In situ copolymerization of ethylene to produce linear low-density polyethylene by Ti(OBu)4/AlEt3-MAO/SiO2/Et(Ind)2ZrCl2

2004 ◽  
Vol 94 (6) ◽  
pp. 2451-2455 ◽  
Author(s):  
Bochao Zhu ◽  
Cunyue Guo ◽  
Zhongyang Liu ◽  
Yuanqi Yin
Keyword(s):  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
In Situ Copolymerization

In Situ Positron Lifetime Measurement for the Strained Polyethylene

2012 ◽  
Vol 733 ◽  
pp. 139-142
Author(s):  
Masanori Fujinami ◽  
Ryutaro Minei ◽  
Chang Gui Liu ◽  
Kenta Hara
Keyword(s):  
Structural Change ◽  
Positron Lifetime ◽  
Tensile Deformation ◽  
Positron Annihilation Spectroscopy ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Day By Day ◽  
Positron Lifetime Measurement

The in situ positron annihilation spectroscopy measurement has been developed and applied to investigate the structural change in free volume on the tensile deformation of linear low-density polyethylene. The pick-off lifetime of ortho-positronium (Ps) decreases by applying the strain and an aging variation cannot be observed. On the contrary the fraction of Ps formation gradually decreases day by day and becomes constant after several days. Further, after release of strain, it returns to the original value. The reason is considered to be that the molecular chains become rigid gradually during deformation and they lose the flexibility.

scholarly journals Identification of the LLDPE Constitutive Material Model for Energy Absorption in Impact Applications

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1537
Author(s):  
Luděk Hynčík ◽  
Petra Kochová ◽  
Jan Špička ◽  
Tomasz Bońkowski ◽  
Robert Cimrman ◽  
...  
Keyword(s):  
Strain Rate ◽  
Material Model ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Stress Strain ◽  
Rate Dependent ◽  
Constitutive Material Model ◽  
Principal Directions ◽  
Constitutive Material

Current industrial trends bring new challenges in energy absorbing systems. Polymer materials as the traditional packaging materials seem to be promising due to their low weight, structure, and production price. Based on the review, the linear low-density polyethylene (LLDPE) material was identified as the most promising material for absorbing impact energy. The current paper addresses the identification of the material parameters and the development of a constitutive material model to be used in future designs by virtual prototyping. The paper deals with the experimental measurement of the stress-strain relations of linear low-density polyethylene under static and dynamic loading. The quasi-static measurement was realized in two perpendicular principal directions and was supplemented by a test measurement in the 45° direction, i.e., exactly between the principal directions. The quasi-static stress-strain curves were analyzed as an initial step for dynamic strain rate-dependent material behavior. The dynamic response was tested in a drop tower using a spherical impactor hitting a flat material multi-layered specimen at two different energy levels. The strain rate-dependent material model was identified by optimizing the static material response obtained in the dynamic experiments. The material model was validated by the virtual reconstruction of the experiments and by comparing the numerical results to the experimental ones.

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