selective self-adhesive silicone for lims.

by:Keyuan     2020-06-17
Liquid injection molding silicone rubber has been widely used for its excellent performance.
It needs less labor.
Cost calculation steps, shorter molding cycle and less possibility of contamination.
In addition to this, it can be easily applied to insert the mold with thermoplastic plastic, because the material is cured by an additional reaction, compared to the peroxide cured silicone, the reaction is at a lower temperature
It does not need a post
Cure treatment because there is no reactionproducts.
However, in order to obtain the adhesion between the rubber and the thermoplastic, the insertion molding requires a start-up process.
This usually causes adhesion problems due to uneven coating, incomplete drying, unclear primer life, etc.
The process itself is time. consuming.
In this article, there are selected sales
By allowing the liquid injection molding material to be combined with the thermoplastic insert rather than with the metal surface of the thermoplastic insert, the adhesive silicone was developed to solve this problem.
Adhesion occurs even after a very short curing time, so optional self-adhesive silicone can be used for primerless insertion molding or co-forming
Injection molding enables a composite material that is firmly integrated with thermoplastic plastics.
In addition, this non-primerless insert into the mold made of composite material in a variety of different conditions, such as high temperature (120[degrees]C)High humidity (85[degrees]C/85%RH), heat cycle (-40[degrees]C6 [equivalence]120[degrees]C)and so on.
Even after 300 hours under the above conditions, it was observed that there were more than 90% cohesive failures inside the rubber.
Material and method material selection
The adhesive silicone rubber tested in this study is made by Shin-
Table 1 shows Etsu and its properties.
The thermoplastic plastic used for adhesive evaluation is a commercial test piece for polycarbonate (PC)
, Polytinone (PBT)
, Polybenzene oxide (PPO), 6,6-nylon (PA66), 6-nylon (PA6)
: Commercial test pieces of metal made of chromium
Stainless steel galvanized iron (SUS)and aluminum (A1).
The adhesive strength test sample of the adhesive strength is formed by using the insert molding.
First, the test pieces of plastic and metal are skimmed with ethanol, and then silicone injection is performed between plastic sheets.
The mold conditions and methods are shown in Figure 1.
Two test pieces were inserted into the mold.
The mold temperature of the standard grade is 120 [degrees]
C and nylon are 165 [degrees]C.
After setting the test piece, the silicone sample was injected and cured.
Remove the cubic silicone rubber from the mold with to avoid debris. [
Figure 1 slightly]
The adhesive strength between silicone rubber and thermoplastic and metal was evaluated using 180 [degrees]
Stripping test specified in JIS k6249.
The test included exposure measurement of the cross-sectional area of 25mm x 10mm to measure the failure rate of the junction point and cohesion in the rubber.
Results and discussions of self-selection
The adhesive materials and their physical properties are listed in Table 1.
There are two grades.
One is the standard level.
The other is the nylon adhesive grade. X-34-
1625A/B is designed to combine with polyamide.
Data on selective self-adhesive strength
The adhesive materials of various materials are shown in figure 2.
These bars show the shear strength and the wire shows the cohesive failure rate.
A 100% cohesive failure sample is shown in this figure.
In this data, X34-
1547A/B has a strong adhesion to polycarbonate, polydingone Ester and polystyrene oxide.
On the other hand, it does not show any adhesion to the metal. This 0% CF (
Failure of cohesion)
Means it\'s stripped off on the interface. [
Figure 2:
In general, the composite of silicone and engineering plastics is exposed to harsh environments.
So, as shown in figure 3, we checked the adhesive durability.
It shows the test data of conductive samples aged at high temperature and high humidity with polycarbonate inserts.
In both cases, the bond strength is very high after 300 hours.
Bonding to the primer occasionally breaks under high humidity conditions, however, as can be seen, our self
The adhesive material can maintain its initial strong adhesion. [
Figure 3 slightly]
Table 1 shows the rows-
Self-selective ups
Adhesive material from 40 Douro. to 70 duro.
You can see that these tensile strength data are better than the typical silicone room temperature vulcanization (RTV)
Adhesive, almost equal to the standard grindable high consistency rubber (HCR).
So when the data shows that 100% of cohesion fails, one can easily imagine how strong the bonding force is.
Because as the hardness of the rubber increases, the interface stress between the rubber and the plastic will become larger, so it is not easy to get good adhesion with the rubber with high hardness.
Adhesion performance data of X 34-
1625A/B with 6, 6-nylon,6-
Figure 4 shows nylon, polyaromatic amine and chrome-plated metal.
