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University of Akron

1. Kashfipour, Marjan Alsadat. Thermal Conductivity Enhancement Of Polymer Based Materials.

Degree: PhD, Chemical Engineering, 2019, University of Akron

Enhancing the thermal conductivity (TC) of polymeric materials for thermal management applications has attracted attentions because of their beneficiary features such as light weight, anti-corrosive, low cost, flexibility and controllable electrical conductivity. Since phonons are the dominant heat carriers in insulating materials, creating pathways for better phonon transfer and decreasing the phonon scattering inside the matrix are the major strategies for TC enhancement. TC of bulk polymers is much less than their single chains because of the chains entanglement that increases the phonon scattering. Therefore, any approaches that decreases the entanglement of chains or enhances their alignment can be used for TC improvement. Traditionally, TC of insulating materials have been enhanced by incorporation of thermally conductive fillers. Formation of a continuous network of these fillers and their alignment can enhance TC even further in the desired direction. The network of fillers can be achieved at high content of fillers that is accompanied with sacrificing other properties such as mechanical properties and results in high cost of final products. As a result, alternative approaches that can form such a network at low content of fillers have attracted attentions.Here, we present three different approaches, which were utilized for TC enhancement of different systems. First, induced co-continuous morphology of an immiscible polymer blend, blend of high density polyethylene (HDPE) and poly (methyl methacrylate) (PMMA) was used for localization of carbon nanofibers (CNFs). The co-continuous morphology of immiscible polymer blends has been previously used for formation of continuous network of electrically conductive fillers and electrical conductivity (EC) enhancement. This method, known as double percolation method, requires both the composition of polymers and fillers reach to percolation threshold above which they form co-continuous phase morphology and continuous network of fillers, respectively. Being inspired by this method and considering the involved parameters in tuning the morphology and distribution of fillers, we could show that processing temperature that affect the viscosity ratio of components and distribution of fillers is a key role for EC and TC enhancements. To investigate the effect of temperature on the morphology and distribution of fillers, two different temperatures of 150 and 230 °C were used for processing the blend with different contents of CNFs. The samples that were processed at 230 °C showed finer morphology and higher EC than the processed samples at 150 °C for all the content of CNFs. While, the samples processed at 150 °C showed higher TC and coarser morphology. The difference in the trends of TC and EC is because of their different mechanisms. The finer morphology and better distribution of fillers at 230 °C is accompanied with formation of more interfaces that increases the interfacial phonon scattering and decreases TC consequently. To our knowledge, this is the first study… Advisors/Committee Members: Zhu, Jiahua (Advisor).

Subjects/Keywords: Chemical Engineering; Polymers; Thermal conductivity, insulating material, sugar alcohol, phase change material, immiscible polymer blend, co-continuous morphology, crystal packs, aerogel, plasticizer, antiplasticizing

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APA (6th Edition):

Kashfipour, M. A. (2019). Thermal Conductivity Enhancement Of Polymer Based Materials. (Doctoral Dissertation). University of Akron. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422

Chicago Manual of Style (16th Edition):

Kashfipour, Marjan Alsadat. “Thermal Conductivity Enhancement Of Polymer Based Materials.” 2019. Doctoral Dissertation, University of Akron. Accessed September 21, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422.

MLA Handbook (7th Edition):

Kashfipour, Marjan Alsadat. “Thermal Conductivity Enhancement Of Polymer Based Materials.” 2019. Web. 21 Sep 2019.

Vancouver:

Kashfipour MA. Thermal Conductivity Enhancement Of Polymer Based Materials. [Internet] [Doctoral dissertation]. University of Akron; 2019. [cited 2019 Sep 21]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422.

Council of Science Editors:

Kashfipour MA. Thermal Conductivity Enhancement Of Polymer Based Materials. [Doctoral Dissertation]. University of Akron; 2019. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422

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