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Ultrasonically aided extrusion in preparation of polymer composites with carbon fillers

Zhong, Jing
http://rave.ohiolink.edu/etdc/view?acc_num=akron1460413630

Abstract Details

, Doctor of Philosophy, University of Akron, Polymer Engineering.
The dispersion of nanofillers in polymers has been the biggest challenge in exploiting the full use of the nanocomposites. The purpose of the present study is to investigate the effect of ultrasonically aided extrusion in improving the dispersion of various nanofillers in the polymer composites. In the study, polyetherimide (PEI)/graphite, polypropylene (PP)/carbon black (CB), PP/carbon nanotube (CNT) and PP/graphene nanoplatelet (GNP) composites were prepared using a twin screw extrusion without and with imposition of ultrasonic waves. Three different screw configurations were designed to study the efficiency of ultrasonic treatment in the extrusion. Two compounding methods were utilized in preparing the PP/CNT composites. One is the direct compounding (DC) method and the other one is the masterbatch dilution (MD) method. The efficiency of nanofiller dispersion in these two methods was compared. Four kinds of PP of different molecular weight and molecular weight distribution were used in preparation of PP/CNT composites. The mechanism of ultrasonic cavitation was also investigated. The rheological, mechanical, thermal and electrical properties and morphology of all the PP composites were systematically studied to elucidate the processing-structure-properties relationship. The simulation of the nonlinear rheological behavior of PP/CNT composites was carried out. The results showed that the ultrasonic treatment is more efficient in improving the dispersion of expanded graphite (EG), CNT and CB than GNP and original graphite in polymer matrix. Among the three screw designs, the dispersion of nanofillers in polymer was found to be more related to the presence of kneading elements than the reverse elements and residence time. At higher pressure in the ultrasonic zone, the degradation of PP was less severe than at lower pressure. The ultrasonic treatment had a more prominent effect in improving the dispersion in the MD method than in the DC method. In the MD method, the effect of ultrasonic treatment was only obvious when it was applied in the masterbatch preparation step rather than in the dilution step. Outside and inside ultrasonic bubble cavitation mechanisms in nanofiller agglomerates were proposed in order to explain the effect of ultrasonic treatment in polymer composites. It was found that the inside bubble cavitation mechanism was dominant in improving dispersion of nanofillers in polymer melt. With a better filler dispersion, a lower electrical and rheological percolation threshold was achieved and the elongation at break was increased, but the yield stress, Young’s modulus and crystallization behaviors were slightly affected.
Avraam Isayev, Dr. (Advisor)
Plastics; Polymers
carbon nanotube CNT, graphene nanoplatelets GNP, carbon black CB, polymer, polyetherimide, polypropylene, twin screw extrusion, ultrasound, rheology, composites

Recommended Citations

Citations

  • Zhong, J. (n.d.). Ultrasonically aided extrusion in preparation of polymer composites with carbon fillers [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460413630

    APA Style (7th edition)

  • Zhong, Jing. Ultrasonically aided extrusion in preparation of polymer composites with carbon fillers. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1460413630.

    MLA Style (8th edition)

  • Zhong, Jing. "Ultrasonically aided extrusion in preparation of polymer composites with carbon fillers." Doctoral dissertation, University of Akron. Accessed APRIL 26, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460413630

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.