Evaluation of PP/Wood Flour Composite Processing Using Computer Simulation

Abstract

Aiming the development of novel composites reinforced with natural fibers from vegetable origin, it is important the understanding and control of processing parameters in twin-screw extruders. The temperature profile and the screw components, as well as the extrusion speed, compromise the distribution and dispersion of the fibers in the matrix and consequently in their rheological behavior, which reflects in the mechanical, chemical and morphological properties of the composites and products obtained from them. One new tool, used to understand processing parameters in composites, is computer simulation. In this study, we used the WinTXS Software to evaluate the influence of process parameters in the polypropylene matrix composite reinforced with 30 vol% wood flour. Parameters such as shear rate, temperature, melt viscosity, and viscous dissipation were evaluated. It was observed that increasing screw speed, the temperature increased, which results from the viscous dissipation. Under these conditions, the shear rate and melt viscosity were reduced.

Rheological Properties of Wood Plastic Composites Based on Polypropylene and Birch Plywood Residues - Sanding Dust

“…Several authors have investigated WPCs based on virgin polyethylene [1, 4-7, 9, 10, 12-18], recycled PP [3,15], and virgin [2,20,21] and recycled polyethylene [19] rheological properties. One of the main methods of rheological investigations is capillary rheometry at different shear deformation rates, for example, from 10-20 s-1 up to 10.000-15.000 s-1 [12][13][14][17][18][19]. It was observed that the rheological properties of the WPCs based on PP at shear rates up to several thousand s-1 significantly depend on the filler content in the polymer matrix [12][13][14]17,18].…”

“…One of the main methods of rheological investigations is capillary rheometry at different shear deformation rates, for example, from 10-20 s-1 up to 10.000-15.000 s-1 [12][13][14][17][18][19]. It was observed that the rheological properties of the WPCs based on PP at shear rates up to several thousand s-1 significantly depend on the filler content in the polymer matrix [12][13][14]17,18]. At the same time, at higher shear rates, a faster decrease in the viscosity of the composites was determined [17].…”

“…Rheological properties and melt flow index values of PP composites also influence crystallization processes in the PP matrix in the presence of wood fibers [7]. In the last years, researchers studying the rheological properties of WPCs with PP [16,18] and polyethylene [20,21] matrices have approbated the different flow modeling variants. Process simulations were performed using the recently developed global computer model of WPC extrusion to predict the process parameters (flow rate, pressure, temperature, melting rate, etc.)…”

“…It was concluded that the location of the operating point, which defines the thermomechanical process conditions, is fundamentally dependent on the rheological characteristics, including yield stress and wall slipping [16]. The authors [18] offer one new tool used to understand processing parameters. Parameters such as shear rate, temperature, melt viscosity, and viscous dissipation were evaluated, and it was observed that with increasing screw speed, the temperature increased, which resulted from viscous dissipation, and the shear rate and melt viscosity were reduced.…”