The Effects Of Hot Stretching On Morphology And Properties Of PET/PE/CB Conductive Composites

Electrical conductive polymer composite is one kind of functional materials that has received much interest in the past two decades. Dispersive-compound electrical conductive composite has received much more attention among them. The electric conduction of this material is gained by filling conductive particles or fibers, such as carbon black, carbon fiber, metallic powder and metallic fiber etc. into one or more polymers. It has many advantages, such as light qualities, light abrasion, easy processing and stable conductibility etc.. In recent years, requirements of markets are increasing. Compared to other conductive fillers, carbon black has the following advantages: gaining random specific conductance by controlling contents, cheap, a great variety of CB with specific properties to choose etc.. So carbon black-filled electrical conductive composite received more interest. In this investigation Carbon black-filled electrical conductive composites of poly(ethylene terephthalate)/polyethylene were first prepared through the single-screw melt-blended extrusion, then drawing, followed by the quenching and subsequent press molding. The relationships among the influencing factors including composition, hot stretching ratio and compatibilizer, morphology and properties of composites were systematically investigated. Positive temperature coefficients effect and crystallization behaviors of composites were preliminarily analyzed. Specific experimental works and conclusions obtained as follows:Preparation of carbon black filled PET/PE blends. First PET and CB were dried in a vacuum oven at 100癈 overnight. Second PET and CB were mixed in an internal mixer and PET/CB compounds were obtained, termed PET/CB "masterbatches". Third the "masterbatches" wereporphyrized, and the "masterbatches" and PE were premixed, and were extruded by an extruder. The extrudate was hot-stretched by a take-up device with two pinching rolls to make the microfibers formation, and then palletized. The resulting blends were subsequently compression molded to obtain 4mm-thick plaques and to hold PET fiber formed during stretching.Properties measurements and characterization of CB-filled electrical conductive composites of PET/PE. Tensile properties and impact properties measurements were done at room temperature. The volume resistivity of rectangular samples was measured using a ZC36 Electrometer and a high 240A voltage supply, for samples with a low resistivity level a DT-9205B digital multimeter was used, silver paint was applied to ensure complete contact between sample and electrodes, namely, to eliminate the contact resistance. The phase morphology of blends was also studied using a JEOL JSM-5900LV scanning electron microscope (SEM).The effect of CB content on morphology and properties of PET/PE/CB composites. Hot stretching ratio (HSR) was maintained at 3.96, CB content was changed. The results indicate that when the CB content increases, the room temperature resistivity of composites decreases. At the CB content of 12phr, the room temperature resistivity of blends sharply reduces, and composites change from insulator to conductor, the value is entitled the percolation threshold; At the CB content of 20phr, the room temperature resistivity of composites achieves 10² Ω cm. But as the CB content increases, the disperse phase (PET phase) changes from nemaline to particles, at the same time mechanical properties of blends decrease.The effect of HSR on morphology and properties of PET/PE/CB composites. When the CB content was maintained at 20phr and HSR was changed. The results showed that as the HSR increases, the room temperature resistivity of blends rapidly decreases. After the HSR reached 3.96, its room temperature resistivity was about 10²Î© cm, and changed very small, its mechanical properties also appreciably changed. But as the HSR increases, the dispersed phase of the blends has some degree orientation. This shows that at some CB content, CB-filled electrical conductive composites have fiber.The effect of...