lsr sponge having open cell structure. - free online library

by:Keyuan     2020-06-06
Silicone rubber sponge has been widely used in many fields such as electronic appliances, commercial machinery and automobiles.
It has two excellent properties: one as silicone rubber and the other as a rubber sponge.
Therefore, silicone sponges are sealed and hot in many-
Insulating paper and roll applications for printers, copiers and fax machines.
In recent years, its application in rolling applications has developed rapidly.
As shown in Figure 1, the fuser roller fixes the toner image on paper by heating.
Recent trends require higher thermal conductivity of heaterrollsspeed printing.
At the same time, the thermal conductivity of the pressure roller is also declining.
Rollers with low thermal conductivity can maintain the heat inside the system.
This leads to low energy type systems and is able to produce compact personal printers. [
Figure 1 slightly]
First, we will explain the difference between the current air-blown sponge and our new one.
The current silicone rubber sponge is prepared by adding a pyrolysis foaming agent to the high consistency silicone rubber (HCR type).
When the HCR is cross-linked at high temperature, the decomposition of the foaming agent will cause the foaming reaction.
On the other hand, the new sponge described here is prepared by mixing the hollow filler with the liquid silicone rubber (LSR)
And only cross-linking reaction is required.
Therefore, this new type response has several advantages compared to the traditional gas blown type.
In Figure 2, the electron microscope picture shows the obvious difference: * The new sponge has a smaller, more uniform cell size;
* Since no gas blowing process is required, the new sponge can be cured in the mold; * a flat-
Skin surface can be made (
No need for polishing process); * very thin (less than 1 mm)
Sponge parts can be produced;
* Very low hardness (
Less than 10 m)
Sponge can be made; and* open-
Cell structure sponges can also be made by adding special reagents. [
Figure 2:
There are two types of hollow filler.
One is the inorganic filler such as glass filler and ceramic filler;
The other is an organic filler made of organic resin.
In the case of inorganic fillers, it is difficult to be soft (low durometer)
The sponge is because of the hard shell of the filler.
In addition, due to the high thermal conductivity of the filler itself, it is not possible to obtain the required low thermal conductivity.
Figure 3 shows the effect of hollow filler load on thermal conductivity.
This indicates that it is difficult to obtain a low thermal conductivity sponge using an inorganic hollow filler. If verythin-
The use of inorganic hollow filler with Shell to reduce the thermal conductivity, the product is difficult to mix. [
Figure 3 slightly]
There are two kinds of organic hollow fillers: one is pre-
The inside of the expansion type contains gas, and the other is the inside of the thermal expansion type contains a low boiling point liquid.
The latter type of filler requires a filler expansion process, which causes the same problem as the gas blowing type mentioned earlier.
In this article, we present the properties of a new type of liquid silicone sponge obtained from organic hollow fillers (microballoon)blending.
In addition, low compression set, open-
Cell sponges made of this new sponge material mixed with special reagents will be shown.
Performance of new liquid rubber sponge for experimental materials (X-34-2273A/ B)
As shown in Table 1. X-93-
3027, an open transparent liquid
Cell structure is also used.
Thermal conductivity measurement of 6mm thick rubber sheet by Kemtherm QTM-D3.
The methanol immersion test sample was prepared by cutting a plate of 6mm x 30mm from the mold board.
These samples are soaked in 1L methanol for two, four and 16 hours and are soaked in stainless steel mesh above the sample to prevent the sample from floating.
Results and discussion of X-thermal aging34-
Figure 4 and Figure 5 show 2273A/B.
Press 120 [Press curingdegrees]
C 10 minutes.
They show that both hardness and specific gravity change rapidly during the initial stage of aging.
After a drastic change in the initial phase, both properties show a steady line.
It can be assumed that this change is caused by the nature of the micro-balloons mixed in the material. [FIGURES 4-5 OMITTED]
The micro-balloon is made of thermoplastic resin that is not easy to break but is deformed by mechanical pressure.
These properties are the result of their elasticity.
In liquid silicon materials, they shrink because micro-balloons are subjected to uniform pressure on each surface.
Therefore, if the liquid material containing the micro-balloon is poured into the mold cavity and cured with hot vulcanization, it will solidify in the compressed state.
