Nondestructive testing of defects in adhesive joints

In-situ generation of silica in epoxy matrix and modified epoxy matrix via solgel
process
K.K.Iynesh Kumar and B.Kothandaraman
Department of Rubber and Plastics technology, Madras Institute of Technology, Anna University,
Chennai, India.
Email: iyneshkumar@gmail.com bkraman@mitindia.edu
ABSTRACT
The precipitation of nanosilica was done through Sol-Gel process with Tetraethoxysilane (TEOS)
as silica precursor at room temperature. The choice of epoxy as a matrix was made because of its polar
nature which can interact with in-situ generated silica. The amine containing polydimethylsiloxane
(PDMS) was used as liquid rubber modifier.
The precipitation was done directly on the organic matrix in the presence of Water,
Tetraethoxysilane (TEOS) and Ethanol as mutual solvent. The nanocomposite was cured by triethylene
tetramine at room temperature. To enhance bonding between organic and inorganic matrix
Dichlorodimethylsilane (DDS) was used as a coupling agent.
Dispersion of silica particles was observed through Atomic force microscope (AFM). Infrared
spectroscopic studies indicated the occurrence of chemical interaction within the epoxy/silica under
ambient conditions. The glass transition temperature (Tg) was investigated through Differential scanning
calorimeter (DSC). The thermal stability and filler content of the material were predicted through
Thermogravimetricanalyser (TGA). The mechanical reinforcement within the material was demonstrated
through flexural behavior of the material.
INTRODUCTION
The sol-gel process, which is mainly based on inorganic polymerization reactions, is a
chemical synthesis method initially used for the preparation of inorganic materials such as glasses and
ceramics. Its unique low-temperature processing characteristic also provides unique opportunities to make
pure and well-controlled composition organic/inorganic hybrid materials through the incorporation of low
molecular weight and oligomeric/polymeric organic molecules with appropriate inorganic moieties at
temperatures under which the organics can survive. The organic/inorganic hybrid materials made in this
way, which have been termed “creamers” by Wilkes [1] and “ormosils” or” ormocers” by Schmidt[2].,
are normally nanocomposites and have the potential for providing unique combinations of properties
which cannot be attained by other materials .
For the past decade, organic/inorganic nanocomposites prepared by the sol-gel process
have attracted a great deal of attention, especially in the fields of ceramics, polymer chemistry, organic
and inorganic chemistry, and physics. The preparation, characterization, and applications of
organic/inorganic hybrid materials have become a fast expanding area of research in material science. The
major driving forces behind the intense activities in this area are the new and different properties of the
nanocomposites which the traditional macroscale composites and conventional materials don’t have. For
example, unlike the traditional composite materials which have macroscale domain size of millimeter and
even micrometer scale, most of the organic/inorganic hybrid materials are nanoscopic, with the physical