Rigid Amorphous Fraction as an Indicator for Polymer-Polymer Interactions in Highly Filled Plastics

Abstract

Above a percolation threshold a flow restriction has to be overcome by higher pressure in plastic processing. Besides amount and geometry of fillers, the interactions of polymer and filler are important. By differing the amorphous phase of polymers into a rigid amorphous and a mobile amorphous fraction, predictions about interactions are possible. The objective is the generation of a flow restriction and the combined investigation of polymer–particle interaction. SiO2 was used up to 50 vol.% in different spherical sizes in PLA and PP. A capillary-rheometer was used as a tool to create a yield point and by that investigations into the state of the flow restriction were possible. All produced compounds showed, in plate-plate rheometry, an increase in viscosity for lower shear rates and a significant change in the storage modulus. In DSC, hardly any specific rigid amorphous fraction was detectable, which suggests that there is a minor interaction between macromolecules and filler. This leads to the conclusion that the change in flow behavior is mainly caused by a direct interaction between the particles, even though they are theoretically too far away from each other. First images in the state of the yield point show a displacement of the particles against each other.

A molecular dynamics approach to modelling oxygen diffusion in PLA and PLA clay nanocomposites

“…Experimentally, this phenomenon is responsible for the formation of a RAF, indicating a realistic portrayal of polymer behaviour in composite models. [40]- [42] Figure 6 -A heatmap representing the diffusion of PLA carbon atoms relative to their location, where darker shades represent more mobile species. Yellow lines indicate the location of the pyrophyllite surface.…”

“…The formation of a RAF surrounding filler particles in composite systems has been previously observed experimentally in composite systems. [40][41][42] To evaluate whether this phenomenon was manifested in composite models, we characterised chain mobility throughout the polymer environment. Diffusion coefficients were calculated for each carbon (C b ) of every polymer chain individually, which was then mapped to the location of the atom over the MD trajectory.…”

“…Experimentally, this phenomenon is responsible for the formation of a RAF, indicating a realistic portrayal of polymer behaviour in composite models. [40][41][42]…”