Research On Crystallization Behavior Of Polypropylene/magnesium Hydroxide Composites

Polypropylene is a very material with good performance in everyway, and it has many applications, however the lack in the fire resistancerestricted its applications. Magnesium hydroxide is a good fire retardantwhich can obviously improve the polypropylene’s fire resistance by blendwith it. Nowadays, the academic research on the polypropylene/magnesium hydroxide system is focus on the mechanical properties andfire resistance. But there are few reports on the crystallization of thepolypropylene/magnesium hydroxide composites system, since theinfluence of crystallization is very important for the polymer materials; itis very significant to study the crystallization of polypropylene/magnesium hydroxide. Therefore, this study did many works in thecrystallization of polypropylene/magnesium hydroxide, main works asfollows:Magnesium hydroxide and polypropylene composites was obtainedby blending magnesium hydroxide and polypropylene in Haack mixer.The crystallization kinetic performance of polypropylene andpolypropylene/magnesium hydroxide composites was tested by DSC. The crystallization kinetic parameters were calculated by the exothermiccrystallization curve from DSC. It is shown that magnesium hydroxidehas raised the crystallization of polypropylene, and reduced the halfcrystallization time, the Avrami constant is approximately equal to3. Theresults indicate that the magnesium hydroxide has heterogeneousnucleation effect on the crystallization of polypropylene matrix.The thermodynamic performance was also tested by the DSC. It isshown that the crystallization curve moved to the right, and crystallinitywas raised after the addition of magnesium hydroxide.The morphologic observations of polypropylene and polypropylene/magnesium hydroxide composites were observed by polarizationmicroscope. It is found that crystallization time of pure polypropylenewas longer, spherulite was bigger and more regular, the right angledintersection was obvious, the spherulite edge was clear. On the contrary,the crystallization time of polypropylene/magnesium hydroxidecomposites was shorter, spherulite was smaller, spherulite edge wasfuzzy.XRD test on the pure polypropylene and polypropylene/magnesiumhydroxide composites was shown that the diffraction peaks of crystaland β crystal were basically unchanged after the addition of magnesiumhydroxide, it did not has a induced crystallization effect to the β crystal inthe polypropylene matrix. Finally did an oxygen index test to pure polypropylene andpolypropylene/magnesium hydroxide composites. The results showedthat the oxygen index of material increased from17of purepolypropylene to26.5when added magnesium hydroxide to40%, flameretardant effect was obvious.