Zhengzhou Wang

The grafting of vinyltrimethoxysilane (VTMS) onto polypropylene (PP) was carried out in a melt process, and the cross-linking in the hot water. The influence of coagents, i.e., styrene (St), divinylbenzene (DVB), triallyl isocyanurate (TAIC) and trimethylolpropane triacrylate (TMPTA) on the grafting degree, gel percentage, melt flow index (MFI) of the VTMS modified PP were investigated. It was found that the incorporation of the coagents influenced the grafting and cross-linking of VTMS. The crystallization behavior and crystal structure of the coagent assisted VTMS-cross-linked PP were studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXAD), respectively. The thermogravimetric analysis (TG) studies indicate that the thermal stability of VTMS-cross-linked PP was improved by the incorporation of coagents.

Effect of metallic oxides on flame retardancy and the thermal stability of styrene butadiene rubber (SBR) composites based on ammonium polyphosphate (APP) and pentaerythritol (PER) was studied by the limiting oxygen index (LOI), UL 94, the cone calorimeter tests, and thermogravimetry analysis (TGA), respectively. Scanning electron microscopy (SEM) and wide‐angle X‐ray diffraction (WAXD) were used to analyze the morphological structure and the component of the residue chars formed from the SBR composites accordingly. The addition of zirconium dioxide (ZrO₂) at a loading of 3.4 phr could improve the UL 94 test rating of the composite to V‐0. The TGA data illustrated that the metallic oxides could enhance the thermal stability of the SBR/Intumescent flame retardant additives (IFRs) composites at high temperature and increase the residue. Cone calorimeter test gave much clear evidence that the incorporation of ZrO₂ into SBR/IFRs composites resulted in the significant deduction of the heat release rate (HRR) values, and the SEM images showed that the char layers of the composites containing the metallic oxides became more compact. From the WAXD pattern, zirconium phosphate (ZrP₂O₇) may be formed by the reaction between ZrO₂ and APP. Due to the addition of ZrO₂ and the formation of ZrP₂O₇, the flame retardancy of the composite was improved. Copyright © 2009 John Wiley & Sons, Ltd.

The thermal degradation of flame-retarded ethylene-vinyl acetate copolymer (EVA) composites containing hydrotalcite (LDH) and red phosphorus (RP) are studied by thermogravimetric analysis. Four kinetics analysis models, i.e., the Kissinger method, the Flynn-Wall method, the Friedman method, and the Kissinger-Akahira-Sunose (KAS) method, are used to study the thermal degradation kinetics of the EVA/LDH composites. The apparent activation energy (E _a ) data calculated from the four methods are compared. The E _a results indicate that the addition of LDH and RP affects mainly the first thermal degradation stage of EVA.

Microencapsulated ammonium polyphosphate (MCU‐APP) with urea–melamine–formaldehyde (UMF) resin is prepared by in situ polymerization, and is characterized by FTIR and XPS. The microencapsulation of APP with the UMF resin leads to a decrease in the particle's water solubility. The flame retardant actions of MCU‐APP and APP in PP are studied using limiting oxygen index (LOI) and UL‐94 test, and their thermal stability is evaluated by thermogravimetric analysis. It is found that the LOI value of the PP/MCU‐APP composite is higher than the value of the PP/APP composite. In comparison with the PP/MCU‐APP composites, the LOI values of the PP/MCU‐APP/DPER ternary composites at the same additive loading increase, and UL‐94 ratings of most ternary composites are raised to V‐0. The water‐resistant properties of the PP composites containing APP and MCU‐APP are studied. Moreover, the combustion behavior of the PP composites is investigated by the cone calorimeter. Copyright © 2008 John Wiley & Sons, Ltd.

With a melamine-formaldehyde (MF) resin coating layer, microencapsulated ammonium polyphosphate (MCAPP) is prepared by in situ polymerization and is characterized by XPS and water leaching test. The microencapsulation of APP with the MF resin leads to a decrease in the particle's water leaching rate. The flame-retardant action of MCAPP and APP in EVA are studied using LOI and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis (TGA). The LOI value of the EVA/MCAPP composite at the same loading is higher than the value of the EVA/APP composite. In comparison with the EVA/MCAPP composites, it is found that the LOI values of the EVA/MCAPP/PER and EVA/MCAPP/DPER ternary composites at the same additive loading increase, and UL 94 ratings of most ternary composites are raised to V-0. The water-resistant properties of the EVA composites are studied, and the results of the composites containing with APP and MCAPP are compared. Moreover, the peroxide cross-linking of the EVA composites is investigated, and the mechanical properties and thermal stability of the composites increase after the cross-linking.

Halogen-free flame-retarded linear low density polyethylene (LLDPE) composites were prepared in a melt process using magnesium hydroxide (MH) as a flame retardant. The effects of surface modifiers on mechanical properties and rheological behavior of the filled LLDPE have been studied. The results show that the use of surface modifiers with low molecular weight (MW) such as stearic acid or its salts, and silane coupling agents can improve greatly the elongation at break of the composites, and decrease the tensile strength in most cases. However, PE- g -DBM (LLDPE grafted with dibutyl maleate) as a polymeric compatibilizer can make the strength and elongation at break of the composites increase simultaneously. It was found from the rheological measurements that the composites containing low MW surface modifiers exhibited a lower viscosity compared with that of the composites without them, whereas the use of PE- g -DBM compatibilizer increased the viscosity of the composites. In addition, their effects on the morphological structure of the flame-retarded LLDPE composites containing surface modifiers have been investigated using scanning electron microscope (SEM).

The flame-retardant effects of nano magnesium hydroxide (NMH) and nano hydrotalcite (NLDH) in ethylene-vinyl acetate copolymer (EVA) are studied by using the limited oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM). The LOI values of both EVA-NMH and EVA-NLDH blends increase gradually on increasing the NMH and NLDH content, respectively. The LOI value of EVA-NLDH is higher than that of EVA-NMH at the same additive level. In the UL-94 test, for EVA-NMH blend, there are no ratings at all even if the loading of NMH is up to 150 phr (60%). However, the EVA-NLDH blend at the additive level of 120 phr reaches the V-1 rating, and the blend with 150 phr NLDH reaches the V-0 rating. The heat release rate (HRR) data of EVA-NLDH blends are much lower than that of the EVA-NMH blends. From the LOI, UL-94, and HRR data, it can be seen that the flame-retardant effect of NLDH is better than that of NMH. The TG and differential TG (DTG) data show that additives NMH and NLDH increase the thermal stability of the EVA copolymer. The LRS results confirm that the charred layers formed during the burning of the nano EVA blends have a graphite-like structure. The mechanical properties of EVA-NMH blends are better than those of EVA-NLDH blends.