| Polyropylene (PP) is a widely used commodity thermoplastic with a number of desirable properties. The high performance and multiple functions of PP have been arose more attention, and it's also the key point of the theory study and application research in polymer field. The main content of this dissertation is to prepare flame-retardant PP composite with favorable properties; the relationships between structure and property of the composite have also been studied and discussed.The content of this thesis includes four sections: Chapter 1, introduction; chapter 2, structure and property of the PP/ ammonium polyphosphate (APP) composite; chpter 3, the preparation of POE grafted with GMA (POE-g-GMA); and chapter 4, the influence of POE-g-GMA on the structure and property of PP/APP composite.(1) In the introduction, the author reviewed the significance of the flame retardance modification, the flame retarding mechanism, the flame retardant in common use and the development process of flame retardance of PP at first; pointed out various methods of the graft functionalization of polyolefm; depicted the preparation methods and properties of filled PP composites; analyzed the toughness of polymer andgeneralized the toughening mechanism of elastomer toughen polymer system; described the recent progress of the ternary blends of PP/elastomer/inorganic filler system.(2) Next, the flame retardant modification of PP with APP was prepared. The results indicated that adding suitable content APP into PP could prepare PP composites with fine flame retardance property. TG analysis showed that the addition of APP broadened the temperature region of thermal degradation and impelled the formation of residual char. The filler had influence on the mechanical properties. With the contents of APP increased, the flexible strength and modulus increased obvious, on the other hand, the elongation at break and the impact strength especially decreased greatly in the APP filled PP composite. The MFR of the PP/APP composites increased after the addition of APP, it meant APP was propitious to improve the fluidity of PP and the process property. Though the apparent viscosity and the apparent shear stress of PP/APP composite was lower than the pure PP in the low shear rate range, the rheological behavior of PP/APP composite was also belong to non-Newtonian fluid as PP. The spherulite morphology of the PP in the PP/APP composite was influenced by the APP greatly. With the increasing of APP content, the dimension of the spherulite reduced, but it had little influence on the form of crystallite, the a -form crystallite still was dominant. It was proposed the PP crystal was epitaxy to the APP particle. The isothermal andnon-isothermal crystallization kinetics of the composites were researched. The results showed APP had strong nucleating effect on the crystallinity of PP. The Avrami value n were about 2.7~3.2 which showed obvious heterogeneous nucleation feature. The values of crystallization rate constant kn and time of half crystalline degree tU2 both decreased withthe increase of the content of APP. The crystal process could be developed in higher temperature and the crystal rate could be improved greatly, but APP had little influence on the crystalline degree and melting temperature.(3) By using the method of melting reactive extrusion, the influences of GMA monomer concentration, initiator concentration and material resting time on POE-g-GMA grafting degree were investigated. Based on theoretical analysis, manufacturing conditions for POE-g-GMA were proposed from which grafted POE with desired property was successfully prepared.(4) Using reacting extrusion prepared POE-g-GMA as compatibilizer, the toughed PP/APP composite was prepared in this paper. Influences of the POE-g-GMA content on the mechanical properties, flame retardant properties, thermodegradation and flowing properties of the PP/APP composites were investigated. Effect of the grafted POE on the dynamic mechanical response of the composites was analyzed. Effects of POE-g-GMA on the crystal rate, crystalline degree and crystallizationkinetics were discussed in detail. The results showed that the toughness of PP/APP composite was improved greatly after the adding of the POE-g-GMA. The toughness of the composite was related with the grating degree. Higher grafting degree was helpful for getting higher toughness. SEM photographs showed that the APP particles were dispersed more uniformly and the interface between the two phases became nebulous after POE-g-GMA was added to the composites, and this meant the grafted POE played an important role of compatibilizer. The LOI of the PP/APP composites was improved when proper content POE-g-GMA was added in. TG analysis indicated that the addition of POE-g-GMA promoted the carbonization and char formation of the composites during the thermal decomposition process. Dynamic mechanical analysis revealed that the addition of POE-g-GMA not only improved the peak of E" and tgS at room temperature, but also created new peaks of E" and tgd at low-temperature region; both of these phenomena were related to the improvement of the toughness of the composites. The presence of POE-g-GMA appears to have improved the interfacial interaction between APP particles and the matrix and reduced the active energy of the glass transition temperature, which meant the glass transition of the molecular section of PP could be carried through easier. The results obtained from the isothermal crystallization behavior demonstrated that the addition of POE-g-GMA reduced the equilibrium... |
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