Rheological Properties Of Low Density Polyethylene Research Articles

Investigation of the rheological properties of low-density polyethylene (LDPE) modified bitumens using two plastic wastes

Investigation of the rheological properties of low-density polyethylene (LDPE) modified bitumens using two plastic wastes

Bactericidal Properties of Low-Density Polyethylene (LDPE) Modified with Commercial Additives Used for Food Protection in the Food Industry

This study investigated the influence of commercially available food preservatives: Natamax® (containing natamycin) and Nisaplin® (containing nisin) on the antimicrobial properties of LDPE film, commonly used for food packaging. Studies have shown that the addition of 3% Natamax® or, alternatively, the addition of 5% Nisaplin® provides an LDPE film with effective antimicrobial protection. The applied biocides did not significantly affect the strength and rheological properties of LDPE. However, differences in optical properties were observed. The transparency of the samples decreased slightly with the addition of 3% or 5% Natamax® (by approx. 1% and 3%, respectively). A significant change was observed in the film haze, the addition of 5% Natamax® increased this parameter by approx. 80%, while 5% Nisaplin® increased it by approx. 19%. Both Natamax® and Nisaplin® agents can be successfully used to manufacture food packaging materials with antimicrobial protection. Natamax® showed a stronger bactericidal effect, while Nisaplin® changed other properties less significantly.

Mathematical Modelling of Rheological Properties of Low-density Polyethylene Produced in High-Pressure Tubular Reactors

Abstract Low-density polyethylene (LDPE) is a commodity polymer widely used in a variety of applications. Due to the complexity of its molecular structure, which includes molecular weight distribution and randomly distributed long-chain branching, its rheological behavior is varied. In the present work, a mathematical model is used to predict molecular and rheological properties of LDPE produced in a high-pressure tubular reactor under different operating conditions. The agreement between flow curve predictions and experimental data is very good, demonstrating the potential of this model as a predictive tool for industrial producers.

The effect of the addition of a slip agent on the rheological properties of polyethylene: off-line and in-line measurements

Abstract The article describes an investigation into the effect of a slip agent on the rheological properties of low-density polyethylene. As a slip modifier, oleamide was used in the amounts of 0.5, 1.0, 2.0, 3.0 and 4.0 wt.%, respectively. The process of polymer modification was carried out in a twin-screw extrusion process. The effect of the slip agent on the mass flow rate index was determined. The specific plasticisation energy of the modified polymer was also assessed based on the change in the torque of a batch mixer. The assessment of the effect of the addition of oleamide on the change in the flow and viscosity curves was made using an off-line (plastometer) and an in-line (extruder rheometer) measuring technique. The rheological parameters were determined based on the Ostwald-de-Waele power law model. The operation of the plastometer was brought closer to the principles of operation of the capillary rheometer by applying variable piston loading. In in-line measurements, an extrusion head with replaceable cylindrical dies was used. Using two rheological measuring techniques made it possible to determine the low-density polyethylene viscosity variations and the values of flow power law index (n) and consistency factor (K) in a wide shear rate range.

Rheological properties of low-density polyethylene filled with hydrophobic Co(Ni)-Al layered double hydroxides

Abstract Cobalt/aluminum and nickel/aluminum layered double hydroxide (LDH - M+2:Al molar ratio of 3:1) were intercalated with dodecylsulphate (DDS), laurate (LAU), stearate (STE) and palmitate (PAL) and used as filler in low-density polyethylene (LDPE) in percentages between 0.2 and 7.0wt%. After injection molding, the samples were submitted to morphological characterization by scanning electron microscopy (SEM), analysis of thermal behavior by differential scanning calorimetry (DSC) and investigation of rheological properties. All Co/Al-LDPE samples showed the formation of a high temperature polymer crystal domain, induced by the LDH filler. The rheological properties indicated in general a reduction of shear modulus due to incompatibility between some regions of LDH and LDPE, which promoted phase separation. However, interaction with the LDH surface indicated higher affinity of the Ni/Al-LDH for the LDPE compared to Co/Al-LDH, forming permanent networks.

