matching fvmq compound technology with finish processing equipment.

by:Keyuan     2020-06-13
Unique physical properties of fluorine-silicone compounds (FVMQ)
There has never been a greater need like today.
In applications requiring exposure to jet or automotive fuels, solvents, and/or oil, the use of fluorine-silicone has increased
Automotive applications.
As more and more manufacturers begin to manufacture products using fluorine-silicone compounds, optimizing the production of processed and acceptable parts becomes important but difficult.
At the same time, the development of composite technology provides greater flexibility to meet the requirements of standard rubber processing equipment.
For these reasons, it is important to understand practical methods of material process requirements, as they are related to elastic finishing equipment and technology.
By considering the features of specific processes and equipment before the impact of materials, fluorine silicone suppliers are more capable of developing an efficient processing on typical elastic finishing equipment that not only meets end-user performance requirements
In the mixing and manufacturing process of fluorine silicone rubber, it is essential to understand the relationship between the current composite technology and the various finishing processes adopted.
Whether it\'s starting with a standard fluorine-silicone base, developing compounds for internal use, or buying off-the-shelfto-
Use Complete-material
Compound, coloring and catalysis, the more information on hand, the better.
Even if there is no mixing equipment suitable for fluorine-Silicon collisions, a basic understanding of the components used and their potential process effects is always helpful, especially when solving manufacturing workshop problems.
Even when the trouble shooting work fails to solve the problem, this knowledge will help support the service team to solve the problem quickly and minimize downtime.
Like any other effort, in many of the processes currently in use, there is no right way to use fluorine-silicone compounds to optimize manufacturing or solve problems.
The suggestions put forward here can be used to solve a specific problem, but it does not mean that all situations are covered.
Fluorine silicone rubber compounds have unique advantages in matching specific composite technologies with various manufacturing processes.
For example, something that works for an extrusion chamber may not work for injection molding.
The extension tape of fluorine silicone rubber fabric brings a series of problems different from the solution (dispersion)
Coating FSR on the same fabric.
In most cases, the basic composition of the fluorine-silicone composite is very similar to the one used for dme-Vinyl silicone (VMQ)compounds.
The filler, pigment, curing system and some modifiers are exactly the same, but there are obvious exceptions.
Fluorine silicon based materials (FVMQ)
Like VMQ, pre-provision is usually provided
As a basis, it is not usually sold in its pure polymer form.
The base is designed to cover numerous physical performance requirements for the home of the fluorine silicon base (
Designed to meet similar attributes and processing guidelines)
There are usually two or more types of durometer to choose from.
The hybrid base in the product line enables manufacturers to obtain intermediate performance that meets specific specifications and optimizes cost efficiency.
If the specification (
Resistant to fuel, solvent or oil)
It is also possible to use an economic mixture of fluorine Silicon and vmq type.
The filler used in the fluorine silicon compound is basically the same as the one used in the VMQ material.
The most common is based on si [O. sub. 2](silica).
Silica can be carried out by gas phase method, precipitation method or grinding method.
The information or difference observed when using the gas phase method silica composite fluorine silicone rubber is that the untreated gas phase method silica reacts less than the vmq type gas phase method silica and can be used more
Because of this, the curl hardening of fluorine-silicone rubber compounds is slower than similar --
Filled VMQ compound.
In addition to the most common silicon powder, cloud powder, cloud powder and other extracted silicon powder can be used.
Most of these filters are naturally extended to meet specific fluid resistance, compression setting, or economic goals.
Pigments can be organic or inorganic, and the most common thing is to act as Masterbatch in a fluid or polymer (gum)carriers.
As a group, organic pigments are affected by high temperature during curing or post-treatment
As a reaction to the peroxide catalyst, some can change the color.
Organic matter is usually more stable in color and has less reaction to the peroxide or platinum curing system.
Black black is a notable exception that can greatly shorten the shelf stability and effectiveness of some peroxide.
The use of a platinum curing system may also inhibit curing.
