF（mass fraction）in the PVDF composite with 7%GF（mass fraction）could effectively eliminate the NTC phenomenon of the composite.
文摘正温度系数(Positive temperature coefficient, PTC)材料是一种电阻随温度变化的热控功能材料,然而,传统的PTC材料由于高室温电阻率以及负温度系数效应而限制了其在电子设备热控领域的应用。本文基于石蜡/乙烯–醋酸乙烯酯共聚物混合基体,利用多壁碳纳米管和炭黑杂化填料的协同效应制备得到具有室温居里点、低室温电阻率和优异电阻正温度效应的新型PTC材料。研究了基体配比、填料含量对室温电阻率和PTC性能的影响,并采用羧甲基纤维素对其负温度系数效应现象进行改善。此外,对新型PTC材料的自适应热控性能进行了研究和分析。研究发现:与普通的电阻加热器相比,PTC加热器具有自适应控温能力,并且在没有任何外部控制系统的条件下可以将被控设备的温度控制在正常工作温度范围内。
文摘The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stage, PAS particles in the crystal region of PE are expelled to the amorphous region; in the second stage, PAS particles aggregate due to small surface areas and PE chains are adjusted continuously, which makes the crystal region complete; PAS particles are separated from each other and the total energy increases in the third stage. During the whole dispersing process, PAS particles are more stable in the amorphous region than in the crystal region. All the simulation results are in good agreement with the experimental results.