These rods exhibit very strong adhesion to the main commercial types of polyamide.
At the same time, it has no adhesion to chrome-plated metal.
Of course, the cohesive failure value indicates a significant difference between polyamide and metal. [
Figure 4 slightly]
Figure 5 shows adhesion durability data for 6, 6-nylon.
Figure 6 shows the data of 6 nylon in thermal aging (120[degrees]C)
Aging at low temperature (-35[degrees]C)
High humidity resistance (85[degrees]C/85%RH)
Temperature cycle (-40[degrees]C to120[degrees]C).
Even if it lasts 300 hours in those harsh environments, this material maintains excellent adhesion.
Due to the repeated interface stress caused by the difference in thermal expansion rate between rubber and plastic, this temperature cycle is also a repeated test method.
As can be seen, starting from below, the initial strength will not change during 300 cycles per hour40[degrees]C to 120[degrees]C. [FIGURES 5-6 OMITTED]
The mechanism of selective adhesion is shown in Figure 7.
Compared to most thermoplastic materials, silicon-based adhesives are not used as adhesion agents because they exhibit stronger adhesion with inorganic materials such as metal mold surfaces.
Therefore, we use some other chemicals as adhesion enhancing agents instead of silicone in the past, which have neither silicone alcohol base nor silicone alcohol base.
The important point is the interaction between rubber and plastic, which is due to the chemical bond between the two layers or the compatibility between races.
Of course, the adhesive should react with silicone rubber, otherwise it will only migrate to thermoplastic if it is in contact. [
Figure 7 Slightly]
Figure 8 shows co-
Injection or twice.
Injection molding.
First, in the case of a temperature of 120 [, the melted polyamide is injected vertically into the chamber on both sides of the molddegrees]C.
Then rotate the left mold and then inject silicone at the right mold of 120 [degrees]C.
Heating at30 on the silicone side of the mold [degrees]C to 168[degrees]C.
The sample shape is displayed.
It is a round roller coaster about 8 cm in diameter. [
Figure 8:
Adhesion results are shown in Figure 9.
We can\'t measure the shear strength on the shape of the roller coaster, so we are from 1-
5 indicates the degree of adhesion.
Excellent adhesion of the five fingers (
100% cohesive failure).
One means no adhesion.
In Figure 10, we changed the mold temperature from 130 [degrees]C to 168[degrees]C.
At higher temperatures, we can see better adhesion. At over 160[degrees]
C. we can get 100% of the cohesive failure.
In this figure, when the mold temperature is fixed at 168 [, we change the mold time between the mold closing and the mold opening from 15 seconds to 60 secondsdegrees]C.
The results are clear.
Even after only 15 seconds, we can get enough adhesion. [FIGURES 9-10 OMITTED]
Even in the same thermoplastic plastics shown in this study, due to their polymerization method, degree of refinement and type of additive, some grades are not suitable for the addition reaction of silicone rubber, or can not fully demonstrate adhesion.
These need to be checked separately.
The shear bond strength test data of standard materials for Engineering Plastics and new materials specially designed for polyamide were obtained.
Results of shear strength (MPa)
As shown in Table 2.
In this table, the different hardness of the standard material shows the same shear bonding strength as the PC. PBT and PPO.
In addition, the shear strength with the metal is at a lower level.
From this data,
Adhesive silicone enables process engineers to utilize the productivity and reliability of the production of silicone rubber and thermoplastic composites by eliminating the triggering process.
In addition, the composite made of this primerless insert molding exhibits excellent adhesive durability under various harsh conditions such as high temperature (120[degrees]C)
High humidity (85[degrees]C/85%RH), heat cycle(-40[degrees]C+[equivalence]120[degrees]C)and so on.
Even after 300 hours under the above conditions, more than 90% of rubber cohesive failure was observed.
Conclusion Selective self
Adhesive silicone has been developed as a liquid injection molding material for bonding to a thermoplastic insert but not to the metal surface of the mold.
Adhesion occurs even after a very short curing time, so that it can be used for forming orco-without primerless inserts-
Injection molding enables a composite material that is firmly integrated with thermoplastic plastics.
\"Selective Self-confirmation\"
Adhesive silicone for LIMS \"is based on apapaper given at the rubber department meeting in October 2001.
\"Factors affecting the volatile levels of silicone in synthetic silicone rubber\" is based on a paper given at the rubber department meeting in September 1999.
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