Patent Application
20070295714
Many aspects of the present composite and apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present composite and apparatus.
Referring to
The flexible polymer matrix 10 can be selected from the group consisting of silicone elastomer, polyurethane, epoxy resin and combinations thereof. The carbon nanotubes 12 can be either single-walled nanotubes or multi-walled nanotubes. Preferably, a length of the carbon nanotubes 12 is in the range from 1 micrometer to 10 micrometers. Preferably, a percentage of the carbon nanotubes 12 by weight is in the range from 0.1% to 4%.
Referring to
Preferably, an additive is dispersed in the flexible polymer matrix. The additive can be an antioxidant such as N,N′-diphenyl 1,4-phenylenediamine or a flame retardant such as chloroparaffin, chloro-cycloparaffin, tetrachlorophthalic anhydride, phosphate ester, halogen substituted phosphate ester and combinations thereof. The approximate percentage by weight of the flame retardant can be in the range from 1% to 10%.
The flexible electrothermal composite can generate heat at a low level. For example, if 36 volts is applied between two ends of a piece of this kind of electrothermal material having a size of 30 (length)×30 (width)×0.05 (height) centimeters, with carbon nanotubes constituting a percentage by weight of about 2.5% and with an average nanotube length of about 5 micrometers total power consumption should be less than one watt. The flexible electrothermal composite is suitable for use in low temperature heating apparatuses such as seat warmers, electric blankets, heated belts, immersion suits etc.
Compared with electrothermal materials that are comprised of metal or alloy, the flexible electrothermal composite in accordance with the first embodiment has the following advantages. First, the polymer matrix is flexible thus it can deform under external force and resiles when the external force is released. The polymer matrix is less toxic thus it is more suitable for use in a heating apparatus that comes into contact with the human body. The carbon nanotubes form a network in the matrix, the network can improve heat conductivity and intensity of the flexible electrothermal composite.
The flexible electrothermal composite in accordance with the first embodiment can be manufactured by following method, which comprises the steps of:
In step (a), a solution of a polymer precursor is prepared. The polymer precursor generally includes a prepolymer or a monomer. The prepolymer can be selected from the group consisting of silicone elastomer prepolymer, polyurethane prepolymer, epoxy resin prepolymer and combination thereof.
In step (b), carbon nanotubes are immersed in the solution and ultrasonically cleaned. In the preferred embodiment, the carbon nanotubes can be formed by chemical vapor deposition, arch discharge, or laser ablation. The carbon nanotubes may include multi-walled nanotubes, single-walled nanotubes or a mixture thereof. Diameters of the carbon nanotubes are in the range from 1 to 10 micrometers.
In order to avoid the carbon nanotubes conglomerating with each other in the solution, step (b) preferably further includes the steps of: ultrasonically cleaning the solution for a few minutes; disturbing the solution by using an ultrasonic disturber to disperse the conglomerated carbon nanotubes; and ultrasonically cleaning the treated solution for a few minutes to uniformly disperse the carbon nanotubes therein. By means of the disturbing by the ultrasonic disturber and the ultrasonic cleaning, the carbon nanotubes can be effectively and uniformly dispersed.
Step (c) is to polymerize the polymer precursor with an initiator and to obtain a polymer matrix having carbon nanotubes uniformly dispersed therein. In the illustrated embodiment, the initiator includes a solution of ethanol or deionized water having component B of the polyurethane dispersed therein. The initiator is added in the solution of the prepolymer having component A of the polyurethane, in order to polymerize the polymer. A proportion by weight between the initiator and the prepolymer is preferably about 5:1. Then, after ultrasonically cleaning the mixture solution, sediment is collected. The sediment is a polymer matrix having carbon nanotubes therein. In the illustrated embodiment, the obtained polymer is a black grease material. The carbon nanotubes are uniformly dispersed therein.
Referring to
Referring to
Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200610061170.6 | Jun 2006 | CN | national |
