Method for producing conductive polymeric coatings with positive temperature coefficients of resistivity and articles made therefrom
First Claim
1. A method for making a spreadable conductive polymeric coating having a positive temperature coefficient of resistivity, comprising the following sequential steps:
- placing an aromatic solvent in a heated stirring vessel, stirring, and heating to a temperature between 40 and 60 degrees Celsius;
adding a quantity of substrate-forming material selected from the group consisting of thermoplastic resins, uncured thermosetting resins, and elastomers, which contains no diene monomer, equal to 25% to 40%, by weight, of a conductor powder to be added in a later step and continuing to stir;
adding a quantity of a paraffin equal to 25% to 40%, by weight, of the conductor powder to be added and continuing to stir until all solids are dissolved;
adding a fine conductor powder selected from the group consisting of graphite, carbon black, metal powder, metal-coated microbeads, and mixtures thereof, and continuing to stir until a smooth paste is formed; and
mix-kneading the paste until a substantially uniform dispersion of the fine conductor powder in the paste is achieved.
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Abstract
A method is provided for making a spreadable conductive polymeric coating having a positive temperature coefficient of resistivity including the steps of mixing aromatic solvents in a heated vessel, stirring, and heating to a temperature between 40 and 60 degrees Celsius; adding a quantity of substrate-forming elastomer, which contains no diene monomer, equal to 25% to 40%, by weight, of a conductor powder to be added in a later step; adding a quantity of a paraffin equal to 25% to 40%, by weight, by weight, of the conductor powder to be added and continuing to stir until all solids are dissolved; adding a fine conductor powder and continuing to stir until a smooth paste is formed; and mix-kneading the paste until a substantially uniform dispersion of the fine conductor powder in the paste is achieved. The paste, when suitably thinned, can be screen printed or otherwise spread on a wide variety of surfaces and thermally cured to form a thin conductive layer having a PTC of resistivity for use in heating without the need for thermostatic control of the temperature. The pastes can be formulated for a variety of PTCs.
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Citations
16 Claims
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1. A method for making a spreadable conductive polymeric coating having a positive temperature coefficient of resistivity, comprising the following sequential steps:
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placing an aromatic solvent in a heated stirring vessel, stirring, and heating to a temperature between 40 and 60 degrees Celsius; adding a quantity of substrate-forming material selected from the group consisting of thermoplastic resins, uncured thermosetting resins, and elastomers, which contains no diene monomer, equal to 25% to 40%, by weight, of a conductor powder to be added in a later step and continuing to stir; adding a quantity of a paraffin equal to 25% to 40%, by weight, of the conductor powder to be added and continuing to stir until all solids are dissolved; adding a fine conductor powder selected from the group consisting of graphite, carbon black, metal powder, metal-coated microbeads, and mixtures thereof, and continuing to stir until a smooth paste is formed; and mix-kneading the paste until a substantially uniform dispersion of the fine conductor powder in the paste is achieved. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification