Thermal, Mechanical Sensitivity And Electric-Heating Effect Of Carbon Black/Silicone Rubber Composites

The conductive composite is a kind of functional materials with electrical conductive,sensitive, and electric-heating effect characteristics which have important value in the field oftesting, heating and electronic engineering. The three functional characteristics of the polymermatrix composite filled with carbon black are analyzed with theoretical and experimentalmethods which would provide basic theory and data support for its engineering application.Conductivity is the foundational characteristic of composite materials which aremulti-functional. Through microscopic observation, model simplification and mechanismanalysis the conductive theoretical model of the composites filled with carbon black particle isestablished. The carbon black particles appear as two kinds of structure-"aggregate" and"chain" which connects with "aggregate" according to SEM images. The "aggregate" and"chain" are simplified to "large particles" structures which can be deformed and the carrierstransfer between the "large particles" through mutual contact and the tunneling effect. Aconductive model is established according to the simplified model and the theory of tunneleffect. It is found that the excellent electrical characteristic is mainly due to the conductivenetwork connected by the "aggregate" and "chain". When the carbon black filling quantityexceeds4%, the fine conductive filled conductive composite can be obtained; the conductivecomposite materials have pure resistance property when DC voltage or constant low frequencyAC voltage motivating and the samples'impedance frequency changes with the AC frequencyshows that the "tunnel effect" hypothesis in the conductive model is correct.The electric heating effect is analyzed through the conductive mechanism and model. Theelectrons flow directionally in the conductive network which leads directly to electric heatingeffect when the voltage loading. The large area electric-heating film is produced for the firsttime by the carbon black filled rubber based conductive composite through the formulationand process design. The electric-heating test shows that the element' heating power is affectedby the load voltage and resistance. Large area electric-heating film test results show that thepower of the heating film which thickness is117μm and the carbon content is14%reach1430.46W/m~2at220V voltage. The film is a kind of high-quality planar heating material.The sensitivity test shows that the tensile strain-resistance curves when the value up to25%and the test temperature reaches-35℃have good linear relationship and repeatability. The pressure-resistance curves have the same results when the stress reaches20MPa. After manytemperature cycles, the repeatability of temperature-resistance curves are also better. It isfound that the mechanic-resistance sensitivity coefficient is about2.5to3, significantly greaterthan the thermal-resistance sensitivity coefficient (about0.15to0.6). A lot of testing andanalysis results show that, compared with the common "body structure" sample, the "filmstructure" sample has more superior characteristics in electric-heating and sensitivity. Thethermal-resistance and mechanic-resistance model are established according to the conductivemodel. The mechanic-resistance model is established based on the tunnel effect theory and thedeformation coefficient λ is introduced in the first time. The new thermal-resistance model twois established based on the mechanic-resistance model and the thermal-mechanic-resistancemodel is established according to the two models. It's showed that the "tunnel resistance"existing in the conductive network is decided mainly to sensitivity of the composite. The λ andβ fitted values are obtained according to the multiple sets of test data which are set into themodel to be calculated. The comparison results show that the calculated and experimentalvalues agree well. Finally, one-dimensional compression stress-resistance model is establishedthrough the introduction of the modulus E′.Finally, according to the conductive, electric-heating effect mechanism andthermal-mechanical-resistance model of carbon black/silicone rubber compound material, thelarge area electrical-heating film, one-dimensional large deformation test film components andlarge area sensing film are developed based on a mass of experimental study. The functioncharacteristics of the film are studied at application foundation further. The heating test oflarge area heating thin film shows that the electric-heating film has excellent heating capacity,stable power and efficiency reached99%; one-dimensional large deformation test shows thatthe sensing element produced by the conductive composite materials can be used inengineering and the field of experimental for testing; The Stress and deformation distributiontest technology is developed firstly through the EIT technique and the sensitive film. Thepreliminary test results showed that the technique can detect the unusual resistance (stress,deformation) value.