scholarly journals Dependence of the structural parameters and properties of low density polyethylene on the synthesis conditions

1999 ◽  
Vol 64 (10) ◽  
pp. 577-587
Author(s):  
Dragoslav Stoiljkovic ◽  
Radmila Radicevic ◽  
Milovan Jankovic
Keyword(s):  
Experimental Data ◽  
Structural Parameters ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Structure And Properties ◽  
Synthesis Conditions ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Mathematical Relationships ◽  
Polymerization Conditions

In a previous publicaitons from the authors.laboratotry a method was developed to predict the structure and properties of low density polyethylene (PE-LD) that could be obtained over a very wide range of polymerization conditions. The method was proved using experimental data from the literature. However, some shortcomings of the method were noticed. The aim of this work was to overcome the shortcomings and to enable the better manipulation of experimental data using a computer. A computer program has been developed to establish the mathematical relationships between ethylene entropy and the structural parameters and density of Pe-LD. All available experimental data (more than 300 experimental points) have elaborated and confirmed our mathematical models and our theoretical predictions.

A Comparison of Rheological Models and Experimental Data of Metallocene Linear Low Density Polyethylene Solutions as a Function of Temperature and Concentration

2016 ◽  
Vol 12 (3) ◽  
pp. 4322-4339
Author(s):  
Salah Hamza
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Rheological Properties ◽  
Power Law ◽  
Low Density Polyethylene ◽  
Effect Of Temperature ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Shear Rates ◽  
Wide Range

Knowledge of rheological properties of polymer and their variation with temperature and concentration have been globally important for processing and fabrication of polymers in order to make useful products. Basheer et al. [1] investigated, experimentally, the changes in rheological properties of metallocene linear low density polyethylene (mLLDPE) solutions by using a rotational rheometer model AR-G2 with parallel plate geometry. Their work covered the temperature range from  to  and  concentration from  to . In this paper, we reconsider Basheer work to describe the rheological behavior of mLLDPE solutions and its dependence on concentration and temperature.Until now, several models have been built to describe the complex behavior of polymer fluids with varying degrees of success. In this article, Oldroyd 4-constant, Giesekus and Power law models were tested for investigating the viscosity of mLLDPE solution as a function of shear rate. Results showed that Giesekus and power law models provide the best prediction of viscosity for a wide range of shear rates at constant temperature and concentration. Therefore, Giesekus and power law models were suitable for all mLLDPE solutions while Oldroyd 4-constant model doesn't.A new proposed correlation for the viscosity of mLLDPE solutions as a function of shear rate, temperature and concentration has been suggested. The effect of temperature and concentration can be adequately described by an Arrhenius-type and exponential function respectively. The proposed correlation form was found to fit the experimental data adequately.

Simulation of an Industrial Linear Low Density Polyethylene Plant

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Ali Farhangiyan Kashani ◽  
Hossein Abedini ◽  
Mohammad Reza Kalaee
Keyword(s):  
Steady State ◽  
Average Molecular Weight ◽  
Molar Fraction ◽  
Operating Conditions ◽  
Low Density Polyethylene ◽  
Process Equipment ◽  
Flow Index ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Wide Range

In this paper, an industrial linear low density polyethylene (LLDPE) production process including two serried fluidized bed reactors (FBR) and other process equipment was completely simulated in steady state mode. Both of FBRs were considered like two serried continuous stirred tank reactors (CSTR). In this simulation, a kinetic model that is based on a multiple active site heterogeneous Ziegler-Natta catalyst was used for simulation of reactions in two FBRs. Simulator by using this model is able to predict the important attributes of LLDPE like melt flow index (MFI), density (ρ), polydispersity (PDI), numerical and weight average molecular weight (Mn, Mw) and co-polymer molar fraction (SFRAC). On the other hand, this simulator can be applied in wide range of changing in inlet operating conditions. The results of the simulation are compared with industrial data of LLDPE plant. A good agreement is observed between the simulator predictions and actual plant data. Finally, by using of the simulator, the steady state operating conditions for producing different grades of polyethylene are obtained.

Mechanical properties and morphology of low density polyethylene/polydimethylsiloxane immiscible blends: modeling and influence of curing agent

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohammad Razavi-Nouri ◽  
Jalil Morshedian ◽  
Morteza Ehsani ◽  
Farhad Faghihi
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Tensile Properties ◽  
Mechanical Model ◽  
Low Density Polyethylene ◽  
Morphological Observation ◽  
Low Density ◽  
Curing Agent ◽  
Immiscible Blends ◽  
Equivalent Mechanical Model

AbstractThe tensile behavior of low density polyethylene/polydimethylsiloxane immiscible blends was investigated with respect to morphological variation of the blends. Experimental data of elastic modulus was compared with theoretical predictions of parallel model (mixing rule), as the upper bound of modulus, Halpin- Tsai model, and a two-parameter equivalent mechanical model proposed by Kolarik, which takes into account the continuity of minor phase. As the predictions of these models were not in good quantitative agreement with experiment, some modifications were made to the Kolarik model. Furthermore, a new approach for determining equivalent mechanical model parameters was proposed based on the calculation of phase continuity parameters as a function of composition. Using this approach, the values predicted for elastic modulus were found to be in good agreement with the experimental data. Moreover, the influence of a peroxide curing agent on the tensile properties of the blends was studied. The improvement of the tensile properties of the blends could have resulted from two contributions: the effect of curing reaction on the tensile properties of constituents and the better interfacial adhesion, because of possible interfacial reaction, as indicated by morphological observation.

