30. April 2013   11:36 am
Dr. K. L. Mittal, Dr. Robert H. Lacombe

Dr. K. L. Mittal, Dr. Robert H. Lacombe

PLASTIC SURFACE MODIFICATION: Surface Treatment and Adhesion, by Rory Wolf (Carl Hanser Verlag, Munich 2010)

Apropos of the upcoming 9th International Symposium on Polymer Surface Modification it is fitting to review a recently published volume which deals extensively with this topic.

Apart from a brief overview of polymer adhesion issues dealing with inks, coatings and adhesives the book deals extensively with the following plasma related surface modification technologies:

  • Flame Plasma Discharge
  • Corona Plasma Discharge
  • Chemical Plasma Discharge
  • Vacuum Plasma Processes
  • Atmospheric Plasma Processes
  • Ozonation

The treatment of the above technologies is very much slanted toward large scale manufacturing processes such as bare and covered roll operations and a variety of production line configurations designed for large scale output of plastic sheets and/or molded parts.

Table 8.11 from the text, for example, gives a quick overview of the applications of plasma technology. Vertically Listed in this table are more than 40 different items of large scale manufacture such as auto bumpers, tubing, petri dishes, circuit boards… etc. Reading horizontally is a list of 19 engineering thermoplastics that are commonly used to fabricate the items listed and for each polymer one or more recommended surface treatment methods are given.

Thus, say one is interested in treating plastic bottles. Reading from the table we find that polyethylene, poly carbonate, poly ethylene terethalate, polypropylene and poly vinyl chloride are the most commonly used polymers. Reading down the column for polypropylene, for example, we find that flame and plasma are the recommended treatments and that one can expect that the surface energy can be increased from 29 dynes/cm to somewhere in the range of 40-48 dynes/cm.

The number of coating technologies covered is quite amazing. The volume covers some 12 different manufacturing scale coating methods including:

  1. Gap coatings
  2. Immersion coatings
  3. Curtain coatings
  4. Rotary screen coatings
  5. Gravure coatings
  6. Reverse roll coatings
  7. Metering rod coatings
  8. Slot die (extrusion) coatings
  9. Hot melt coatings
  10. Flexographic coatings
  11. Silk screen coatings
  12. Nano coatings

It seems that the number of applications is truly unbounded. My favorite application covered in the book is the Radio Frequency Identification Tags (RFID). These high tech labels look little different from the common mailing variety but contain a small microchip (0.25mm square) connected to a flat antenna all sandwiched between multiple base and overcoat layers which serve to protect the device from the elements and rough handling and further allow it to adhere to the package it is intended to identify. When probed by a nearby scanner the chip can reveal a range of useful information identifying the contents of the package such as product type, color, size, serial number…etc. Interestingly the chip requires so little power it can run on the radiation energy emitted by the scanner.

One can easily imagine a number of delamination failure mechanisms which can destroy the function of such a device including flexing during application and thermal stresses due to large temperature swings (imagine a package being shipped from Miami Florida to Noam Alaska during the northern winter). Thus, not surprisingly, plasma technology is being used to both clean and surface treat the various layers used in the manufacture of RFIDs.

My main complaint with the volume is the rather cavalier treatment of physical data in the numerous graphs given on adhesion strength. No fewer than 5 nonstandard measurement units are in use. Thus we find in figure 7.5 the picturesque G/in units! Figure 5.4 uses the slightly more reasonable g/15mm units, figure 6.10 features N/15mm and figure 5.5 the truly archaic lb/in. Many plots such as figures 6.2 and 6.3 come with no label for the vertical axis whatever. All of this detracts from what is a most interesting and informative volume. One would hope that follow on editions would attempt to standardize the treatment of physical data by using standard SI units throughout.

However, technical misgivings aside, we can enthusiastically recommend this volume to anyone interested in an overview of the truly astounding range of manufacturing processes that are being affected by modern surface treatment technologies and by plasma methods in particular.

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2. April 2013   9:03 am
Dr. K. L. Mittal, Dr. Robert H. Lacombe

Dr. K. L. Mittal, Dr. Robert H. Lacombe

Welcome to our new blog: It is our pleasure to contribute to the Plasmatreat blog site a section dealing with various aspects of surface science and technology and how it impacts various day to day projects dealing with product development and manufacturing. In this regard we have chosen to label the blog as the SURFACE SCIENCE CORNER.

Though the Plasmatreat site deals mainly with issues confronting the open air plasma technology the general aspects of surface science play a vital role in the ultimate success or failure of this methodology as it does also with all other surface modification techniques. Thus the material presented will deal with a fairly wide range of issues of both direct and indirect relevance to the treatment of surfaces with plasmas.

INTRODUCTION

As this is the inaugural issue of the blog it is appropriate that we give a short resume of our backgrounds and how they relate to surface science.
We are Drs. Mittal and Lacombe and our interest and expertise in surface science stems from some 30 years experience in the microelectronics industry. A typical microchip device can consist of a dozen or more layers of insulator, semiconductor and metal materials each on the order of a micrometer or less in thickness. Thus a sizable fraction of the structure can be considered as either a surface or an interface between two surfaces thereby giving rise to a wide range of interactions not all of which are amicable to the overall stability of the device. The microelectronics industry was in fact one of the first to utilize plasma technology on a wide scale both for cleaning purposes and for etching fine lines in photoresists.

