scholarly journals Craze initiation in glassy polymers: Quantifying the influence of molecular orientation

Polymer ◽  
2011 ◽  
Vol 52 (18) ◽  
pp. 4045-4053 ◽  
Author(s):  
Davide S.A. De Focatiis ◽  
C. Paul Buckley
Keyword(s):  
Molecular Orientation ◽  
Glassy Polymers ◽  
Craze Initiation

Criteria of Craze Initiation in Glassy Polymers

1971 ◽  
Vol 42 (11) ◽  
pp. 4188-4196 ◽  
Author(s):  
Tsuey T. Wang ◽  
M. Matsuo ◽  
T. K. Kwei
Keyword(s):  
Glassy Polymers ◽  
Craze Initiation

A micro-indentation method for probing the craze-initiation stress in glassy polymers

Polymer ◽  
2003 ◽  
Vol 44 (8) ◽  
pp. 2481-2491 ◽  
Author(s):  
H.G.H van Melick ◽  
O.F.J.T Bressers ◽  
J.M.J den Toonder ◽  
L.E Govaert ◽  
H.E.H Meijer
Keyword(s):  
Glassy Polymers ◽  
Indentation Method ◽  
Craze Initiation ◽  
Micro Indentation ◽  
Initiation Stress

Craze initiation in glassy polymers – Revisited

Polymer ◽  
2011 ◽  
Vol 52 (10) ◽  
pp. 2319-2327 ◽  
Author(s):  
A.S. Argon
Keyword(s):  
Glassy Polymers ◽  
Craze Initiation

Growth Mechanism, Local Stresses, and Young's Moduli of Micro-Deformation Zones in Glassy Polymers Films by AFM

1993 ◽  
Vol 308 ◽  
Author(s):  
A.C.-M. Yang ◽  
M.S. Kunz ◽  
T.W. Wu
Keyword(s):  
Stress Distribution ◽  
Shear Deformation ◽  
Strain Softening ◽  
Glassy Polymer ◽  
Glassy Polymers ◽  
Young’S Moduli ◽  
Atomic Force ◽  
Local Stresses ◽  
Craze Initiation ◽  
Micro Deformation

ABSTRACTBy studying the topography of crazes and shear deformation zones in polymer films with the Atomic Force Microscope (AFM), it was found that crazes and shear deformation zones grew by a micro-necking process. This discovery indicates that when a glassy polymer undergoes local deformations, the material drawn into the deformation zones continues to be deformed until a much later time than that previously understood. Details of the craze micro-necking mechanism and its important implications will be discussed. Based on the necking mechanics, it was shown that craze initiation and growth can be examined using a modified Considere construction, and the stress distribution within a micro-deformation zone was investigated by assuming the Bridgman's theory. The results of the stress analysis are in excellent agreement with the breakdown behavior of crazes observed experimentally. The Young's moduli of the crazed and sheared polymers within the tiny deformation zones were also measured using a simple new AFM technique. Evidence of strain softening was clearly observed in that both the Young's moduli of crazes and shear deformation zones were very low compared to that in the bulk.

On criteria for craze initiation in glassy polymers

1988 ◽  
Vol 23 (11) ◽  
pp. 3927-3932 ◽  
Author(s):  
M. Kawagoe ◽  
M. Kitagawa
Keyword(s):  
Glassy Polymers ◽  
Craze Initiation

Polarized microbeam FT-IR analysis of single fibers

1996 ◽  
Vol 54 ◽  
pp. 206-207
Author(s):  
Liling Cho ◽  
David L. Wetzel
Keyword(s):  
Molecular Orientation ◽  
Transition Point ◽  
Polymer Fibers ◽  
Single Fiber ◽  
Wire Grid ◽  
Polyester Fibers ◽  
Ft Ir ◽  
Ir Analysis ◽  
The Relationship ◽  
Wire Grid Polarizer

Polarized infrared microscopy has been used for forensic purposes to differentiate among polymer fibers. Dichroism can be used to compare and discriminate between different polyester fibers, including those composed of polyethylene terephthalate that are frequently encountered during criminal casework. In the fiber manufacturering process, fibers are drawn to develop molecular orientation and crystallinity. Macromolecular chains are oriented with respect to the long axis of the fiber. It is desirable to determine the relationship between the molecular orientation and stretching properties. This is particularly useful on a single fiber basis. Polarized spectroscopic differences observed from a single fiber are proposed to reveal the extent of molecular orientation within that single fiber. In the work presented, we compared the dichroic ratio between unstretched and stretched polyester fibers, and the transition point between the two forms of the same fiber. These techniques were applied to different polyester fibers. A fiber stretching device was fabricated for use on the instrument (IRμs, Spectra-Tech) stage. Tension was applied with a micrometer screw until a “neck” was produced in the stretched fiber. Spectra were obtained from an area of 24×48 μm. A wire-grid polarizer was used between the source and the sample.

Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions

1990 ◽  
Vol 48 (4) ◽  
pp. 1092-1093
Author(s):  
Wendy Putnam ◽  
Christopher Viney
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Polymer Processing ◽  
Molecular Alignment ◽  
Global Alignment ◽  
Shear Direction ◽  
Axial Strength ◽  
Strength And Stiffness

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.

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