More common consideration in the inorganic pigment family is the presence of heavy metals in certain colors. Although high-
Quality, stable colors can be obtained using them, and if the product is intended to be exported, restrictions on these colors can be a problem.
This component is added to the fluorine silicone compound to change the curing performance or correct the processing defect.
These molds can be used to improve the high temperature performance of uncured parts using acid, release of molds or reduce Bloom (diacyl)
Peroxide catalyst.
In addition to the well, drugs can also be treated
Known peroxide commonly used in fluorine-silicone and VMQ-type silicone (table 1), platinum (addition)
Another option for fluorine silicone is curing.
In most applications, more than one curing agent is suitable for a specific process, and in some cases it may be beneficial to mix two types of curing agents in one compound.
Choosing which curing agent to use is closely related to the process of making the part and the complexity of the part design and its maximum cross section.
Recycling in the process of excessive flash or low production to produce a large amount of waste ([Greater than]5-10%)
Recycling may be an option.
In general, the use of recycled fluoride silicone can improve economic benefits, but special attention should be paid to avoiding cross-cuttingcontamination.
The high cost of the original compound and the key properties of many fluorine-silicone applications should limit the addition of recycled rubber, used only in the same original compound (table 2).
However, the use of recycled materials does affect the way compounds are manufactured.
Materials that are composite with recovery may not be advisable for extrusion or pressing operations in which surface finishes may be affected by recycled materials.
Reclaimedfluoro silicone rubber also does not enter the solution well and should be avoided in solution coated fabric processing.
In the molding operation, the shrinkage after molding and curing will be less than the pure compound.
The compressed set value is usually increased.
Fluorine-silicon compounds can be prepared by a method similar to organic thermosolid compounds.
In some cases, the same mold can be used.
There are three main molding methods for manufacturing fluorine silicone rubber parts.
These three are all similar as they form rubber through the application of heating and pressure.
The differences between these methods are related to mold loading techniques and reliance on manual manufacturingautomation.
Compression molding is probably the most common molding method for fluorine silicon, and compression molding technology has been optimized over the years.
From the point of view of fluorine silicone rubber, the following should be part of any review of the compressed molding fluorine silicone rubber compound;
Any fluorine silicon base can be used for compression molding.
In compression molding, uncured rubber generally does not have a long stroke and is therefore less sensitive to flow properties.
Because of this, high filler (
Especially grinding Quartz)
The load can be used for a soft fluorine silicone base.
However, the extension filler does increase the resin and reduce the tensile strength and tensile properties.
In most cases, the compressed set is improved.
Gas phase silica can also be used, but the level of use is much lower and the cost is high. ground quartz.
The precipitated silica is between the two (
Maximum usage level and cost).
Pigments and modifiers these composite components are usually added to smaller horizontal sand with little effect on the compression molding variables.
If the molded part does not have a particularly thin cross-section, the recovered particles may limit the flow of fluorine-silicon compounds into the mold and the recovery can be used successfully.
Curing mechanism all curing mechanisms may be suitable for compression molding, but there are some considerations.
Many compression molds are multi-designed and are usually manually loaded.
Even with the loading plate, for low temperature peroxide or some Platinum, the time from pre-forming loading to mold closing can be too long
The catalytic fluorine silicone can be cured in advance.
Scorched will affect the surface condition and cause or not
Fill the part because the viscosity increases as the compound starts to solidify.
Compression molding technology is a good understanding.
Due to the involvement of fluorine-silicone compounds, the following is a note: * If both fluorine-silicone and organic rubber use molds, fluorine-silicone may show greater shrinkage than organic compounds.
In addition, packing loading (
High load causes smaller shrinkage)
Temperature (
More shrinkage at high temperature)
Can it be used to offset variables that are tightly contracted? Tolerance parts.
* The shape of the prefabricated body should be uniform and contain enough mixture to fill the cavity and produce a small amount of flash.
In many molds, the weight is 5-
It is enough to exceed 10% of the actual part weight.
