Oxygen-enriched radical has a polar character. It increases surface energy and raises hydrophilic property. Fig. 5 shows variations of surface energy when 200W low-pressure mercury lamp irradiations were given in the atmosphere at different times of PBT and PPS 3). The surface energy was evaluated with a wetting reagent. 4)
As exposure increased, the "wetting exponent" increased rapidly in the beginning and slowly later. Fig. 6 shows the relations between strength and irradiation when the same PPS and PBT as processed in Fig. 5 were adhered with a two-component epoxy adhesive. Like the wetting exponent, the adhesion power got stronger as the exposure increased.
However, when the adhesion strength reached its peak at a certain amount of exposure, it started to decrease. This does not mean any mistake of data. It is necessary for adhesives to be well soaked into adherend surfaces, while adhesives have their own surface tension. The maximum adhesion power can be attained when the adherend and the surface tension of adhesives are equivalent, namely when the surface tension of both polar component and non-polar components are equivalent and the boundary tension becomes zero.

The UV/Ozone method does not secure any universal effects to modify adhesion power, and its effects largely depend on materials.
Although we have no adequate data yet, we show you differences in modifying effects of materials, namely trends of modification as per Table 1.

Table 1.The trends of modifying effects of materials by UV/Ozone(R3)

Materials	Criticalsurface tension(dyne/cm)	Modify.effects	Note
PPS Fortron 6165A4(GF)			Practical use:Passenger cars etc
PBT VALOX 310-SEO-1001			Practical use:Passenger cars etc
Nylon6.6
Nylon 46 TS-200F6	46
PET FR-PET C9093	43
LCP XYDAR 6330(GF)/ V			Flexible multi-layer printed circuit board
Polyamid 12 Dyamid L-1930 Dyamid L-1940
PEEK VICTREX PEEK 450G
Polysulfone UDELP-1700GF-130NT(GF)
Polyetherimid ULTEM 2300-1000
Denatured PPO NORYL SEIJ-701
Polyimide			FPC
Polystyrene	33-36		Plastics aquarium
Fluorocarbon polymer	18-21	×
Polyvinyl acetal		×
PP(homo)	27-29	×	Simple UV/Ozone method
PP(homo)			UV sensitizing method
PP(Blended)			Devices of a passenger car
PE	31-32	×
Vulcanized rubber			Brake of a motorcycle
Epoxy resin (GF)			Coating of the track coil core of Maglev train
Aluminum			Condenser foil
Stainless steel

Description of code
1: 2:×,Practical result of SEN LIGHTS
:Very strong(>85kg/cm2) :Good result ×:Non effective
:Strong (45~85kg/cm2)
:Weak(20~60kg/cm2)
Glue: Epoxy resin AV138/HV998

We think that to make this table more complete will be an important issue for future expansion of the technology.
The technology is not effective for fluorocarbon polymer or polyvinyl acetal, but many engineering plastics enjoy its good effects.
It is also practically applied to metals such as aluminum and stainless steel though fewer cases than plastics.6)
It is known that you can enhance modification with a sensitizer of such material that cannot attain any adequate modification in a simple UV/Ozone method.
In case of polypropylene for example, there is prohibited use of organic chlorinated solvents, this technology is no longer used without seeing the light of the day, with the only and last example of pre-coating process of the automobile mudguard as shown in Fig. 1.
Recently a variety of photo sensitizers have been researched for development to take the place of organic chlorinated solvents.
Among them we see an instance of development of excellent liquid crystal polymer film of the flexible multilayer micro printed circuit board, by means of applying a 254nm UV irradiation to liquid crystal polymer in presence of a photo sensitizer and by means of graft polymerization of vinyl monomer of polymer character.
In the laid-open disclosure of public patent bulletin, they describe coating of hydrazine solution to LCP film and then applying a 120 second irradiation of 200W low-pressure mercury lamp (a practical case of the UV sensitizing method), and also give a detailed comparison of modification results among the plasma treatment in the nitrogen/ammonium gas atmosphere, the conventional UV/Ozone method and the plasma treatment in the presence of oxygen.
The quotation of the results only are shown in Table 2.

Table 2.The detailed comparison of the modification results on the LCP film

Description of the methods
Practical case 1:UV sensitizing method (Sensitizer of hydrazine solution +UV irradiation)
Practical case 2: Plasma process (Nitrogen/Ammonium gas atmosphere)
Comparative case 1:UV/Ozone method
Comparative case 2:Plasma process(presence of oxygen)