Professor
Jayaraman's research group at Michigan
State University is developing processing strategies,
flow models and design tools for shaping polymeric
materials into products for various industry sectors:
automotive, energy and building or construction.This research is
applied to develop processing strategies for polymer
composites, recycled polymers and polymer
nanocomposites to make foam core panels, multilayer
blown film, stronger light weight building materials
and porous plastic sheets. Dr. Jayaraman's research
interests and expertise are processing, rheology and
microstructure development in polymer materials.
Current Projects
ENHANCING
THROUGH-PLANE ELECTRICAL CONDUCTIVITY IN VINYL
ESTER MOLDING COMPOUNDS When electrically conductive anisometric
nanoparticles are dispersed well in a non-conducting
polymer medium such as vinyl ester, interparticle
percolation leads to good conduction in-plane of the
molded composite sheet at relatively low volume
fractions. However, anisometric micro and
nanoparticles tend to align in-plane during
compression molding, resulting in poor through-plane
conductivity. Systematic guides and procedures were
developed in this work for selecting and using filler
components including graphite powder, carbon black and
functionalized graphene nanolayers to obtain values of
100 S/cm for the through-plane conductivity of the
molded vinyl ester composites. The highest values of
through plane conductivity were achieved by adding to
this mix, high surface-area graphene nanolayers which
were functionalized for effective dispersion. This
allows the nanolayers to situate evenly and orient
closer to the through-plane direction within the resin
pockets. Detailed scanning electron micrographs of the
composites reveal the structure-property relationships
which enable this high through-plane conductivity.
Characterization and
Forming of Carbon-Fiber Composites with Mixed
Architecture The objective of this project is to
design and evaluate laminates that combine
unidirectional (UD) carbon fiber prepregs and twill
weave carbon fabric prepregs for forming and molding
D-shaped composite beams. Such beams have applications
in biomedical implants.
Dimensional Stability of Low-Cost
Thermoplastic Composite Molds
This is a collaborative
project with ESI Inc.to design and fabricate by
extrusion deposition additive
manufacturing molds with known
orientation distribution out of thermoplastic
composite and test them under compressive
loads at high temperatures in order to develop
predictions for performance of such molds.
Melt Rheology
of Polyolefin-Clay Nanocomposites with Coupling Agents Polymer nanocomposites with layered
silicates have two different types of interface
sites: edges with hydroxyl groups and gallery
faces with oxygen atoms. The polymer-particle
interface at either site may be strengthened by
silane coupling agents. Effects of reactive
coupling by the silane and a long chain polymeric
compatibilizer at different interface sites have
been investigated on the morphology and rheology
of polypropylene nanocomposites in the
melt-compounded state. In the illustration below,
two
different organoclays were used to obtain the
different coupling
effects. The
resulting state of dispersion and uniaxial
extensional viscosity behavior are shown in the
adjacent figure. Reactive
coupling at the interface produces finer dispersions
and strain hardening in uniaxial extensional flow of
polymer-layered silicate nanocomposites; more so
with both coupling at faces and edges. Note that the
organoclays
used in the two cases are
different: the aspect ratio of
the organoclay is lower in the
second case -- hence the viscosity
level is lower in the
second case; however, the
extent of strain hardening however
is clearly higher when the
silane coupling is obtained at
both edges and faces.
Molding of Flexible
and Rigid Polypropylene Foams and TPO
foams with Nanostructured Additives
Foaming of linear polypropylene melts
with chemical blowing agents gives mean cell sizes
in the range of 37 to 150 microns when the linear PP
is compounded with nanoclay and coupling agents.
see
US Patent #9,279,046
High Performance Additives
with Nanoparticles for PolypropyleneFilm
New
masterbatch additives have been developed that may
be compounded with bulk polyolefins and used to
produce films with good tensile strength and tear
strength while also having much improved barrier
to water vapor.
These films were produced by two different
methods: (1) film blowing and (2)
equibiaxial stretching of extruded film.