* In compression molding, the surface finish of the mold also affects the flow of the material.
Highly polished steel is generally conducive to good flow.
Chromium or other finishes may improve the removal of parts, particularly helpful for the transfer and injection molding of fluorine-silicone compounds.
This method of transferring the mold is especially suitable for large amounts of flow that are difficult to design into the mold, or for small parts where the part structure tends to capture air. A well-
The designed mold can generate parts with no flash in the early days.
Factors that affect the composition of fluorine-silicone compounds include the following: Basic filling materials generally, any fluorine-silicone base can be used in transfer molding.
A high level extension filler can be tried, but the part size and gate size need to be considered.
Very small exits can create turbulence and increase trapped air.
In addition, a small gate with a high filling volume may produce too much friction heat, resulting in premature scorching.
Pigments and modifiers these composite components are usually added to smaller horizontal sand with little effect on transfer molding variables.
Recycling can be used in most cases.
Larger parts with thicker cross sections are less affected by any potential surface or flow problems.
Before committing to the use of recycled fluorine silicone rubber, very small parts or parts with small gates should be carefully tested.
Usually, high temperature (dialkyl)
Molding grade peroxide is the preferred curing agent.
Even with thermal isolation, the low temperature peroxide is burnt in the transfer tank.
Dwell time in a warm transfer tank may also be a problem with the platinum curing mechanism.
Technology, if possible, it is best to separate the transfer heat from the mold. A water-
Better cooling transfer tank.
If a heating or heat transfer pan is used, minimize the time of contact between fluorine-silicone compounds and heat before filling the mold.
In almost all cases, there is no need for heating of this compound to improve the flow.
The injection molding cycle is short, the curing time is short, and the viscosity is low (good flow)
Make Injection Molding very suitable for fluorine silicon compounds.
Mold Design and gate size and location (s)
Is the key factor to optimize the injection molding process.
Due to the high pressure and fast filling of the mold, a short curing residence time can be designed as a fluorine silicon compound.
Other component factors include the following: although for complex parts or designs with extreme bottoms, the base with high tear strength is more suitable for injection molding.
Due to the pressure realized in the injection part of the mold cycle, attention should be paid to the type and quantity of the filler used.
The highly filled compound does not have a small gate, which creates significant friction heat and can start skin curing before filling the mold.
Even the slight degree of premature curing increases the viscosity, resulting in a further accumulation of friction heat.
Due to the chemical interaction of some pigments, pigments and modifiers should be carefully selected when using colored fluorine silicon.
In the injection part of the molding cycle, the degree of shear leads to color stripes, spots, or stripes.
Sometimes pigs at a higher level will solve the problem.
One modifier that needs to be considered is the internal mold used for injection molding.
The injection molding process is the largest labor intensity in all molding processes, and the time saved in the molding process is usually worth it.
Recycling can be used, but thin cross-section materials may end up with textured surfaces due to particle size.
In addition, under the most common curing agent selection, the recovery part of the compound is not cross-linked with the original polymer.
The most common curing mechanism (Recommended)
The cure is a variety of high temperature and peroxide (dialkyl)and platinum.
The curing speed of the two-based peroxide is slow, usually providing sufficient time to fill the mold cavity before cross-linking.
Platinum-cured compounds have the flexibility to adjust the burning time to match the filling rate.
The curing rate of platinum curing compounds is very fast and will not be suppressed by oxygen.
Not as hightemperature (dialkyl)
The peroxide, thin flash is fully cured when platinum-catalytic compounds are used.
Whether it is to use a filling box or a strip feed, the feeding part usually does not require additional heat;
It is not necessary to reduce viscosity. * In multi-
Balancing the gate is an important step in optimizing the flow. * Vents (
With or without vacuum)
Due to the fast filling time and the short coke burning time, it may be necessary to eliminate the trapped air.
* Highly polished steel, chromium or other plating can shorten the overall mold cycle by reducing the part removal time.
