THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Friday, April 20, 2018

10:00 AM
in MRDC 3515

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Jing Shi

"Cost-effective Processing of Immiscible Polymer Blends into Value-added Fiber-based Products"

Committee Members:

Prof. Donggang Yao, Advisor, MSE

Prof. Meisha Shofner, MSE

Prof. Youjiang Wang, MSE

Prof. Karl Jacob, MSE

Prof. Yulin Deng, CHBE

Abstract:

With the development of man-made polymers, the use of plastics has increased dramatically. Since most polymer-based plastics take hundreds of years or longer to degrade and its production consumes much energy, the wide use of plastics brought serious environmental problems. The recycling of plastics can help with these problems by decreasing oil consumption and reducing the amount of plastic waste that goes into landfills and natural environments. Since the majority of plastics to be recycled comes in a way of co-mingled mixtures, the current polymer recycling industry generally separates the polymer mixture into pure polymers before reprocessing them. Otherwise, the immiscibility and poor interfacial adhesion between different polymers will cause poor mechanical properties. However, the sort-out operation prior to recycling is expensive, time-consuming and sometimes even impossible. Therefore, removing the need of separation and being able to directly recycling mixed immiscible polymers are important. In this work, we introduce the concept of “a nearly co-continuous morphology” and propose to employ such a morphology for materials processing and products realization when immiscible polymer blends especially in a form of waste are encountered. This nearly co-continuous structure is considered significant from both engineering and economics perspectives by creating a cost-effective and yet capable process for achieving desired properties and performances of products, especially fiber based products. To demonstrate this new paradigm of polymer processing, three case studies, in which immiscible polymer blends are made into fibers with different value-added properties, will be performed. The first case study uses the blend of polypropylene (PP) and polystyrene (PS) to show that fiber with good mechanical properties can be produced despite the immiscibility. The second case study uses the blend of PP and PS and also the blend of polyethylene-octene elastomer (POE) and PS to obtain fiber with shape memory effect. In the third case study, the blend fiber made from polycaprolactone (PCL) and POE shows super-contraction capability upon heating. With this exploration, we hope to provide potential approaches of direct recycling of co-mingled plastics without the need for the costly and time-consuming separation procedure. The thesis work will further employ modeling and analysis to facilitate process design and scale-up.