▎ 摘　　要

NOVELTY - Preparing a polyurethane prefabricated direct-buried thermal insulation composite pipe, comprises nesting the working pipe and fixing in the outer protective pipe, forming a cavity between the working pipe and the outer protective pipe, and passing the prepared polyurethane stock solution through a high-pressure foaming machine and pouring into the cavity for free pressure foaming to form a polyurethane insulation layer. USE - The method is useful for preparing a polyurethane prefabricated direct-buried thermal insulation composite pipe. ADVANTAGE - The polyurethane insulation layer has high strength, good ring stiffness, and light weight, and has high waterproof performance. DETAILED DESCRIPTION - Preparing a polyurethane prefabricated direct-buried thermal insulation composite pipe, comprises nesting the working pipe and fixing in the outer protective pipe, forming a cavity between the working pipe and the outer protective pipe, and passing the prepared polyurethane stock solution through a high-pressure foaming machine and pouring into the cavity for free pressure foaming to form a polyurethane insulation layer; where the polyurethane stock solution includes activated carbon-graphene embedded material, and the preparation of the embedded material includes: a) ball milling 5-10% tungsten carbide, 2-10% graphene powder for 1-2 hours, then adding activated carbon and continuing ball milling for 20-30 minutes to obtain the ball milled mixture; (b) adding the ball mill mixture into water, adjusting the pH to 7.2-7.9, performing ultrasonic treatment under agitation, and centrifuging the ultrasonic-treated solution to obtain a precipitate; (c) treating the precipitate at a high temperature of 350-550degrees Celsius for 20-30 minutes to obtain activated carbon-graphene powder; and (d) using melamine resin to embed the activated carbon-graphene powder to obtain activated carbon-graphene embedded material.