Fabrication and Properties of PP Foam Composites Reinforced and Toughened by Hollow Glass Beads and POE
|School||Nanjing University of Aeronautics and Astronautics|
|Course||Materials Processing Engineering|
|Keywords||foamed composites hollow glass beads polyolefin elastomer compatibilizer polypropylene interface mechanical properties|
The green and environmental-protective foamed Polypropylene (PP) is of many excellentintegrated performances, such as perfect thermal stability, environment adaptability and highmechanical properties. It has been widely applied in lots of fields including automobile and aviationindustries. The researches and developments of foamed PP have received extensive interests at abroadand home. The foamed PP composite prepeared through post-foaming process in designed dies wasinvestigated. The infuluences of hollow glass beads (HGB), elastomer and interfacial compatilizers onthe reinforcement and toughening of PP foam composites were investigated systematically. Theevolutions of the cellular structures, interfacial bonding and mechanical properties of PP foamcomposites were studied by means of SEM, FT-IR, electronic universal testing machine andImage-Pro Plus software in detail in this thesis.The investigations of foamed effect indicate that the introduction of HGB is able to efficientlyimprove the melt strength and the foamed effects of PP/HGB co-blends for the nucleation pointincreased. The modified PP foam composites exhibite a closed and spherical-like cell structure, andaverage cellular diameters are reduced from946μm for pure PP to568μm for the composites withHGB, and cell density increases5times. Furthermore, the PP/HGB/POE ternary foam compositeswith average cell size of516μm and celldensity of6500cells/cm3can be obtained by adjusting thePOE. The individual introduction of optimized amounts of PP-g-MAH or POE-g-MAH interfacialcompaitilizer both facilitates the formation of excellent cellular structures and uniform distribution ofthe cell size in PP/HGB binary composites.The analysis of interfacial properties shows that the HGB pretreated by silane coupling agentsignificantly decreases interfacial tension with PP, facilitates the wettability of PP to HGB andimproves the distribution of reinforcing fibers in the matrix. Furthermore, chemical bonding betweenHGB and PP matrix takes place, which is resulted from interfacial reaction between MAH and amidogroups by the incorporation of compatilizers. The novel morphology of POE-g-MAH particlesadhered to the surface of HGB in PP/HGB composites is observed, indicating their interfacialproperties are greatly enhanced.The mechanical testings indicate that modified HGB can remarkably increase the mechanicalproperty of PP/HGB foam composites. When15%HGB were introduced, the peak values of impacttoughness, flexural strength and compression strength of HGB/PP foamed composites were obtained with the increments by104%,89.8%and180%, respectively. With the increased mass fraction ofPOE, the impact toughness of PP/HGB/POE foam composites is increased dramatically and the peakvalue of two point four-fold higher than PP/HGB sample is obtained, but their flexural andcompressive strength slightly decline. The studies also show that the effects of PP-g-MAH andPOE-g-MAH on the mechanical properties of PP/HGB foam composites are absolutely different, i.e.the former is more favorable for improving the flexural and compressive strength with the biggestincrease of56.6%and39.8%, respectively, while the latter seems good at increasing the impacttoughness of PP/HGB foam composites with a maximum amplification of96%, which is far morethan that of PP-g-MAH (51%).