Melt fracture of linear low-density polyethylenes: Die geometry and molecular weight characteristics

2018 ◽  
Vol 30 (5) ◽  
pp. 053103 ◽  
Author(s):  
Marzieh Ebrahimi ◽  
Tanja Tomkovic ◽  
Guochang Liu ◽  
Antonios A. Doufas ◽  
Savvas G. Hatzikiriakos
Keyword(s):  
Molecular Weight ◽  
Low Density ◽  
Melt Fracture ◽  
Die Geometry ◽  
Molecular Weight Characteristics

Synthesis and molecular-weight characteristics of n-vinylpyrrolidone and 2-methyl-5-vinylpyridine copolymers

2012 ◽  
Vol 46 (8) ◽  
pp. 478-481 ◽  
Author(s):  
S. A. Kedik ◽  
A. V. Panov ◽  
I. V. Sakaeva ◽  
Yu. V. Kochkina(Cherta) ◽  
D. V. Eremin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Characteristics

CATIONIC COPOLYMERIZATION OF ISOBUTYLENE WITH ISOPRENE: KINETICS OF THE PROCESS AND DETERMINATION OF KINETIC CONSTANTS

2015 ◽  
Vol 88 (4) ◽  
pp. 574-583 ◽  
Author(s):  
N. V. Ulitin ◽  
K. A. Tereshchenco ◽  
D. A. Shiyan ◽  
G. E. Zaikov
Keyword(s):  
Experimental Data ◽  
Molecular Weight ◽  
Cationic Polymerization ◽  
Methyl Chloride ◽  
Theoretical Description ◽  
Kinetic Constants ◽  
Molecular Weight Characteristics ◽  
Cationic Copolymerization ◽  
Kinetics Of

ABSTRACT A theoretical description has been developed of the kinetics of isobutylene with isoprene (IIR) cationic polymerization in the environment of methyl chloride on aluminum trichloride as the catalyst. Based on experimental data on the kinetics of copolymerization (isobutylene conversion curve) and the molecular weight characteristics of the copolymer of IIR, kinetic constants for the process were found. Adequacy of the developed theoretical description of the kinetics of the IIR copolymerization process was confirmed by comparing the experimental molecular-weight characteristics calculated by this description, independent characteristics, and IIR unsaturation.

Role of molecular architecture in interfacial self-adhesion of polyethylene films

2017 ◽  
Vol 33 (3) ◽  
pp. 235-261 ◽  
Author(s):  
Zahra Najarzadeh ◽  
Abdellah Ajji
Keyword(s):  
Molecular Weight ◽  
Adhesion Strength ◽  
Film Surface ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Molecular Architecture ◽  
Melt Temperature ◽  
Long Chain ◽  
Long Chain Branch ◽  
Chain Branch

The influence of molecular architecture on interfacial self-adhesion above polyethylene film melt temperature was examined in this study. The investigated molecular structures include molecular weight (Mw), molecular weight distribution, long chain branch amount and distribution and short chain branch among and along polyethylene chains. The long chain branches concentration was quantified using gel permeation chromatography and short branches concentration using nuclear magnetic resonance techniques. The adhesion strength was measured immediately after melt bonding using a T-Peel test. The results showed that increasing Mw resulted in higher adhesion strength in linear metallocene ethylene α-olefins. Low long chain branch concentrations hinder reptation motion and diffusion, and result in lower adhesion strength. Low density polyethylene with highly branched chains yielded very low self-adhesion. A drastic difference in adhesion strength between metallocene and conventional linear low density polyethylene is attributed to homogeneity versus heterogeneity of composition distribution. The low interfacial self-adhesion in conventional polyethylene was concluded to be due to enrichment of highly branched low molecular weight chains at the film surface. These segregated chains at the interface diffuse before the high molecular weight chains located in the bulk.

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