The Effect of Matrix Molecular Weight on the Dispersion of Nanoclay in Unmodified High Density Polyethylene

The effect of molecular weight on the dispersion of relatively polar montmorillonite (MMT) in non polar, unmodified high density polyethylene (HDPE) was examined. Polymer layered silicate (PLS) nanocomposites were compounded using three unmodified HDPE matrices of differing molecular weight and an organically modified MMT in concentrations ranging from 2 wt% to 8 wt% via single screw extrusion. The weight average molecular weights of the HDPE matrices used in this study ranged from 87,000 g/mol to 460,000 g/mol. X-ray diffraction (XRD), mechanical testing, dynamic mechanical thermal analysis (DMTA), as well as dynamic and capillary rheometry were performed on the nanocomposites. Nanocomposites generated from the high molecular weight (HMW) HDPE matrix exhibited increased intercalation of the MMT as shown by XRD as well as greater improvements in the Young's modulus compared to nanocomposites generated from both the low (LMW) and middle molecular weight (MMW) matrices. This was attributed to higher shear stress imparted to MMT during compounding from the more viscous matrix facilitating their separation and orientation during injection molding. DMTA showed that the torsional response of the HMW nanocomposites was not as great compared to their LMW and MMW counterparts as observed from a lower percentage enhancement in the storage modulus (Gâ ) and estimated heat distortion temperature (HDT) due to anisotropy in mechanical properties. Dynamic rheology indicated that a percolated network did not exist in any of the nanocomposites as shown by no change in the terminal behavior of Gâ upon addition of clay.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Chemical Engineering

Department dc:contributor.department

Chemical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2006

Author dc:creator

• Chu, David

Chair dc:contributor.committeechair

• Baird, Donald G.

Committee members dc:contributor.committeemember

• Goldstein, Aaron S.
• Davis, Richey M.

• high density polyethylene
• molecular weight
• nanoclay

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-06282006-154608

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/33796