Shuchun Hu

Combustion Behaviour and Synergistic Effect of Zinc Borate and Microencapsulated Red Phosphorus with Magnesium Hydroxide in Flame-Retarded Polypropylene Composites

In this paper, the limiting oxygen index (LOI), Underwriters’ Laboratories-94 (UL-94) test, cone calorimeter test (CCT), and thermogravimetric analysis (TGA) were used to study the flame-retardant properties of polypropylene (PP) composites and the synergistic flame-retardant effects of zinc borate (ZB) and/or microencapsulated red phosphorus (MRP) with modified magnesium hydroxide (MH) on PP. The experimental results showed that the addition of ZB and MRP had a great effect on the flammability of the PP composites. The data obtained from the CCT indicated that the heat release rate (HRR), the effective heat of combustion (EHC), and the mass loss of the flame-retarded PP composites decreased markedly with increasing addition of ZB and/or MRP. The data obtained from the TGA curves indicated that the thermal stabilities of PP/MH/ZB and PP/MH/ZB/MRP composites were better than those of PP/MH composites.

Mechanical Properties and Crystallization Behavior of Polycarbonate/Polypropylene Blends

The mechanical properties, morphology, and crystallization behavior of polycarbonate (PC)/polypropylene (PP) blends, with and without compatibilizer, were studied by tensile and impact tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The tensile and impact strengths of PC/PP blends decreased with increasing the PP content due to poor compatibility between the two phases. But the addition of compatibilizer improved the mechanical properties of the PC/PP blends, and the maximum value of the mechanical properties, such as tensile and impact strengths of PC/PP (80/20 wt%) blends, were obtained when the compatibilizer was used at the amount of 4 phr. The SEM indicated that the compatibility and interfacial adhesion between PC and PP phases were enhanced. DSC results that showed the crystallization and melting peak temperatures of PP increased with the increase of the PP content, which indicated that the amorphous PC affected the crystallization behavior. However, both the PC and compatibilizer had little effect on the crystallinity of PP in PC/PP blends based on both the DSC and XRD patterns.

Thermal Degradation and Flammability Behaviour of Hdpe/Eva/Eg Composites

In this work, high density polyethylene (HDPE), ethylene-vinyl acetate (EVA) copolymer and expandable graphite (EG) flame retardant composites were prepared by using a twin screw extruder technique. The thermal stability and flame retardant properties of the composites were investigated by the thermogravimetric analysis (TGA) and cone calorimeter, respectively. The char morphology after combustion was also further characterized. The experimental results indicated that intumescent EG greatly enhanced the thermal stability and fire resistance of polymer matrix materials. The presence of EG improved the degradation temperature of HDPE/EVA blend and increased its char residue at high temperature. The results from cone calorimeter demonstrated that the addition of EG led to the decrease of the heat release rate (HRR), total heat release (THR) and smoke production rate (SPR) of materials and could retard the emission of the toxic and flammability gases by promoting the formation of a compact char layer. This char layer will prevent the polymer matrix further degradation and protect it effectively from heat penetrating inside, resulting in lower weight loss rate and better flame retarded property.