Date of Award
Master of Science in Chemistry (MSChem)
Dr. Jeanne H. Norton
Dr. Charles Neef,
Mr. Paul Herring
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.
Givehchi, Hamid Reza, "Method Development to Quantify the Reinforcing Properties of Silica Fillers" (2019). Electronic Thesis Collection. 274.