▎ 摘　　要

NOVELTY - Foamed polypropylene bead comprises a foaming core layer and a skin layer, where the skin layer covers the core layer. The core layer includes 20-40 wt.% polyethylene A, 60-80 wt.% polypropene B, 0-20 wt.% polypropylene C, 0-10 wt.% thermal conductive aid. The skin layer is composed of 40-80 % polypropane D and 20-60 % polyolefin E. The weight ratio of the skin layer to the core layer is 1:99-10:90. USE - Foamed polypropylene bead is used for molded article. ADVANTAGE - The composite particle has a structure, where the core layer is coated with the skin layer, and the skin layer matrix resin has low melting point, easy to sinter and good in compatibility with the main base material resin used by the core layer. The core layer resin adopts a specially selected mixture, and the expanding aid further promotes the molding expansibility, so that the EPP beads have more excellent molding expansion under the molding pressure of 1.4 bar, and the excellent apparent quality of a molded portion is reflected while firm sintering is realized. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a method for forming the expanded polypropylene beads, which involves (a) mixing the polypropylene A, the polypropylene B, the polypropylene C, the heat conducting auxiliary agent, the expansion assistant, the cell nucleating agent and other assistants, extruding and granulating to obtain core masterbatch; (b) mixing the polypropylene D, the polyolefin E and other auxiliary agents, extruding and granulating to obtain a skin layer masterbatch; (c) using the core layer masterbatch and the skin layer masterbatch to co-extrude to obtain composite particles with a skin layer covering the core layer; and (d) subjecting the composite fine particles to high temperature and autoclave foaming treatment; and (2) a molded article, which is made of the expanded polypropylene beads or the preparation method of expanded polypropylene beads that are are obtained by water vapor sintering molding, preferably, the density of the molded part is 58-62 kilograms/meter-cue (Kg/m3), the compressive stress of 50% strain is not below 500 kilopascasl (KPa).