Date of Award

Spring 4-10-2019

Document Type

Thesis

Degree Name

Master of Science in Chemistry (MSChem)

Department

Chemistry

First Advisor

Dr. Jeanne H. Norton

Second Advisor

Dr. Charles Neef,

Third Advisor

Mr. Paul Herring

Abstract

Polysiloxane polymers are widely used as a high-temperature resistant materials with the ability to maintain flexibility at extremely low temperatures. Unfortunately, polysiloxane elastomers generally exhibit low strength and poor mechanical properties and have no practical use unless they are reinforced. These elastomers can be mechanically improved through the use of reinforcing silica-based fillers. It is known that silanol groups on the surface of silica filler particles can interact with the polysiloxane backbone. Interactions of silanol groups on the fillers’ surfaces with the polysiloxane backbone through hydrogen bonding may hinder the mobility of the polymer chain and can improve thermal, physical, and rheological properties of the reinforced polysiloxane. Silica fillers can also undergo a filler-filler interactions, causing filler aggregation and agglomeration. These filler-filler interactions may improve or disrupt the overall properties of the filled polysiloxane based on a particular filler’s surface area, silanol group orientation, or concentration. Therefore, the surface study of filler becomes critical in order to predict the reinforcing behavior of fillers with the polysiloxane polymer backbone and other filler particles.

This work seeks to quantify silanol group concentration on the surface of different silica fillers and investigate the effects of silanol group concentration on the rheological properties of filled polysiloxane polymers. Through the analysis of rheological data, this work can predict the reinforcing capabilities of each filler and will allow tailoring of future materials based on those predictions. Silanol group concentration on a particular silica filler’s surface depends on the synthesizing method, surface area, and surface hydrophobicity. In this study, silanol concentration on the surface of eight commercially-available amorphous silica fillers will be calculated by using Zhuravlev model via thermogravimetric analysis (TGA). Subsequently, fillers will be combined with vinyl-terminated polydimethylsiloxane (PDMS) to produce a filled polysiloxane material. Oscillatory rheometry and flow rheometry will be used to determine rheological responses and, therefore, determine the effects of silanol concentration on rheological properties in filled polysiloxane materials.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.