LSR VS Solid Silicone Rubber

What is the difference with LSR ( liquid silicone rubber )and solid silicone rubber?

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Liquid silicone rubber and solid silicone rubber can be distinguished by making process, appearance, smell , molding process, industry useful and cost.

Making process:

Liquid silicone rubber

Solid silicone industry based on sodium silicate (sodium silicate) as raw material, hydrolysis produce gel in the acid medium, and then made from silica gel by aging, washing, drying process, according to the water content is different, for the translucent or white solid. Goods sold are irregular granular, globular, micro spherical silica gel, which has good wear resistance, used as the catalyst carrier in fluidized bed operation.

Liquid Silicone is liquid shape before being formed, and has fluidity, fast vulcanization, environmental protection and safety. It can meet the requirements of food grade certification, and has the advantages of tearing strength, resilience, heat yellowing and thermal stability. Liquid silicone is divided into encapsulated silicone rubber, silicone rubber mold, sealant and other types of liquid silicone, divided into A glue and B glue, using quantitative device to control both of 1:1 ratio, and then through the static mixer to fully mixing, injection injection feeding pipe after injection molding production. The liquid silica gel was injected into the hot runner mold and made of silica gel products, which can achieve the advantages of one molding, no waste and automation.

The main point of Liquid silicone rubber:

Resistance to steam and humidity
Flame retardancy
Low creep and compression set
Weatherability
Vibration absorption
Corrosion resistance
Resistance to mold, mildew, and bacteria growth
UL component recognition

Liquid silicone can be cured at room temperature and can be cured at high temperature. The curing process can be completed in a few seconds by high temperature curing. Liquid silicon rubber is a typical liquid silicon rubber, which is soft, nontoxic, tasteless and transparent. Medical safety is the high safety of food.

Solid silicone rubber

silica sol liquid silicon sol is important carrier of the material, industry usually by ion exchange method makes the silica sol sodium silicate sodium off system. It is translucent milky liquid, the content of silica in the sold goods is commonly 20% ~ 30%, and the most high is 50%, the colloidal particles diameter of 100 ~ 200 a, some items of a. A high concentration of silica sol is usually with the aid of trace amounts of sodium oxide to maintain its stability. Colloidal silica drying after into porous solids. For example, in production by oxidation of propylene ammoniation of acrylonitrile (oxygen) phosphorus molybdenum &#; bi &#; / silicon oxide catalyst, is to contain active component solution mixed with silica sol, the spray drying method into micro spherical catalyst.

The main properties of solid silicone Rubber:

1. excellent transparency

2. excellent tear strength (35N / mm)

3. excellent springback, yellowing resistance and heat-resistant aging

4. good thermal stability and weatherability (using temperature -60 C ~ 250 C)

5. after mixing A / B at 20 C, the safe operation time in the sealed state is 5 days, and the safe operation time is shortened when the temperature rises.

Appearance:

Liquid silicone rubber is in a liquid state and has fluidity;

Solid silicone rubber  is in a solid state and has no fluidity.

Smell:

Liquid silicone rubber has high transparency, no peculiar smell, and the injection molded silicone products has a glue injection port. The LSR molded silicone products is odorless.

Solid silicone rubber have to use  the flavor of curing agent or other curing agents, and the product has no glue injection port.  With different odor accroding to the difference grade. 

Molding process:

Liquid silicone is a food-grade/Medical Grade material with high transparency and high safety. No auxiliary materials such as vulcanizing agent are added during molding, and it is sealed and fed for injection molding;

Liquid silicone is injection molding liquid silicone rubber (LSR): its full name is injection molding liquid silicone rubber, and vulcanization equipment is an injection molding machine.

The injection molding machine has a very simple process (no need for manual processes such as batching, rubber mixing, cutting, and placing in the high-temperature glue process, only one worker needs to take the product), and the product has high accuracy (all manual procedures before molding All are replaced by machines), high output (A / B glue mixed at a temperature of 130 degrees for a few seconds), many advantages such as saving labor, electricity, and materials, can produce all products produced by high-temperature glue.

