new opportunities for using silicone rubber.
Painting and bonding are almost impossible due to low surface energy and viscous and static surfaces.
Nanon has developed two technologies, soft plasma and enhancement, which create more possibilities using silicone rubber.
Soft plasma is a surface.
Treatment process of polymerization Nano
Silicone rubber has a scale layer with a hydrophilic functional base on the surface.
The permanent layer is tightly combined with many types of glue or paint.
Enhanced to remove unwanted residues in silicone rubber in the environment
This process is an alternative to the conventional thermal tempering process used for post-processing
Cured silicone rubber.
This paper will introduce the different applications of these technologies.
What is plasma?
Plasma is an ionised gas. While, e. g.
The Sun or star is completely transformed and the artificial plasma used for surface treatment only contains about 0. 1-
Ions and electrons of 10 ppm.
The rest are neutral species.
By exposing the gas to the energy field at low pressure, artificial plasma can be achieved.
When the plasma is triggered, the electrons are accelerated in the electric field.
When hitting an atom or molecule of a gas, ionization or debris may occur.
Positively charged ions from the gas phase impact the surface of the substrate and destroy the chemical bond of the outer layer.
This causes surface etching due to evaporation of atoms and small fragments.
Etching clean the surface and in the plasma-
The aggregation layer can be bonded later.
Plasma polymerization applies the monomer to the plasma and activates the polymerization on the surface of the substrate.
The power input of the plasma has a direct effect on the properties of the plasma reaction.
At high energy, the monomer introduced into the plasma is completely broken, and free radical formation occurs in the gas phase, resulting in a high cross-linked polymer.
At low energy, the monomer structure was retained and Free Radical Polymerization occurred on the substrate surface.
Plasma Polymerization by different energy levels Ethyl-2-
Take acrylic as the monomer.
It is evaporated and sent into the plasma chamber, in ar-
Plasma at different energy levels
As a substrate, salt-
Crystals are used.
After this process, the crystal is analyzed in the thermal infrared spectrometer by transmission measurement (figure 1). [
Figure 1 slightly]
1,745 typical peak [cm. sup. -1]and 1,249 [cm. sup. -1]
The area is reduced when the power level is increased.
This means that estergroup cannot withstand high energy levels without degradation of soft plasma rna, which is the trade name of the low pressure plasma treatment and polymerization technology developed by NKT Research.
Soft plasma allows plasma polymerization at very low energy without causing serious damage to the substrate or functional group of the monomer.
To get this low energy plasma
Phase AC plasma using 50 hz.
The surface of the electrode provides the creation of homogeneous 3D-
The plasma provides the possibility to handle items of various geometric shapes.
In theory, plasma polymerization can be carried out with various monomer to obtain ideal surface properties.
However, a single omer must meet the conditions for vacuum evaporation at room temperature.
It depends on which functional group is required on the surface to better bind to the top coating.
In order to obtain the required surface properties, vinyl acrylic compounds with a suitable functional base are generally used as the monomer.
When plasma reprocessing is performed, silicone rubber coating coated with polyurethane-coated silicone robberswitch PU becomes possible (figure 2).
NH-generated by plasma treatment--andCN--
The group of surfaces, giving higher surface energy and a good combination with the top of the PUcoating. [
Molding of nylon and silicone rubber
Forming nylon with silicone rubber, if primerchemistry and special silicone rubber are not used, it is difficult to obtain good adhesion between materials (figure 3). [
Figure 3 slightly]
Using soft plasma, we apply silica gel-
Like a surface with low surface energy on a polyamide, after which it is able to adhere with excessive adhesion
Molded silicone robbers (figure 3).
Cold tempered (Cohancement)
When we started plasma treatment of silicone, we quickly had to solve the problem of volatile substances evaporated by silicone.
These silicone aggregates migrate to the surface vacuum treatment of the material, and the plasma is aggregated on the anode film instead of the silicone surface.
It is impossible to coat again.
