Effect of filling on the first difference of the normal stresses in a melt of low-density polyethylene with steady-state shear flow

1973 ◽  
Vol 6 (3) ◽  
pp. 490-491
Author(s):  
L. A. Faitel'son ◽  
A. I. Alekseenko
Keyword(s):  
Steady State ◽  
Shear Flow ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Normal Stresses

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.

scholarly journals DETERMINATION OF LOW OXYGEN TOLERANCE LIMITS FOR SEVERAL APPLE CULTIVARS

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 592g-593
Author(s):  
Christopher D. Gran ◽  
Randolph M. Beaudry
Keyword(s):  
Steady State ◽  
Anaerobic Respiration ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Low Oxygen ◽  
Tolerance Limits ◽  
Partial Pressures ◽  
Lower Oxygen ◽  
Apple Cultivars

The oxygen partial pressure associated with the respiratory quotient (RQ) breakpoint (ie., lower oxygen limit) was determined for fruits of several apple cultivars stored at 0°C. Fruits were sealed in low density polyethylene pouches of various thicknesses and known permeability to determine O2 uptake, CO2 production, and respiratory quotients (RQ) at various O2 partial pressures. There were differences in the shape of O2 uptake versus steady state O2 curves between cultivars. While some cultivars showed steady declines in respiration rate from 8 kPa O2 to < 1 kPa, other cultivars showed no decline in respiration until O2 levels fell below 3 to 4 kPa. Fruits having elevated RQ values had greater levels of headspace ethanol in the polyethylene pouches, which confirmed anaerobic respiration. The lower oxygen limit ranged from a low of approximately 0.75 kPa for cultivars Northern Spy and Law Rome to high of 1.5 kPa for McIntosh.

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