Biomedical subjects

Lawrence T Drzal

Publications and source records attributed to Lawrence T Drzal.

3 recordsLinked to original sources

PubMed2006

Characterization and thermophysical properties of unsaturated polyester-layered silicate nanocomposites.

The thermophysical properties of unsaturated polyester (UPE) nanocomposites reinforced by organo-montmorillonite clay nanoplatelets are reported. The organo-clay nanoplatelets were sonicated in acetone for 2 hours to be dispersed in the UPE matrix. Vacuum extraction removed not only the acetone but also the styrene present in the UPE solution. The same mechanical and thermophysical properties of UPE were regained after adding the lost amount of styrene to the UPE solution. Both delaminated and intercalated clay morphologies were observed by transmission electron microscopy. It was found that the sonication process was effective to delaminate clay nanoplatelets for more homogeneous dispersion, dependent on organic chemical modifications for clay nanoplatelets. A higher storage modulus enhancement was obtained when the organo-clay nanoplatelets were delaminated and more homogeneously dispersed. The reinforcing effect of both delaminated and intercalated clay nanoplatelets was theoretically evaluated with the Halpin-Tsai equations. It was evaluated that the aspect ratio of delaminated clay nanoplatelets was approximately 150. The increase of the storage modulus below and above the glass transition temperature was achieved without reducing glass transition temperature and Izod impact strength with increasing clay content.

Materials Testing↗

PubMed2005

Recent advances in biodegradable nanocomposites.

There is growing interest in developing bio-based products and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis. Biodegradable bio-based nanocomposites are the next generation of materials for the future. Renewable resource-based biodegradable polymers including cellulosic plastic (plastic made from wood), corn-derived plastics, and polyhydroxyalkanoates (plastics made from bacterial sources) are some of the potential biopolymers which, in combination with nanoclay reinforcement, can produce nanocomposites for a variety of applications. Nanocomposites of this category are expected to possess improved strength and stiffness with little sacrifice of toughness, reduced gas/water vapor permeability, a lower coefficient of thermal expansion, and an increased heat deflection temperature, opening an opportunity for the use of new, high performance, lightweight green nanocomposite materials to replace conventional petroleum-based composites. The present review addresses this green material, including its technical difficulties and their solutions.

Alkanes↗

PubMedDate not supplied

"Green" nanocomposites from cellulose acetate bioplastic and clay: effect of eco-friendly triethyl citrate plasticizer.

"Green" nanocomposites have been successfully fabricated from cellulose acetate (CA) powder, eco-friendly triethyl citrate (TEC) plasticizer and organically modified clay. The effect of the amount of plasticizer varying from 15 to 40 wt % on the performance of the nanocomposites has been evaluated. The morphologies of these nanocomposites were evaluated through X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) studies. The mechanical properties of nanocomposites are correlated with the XRD and TEM observations. Cellulosic plastic-based nanocomposites with 20 wt % TEC plasticizer and 5 wt % organoclay showed better intercalation and an exfoliated structure than the counterpart having 30/40 wt % plasticizers. The tensile strength, modulus and thermal stability of cellulosic plastic reinforced with organoclay showed a decreasing trend with an increase of plasticizer content from 20 to 40 wt %. The nano-reinforcement at the lower volume fractions (phi < or = 0.02) reduced the water vapor permeability of cellulosic plastic by 2 times and the relative permeability better fits with larger platelet aspect ratios (alpha = 150).

Aluminum Silicates↗