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 Macromolecular Insights into the Altered Mechanical Deformation Mechanisms of Non-Polyolefin Contaminated Polyolefins

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 239
Author(s):  
Ruben Demets ◽  
Marie Grodent ◽  
Karen Van Van Kets ◽  
Steven De De Meester ◽  
Kim Ragaert
Keyword(s):  
Interfacial Adhesion ◽  
Tensile Deformation ◽  
Linear Structure ◽  
Polyamide 6 ◽  
Deformation Mechanisms ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Pure Material ◽  
Polymer Type

Current recycling technologies rarely achieve 100% pure plastic fractions from a single polymer type. Often, sorted bales marked as containing a single polymer type in fact contain small amounts of other polymers as contaminants. Inevitably, this will affect the properties of the recycled plastic. This work focuses on understanding the changes in tensile deformation mechanism and the related mechanical properties of the four dominant types of polyolefin (PO) (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP)), contaminated with three different non-polyolefin (NPO) polymers (polyamide-6 (PA-6), polyethylene terephthalate (PET), and polystyrene (PS)). Under the locally elevated stress state induced by the NPO phase, the weak interfacial adhesion typically provokes decohesion. The resulting microvoids, in turn, initiate shear yielding of the PO matrix. LLDPE, due to the linear structure and intercrystalline links, is well able to maintain high ductility when contaminated. LDPE shows deformation similar to the pure material, but with decreasing ductility as the amount of NPO increases. Addition of 20 wt% PA-6, PET, and PS causes a drop in strain at break of 79%, 63%, and 84%, respectively. The typical ductile necking of the high-crystalline HDPE and PP is strongly disturbed by the NPO phase, with a transition even to full brittle failure at high NPO concentration.

scholarly journals Microstructural Origin of the Double Yield Points of the Metallocene Linear Low-Density Polyethylene (mLLDPE) Precursor Film under Uniaxial Tensile Deformation

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 126
Author(s):  
Obaid Iqbal ◽  
Jean Claude Habumugisha ◽  
Shengyao Feng ◽  
Yuanfei Lin ◽  
Wei Chen ◽  
...  
Keyword(s):  
Yield Point ◽  
High Performance ◽  
Monoclinic Phase ◽  
Tensile Deformation ◽  
Low Density Polyethylene ◽  
Uniaxial Tensile ◽  
Precursor Film ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Double Yield

The microstructural origin of the double yield points of metallocene linear low-density polyethylene (mLLDPE) precursor films has been studied with the assistance of the synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS). It has been shown that the microstructural origin of the double yield points is highly related to the initial orientation of the original precursor film. For less oriented mLLDPE precursor films, the rearrangement of lamellae and the appearance of the monoclinic phase are the microstructural origins of the first yield point. In comparison, for the highly-oriented mLLDPE precursor film, only the orthorhombic-monoclinic phase transition appears at the first yield point. The melting-recrystallization and the formation of the fibrillary structure happen beyond the second yield point for all studied mLLDPE precursor films. Finally, the detailed microstructural evolution roadmaps of mLLDPE precursor films under uniaxial tensile deformation have been established, which might serve as a guide for processing high-performance polymer films by post-stretching.

Sign in / Sign up

Export Citation Format

Share Document