* Reduced injection speed (ram pressure)
Applied to high filled compounds to control the friction heating through the gate.
In order to balance the effect of heat, a lower mold temperature may also be required.
* It is highly recommended to use the fluorine silicone compound cold runner system.
* In general, the fresher the compound, the easier it is to flow and the faster it is to fill.
General trouble shooting is the deformation of molded parts, which usually occurs on the mold parting line.
Normally, the flash of this area disappears and leaves a rough indent in the part.
The back skin is most common in compression molding, but may also occur during delivery and injection molding.
Potential reasons include burrs or roughness in the mold parting area, or twisted molds that are not fully sealed.
Molding at too high temperatures can be the main reason for this.
The mechanical solution is obvious: if the selected curing agent is formed at too high a temperature, reduce the mold surface temperature or switch to a higher temperature (dialkyl)
The peroxide or platinum curing system may be helpful.
In injection molding, injection can reduce friction heating at a slightly lower pressure, which may reduce the posterior skin.
The ScorchThis phenomenon is due to the premature curing of fluorine silicone rubber before the mold is fully filled.
The symptoms include a large amount of flash hand incomplete cavity in the same part;
Deformation part;
\"Ripple\" or texture of the surface curing.
First check the hot spots in the mold and make sure to apply little or no heat to the fluorine silicone compound before injection or transfer molding.
In compression molding, the time from placing the preforming on the surface of the hot mold to the completely closed mold should be as short as possible.
In all cases of burning, the other option is to evaluate a higher temperature (dialkyl)
Peroxide or modified platinum-
Cure the fluorine silicon compound with an additional inhibitor or a reduced platinum concentration.
When the air is trapped in the mold, it may change the look or feel of the part in many ways.
When using acid (diacyl)
Peroxide or platinum in the air is usually shown as an opaque spot.
This part will be fully solidified, but a huge potential will be shown through the opaque areaLook at the paragraph.
When using high temperature peroxide (dialkyl)
This can be suppressed in the presence of oxygen, which may appear tacky to touch and uncured.
In order to minimize the closed air in the compressed mold, quickly reduce and re-apply the mold pressure to \"impact\" the mold.
In addition, make sure that the shape and position of the pre-made rod will fill the cavity from one side and effectively squeeze the air out of the other side when the air fills the mold.
While the possibility of closing air in injection molding is small due to the high injection pressure, in parts with extreme cuts and/or sharp edges, this can be a problem.
In these cases, the mold should be ventilated at the sharp edges and in the bite area.
If the problem persists, a vacuum assist can be used to remove the air from the vent.
If this still does not solve the problem, transfer molding may be an option worth evaluating.
Small, Brown (
Or yellow Brown)
Due to one of the two problems, the spots in the mode fluorine silicone part are almost always the same.
The first is too much mold release.
The second is the pollution of the pre-made stick (
Compression molding in particular)
For example, is there an organic lubricant in the compound.
Pollution of pre-made rods is a problem of housekeeping technology.
The oil that enters the fluorine silicone is usually entered into the compound from the mill or mixer.
Spots can be seen after molding, but usually the most obvious after curing.
The higher temperature after curing causes the contaminated organic component to carbonize, resulting in brown spots.
In general, fluorine silicone rubber compounds can benefit from grinding before forming.
The shear action in this relatively fast process should reduce the viscosity of the fluorine silicon compound and improve the flow properties of the mold.
Using old compounds without refreshing can cause flow markers and one or more other issues mentioned.
If refresh is not selected, the inventory of mixed fluorine-silicone compounds should be kept to a minimum.
Extrusion of fluorine silicone rubber compounds can be extruded to make many products, including washers, tubes, wire insulation and various special-shaped seals.
Although this process is similar to organic rubber extrusion, there are also significant differences.
In general, fluorine silicon compounds have low viscosity compared to organic materials, so they should be extruded at room temperature.
