Radiation Grafting Assisted Preparation of Layered Structure Polypropylene Foam with Superthermal Insulation and Hydrophobic Properties via a Supercritical CO2 Batch Foaming Process

Abstract

A layered porous, high heat insulation, waterproof, and recyclable polypropylene (PP) foam was prepared by radiation grafting assisted supercritical CO₂ foaming. First, dodecafluoroheptyl methacrylate was grafted on PP powder via radiation-induced graft polymerization. Then the grafted product (PP-g) with a grafting rate of 12.8% was blended with PP powder, and subsequently the blends were foamed. The obtained PP/PP-g (10) foam exhibited a highly oriented layered cell structure and large expansion ratio, which largely increased the number of air layers of heat conduction and the length of the conduction path, so an ultralow heat transfer coefficient of 29.3 mW/m·k was achieved. In addition, the raspy surface of the PP/PP-g (10) foam possessed a highly hydrophobic property (water contact angle: 146.7 ± 0.5°). The method provides a new strategy for improving the thermal insulation and hydrophobic performances, which has outstanding potential application in lightweight thermal insulation materials.