Research Survey of conductive silicon rubber

Silicone rubber has good heat resistance , weather resistance and cold resistance , but also with other elastomers can not be achieved on the chemical and physical stability. However, the poor performance of the ordinary conductive silicon rubber , electrically conductive filler may be added to improve the conductivity, the conductive fillers are commonly used in metal powder ( such as silver powder, copper powder and nickel powder , etc. ) and non-metallic materials ( such as graphite , carbon black, carbon nanotubes conductive fibers, etc. ) . Compared with the metal powder , a conductive non-metallic materials , although the performance is poor, but to ensure the physical properties of silicone rubber. Here is a brief overview of reducing under study conductive silicone rubber :

　　A conductive silicone rubber conductive paths conductivity mechanism and theory

　　Early considered from the conductivity of the conductive polymer in the polymer dispersed conductive particles contact each other , i.e., the conductive paths theory ; conductivity of the conductive composite material from the combined effect of the matrix and the filler is determined . When the amount of the conductive particles is small, the conductive particles are uniformly dispersed in an insulating matrix , there is no contact between the conductive particles , and therefore the matrix material is in its insulation. With the addition of conductive particles is increased, the pitch of the conductive particles becomes small, and the contact portion of the particles interact and mesh to form a similar linear form in the system , when increasing the amount of conductive particles to a certain extent , the performance of the composite material good electrical conductivity , which is the result of the formation of the conductive particles contact each passage . Forming a conductive network so that the maximum in the system is the key to improve conductive properties .

　　Second, the classification of conductive silicone rubber

　　A metal powder -filled

　　Metal powders are good electrical conductors , the metal powder is filled into the silicone rubber can improve its conductivity.

　　2 , non-metallic powder -filled

　　Some non-metallic powder having high electrical conductivity , which was filled into a silicone rubber , can be obtained not only the good conductivity of silicone rubber , silicone rubber also able to maintain the original performance advantages.

　　Third, the electrical properties of the conductive silicone rubber

　　1 , piezoresistive effect

　　The piezoresistive effect refers to the material is deformed by external force , the resistivity change phenomenon. Found that carbon black filled conductive silicone rubber resistivity increases as the external pressure increases first and then decreases with the increasing amount of filler , the critical pressure. Xie springs n with exponential relaxation equation and fitting silicone rubber relaxation in the external force , the results show that the greater the force , the shorter the rubber relaxation time . At the same time they use the quantum fluctuations tunnel conductivity according to equation describes the relationship between the theory of the balance of resistance and conductive rubber tension .

　　2, the resistance-temperature characteristic

　　Resistance-temperature characteristic is the resistance changes with temperature change phenomenon includes three types: a positive temperature coefficient , a negative temperature coefficient and the critical temperature coefficient.

　　Fourth, to improve the properties of conductive silicon rubber conductive pathway

　　1 , the development of new conductive filler

　　Development of nano- and ultrafine conductive silicone rubber conductive filler is to improve the performance of one of the ways .

　　2, the conductive filler surface-modified

　　Research shows that the use of tri -butyl peroxide vinyl silane ( coupling VTPS) of silver-plated copper surface treatment , both to improve the performance of filled silicone rubber mixing process , but also improve the added amount of silver-plated copper , but also to improve the binding of silver-plated copper and silicon rubber.

　　3 , the optimization process

　　Process is an important factor in the conductive properties of the silicone rubber . The study found that larger silicone rubber and filler mixing methods on the filler dispersion . Using a three-roll mill mixing, uniform distribution of carbon black particles , the presence of agglomeration ; mixing using high-speed mixer , a uniform distribution of carbon black particles , little clumping . In addition , the mixing intensity is too large or too long mixing time but will reduce the conductivity properties of the silicon . Curing time and curing temperature of the conductive properties and physical properties of the conductive silicone rubber is also affected.

　　With the changing times, conductive silicon rubber has become a new functional materials , electromagnetic shielding, regard conductive, antistatic , automatic control and positive temperature coefficient of the material and the planar heating element and so has broad application prospects . However, compared with other electrically conductive material , the lower the conductivity of the conductive silicone rubber , can not be applied on many occasions . Therefore, the study of the mechanism of conductivity and conductivity model should also vigorously develop new conductive filler, research matrix and conductive filler composite technology, and constantly improve the conductivity of conductive silicone rubber.