Spot temperature above 50 [degrees]
C. burning may occur in the extruder during extrusion, resulting in different profile measurements (
Due to the high viscosity in the extruder)
And may result in a loss from the part of the curing agent to the less complete curing of the volatile.
In general, fluorine silicone rubber compounds flow easily in the extruder and expand when leaving the mold.
Fluorine silicone parts are usually less strong than the green of organic rubber and should be cured (or `B\'staged)immediately.
Most fluorine-silicone compounds are cured by hot air (HAV)
Immediately after extrusion.
Continuous vulcanization (CV)
Used for some wire insulation applications, but not typically for fluorine-silicon compounds.
From the point of view of the composite composition, the following are typical of the formulation of fluorine-silicone for extrusion: BaseMany fluorine-silicone base can be composite for extrusion, however, unfilled compounds (
Or no modifier.
A smooth surface or even a cross section may not be produced.
FillersFillers can improve the extrusion performance of most compounds.
Using any type of filler increases the viscosity of the compound and produces more consistent back pressure in the extruder barrel.
Using extended fillers can destroy some of the nerves seen in some unfilled fluorine-silicone compounds.
Pigments and modifiers due to the limited number of curing agents used for curing fluorine-silicone extrusion, the possibility of pigment interaction should be evaluated before use.
Various curing meters (
RPA ).
Potential interactions can be well indicated.
Modifiers can play an important role in optimizing the extrusion properties of fluorine-silicon compounds.
Softening additives can make highly filled compounds more smooth from the mold, while unfilled compounds can benefit from additives designed to increase green strength.
If acid is used (diacyl)
Do not accept the extrusion peroxide cured after the oven, it is recommended to have a modifier containing acid receptors to improve the high temperature performance and reduce the peroxide.
Recycling is generally not recommended for thin
Wall extrusion but can be used for thicker profiles.
Using the screen in the extruder to control and maintain consistent reverse pressure may have a tendency to capture recycled particles, resulting in higher barrel pressure, changes in profile cross-section, and changes in profile output.
Cured mechanismsFor HAV-
Cured profiles, both from low temperature, aciddiacyl)
Catalysts based on peroxide or platinum can be used.
In some cases, high temperature is used (dialkyl)
Peroxide can be used to improve thermal aging and pressure resistance.
Due to the nature of the HAV curing furnace, it is generally not recommended to use high temperature peroxide that can be suppressed by oxygen.
Parts squeezed with oxygen
Inhibition of high temperature (dialkyl)
The peroxide usually has a sticky surface and high porosity and is generally not cured.
The screws used by the technology for extrusion of fluorine-silicone compounds should be screws designed specifically for fluorine-silicone or VMQ silicone.
Extruder manufacturers can recommend the best design for the planned pipe or profile type.
* Circuit breaker board for holding screen (60-200 mesh)
It may be necessary to maintain high, or even reverse pressure, to provide a consistent profile cross-section and to help remove trapped air from the compound.
* In order to maintain the composite temperature of cooling, it is recommended that the extruder barrel be cooled.
* Some height fill, light-
Color extrusion can produce an extrusion with dark stripes, which is usually caused by metal wear particles caused by the hard, abrasive properties of some extension fillers.
In some cases, barrels can be modified to minimize the occurrence of this situation.
* When making thin
Wall pipe, when preventing the profile collapse in the extruder, low pressure air is usually introduced into the inside of the tube.
* Like fluorine-silicone molding, most fluorine-silicone rubber formulations will benefit from factory renovations before extrusion.
This process can further remove any trapped air and provide a consistent viscosity to reduce start-upup waste.
Olderinventory may need a different extruder set if there is no refresh Step
Better than the fresh supply of the same compound.
* Oven temperature can be from 250-650 [degrees]
C, usually at 300-425 [degrees]C.
Sometimes a short box (0. 3-
1 m long)
Used to set the cure before the extrusion enters the horizontal oven on the conveyor.
The softer fluorine silicon compound that does not use the heat box may have a slight out-of-
Round, or can be presented on the texture of the HAV oven belt.
