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
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:
- Gap coatings
- Immersion coatings
- Curtain coatings
- Rotary screen coatings
- Gravure coatings
- Reverse roll coatings
- Metering rod coatings
- Slot die (extrusion) coatings
- Hot melt coatings
- Flexographic coatings
- Silk screen coatings
- 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.Recommend