טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBrook Irena
SubjectConductive Hybrid Ternary Elastomeric Nano-composites
DepartmentDepartment of Polymer Engineering
Supervisors Professor Emeritus Moshe Narkis
Professor Yachin Cohen
Full Thesis textFull thesis text - English Version


Abstract

Since the discovery of carbon nanotubes (CNT's) and intrinsically conductive polymers such as Polyaniline (PANI) the research has focused on the development of novel future materials by combining CNT and PANI to achieve their complementary properties. The lack of published information regarding systems comprising PANI and CNT both dispersed in an elastomeric matrix promotes the development of novel hybrid nanocomposites. The main objective of this research is to develop and study new ternary hybrid nano-composite systems consisting of elastomeric matrix, and conductive nanoparticles. This research describes a hitherto studied methodology of the development of conductive elastomeric nanocomposites. This research comprises four major steps: 1) Procedure developing; 2) Comparison of two fabrication methods; 3) Assessment of the developed route with different types of nano-filler; 4) Adjusting the fabrication method to electro-mechanical sensor production.

Electrically conductive elastomeric nanocomposites containing CNT and PANI were developed and studied in the present investigation. The synthesis procedure included an in-situ inverse emulsion polymerization step of aniline doped with dodecylbenzene sulfonic acid (DBSA) in the presence of CNT and dissolved styrene-isoprene-styrene (SIS) block copolymer. The dispersions obtained are processed by two preparation methods: precipitation-filtration and a drop-cast route. Achievement of uniform and stable dispersions of CNT within the elastomeric matrix is considered a challenge. The techniques developed result in uniform exfoliated PANI coated nanotubes within the elastomeric matrix. The presence of CNT/PANI in the SIS elastomeric matrix affects the thermal, mechanical and electrical properties of the nanocomposites. The formation of continuous three-dimensional CNT/PANI networks, enhancing the nano-composite properties, is observed by HRSEM. The two processing techniques result in significantly different structures, which affect the physical properties of the materials produced. A relatively low percolation threshold for both methods was determined. High electrical conductivity values were obtained in the ternary component systems.

Hybrid materials containing silver and polyaniline nano-particles reinforcing a thermoplastic elastomeric matrix were developed and studied according to the aforementioned technique. The unique dispersion of the conductive nano-particles, i.e. distinct architecture, provides an opportunity of developing materials of tunable electrical and mechanical properties.

An intrinsic coupling of rigid electronics and soft, flexible materials makes them ideal candidates for multi-functional systems in strain sensor applications. The electro-mechanical sensors have demonstrated a stable and fast dynamic response with a uniform electrical amplitude to the applied strain cycles for two diverse polymer matrices. An accurate dynamic behavior, where the maximum peak of relative electrical resistance coincides with the maximum strain peak was achieved. The relatively high calculated sensitivity factor demonstrates that the nanocomposites developed possess a good sensing performance.