LSR molding process:

• 1. LSR A + B components typically come in suitable injection molding equipment and then heat-cured into a molded rubber part. A process controlled pumping kit presses down on the buckets to force the material into static mixer and feed into the injection unit.
• 2. Then, streams of pigment can be added and controlled. In the injection, press material will be mixed together additionally with a screw and pushed forward to create a &#;shot&#; of material, or the amount needed to fill the mold.
• 3. After the material is injected into the mold, it will then stay clamped together to cure the LSR. Then, either an operator or a robot will remove the cured product from the mold and the cycle repeats. It is a very quick efficient process.
• 4.Secondary steps like post bake can help reduce volatilities and improve compression set. And the deflashing process removes unwanted flashing. It&#;s then cleaned to remove foreign material and packaged for shipment.

Solid silicone rubber is a transparent material, and a vulcanizing agent needs to be added during molding to speed up the vulcanization molding time.  Solid silicone part is compression-molded, and after being kneaded by raw materials, it is cut into a size and thickness suitable for molding, and then placed in silicone mold, manual demoulding.

The solid silicone rubber compression molding: This enables the silicone to cure once introduced to heat. To add pigment to the silicone, the silicone must be mixed using a two-mill roll. This is a labor-intensive process that has the possibility for contamination of the silicone. Once the material is pre-catalyzed and pigment is added it is weighed and often shaped to the approximate size and configuration of the desired part. It is then placed directly into the mold cavity. The rubber is then compressed between the top and bottom plates. These plates are heated to melt the silicone and vulcanize (cure) the silicone.

After the cutted silicon rubber ready the compression molding process:

• 1.The mold is prepared by being heated and sealed

• 2.Uncured Silicone (preform) is placed in the mold cavity

• 3.The mold is closed

• 4.Heat and pressure are applied (according to programmable logic controls and in accordance with temperature and pressure parameters)

• 5.The mold is opened and the cured rubber is removed

• 6.Post-molding processes include deflashing, inspection, postcuring, etc.

Industry use:

Liquid silicone rubber is generally used in baby products, kitchen products and medical products, and it can directly contact food and human body;

Want more information on Clear Liquid Silicone? Feel free to contact us.

Solid silicone rubber is generally used in daily necessities, industrial miscellaneous parts, and auto parts.

Cost

Liquid, The cost for raw material and production, is higher than solid.

Conclusion

According to the above information, you can see there are much difference of the LSR (liquid sillicone rubber) and Solid silicone rubber.

You also can see the following sheet to know them more simply.

The Fumed silicone rubber can pass the FDA in Eu request = LFGB Standard.

In ZSR Group has rich experience in producing Custom silicone products with LSR and solid silicone rubber. We also can help selet the right material (LSR or Solid silicone rubber) according to your project.

Any Silicone products or Silicone project need technical support, you also can custom Silicone products at ZSR Group. We will support your Silicone products from idea to life. 

 If you like the article or you need more information from us,  please leave a message or contact us by [ protected], Any inquiry from you is welcome.

About Author:

Z.S.R International Group

Z.S.R International Group(Hong Kong) co., Limited,  is a one-stop supplier for molded silicone products and silicone products molding solution provider in the consumer products field. We offer OEM services from product design to Silicone products contact manufacturing. We have the capability for LSR molded silicone products, solid silicone molded products, molded silicone multi-colored products. We also can custom molded silicone, custom molded LSR, custom molded dripping injection dispensing (co-injection) silicone multi-colored products, custom tooling.

Liquid silicone and solid silicone can be distinguished by physical appearance, the field of use, and the molding method.

The different appearance between liquid silica gel and solid

There are two physical appearance differences between what we usually call silica gel, one is flowing liquid and the other is solid.

1, Liquid silica gel is in a liquid state and has fluidity. It is a highly transparent and safe food-grade material. It does not add auxiliary materials such as vulcanizing agents during molding and is sealed for molding.

2, The solid silica gel is in a solid state and has no fluidity. It is also a transparent and environmentally friendly material. When curing, it is necessary to add a vulcanizing agent to speed up the vulcanization molding time, and open-mold injection molding.

