Influence of the Design Solutions of Extruder Screw Mixing Tip on Selected Properties of Wheat Bran-Polyethylene Biocomposite

Abstract

The study investigated the impact of the extruder screw design solution—the intensive mixing tip used—on the course of the extrusion process and the properties of the obtained biocomposite extrudate. A lignocellulosic wheat bran biocomposite based on a low-density polyethylene matrix was extruded. Three mixing tips of the screw were used interchangeably: apineapple tip, a cut rings tip, and a Maddock tip. The experimental tests carried out included the production of an extrudate with a mass content of bran altered within the range from 10% to 50%. Processing properties such as the melt flow rate (MFR) and mass flow rate of the extruded biocomposite were determined. Selected physical, mechanical, and structural properties of the biocomposite extrudate obtained with the use of the three tested mixing tips at five bran contents were tested.

Biocomposites Based on Plasticized Wheat Flours: Effect of Bran Content on Thermomechanical Behavior

“…It is known that the shear stresses applied during the plasticization phase can produce effects on the destruction of starch granules and, consequently, on the mechanical characteristics of the materials. In order to take into account the effect of the rheological characteristics of the system, the tests were repeated for materials with different PCL fractions [ 29 , 30 ]. A higher speed of rotation of the screws during plasticization in the extruder produced a general improvement of the mechanical properties, both in terms of strength and, albeit to a lesser extent, of strain.…”

Analysis of Selected Properties of Biocomposites Based on Polyethylene with a Natural Origin Filler

“…The moisture content makes processing much more difficult, leading to the formation of pores, surface collapses and dimensional deviations, an increase in pressure in the plasticizing systems of processing machines, and may accelerate the wear of their working elements [18,52]. Research shows that full soaking of biocomposites with a natural filler based on polyethylene, when fully immersed in water, may take up to several dozen hours [70]. Thus, removing the moisture found in the structure of such a composite requires a sufficiently long drying procedure.…”

“…From the processing point of view, several other disadvantages of lignocellulosic fillers can be listed. One of them is the deterioration of the processability in relation to unfilled plastic [70], caused by the increase in viscosity along with the increase in the filler content [73,74]. This results in a reduction in the efficiency of the process and an increased load on drive systems or the need to use additives facilitating processing [50,70].…”

“…One of them is the deterioration of the processability in relation to unfilled plastic [70], caused by the increase in viscosity along with the increase in the filler content [73,74]. This results in a reduction in the efficiency of the process and an increased load on drive systems or the need to use additives facilitating processing [50,70]. Moreover, biofillers are characterized by variations in their chemical composition and structure, depending on geographic and climatic factors, which in turn causes variability in the mechanical and processing characteristics of biocomposites [13,33].…”

“…The quality and composition of biofillers depend on the exposure of the lignocellulosic material to many factors, which can be divided into four stages: plant growth, harvesting stage, obtaining the filler, transport and storage [45,75]. An additional effect of the use of biofillers is their influence on the look of the final product, its color and surface structure [70]. Sometimes this may be a desired characteristic effect, but otherwise, it will require the use of dyes or pigments [55].…”