Polymer / Graphite Conductive Composite Material Preparation And Its Properties

Polymer conductive composites have excellent mechanical performance, processability, simple technics and low cost, which cause great attention of the academe and have been significantly applied in numerous fields. Expanded graphite (EG) with loose and multi-pores structure is composed of many nanosheets with the thickness only 30～80nm inside, which has unique advantage to prepare polymer/graphite conductive composites. The novel electrically conductive composites were prepared, which were composed of Poly(ethylene terephthalate) (PET), nylon 6 (PA6) and expanded graphite (EG). The influences of prepared method and EG content on the microstructure, electrical properties, crystallization behavior, thermal property, dynamic mechanical property, mechanical properties were investigated.1. Study on the Preparation, Structure and Properties of PET/EG Conductive CompositesPET/EG conductive composites were prepared by melt-blending method. EG were prepared by high temperature or microwave, and the microstructure were studied by scanning electron microscopy (SEM), infrared ray spectrum (IR) and X-ray diffraction (XRD). The different conductivity of the composites prepared by two kinds of EG were compared. In order to enhance the conductive performance, the epoxy resin was used to modify EG and make EG exfoliate to get nanosheets by ultrasonic. The influences of the two modified methods on the microstructure and the electrical properties were studied detailedly. The results show that PET/EG and PET/EP-EG all have very low percolation threshold value and excellent conductibility, especially the latter. In addition, DSC,XRD,TG,DMA were used to study the crystallization behavior, thermal property and dynamic mechanical property of the composites. The result shows that the EG addition change the crystal velocity and crystallinity. EG increases the dynamic modulus of the composites. 2. Study on the Preparation, Structure and Properties of PA6/EG Conductive CompositesPA6/EG conductive composites were prepared by melt-blending and solution intercalation. The structure changes of the composites before and after preparation were studied by infrared ray spectrum. The influences of the two methods of MM and SI on the microstructure and the electrical properties were investigated by scanning electron microscopy (SEM) and conductivity measurement. The results show that EG is easier to exfoliate into nanosheets using SI method than MM method, thus the latter have more outstanding conductibility. The research results of DSC,XRD,TG and DMA show that the EG addition has some effect on crystallization behavior, thermal property and dynamic mechanical property of the composites.3. Study on the Conductive Composites of Double Percolation SystemAccording to the double percolation in immiscible polymer blends, PA6/PET/EG conductive composites with the percolation threshold lower than 2vol% were prepared by melt-blending using PA6/PET blends as the matrix. SEM,dissolution experimentation,interfacial tension theory were used to study the distribution of EG in the blends system and its influence on the electrical properties. Finally, we get the conclusion that EG distribute selectively in PET matrix. The processability and mechanical performance were also investigated.4. Study on the Percolation Conductive Behavior of the Conductive CompositesUsing classic statistic percolation theory, the conductivity behaviors of the PET/EG,PA6/EG and PA6/PET/EG composites were investigated, and the percolation thresholds and critical exponents (t) were obtain. The nonuniversal critical exponent should be attributed to the anisotropy of conductivity, the tunneling conduction, the particular structure, the anomaly distributing of the particles and so on.