Characterization of biofiber breakage in composite processing using a capillary rheometer

Abstract

This study used a capillary rheometer to determine the impact that shear and elongational flow have on the breakage of aspen fibers in a polypropylene matrix. Composites were processed at different concentrations, temperatures, and rates of strain. The influence of the processing parameters was also analyzed. The difference in breakage of the fibers was assessed through their weight–average fiber length. Results showed that both types of flow exert influence on the total breakage of the fibers. In some cases, the percentage of breakage in the elongational flow is higher. The level of fiber breakage was similar for all fiber concentrations and shear rates. Temperature influence depended on the type of flow.

Isolation of hydrodynamic parameters for the fibre length attrition in injection-moulded short-fibre polymer composites

“…Based on the works by Goris et al, 8 Quijano-Solis et al 10 and Moritzer et al 9 we concluded that fibre loading plays a significant role in the FB process. In future works, we will use CRIM to isolate the effect of fibre loading on FB designing the test temperature so as to match the same viscosity for each composite.…”

“…In this work, the composite materials used for all tests of Table 3 had the same fibre loading, so we also neglected variations in the effect of fibre–fibre interactions on FB for the different test conditions. Goris et al, 8 Quijano-Solis et al 10 and Moritzer et al 9 studied the effect of fibre loading on FB using Couette and capillary rheometers. They found increased FB as a function of fibre loading, but the effect was less notorious for fibre contents higher than 30 wt.…”

“…7 Few attempts have been reported for the isolation of hydrodynamic parameters (fibre-polymer interactions) in the study of FB. [8][9][10] Most reliable results have been obtained using Couette rheometers. 8,9 Shear rates below 500 s À1 were achieved which can be considered low values for the validation of models for injection moulding.…”

“…At these geometrical conditions, fibre–equipment interactions should not be neglected because individual fibres periodically flip and rotate inside the flowing geometry promoting crashes between fibres and metal walls. 6 Quijano-Solis and Yan 10 have used conventional a capillary rheometer with capillaries 1 mm in diameter to study wood fibre length attrition in polypropylene composites with initial average fibre length around 1 mm. Tian et al 11 have also used conventional capillary rheometer with capillaries 1–3 mm in diameter at shear rates between 80 and 2000 s −1 to study FB with initial fibre average lengths between 3 and 12 mm.…”

Development of bio-derived and biodegradable polyhydroxyalkanoate (PHA)-based wood plastic composites (WPCs)

“…It was reported that the loss in aspect ratio values was less pronounced in smaller fibres (1.5 mm in length and 36 µm in width) than for larger fibres (1.7 mm in length and 48 µm in width) after processing with PP in a Brabender mixer. The authors extended the study to the effect of processing conditions and found that higher extrusion temperature, faster screw speed and higher wood content are conducive to more fibre breakage [Quijano-Solis & Yan, 2014]. The high shear forces from faster screw speed and the higher chance of additional breakage through rough fibre-fibre contacts from higher wood content were suggested to explain the observed more severe fibre breakage.…”