▎ 摘　　要

NOVELTY - High-hardness cardboard comprises 25 pts. wt. pulp, 4-7 pts. wt. chitosan pulp, 24-42 pts. wt. acetic acid, 10-13 pts. wt. acetone, 3-6 pts. wt. sodium hydroxide, 4-7 pts. wt. chloroacetic acid, 15-18 pts. wt. isopropanol, 100 pts. wt. methanol, 4-7 pts. wt. polyetheramine, 1-2 pts. wt. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 2-4 pts. wt. N-hydroxysuccinimide, 3-4 pts. wt. m-xylylene diamine, 9-12 pts. wt.epoxy resin, 7-8 pts. wt. urea-formaldehyde resin, 2-3 pts. wt. boron nitride, 3-6 pts. wt. nano graphene, 1-2 pts. wt. thickener and 1-2 pts. wt. deionized water. USE - High-hardness cardboard. ADVANTAGE - The high-hardness card board has high strength and hardness. The method is simple and can be directly applied to multiple types of paper, at the same time, it further improves the curing effect of the polyether amine to the epoxy resin by grafting the chitosan on polyetheramine. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a preparation method of the high hardness cardboard involves (i) adding 25 pts. wt. of pulp, 200 pts. wt. of deionized water into the reactor, stirring at 300 revolutions per minute (rpm) for 40-60 minutes, then adding 3-6 pts. wt. of nano graphene, 2-3 pts. wt. of boron nitride, and 1-2 pts. wt. of thickener, stirring at 300 rpm for 2-3 hours, and dring to make cardboard; (ii) dissolving 4-7 pts. wt. of chitosan and 24-42 pts. wt. of acetic acid in 10-13 pts. wt. of acetone in the reaction kettle and obtain chitosan acetate; adding 3-6 pts. wt. of sodium hydroxide, 15-18 pts. wt. of isopropanol, stirring at 300-400 rpm at 70 °C, adding 4-7 pts. wt. chloroacetic acid dropwise, for 3-4 hours, and adjusting the pH value after cooling to room temperature, neutralizing, washing and drying with methanol to obtain carboxymethyl chitosan; (iii) adding 4-7 pts. wt. of polyetheramine to the reaction kettle, 100 pts. wt. of deionized water, stirring at 300 rpm, adding carboxymethyl chitosan, 1-2 pts. wt. of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 2-4 pts. wt. of N-hydroxysuccinimide, and continue stirring, controlling the pH of the solution at 5.5, reacting for 3-4 hours, using a dialysis bag for dialysis for 3-5 days, freeze-drying to obtain chitosan grafted polyetheramine; and (iv) adding 3-4 pts. wt. of m-xylylenediamine, 9-12 pts. wt. of epoxy resin, 7-8 pts. wt. of urea-formaldehyde resin, and 100 pts. wt. of methanol in the reaction kettle, and adding the polyetheramine graft after completely dissolving chitosan, stirring at 200-300 rpm for 2-3 hours, immersing in the cardboard and solidifing at high temperature to obtain a finished product.