Just like ordinary rubber, if the volume of the material exceeds the volume of the cavity, an overflow or Flash will be generated.
Figure 6 and figure 7 show the effect of mold pressure on the material.
Pouring and curing materials of various weights in the same cavity of [at120]degrees]
10 minutes C (figure 6).
Figure 6 shows that the specific gravity increases as the material pressure increases. [FIGURES 6-7 OMITTED]
Figure 7 shows the specific gravity of pressure curing (nonpost cure)
And post-curing materials at 200 [degrees]
C four hours.
With the increase of mold pressure, not only the proportion of mold, but also the change of the proportion after curing has become higher.
Figure 8 shows the reason why the specific gravity changes with the mold pressure.
In the process of forming, it will be compressed into a balloon, causing the material to shrink.
The compressed balloon is then cured in place.
When the material is taken out of the cavity, it expands because the reduced balloon needs to restore the original size by releasing the pressure. [
Figure 8:
When the balloon expands, the rubber produces strain, resulting in a force to shrink the rubber.
Therefore, the size after molding is determined by the balance between the balloon expansion force and the rubber shrinkage force.
Then, in more than 180 of late treatmentdegrees]
C, the rubber shrinks to the original mold size due to the decomposition of the balloon.
Next, we will explain the compression set behavior of this new sponge.
For example, X-of compression permanent deformation resistance-34-
About 50% Ar3a/B (at 150[degrees]
C. Compression for 22 hours, compression 25%)
, Too high for the general sealing material, not to mention the toner fixing roller.
However, this deformed rubber almost restores its original shape (
Compression set]congruent to]0)
When you put it in the oven, at150 [degrees]
C a few hours.
The specific gravity of the deformed rubber also shows a value higher than the initial state, and then as the deformed material becomes the initial shape in the oven, the specific gravity returns to almost the initial value.
It is believed that the cell volume of the rubber will shrink during the compression of the oven.
This is evidenced by the specific increase in gravity.
However, due to the low gas permeability at room temperature after mold pressure release, it is difficult for the reduced battery to recover its initial volume, even if the rubber force to restore the initial shape is still sufficient.
Therefore, it is easy to estimate that if each cell is connected together, a low compression set sponge can be obtained so that air can penetrate into the cell even at room temperature.
In Figure 9, open electron microscope photos and low compression settings
Demonstrated cell structure sponge prepared with mixingX-34-2273A/B and X-93-3027 (open-cell agent)
And closed with the originalcell type. In the open-
In the microscopic images of cells, there are many cells that are constructed from microballoons, where a small hole connecting each cell can be seen.
In Figure 10, X-34-
2273 mixed with X93-
3027 showed higher methanol absorption compared to close methanol absorptioncell type(without X-93-3027)
Also shows that by changing X-93-
3027 mixingrino, open-
The cell rate of the sponge can be easily controlled. [FIGURES 9-10 OMITTED]
Finally, a possible mechanism of X-93-
3027 impact on changecell into open-
Cell sponges are shown in Figure 11.
In the case of x-34-
2273A/B without X93-
At 3027, the micro-balloon is evenly dispersed in liquid rubber, resulting in a closed cell sponge. WhenX-93-
3027 mixed in this composition, the micro-balloon partially gathers with the help of the reagent as it does not dissolve in silica gel but has a good affinity for the surface of the micro-balloon.
Then, with the rubber cross-linking forming at high temperature, some balloon shells break down.
Because X93-
3027 reduces the softener of hot plastic, forming a balloon shell. During post-
Curing, decomposition of all micro balloons, evaporation of all reagents, resulting in opening
Transparent rubber sponge. [
Figure 11 omitted]
Conclusion the liquid silicone rubber sponge containing Elastic Hollow filler has many advantages.
The new sponge is compared with the current air-blown sponge.
As for the heat resistance, the organic hollow filler can maintain the excellent performance of silicone rubber by post-curing decomposition.
In addition, by adding specific reagents to the material, this liquid silica sponge can be made into an open sponge
Cell structure sponge with very low compression set (
Less than 10% at 180 [degrees]C for 22 hours).
Specific reagents help air to pass through silicone rubber.
In Table 1, several examples of new liquid sponges are shown.
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