▎ 摘　　要

NOVELTY - Constant temperature test paper substrate comprises filter paper and coating dispersed on filter paper, where the coating comprises 1-5 pts. wt. graphene oxide, 1 pts. wt. cellulose nanofiber, and 10-50 pts. wt. modified carbon nanotubes. USE - The constant temperature test paper substrate is useful for quick design of the conductive layer. ADVANTAGE - The method: does not causes dispersibility of the carbon nanotubes; ensures the firmness of the heating layer; and improves the heating efficiency. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing constant temperature test paper substrate comprising (i) modifying carbon nanotubes to obtain modified carbon nanotube solution, dissolving naphthalenesulfonic acid in water, where the concentration of the naphthalenesulfonic acid is 5-50 g/l, adding carbon nanotubes to the naphthalenesulfonic acid solution to control the concentration of carbon nanotubes at 10-50 g/l, using ultrasonic cells at normal temperature, crushing, ultrasonically dispersing with 150-300 W power for 20-40 minutes to obtain non-covalent bond-modified carbon nanotubes, using a dialysis membrane with a pore diameter of 0.45 mu m to separate excess naphthalenesulfonic acid, where the dialysis time is 12-36 hours, changing the water for every 6 hours, adsorbing naphthalenesulfonic acid on the carbon nanotube through a n-n bond, and the surface of the carbon nanotube has a sulfonic acid group, (ii) adding mixed solution of graphene oxide and cellulose nanofibers to the modified carbon nanotube solution to obtain a coating, adding graphene oxide powder to a 1% concentration cellulose nanofiber solution, controlling the concentration to 10-50 g/l to form a graphene oxide/cellulose nanofiber solution, mixing the graphene oxide/cellulose nanofiber solution and the modified carbon nanotube solution at the volume ratio of 1:1-10, mixing the mixed solution evenly with a mechanical mixer at the speed of 500-1000 rotations/minute for 10-20 minutes, dispersing with an ultrasonic cell pulverizer at the power of 400-600 W for 10 minute to obtain a coating with a solid content of 2-5 wt.%, (iii) preparing the conductive heating layer and complete the coating by using a laboratory rod coater to prepare and using ordinary filter paper as the substrate, and controlling the coating speed at 0.2-0.5 meter/minute, and (iv) drying the coated paper and cutting to obtain an electric constant temperature test paper, coating, drying in an oven at 60-80 degrees C for 40-60 minutes, after that, performing cutting, where the length and width of the electric constant temperature test paper is 1-5 cm, and the area is 1-20 cm2.