When we looked for ways to remove volatile substances, we looked at different methods and found that carbon dioxide (C[O. sub. 2])
Under pressure, it is a good solvent for silicone aggregates. When C[O. sub. 2]
Be pressurized to become liquid or supercritical (figure 4).
In these states, the surface tension is 0-5 mN/m. [
Figure 4 slightly]
Because of its low surface tension, C . [O. sub. 2]
Most materials, especially silicone rubber, are completely wet.
The liquid passes through the silicone rubber and expands it to dissolve the silicone oligomer and-
Products of catalyst and peroxide.
In addition, other compounds will be added to the silicone material, resulting in new properties.
Cold tempered today, most silicone rubber cured at high temperature for several hours to remove-
Product of vulcanization step and remove low molecular silicone compound from rubber.
This process takes a long time, sometimes silicone
Silicone rubber surfaces form dust that breaks down silicone, which leads to difficult problems in subsequent surface treatments.
Another problem is healing (re-polymerization)
Cuts and holes caused by post-Heat
This makes it difficult to finally design the curing steps of silicone rubber products in the mold.
In order to eliminate these shortcomings, a good choice is to use a supercritical or liquid C [O. sub. 2]topost-
Cured silicone rubber.
We have developed a cold tempered process using liquid C [O. sub. 2](at 40 bars, 10[degrees]C)
, Which makes the process cheaper and easier to deal with than in a process under a supercritical condition (at least 31 [degrees]C, 74 bars).
The following analysis was performed: Baby soothers made of silicon fiber (LSR)were post-
Ordinary hot tempered (4 hours,200[degrees]
C. air ventilation)
And tempered by cold (
Water washing liquidC [O. sub. 2], 40 bars, 10[degrees]C, 1 hour).
Subsequently, the residual content of volatile substances was analyzed with EN 14350-
Measure mechanical performance according to customer\'s standards.
GC and GPS analysis of residues according to customer standards.
A visual survey of wound healing was conducted.
Table 1 shows the effect of removing volatile substances and low-molecular silicon oligomer.
Compared with EN 14350 --
2. in addition to volatile substances, the acetone-Sorne method can also be used for the determination of other residues.
In acetone, low molecular residues, do not evaporate at [atmospheric pressure]degrees]
C. dissolve, resulting in a higher weight loss value.
Gas chromatography analysis showed that harmful cylosione was removed in the range D4 to D20.
And within the scope of the D30 (20cST)
Gel penetration chromatography analysis showed a significant decrease in silicon oligomer in trees.
Mechanical properties are shown in Table 2. The C[O. sub. 2]
Treatment has no negative effect on robbers
Similar properties of silicone.
In particular, the values of mold a 100% and 300% indicate that there is no further curing reaction in C [O. sub. 2]process.
However, there are differences compared to the thermal curing values of the compression set, tear resistance and hardness.
These assessments have not changed in C [O. sub. 2]
But it usually changes during hot curing.
Prevention of cutting
Healing wounds did not heal during C [O. sub. 2]
In the process, we can declare that the edges of the cut are less sticky than before treatment.
Liquid C. final size and details of silicone rubber not replaced during treatmentO. sub. 2]
It is learned from the literature that the sterilization effect in cold tempering is [O. sub. 2]
It is an unfriendly environment for bacteria.
Preliminary trials have been started to determine [liquidC [O. sub. 2]
This process can produce the same effect. E.
E. coli has been applied to the surface of silicone rubber and samples have been treated in liquid C [O. sub. 2]for two hours.
Subsequently, the number of bacteria was analyzed by measuring the pH value. The pictures (figure5)
Shows no bacteria on C [O. sub. 2]treated sample.
Because of the conditions in liquid C [O. sub. 2](10[degrees]C, 40 bars)
, One can state that the bacteria are not killed by extreme temperatures, but by the influence of pressure or C [O. sub. 2]. [
Figure 5 Slightly]
This article is based on a paper published at the Rapra Technical Conference. (www. rapra.
By Anne McCann Bartle
NanonA/S Mary Jensen and Thomas Emile Anderson, Denmark (www. nanon. dk)