The presence of a PHEE coating on the surface of the starch granules has a profound effect on the stress level at which nonlinear deformation begins.
In the starch-filled composites, the PHEE coating on the surface of the granules improves the interfacial strength and increases the debonding stress interval.
The higher tensile strength of the starch-filled PE: PHEE blend, at large [[phi].
For the starch-filled blend, the coating on the surface of the granules indicates that the interface between starch and PHEE is stronger than the interface between PE and PHEE.
The effect of the PHEE coating on the tensile properties will be discussed in a subsequent paper (15).
In this study, the effect of PHEE on the dynamic mechanical properties of starch-filled PE has been examined using micro-mechanical models that determine the overall composite modulus by a step-wise homogenization process.
The PHEE was obtained from Dow Chemical (Midland, MI) and the low-density polyethylene, Petrothene 3023, from Quantum Chemicals.
Pre-mixed pellets of PE and PHEE were added at the feed throat while the starch was introduced further downstream.
Preliminary measurements were carried out to investigate possible hysteresis, or deformation history memory of starch-filled PHEE composites.
The experimental results of the complex viscosity as a function of frequency for PHEE and starch/PHEE composites with starch volume fractions from 0.
From this Figure, the relative viscosity at the same stress between the composite viscosity and unfilled PHEE viscosity can be obtained.
At low stress, plots for composites with starch volume fraction [less than] 0,41 display similar curvature to that obtained for PHEE.