Search

Abstract: The rheological properties in terms of melt rheology and extrudate swell of low-density polyethylene (LDPE) filled with sodium chloride (NaCl) of varying particle size (i.e., 45, 75, and 125μm) in the range of 5–25 wt.% were investigated by capillary rheometry. The real shear stress increased monotonously with increasing apparent shear rate, with the rate of change decreasing with increasing apparent shear rate. At an apparent shear rate greater than about 400s−1, the real shear stress increased with increasing salt content and, at a given apparent shear rate, the real shear stress increased slightly with increasing salt particle size. The shear viscosity decreased monotonously with increasing real shear rate. Regardless of the salt content, the extrudate swell increased with the initial increase in the apparent shear rate to reach a plateau value. After a critical apparent shear rate in the range of 500–1200s−1, and regardless of the salt particle size, the extrudate swell decreased with increasing salt content. Lastly, the extrudate swell tended to be suppressed when a capillary die with a high L/D ratio was used. [Copyright &y& Elsevier]

Abstract: Melt rheology and extrudate swell of isotactic polypropylene (iPP) filled with titanium (IV) oxide (TiO2) nanoparticles of varying content (i.e., 5–30 wt.%) and surface characteristics [i.e., uncoated, silica (SiO2)-coated, and stearic acid-coated] during capillary melt-extrusion were investigated. The wall shear stress of both the iPP melt and the melts that contained nanoparticles increased in a non-linear, decreasing-rate manner with increasing apparent shear rate. The incorporation of the nanoparticles generally increased the wall shear stress of the melts, with stearic acid-coated ones exhibiting the least variation in the property values. The shear viscosity, when plotted with the real shear rate on a log–log scale, exhibited a linear, decreasing function with the real shear rate. Clearly, the iPP melts containing stearic acid-coated TiO2 nanoparticles exhibited the lowest shear viscosity values. Lastly, the extrudate swell of the iPP melt and the melts that had been filled with nanoparticles was found to increase with increasing apparent shear rate, while it was found to decrease generally with the addition and increasing amount of nanoparticles. [Copyright &y& Elsevier]

Abstract: The melt rheological and extrudate swelling behavior of neat low-density polyethylene (LDPE) and blends of LDPE and ethylene–octene copolymer (EOC) was investigated using capillary rheometry at 185.0±0.5°C. Dies having different length-to-inner diameter (L/D) ratios were used (i.e., 5/1, 10/11, 10/2, and 30/2mm/mm, respectively). For a given sample material, the real shear stress was observed to increase with increasing real shear rate, and, for a given real shear rate, the real shear stress was generally observed to increase with the addition and increasing amount of EOC. All of the sample materials exhibited the shear-thinning behavior. Both the tensile stress and the elongational viscosity were found to decrease with increasing elongational rate. Generally, both the tensile stress and the elongational viscosity increased with the addtion and increasing amount of EOC, with an exception for the 85/15 and 80/20 LDPE/EOC blends which exhibited a reversed order. Lastly, the extent of extrudate swelling of the sample materials in the small dies (i.e., inner diameter=1mm) was greater than that in the larger ones (i.e., inner diameter=2mm) and the use of a longer die also helped suppress the extent of the extrudate swelling. [Copyright &y& Elsevier]

Melt rheology and extrudate swell of isotactic polypropylene (iPP) filled uncoated and stearic acid-coated CaCO3 nanoparticles in various amounts of filler (i.e. from 5 to 25wt%) during capillary melt-extrusion were investigated. The wall shear stress for both neat iPP and iPP compounds increased in a non-linear manner with increasing apparent shear rate. The apparent shear viscosity for all of the samples investigated was found to decrease in a non-linear manner with increasing apparent shear rate. Addition of uncoated CaCO3 nanoparticles was responsible for increasing the apparent shear viscosity of the compounds, while stearic acid-coated ones did not affect the apparent shear viscosity of the iPP matrix as much. The percentage of extrudate swell was found to increase with increasing apparent shear rate in a non-linear manner, while it was found to increase linearly with increasing wall shear stress. Lastly, the percentage of extrudate swell was found to be a decreasing function of the filler loading. [Copyright &y& Elsevier]