난연성 폴리올레핀 발포체의 광가교 특성에 관한 연구

Abstract

ABSTRACT : Polypropylene materials possess a weak melt strength, which increases the difficulties of foaming compared to other plastics. When the melt strength is too weak, the cell walls separating the bubbles will not be strong enough to bear the extensional force and they are susceptible to coalesce and rupture. As a result, foamed PP products usually have a high open-cell content. Thus, there are unsatisfactory for many applications. In this work, Radiation curing of the polyolefin resins by Electron beam has been of great interest for flame retarding application. It gives much shorter curing time, lower shrinkage, lower tooling cost, improved performance and elimination of hazardous cross-linking agents etc.. Polypropylene and its blends with recycled polyethylene were melt blended with non halogenated flame retardants. The blends were stirred at elevated temperature, while appropriate amount of additives were added to the mixture. The blend samples were placed in a moving belt and exposed to Electron beam(KAERI) system in irradiation dose of the range of 30 ~ 45kGy, respectively. Finally the resulting irradiated blend samples were thermally expanded. SEM, TGA, LOI tester and Cone calorimeter was used for characterization of the resulting foams. As a results, Flame retarding foams were successfully prepared using Electron beam as a cross-linking tool and its optimum dose range was 30 ~ 35kGy for 10 MeV. Maximum expandability of the blended FR foams was 990% and the more recycled polyethylene content in the blend foams, the higher gel content and expandability. The flame retardancy of the resulting foams was in the range of 26 to 27.6 in the LOI value. Carbon mono oxide yields(COY) were about 0.11(Kg/Kg) and their char yields were more than 50%.