The vertical oven is not susceptible to this, but it requires sufficient hot green strength.
* The hot air curing furnace should have an exhaust system that goes through-products.
* Use of roller feed (
Especially when using a band Coil)
Ensure that the filling of the extruder is more consistent, resulting in a constant reverse pressure and a more uniform extrusion profile.
Calendering agent for calendering fluorine-silicone rubber compounds, three-orfour-
Roll type extension machine can be used (figure 1).
In most cases, three
Rollcalender is a vertical stacking design. A four-
The roller calender can also be stacked vertically, but it can also be configured using an inverted L or an oblique Z.
The final product of the calendering process is either a solid sheet of fluorine silicone that is not supported, or a fluorine silicone that is embedded in the carrier fabric or laminated on the film.
The main advantage of the calender process is the production of long and continuous plates with uniform thickness.
Fluorine-silicone rubber compounds are generally postponed at room temperature;
However, some of the heating capacity in a particular compound may be helpful and, if supported, may improve the stickiness of the fabric.
The consideration of the composite composition includes the following: the most basic fluorine silicone rubber base is suitable for pressing. Withfabric-
Supported processing technology, a very thin coating requires some inherent viscosity transfer to the fabric.
It should be noted that some foundations are not pressed to a smooth surface, some experiments and scale
More work needs to be done before a final decision is made.
Filling material in extrusion processing, filling material usually helps to break the nerves that are sometimes noticed in the calender fluorine silicone compound.
The extension filler seems to be the most effective.
In general, this component is not an important factor in the ability to delay the fluorine-silicone compound.
Green additives are an exception.
Degree Of Green intensity (
Related to welding thickness)
It may be necessary to provide enough, even movies, especially in the absence of support.
Recycled fluorine silicone rubber can be used on thicker paper, but due to rough surface, it should be avoided under very thin film thickness.
There are many treatment options during the calving process.
Pressure on steel rollers (
In an oven or autoclave)
Pressure curing (or continuous pressure curing)e. g. , Rotocure)
It is important to consider deciding which treatment mechanism to use.
Most fluorine silicone rubber compounds will benefit from grinding before use.
* It is recommended to extend the unsupported fluorine-silicone compound sheet onto the release liner, which is peeled off after curing.
Generally speaking, a non-
Silicone release liner works best.
* If the transfer to the fabric is bad or intermittent, soak the coating in the solution (10-20%)
Compound (
Then drying and curing)
Will add enough stickiness to the fabric.
* Double peroxide can be used in the calender process.
Low temperature peroxide can be cured (`B\' staged)
Improve subsequent processing operations or provide a more consistent surface finish.
If two passes are equal for two passes, this is also one of the more common techniques
Double-sided coating of fabric on three layersroll calender.
* When using the release pad, peel the paper when warm (
When possible).
If cooling is allowed, the liner is torn or glued together, please re-heat theroll before trying to strip the liner from the sheet. [
Slightly] Illustrations
When deciding whether to buy a finished fluorine silicon compound or a custom mixture,
The house, it is important to understand the sensitivity of various manufacturing processes in order to convert large chunks of compound into functional, profitable parts.
As shown in the figure, the balance end part function with manufacturing processing efficiency has a large number of composite component considerations and alternatives.
As with many applications involving engineering materials, the purchase of materials with the lowest cost does not always provide the lowest total cost.
The biggest difference between a workforce-wide process and a more automated choice must be part of the entire manufacturing decision --making process.
Process experience and material knowledge are critical for the matching and trouble shooting of fluorine silicone rubber compounds and their associated processes.
The use of fluorine silicone rubber composite technology to match economic goals and processing technology will ensure that formulas and equipment are optimized to increase production, reduce scrap levels and reduce downtime, resulting in increased manufacturing profitability. References[1. ]
Dow Corning, 1990, made of silicone rubber. [2. ]
Manufacturing manual for Wilfred Lynch silicone rubber, VanNostrand Reinhold, 1978.
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