Influence of interparticle interaction effects on the rheological properties of low density polyethylene filled with glass beads

The rheological properties of Low-density polyethylene (LDPE) compounds with different fractions of glass beads have been investigated by means of high pressure capillary rheometry. The purpose of this study is to find a functional approach for describing the flow behaviour of suspensions as a function of the volumetric filler content and the applied shear stress or shear rate, respectively. The flow behaviour of suspensions is influenced by interaction effects, which are dependent on the filler particle, its volume content and particle size. While small glass beads exhibit pronounced interparticle interaction effects even at low volumetric filler concentrations, large glass beads show a plateau of negligibly interactions up to approx. 20% volumetric filler content. With introducing a generalized interaction function the flow behaviour of the tested suspensions could be described with reasonable accuracy in consideration of the transition from negligible to pronounced interactions.

Rheology, Mechanical and Thermal Properties of C18-CNT/LDPE Nanocomposites

Abstract Nanocomposites of low density polyethylene (LDPE)/C18 modified multi wall carbon nanotubes (C18-CNT) were prepared by melt blending. The effect of C18-CNT loading and compatibilizer (maleic anhydride modified polyethylene, MAPE) on the morphology, mechanical, thermal and rheological properties of LDPE was studied. FE-SEM images of nanocomposites show reduced agglomeration of the in LDPE/C18-CNT in comparison with uncompatibilized C18-CNT. For uncompatibilized nanocomposites, yield strength and Young's modulus increased with loading of C18-CNT. Ultimate strength, show improvement up to 2 wt% loading. However, percent elongation and toughness were reduced for C18-CNT at all loadings. Apart from elongation and toughness, addition of compatibilizer improved all mechanical properties as compared to pure LDPE and nanocomposites without compatibilizer. Percent crystallinity shows a correlation with Young's modulus. Both, Young's modulus and total crystallinity increased with C18-CNT loading and further increase with the incorporation of compatibilizer was observed. Results of phase angle suggest no presence of network. Also, addition of C18-CNT did not increase strain hardening, maintained extensional viscosity and time of break up to 1.5 s−1 Hencky rate. The C18 modifier is viewed to act similar to a long chain branching on linear polymers. The C18 modification of CNT resulted in reduced viscous and elastic properties of the composites. In turn, this is expected to lead to enhancement in the processing of these composites. Overall, compatibilized C18-CNT resulted in improved mechanical properties and better processing behavior.

Rheological properties of LDPE processed by conventional processing machines

AbstractThe impact of applied processing history and the postprocessing annealing on the rheological properties of low‐density polyethylene (LDPE) have been studied employing various kinds of conventional processing machines. Processing by a corotating twin‐screw extruder (Co‐TSE) and an internal batch mixer depressed the drawdown force, one of the elastic properties of a melt, to a great extent, even though molecular weight and the polydispersity did not change. On the other hand, the sample processed by a two‐roll mill exhibited the drawdown force as high as the original pellets, which is owing to the intermittent stress history instead of the relentless one in the Co‐TSE and the internal batch mixer. Furthermore, the effect of screw configuration in the Co‐TSE has also been investigated. It was found that the processing by conveying screws depressed the drawdown force and melt fracture more than that by kneading blocks as long as the torque and the residence time are the same. The large, abrupt, and frequent change in flow direction in the Co‐TSE with kneading blocks prohibits the molecular orientation, which leads to disentanglement associated with long‐chain branches. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 179–187, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10047

Quantitative relation between shear history and rheological properties of LDPE

AbstractThe role of the applied processing equipment shear history on the rheological properties of low‐density polyethylene was studied in detail. It was found that the shear history depresses the melt strength and the oscillatory shear modulus, especially the storage modulus in low frequency region. This phenomenon is not caused by lowering of the molecular weight, which remained the same as the original, for all shear history samples, indicating absence of mechanical/thermal degradation during processing. Furthermore, annealing the melt processed samples enhances both the melt strength and the oscillatory modulus to the values of the original, unsheared sample. Finally we applied shear history in a cone‐and‐plate rheometer and found that the growth curve of the storage modulus, which can be expressed by a simple equation, is determined by both the duration of the flow and the magnitude of the applied shear stress. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 261–269, 2001