Dr. Mittal has mainly focused on writing about and carefully documenting the various aspects of surface science and how they impacted microelectronic technology. He was editor of the Journal of Adhesion Science and Technology from 1987 to 2012 and has also edited over 100 volumes dealing with surface cleaning, adhesion, high temperature polymers, thin films, surface analytical methods and surfactants in solution. This long experience has given him an encyclopedic knowledge of a wide range surface science topics and, very recently, he has started a new journal called Reviews of Adhesion and Adhesives (RAA).

Dr. Lacombe, while sharing the same office with Dr. Mittal for some 7 years, was more a man of the laboratory setting up equipment, performing experiments and carrying out large scale calculations of the thermodynamic stability of multilevel laminate structures. He was among the first investigators to measure the thermal-mechanical properties of 2 nanometer thick monolayer films which were being investigated as the ultimate photoresists already in the early 1980’s. He was also heavily involved in the field of adhesion measurement and has written the only volume dedicated solely to this topic (Adhesion Measurement Methods: Theory and Practice, CRC Press, 2006).

TOPICS

Let us now conclude this introduction with a brief list of the types of topics that will be covered in future issues. Among the topics of most interest are:

ADHESION: One of the primary uses of plasma technology is to alter the chemistry of a surface in such a way as to increase the surface energy and thus significantly improve the adhesion of candidate coatings. Plasma technology has been very effective in this regard. However, it is also important to know whether the level of adhesion achieved is sufficient for the purpose at hand so the topic of adhesion measurement will also be an important consideration.

SURFACE CLEANING: Surface cleaning is another important application of plasma technology and it is also critical to ascertain the level of cleaning attained to know whether it is sufficient or not. Thus measuring surface cleanliness is a further important issue.

SURFACE ANALYTICAL METHODS: The ability to analyze the chemical and physical nature of a surface is of course critical to both of the above mentioned topics. Thus attention will be paid to the various analytical methods used to investigate surface chemistry such as X-ray Photoelectron Spectroscopy (XPS also going under the alias Electron Spectroscopy for Chemical Analysis, ESCA). The thermodynamic nature of surfaces is effectively investigated through the use of CONTACT ANGLE measurements. This rather prosaic measurement technique, though rather simple in concept, is quite subtle in practice and can provide a wealth of valuable information on the physico-chemical nature of surfaces.

BOOK REVIEWS: Our office receives a number of volumes dealing with all aspects of surface science. From time to time when a particularly relevant volume is received it will be brought to the attention of readers of this blog by way of a critical review.

REVIEWS OF IMPORTANT CURRENT RESEARCH: By way of keeping up to date on all aspects of surface science we organize each year through MST CONFERENCES up to 4 symposia which cover the latest developments in this field. From time to time a particularly relevant presentation will be given and such will also be brought to the attention of readers again through a critical review.

Finally let us conclude with a few remarks concerning the style and presentation level of this blog series. Our basic aim will be to make what is arguably a rather esoteric topic clear and understandable to the non-expert by giving concrete examples and also by avoiding technical jargon to the greatest extent possible. Thus we aim for what might be construed as a SURFACE SCIENCE FOR DUMMIES writing style. The aim, therefore, will be to make surface science topics clear and understandable to a range of individuals who have a need to know this topic but may not have either the background or time to pursue the matter at the level of the technical literature. A famous professor once told a student that if he could explain his work to a barmaid then he indeed knew what he was talking about. We will strive to achieve that level of clarity to the greatest extent possible.

Again we are thankful for the opportunity to contribute to the Plasmatreat blog and we hope all readers will find topics of interest and enjoyment therein.

Best Regards,

Dr. K. L. Mittal, Dr. Robert H. Lacombe

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Category: SOLAR
2. April 2013   1:07 am
Wally Hansen

Wally Hansen
Belmont, CA

A recent material society meeting was a real eye opener.  Dr. Ripudaman Malhotra, energy scientist at SRI International, and co-author of the above titled book, presented a fascinating lecture regarding our energy future.

Energy is measured in so many ways that it is difficult to evaluate actual demand and consumption. We have Btu, tons of coal, barrels of oil, and KWh, mostly measured in kilo, mega and giga-huge terms. A new measurement was needed that could be visualized.

Current world use of Oil is about 1 Cubic Mile in volume.  If we compare other energy sources, in equivalents of cubic miles of oil (CMO), we have a current world consumption of about 3 CMO primarily from Oil, Coal and Natural Gas. By comparison, current Solar and Wind renewables contribute a miniscule 0.03%.

At the rate of world growth, there will be a demand for between 6 and 9 CMO in 50 years.  There is currently plenty of fossil fuels remaining but they are from less conventional sources (shale, tar sands) and will be needed while we switch to new sources. A huge task!

 

Producing 1 CMO/ year from alternate technologies will require:

Hydroelectric:                 200 dams – 4 per year for 50 years

Nuclear:                           2,500 plants – 1 a week for 50 years

Windmills:                       3 million – 1,200 a week for 50 years

Solar CSP                       7,700 solar plants – 3 a week for 50 years

Solar roofs                      4.2 billion – 250,000 roofs a day for 50 years.

 

The good news: The sun offers 23,000 CMO/year as heat, wind, photovoltaic and biomass.  The raw material is available. It is time to go to work.

I would like to thank Dr. Ripudaman Malhotra for the use of this data from an extremely interesting lecture.

I recommend the book,  A Cubic Mile of Oil: Realities and Options for Averting the Looming Global Energy Crisis by Crane, Kinderman and Malhotra.

As always, your comments and questions are welcomed.

Regards,

Wally Hansen

 

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