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Study On Halogen-free Flame Retardant PP/Mg(OH)2/POE Ternary Composites

Posted on:2011-10-10Degree:MasterType:Thesis
Country:ChinaCandidate:X J ZhangFull Text:PDF
GTID:2121360308981393Subject:Materials science
Abstract/Summary:PDF Full Text Request
With the development of the fields of automobile and electronic apparatus, the market demand of flame retardant polypropylene (PP) will keep rapid growth. Although the halide retardants are effective and have little influence on the mechanical and process properties, they gave out heavy smoke with poisonous and corrosive gas, which results in hazards to human's respiratory passage and other organs.With stronger awareness of enivormental protection and security, more and more countries establish law to prohibit or restraint the application of halide retardants in some industries.Therefore, halogen-free, effective and green flame retardant materials and thereof technology have becoming global research hotspot. Presently, magnesium hydroxide is widely used as a halogen-free retardant for polymer materials due to its non-toxicity and inexpensive. However, magnesium hydroxide is incompatibile with polymer as an inorganic retardant and displays low efficiency of flame retardant.Generally, it is only in the case of 40-60 wt% loading level that magnesium hydroxide produces an effect on flame retardant, which seriously deteriorate the mechanical and process properties.To solve those above-mentioned problems, halogen-free flame retardant PP was prepared by melting blend in a twin-screwd extruder, in which magnesium hydroxide and ethylene-co-octane copolymer(POE) were used as flame retardant and toughener, respectively. The flame retardance, mechanical properties, rheology and crystallization of PP/Mg(OH)2/POE ternary composites were investigated, the principal results are listed as following:1.Oxygen index and impact strength for PP/Mg(OH)2 binary composite at the 120 wt% loading level of Mg(OH)2 were 29.5 and 5.25 kJ/m2, respectively; those values were 28.1 and 36.5 kJ/m2 after the incorporation of 30 wt% POE, respectively. Thescanning electron microscope (SEM) images revealed that the addition of POE do contribution to the dispersion of Mg(OH)2 in the PP matrix. 2. The rheological behavior of PP/Mg(OH)2/POE composite was investigated using capillary rheometer. The non-Newton index for all PP/Mg(OH)2/POE composite was lower than 1,indicating that the composite melt was pseudo-plastic and exhibited shear-thinning. The apparent viscosity increased after the incorporation of Mg(OH)2 into PP matrix. By contrast, the addition of POE decreased the apparent viscosity of PP/Mg(OH)2/POE ternary composite, which might be due to that POE phase acted as interface and reduced the friction between between Mg(OH)2 particle and PP matrix.The viscous flow activation energy of composite decreased slightly with the increasing of POE content,it was indicated that temperature-sensitivity of PP/Mg(OH)2/POE composite was weak,that is, the ternary composite can be processed in a wide range of temperature.3.The crystallization procession of PP/Mg(OH)2/POE ternary composite was investigated using differential scanning calorimeter (DSC), and the isothermal and non-isothermal crystallization kinetics were analyzed by several classical equation or theory. The studies on the isothermal crystallization showed that Avrami equation well described the isothermal crystallization of PP and its composites,Mg(OH)2and POE acted as the heterogeneous nucleating agent and increased the crystallization rate of PP; The mode of the nucleation and growth of PP might be a mixture of two-dimensional and three dimensional growth with thermal nucleation. The equilibrium melting point calculated from Hoffman-Weeks theory for PP/Mg(OH)2/POE composites was lower than that for pure PP.The investigation of non-isothermal crystallization showed that Ozawa equation was not suitable to describe the non-isothermal crystallization process,while the modified Avrami and Mo equations took great advantages over treating the non-isothermal crystallization kinetics. Although the incorporation of POE and Mg(OH)2 into PP increased the crystallization nucleating rate of PP in the blends,it didn't change the mechanism of nucleation and the growth of PP crystallites. The data calculated from the Hoffman-Lauritzen theory and its deduction revealed that the addition of POE decreased the absolute values of effective activation energy and the effective activation energy of non-isothermal crystallization.
Keywords/Search Tags:Polypropylene, magnesium hydrate, Poly (ethylene-co-octane), flame retardant, Rheological behavior, Crystallization kinetics
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