Influence of moulding condition on the properties of dressed and functionalized nanocomposites based on low density polyethylene

2021 ◽  
Vol 2 ◽  
pp. 77-86
Author(s):  
R. V. Kurbanova ◽  
◽  
N. T. Kakhramanov ◽  
V. S. Osipchik ◽  
A. D. Guliev ◽  
...  
Keyword(s):  
Flexural Modulus ◽  
Experimental Studies ◽  
Holding Time ◽  
Volumetric Shrinkage ◽  
Breaking Stress ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Technological Properties ◽  
Wide Range ◽  
Casting Pressure

The results of a study of the effect of injection molding on the physicomechanical and technological properties of nanocomposites based on functionalized low-density polyethylene by maleic anhydride and dressed with talc γ-aminopropyltriethoxysilane are presented. As the object of study, nanocomposites with 5.0 and 30 mass. % of dressed talc were used. Properties such as breaking stress, elongation at break, flexural strength, and volumetric shrinkage were investigated. It was found that the introduction of dressed talc in the composition of chemically modified low density polyethylene contributes to some increase in the breaking stress and the flexural modulus of the nanocomposite. Experimental studies were carried out in a wide range of temperatures of the material cylinder and casting pressure. It was found that comparatively high physical and mechanical properties are achieved in samples obtained at higher temperatures in the zones of the material cylinder. Casting pressure ranged from 50 to 150 MPa. It was found that relatively high physicomechanical and technological properties for nanocomposites with 5.0 and 30 mass. % talc content are achieved at a temperature of the material cylinder in the zones 110 – 130 – 160 – 180 °C and a casting pressure of 150 MPa. A significant reduction in volumetric shrinkage is achieved in samples with 30%mass. talc content. The influence of mold temperature and holding time under pressure on the change in the properties of nanocomposites is considered. It is shown that the most optimal mode in the cooling mold for samples with 5.0 mass. % talc content is 50 °C and the exposure time under pressure is 20 s, and for a nanocomposite with 30%mass. talc content — 50 °C and holding time 10 s. The influence of the location of the gate device relative to the surface of the sample on the change in the properties of composite materials is studied. The scientific substantiation of the discovered patterns in changing the properties of nanocomposites is given.

An experimental study on foaming of linear low-density polyethylene/high-density polyethylene blends

2016 ◽  
Vol 53 (1) ◽  
pp. 83-105 ◽  
Author(s):  
Peyman Shahi ◽  
Amir Hossein Behravesh ◽  
Ali Haghtalab ◽  
Ghaus Rizvi ◽  
Fatemeh Goharpei
Keyword(s):  
Bulk Density ◽  
High Density Polyethylene ◽  
Cell Structure ◽  
High Density ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Polyethylene Blends ◽  
Wide Range ◽  
Foaming Behavior

In this research work, foaming behavior of selected polyethylene blends was studied in a solid-state batch process, using CO2 as the blowing agent. Special emphasis was paid towards finding a relationship between foamability and thermal and rheological properties of blends. Pure high-density polyethylene, linear low-density polyethylene, and their blends with two weight fraction levels of high-density polyethylene (10 and 25%wt.) were examined. The dry blended batches were mixed using an internal mixer in a molten state, and then the disk-shaped specimens, 1.8 mm in thickness, were produced for foaming purposes. The foaming step was conducted over a wide range of temperatures (120–170℃), and the overall expansion and cellular morphology were evaluated via density measurements and captured SEM micrographs, respectively. Three-dimensional structural images were also captured using a high resolution X-ray micro CT for different foamed samples and were compared. Rheological and DSC tests for the virgin and blends were also performed to seek for a possible correlation with the formability. Based on the results, blended polyethylene foams exhibited remarkable expansion and highly enhanced cell structure compared to pure polymers. Bulk density, as low as 0.33 g/cm3, was obtained for blends, while for the virgin high-density polyethylene  and linear low-density polyethylene, bulk density lower than 0.5 g/cm3 was not attainable. The lowest density was observed at a foaming temperature of 10–20℃ above the melting (peak) temperature obtained via DSC test. Rheological characteristics, including storage modulus and cross-over frequency value, were also found to be the indicators for the materials foaming behavior. Moreover, blends with 25% wt. of high-density polyethylene exhibited the highest expansion values over a wider range of temperature compared with 90% linear low-density polyethylene/10% high-density polyethylene.

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