Tran Huu Trung, Mai Duc Huynh, Do Van Cong, Nguyen Vu Giang


In this study, waste gypsum (WGS) was used as the filler in blend of high density polyethylene (HDPE) and ethylene vinyl acetate copolymer (EVA) in order to improve the flame resistance of this composite. After modification by ethylene bis stearamide (EBS), modified gypsum (EGS) at various contents was dispersed into HDPE/EVA blend by melt-mixing method to obtain EGS/HDPE/EVA composites. The IR analysis of the EGS showed the interaction between EBS and gypsum. The difference in morphology of HDPE/EVA/EGS and HDPE/EVA/OGS composites was also observed in SEM images. By adding EGS and small amounts of flame retardant additives such as ammonia polyphosphate and zinc borate, the thermal stability and the flame resistance of HDPE/EVA/EGS composites have improved and classified at V2 grade of UL94 standard. Moreover, the second self extinguishing time (t2) of EGS composite is shorter than that of unmodified gypsum (OGS) composite because of the quality char forming after the fist burning and it plays a role as thermal barriers to protect material from heat of the second ignition. About mechanical properties, both tensile strength and elongation at break of the composite decreased with increasing the gypsum content and flame retardant additives because of filler aggregation.


waste gypsum, HDPE, EVA, flame resistance, ethylene bis stearamide

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