Study On Antistatic Semi-rigid Polyvinyl Chloride

Mine accident is the second cause of unexpected death in our country in late years, just inferior to traffic accident. Coal mine is one of the chief mine accidents, and gas is "No. 1 killer" in coal mine manufacture. Gas accident is mostly caused by unreasonable and trustable ventilating system. The accident may be taken place as gas can not be diluted effectively and timely, and accumulates to a certain content. Polyvinyl chloride (PVC), one of general purpose plastics with high production and low cost, is widely applied in many fields. However, the surface resistivity of PVC is high to 10¹⁴～10¹⁷Ω, resulting in easy accumulation of static. This can ignite some gases easily and lead to a lot of calamities. Therefore, the application of PVC without modification in mine and some chemical plant is restricted. Antistatic PVC composite prepared by filling way has a wide application due to ease for processing and low Cost.In this paper, the influence of carbon black (CB),CaCO₃,resin brand and rubber on properties of PVC/CB composite was studied. The electrical, mechanical and theological properties as well as morphology of these composite were studied by surface resistivity, stress-strain behaviour, izod impact strength, capillary rheometer, torque rheometer, DMA, SEM and so on. The main results are as followings:1. PVC/CB composites prepared by higher polymerization degree PVC resin have lower surface resistivity under the same CB condition. With the decrease of polymerization degree of PVC, the CB networking degree decreases. With the increase of DOP content, the conductivity of PVC/CB composites decreases with the same CB content. Compared with the soft PVC material, CB does better electrical conductivity modification to rigid PVC material.2．With increasing content of CB, the surtace resistivity of PVC/CB composite has an obvious percolation threshold. The influence of different CB brand on the electrical property of PVC/CB is different, resulting in different percolation concentration. The comparison of CB networking factor is as followings: SL-36＞V-XC72＞E900＞acetylene CB. Better electrical conductivity property of PVC/CB composite can be achieved as time is less in the mixing process. Banbury mixer and twin roller processing can attain the same surface resistivity of PVC/CB composite. With the increase of CB content, the tensile strength of PVC/CB composite increases, the elongation at break and impact strength, however, decrease. The vical soften temperature and glass transition temperature (Tg) of PVC/CB composite increase as addition of CB, and the glass transition peak width decreases. With increasing content of CB, balance torque and processing energy consumption increase, the apparent viscosity also increase. CB has little influence on apparent viscosity of PVC/CB composite when its filling content and shear rate is high enough.3. CaCO₃ has little influence on the electrical conductivity of PVC/CB composite. The tensile strength and elongation at break of PVC/CB composite decrease with CaCO₃ content, the impact strength of this material however, increases to a maximum and then gradually decreases with CaCO₃ content. CaCO₃ content has little influence on Tg of PVC/CB composite. With the increase of CaCO₃ content, balance torque and processing energy consumption of material gradually increase, the apparent, viscosity also increases.4. With the increase of NBR content, the surface resisitivity of PVC/CB/NBR gradually decreases, NBR makes against the formation of CB network. The tensile strength and shore hardness (D) of PVC/CB/NBR decrease, and the elongation at break increases with NBR content. With the increase of SBR content, the surface resisitivity decreases, CR makes for the formation of CB network. The tensile strength, shore hardness (D) and elongation at break of PVC/CB/SBR all decrease with increasing content of SBR. CR has the least influence on the formation of CB network among these three kinds of rubber, the surface resisitivity of PVC/CB/CR changes little with increasing CB content.