▎ 摘　　要

NOVELTY - Preparing environmentally friendly flame-retardant pipe insulation material comprises (i) adding expanded perlite and graphene into acetone, ultrasonically treating, filtering and drying, adding into polymethylene polyphenyl polyisocyanate, stirring, adding polyoxypropylene glycol, stannous octoate, heating, reacting, filtering, placing the resultant in a freeze dryer, freeze-drying, taking out and crushing, (ii) adding cellulose nanofibers into deionized water, stirring, adding product, stirring, freezing the resulting suspension in liquid nitrogen, transferring to a freeze dryer, freeze-drying, and crushing, and (iii) adding ethyl orthosilicate into absolute ethanol, mixing and adding deionized water, mixing, adjusting pH with oxalic acid solution, adding polypropylene fiber and product, dispersing, placing, adjusting the pH with aqueous ammonia solution, stirring, adding ethanol, aging, removing ethanol, soaking in n-hexane, removing the solvent and drying. USE - The material is useful to re-encapsulate expanded perlite and graphene. ADVANTAGE - The method reduces density, increases porosity, improves toughness of the resulting silica aerogel, enhances interfacial binding force, improves network strength, and forms more hydrogen bonds and improves the mechanical properties of the resulting material. DETAILED DESCRIPTION - Preparing environmentally friendly flame-retardant pipe insulation material comprises (i) adding 20-25 pts. wt. expanded perlite and 5-10 pts. wt. graphene into acetone, ultrasonically treating at 60-70 degrees C with frequency of 54-57 KHz for 30-40 minutes, filtering and drying, adding into 40-50 pts. wt. polymethylene polyphenyl polyisocyanate, stirring at 150-200 revolutions/minute for 10-20 minutes, adding 15-20 pts. wt. polyoxypropylene glycol, 0.5-1 pts. wt. stannous octoate, heating to 87-89 degrees C, reacting at 200-220 revolutions/minute for 4-6 hours, filtering, placing the resultant in a freeze dryer for freeze-drying for 10-12 hours, taking out and crushing to a particle size of 10-50 mu m, (ii) adding 40-50 pts. wt. cellulose nanofibers into 3-5 times deionized water, stirring at 1000-1200 revolutions/minute for 1-2 hours, adding 25-30 pts. wt. product, stirring at 1400-1600 revolutions/minute for 3-5 hours, freezing the resulting suspension in liquid nitrogen for 20-26 minutes, transferring to a freeze dryer, freeze-drying at -50 to -54 degrees C for 3-4 days, placing in a crusher and crushing to a particle size of 100-200 mu m, and (iii) adding 80-120 pts. wt. ethyl orthosilicate to 7-9 times absolute ethanol, mixing for 3-5 minutes and adding 3-4 times deionized water, mixing for 10-12 minutes, adjusting pH to 3-4 with a 0.1-0.2 mol/l oxalic acid solution, adding 15-20 pts. wt. polypropylene fiber and 30-35 pts. wt. product, dispersing at 300-400 revolutions/minute for 30-50 minutes, placing at 70-80 degrees C for 12-14 hours, adjusting the pH to 7.5-8.2 with 0.2-0.3 mol/l aqueous ammonia solution, stirring for 5-8 minutes, adding ethanol, aging for 14-15 hours, removing the ethanol, soaking in n-hexane for 12-14 hours, removing the solvent and drying at 80-90 degrees C for 6-8 hours.