Organization of hydrogen energy technologies training

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• Organization of hydrogen energy technologies
  training
• No. ESF/2004/2.5.0-K01-045
• Main organization - Lithuanian Energy Institute
• Partner - Vytautas Magnus University

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• Introduction to the topic
• In recent years we have witnessed a remarkable
  growth in the use of synthetic organic polymers
  in technology, both for high-tech and for
  consumer-product applications
• Polymers have been able to replace more
  traditional engineering materials such as metals,
  on account of their many desirable physical and
  chemical characteristics (high strength-to-weight
  ratio, resistance to corrosion, etc.) and their
  low cost
• Fundamental differences between polymers and
  other engineering solids have also created
  numerous important technical challenges
• An important example is the characteristic low
  surface energy of polymers and their resulting
  intrinsically poor adhesion

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• Formulation of the problem
• Investigate general terms of adhesion theory
• Review methods of adhesion testing
• Overlook methods of surface treatment of
  plastics advantages of plasma technologies
• Examine plasma effects on polymer surfaces
• Review experimentally received results for
  adhesion changes of polymers affected by plasma

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• The Theory of Adhesion Contact angle equilibrium
• Youngs equation
• ?sa ?lv cos ? ?sl
• Harkins and Livingstons solid-air-plus-vapor
  tensor and modified Youngs equation
• ?sv ?sa pe ? ?sa ?lv cos ? ?sl pe

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• The Theory of Adhesion Work of Adhesion
• The work of adhesion (Wa) is the thermodynamic
  work necessary to separate the liquid from the
  solid without performing any additional work
• When a liquid is separated from a solid, new
  solid-air and liquid-air interfaces are created,
  and solid interface is destroyed. This is
  described by Dupré equation
• Wa ?lv (1 cos ?) pe

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• The Theory of Adhesion Theoretical adhesion
  models
• The absorption or chemical reaction theory, which
  states that bond strength is mainly determined by
  physi- or chemisorption at the interface
• The electrostatic theory of Deryagin, which is
  based on contact charging when two dissimilar
  materials are intimately joined
• The diffusion theory of Voyutskii, which claims
  that the bond strength of polymers is governed by
  diffusion rate across their interface
• The rheological theory of Bikerman, which states
  that the performance of bonded system is governed
  by the mechanical properties of the materials
  comprising the joint, and by local stresses in
  the joint
• The mechanical interlocking or hooking theory,
  based on the micro-geometry of the interface

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• The Theory of Adhesion Types of Adhesion failure

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• Adhesion Testing Cross-Cut test
• A grid pattern of cuts trough the coating is
  made. A standard tape is applied, then quickly
  stripped

classification 0 1
2 3 4
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• Adhesion Testing Tensile Methods
• A stud, normally made of steel, is glued with the
  coating and is subjected to axial or radial
  tension until detachment of paint film occurs.
  The adhesion strength is the maximum tensile
  stress that is possible

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• Adhesion Testing Indentation debonding
• A needlelike indenter is perpendicularly pressed
  into the surface of the coating, most of the
  deformation will occur within the film, but
  there also will be a certain debonding effect at
  the interface

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• Methods of polymer surface treatment

Solvent cleaning Detergent cleaning Mechanical treatment Chemical treatment Primers Flame treatment Exposure to Ultraviolet radiation Drying Glow discharge plasma treatment Corona discharge
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• Advantages of low-pressure plasma surface
  treatment
• Four main effects cleaning, ablation or
  etching, crosslinking, and surface chemical
  modification occur together in a complex
  synergy
• Effects only the surface leaving bulk unchanged
• Can be applied to objects of wide range of sizes
  and all possible geometries, also including fine
  particles such as powders, fibers or flakes
• Causes low or even no environmental problems

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• Experimental scheme
• Working gases air, oxygen, nitrogen
• Working pressure 2.0 at thermopolic
• Scale (about few hundreds Pascal's)
• Exposure time 1, 5, 10, 15, 20 min

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• Experimental results Cross-Cut test results
  (classification)

Air O2 N2
1 2 3 3
5 1 1 1
10 2 1 2
15 0 1 2
20 1 1 2
Gases
Time, min
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• Experimental results Optical microscopy photos
  (air 1 min)

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• Experimental results Optical microscopy photos
  (air 5 min)

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• Experimental results Optical microscopy photos
  (air 10 min)

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• Experimental results Optical microscopy photos
  (air 15 min)

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• Experimental results Optical microscopy photos
  (air 20 min)

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• Conclusions
• Despite the fact that there is quite precise
  definition for adhesion, the fundamental
  principles of adhesion phenomena is still not
  very clear
• There are a lot of methods for adhesion
  measurements. The appropriate method can be
  chosen according to polymer and the film
  properties
• Several surface treatment exists all of them
  having own advantages ad disadvantages
• Plasma treatment can be very promising method for
  polymer surface activation and modification
• Experimentally received results confirm the
  effectiveness of plasma treatment fine level of
  adhesion is achieved after 1 minute of the
  treatment.
• It is also seen that the effect of the plasma
  treatment strongly depends on process time and
  working gas