The difference between liquid silica gel and solid

1, Liquid silicone is generally used in baby products, kitchen supplies, adult products, and medical supplies. It can directly contact food and the human body. Products such as silicone pacifiers, baby bottles, tooth gels, silicone pads, ice trays, cake molds, diving Mirrors, artificial human organs, medical silicone chest pads, silicone dolls, mobile cases, silicone medical balloons, silicone cable ties, etc.

2, Solid silicone is generally used in daily necessities and industrial miscellaneous parts and automotive accessories, products such as buttons, silicone gifts, silicone bracelets, silicone watches, key cases, fingertip gyro, etc.

3, Safety of liquid silica gel and solid silica gel: Liquid silica gel is a highly transparent and safe food-grade material. It does not add auxiliary materials such as vulcanizing agents during molding and is sealed for molding. Solid silica gel is a transparent material. When curing, it is necessary to add a curing agent to speed up the curing time.

The difference between the process method of liquid silica gel and solid silica gel

Liquid silicone is injection molding liquid silicone rubber (LSR): its full name is injection molding liquid silicone rubber, and vulcanization equipment is an injection molding machine.

The injection molding machine has a very simple process (no need for manual processes such as batching, rubber mixing, cutting, and placing in the high-temperature glue process, only one worker needs to take the product), and the product has high accuracy (all manual procedures before molding All are replaced by machines), high output (A/B glue mixed at a temperature of 130 degrees for a few seconds), many advantages such as saving labor, electricity, and materials, can produce all products produced by high-temperature glue.

Liquid silica gel is generally used in the industry to make sodium sol from sodium silicate by the ion exchange method. It is a translucent milky white liquid with high stability. The silica sol becomes a porous solid after drying.

Liquid silicone molding process

1, Compound rubber: This ready-to-use material can be colored and catalyzed according to your processing equipment and end-use.

2, Base material: This type of silicone polymer also contains reinforcing fillers. The rubber base can be further mixed with pigments and additives to form a compound rubber to meet your color and other manufacturing requirements.

3, Liquid Silicone Rubber (LSR): This two-component liquid rubber system can be pumped into a suitable injection molding equipment and then heat-cured into a molded rubber part.

4, Fluorosilicone rubber compound and base material: Fluorosilicone rubber maintains many key properties of silicone. In addition, it has excellent chemical resistance, fuel and oil resistance.

The main chain of rhenium is a synthetic rubber composed of alternating silicon and oxygen atoms with organic groups on the silicon atoms. The organic group in the molecule may be -CH3, -C2H3, or -C6H5, etc., and is correspondingly called methyl, vinyl, or methyl phenyl silicone rubber. Silicone rubber is a special rubber that is resistant to high and low temperatures (-60 to 250 ° C), resistant to ozone, and has good electrical insulation properties.

Organic silicone rubber is a special synthetic elastomer produced by mixing linear polysiloxane with reinforcing filler and vulcanizing under heat and pressure. It perfectly balances mechanical and chemical properties, so it can meet many of today&#;s demanding applications.

Solid silicone molding process

(1) In the industry, solid silica gel uses water glass (sodium silicate) as raw material, hydrolyzed to form a gel in an acidic medium, and then made into silica gel through aging, washing, drying, and other processes. According to the difference in water content, it is half. Transparent or white solid. Commercially available products include irregular granular, spherical, and microspherical silica gels, which are often used as catalyst carriers in fluidized bed operations.

(2) When used as catalyst support, silica gel is usually immersed in a solution containing a catalytically active component, the solution is absorbed in the pores of the silica gel, and the active component is distributed on the surface of the silica gel after drying, activation and other procedures. The pore structure of silica gel has an important influence on the properties of the prepared supported catalyst, such as the pore volume and pore size distribution of silica gel. Traditionally, silica gels with an average pore size of less than 15-20 are referred to as fine-pored silica gels, and those with an average pore size greater than 40-50 are referred to as coarse-pored silica gels.

(3) However, the pore structure is not conducive to the diffusion of reactant molecules, but it will reduce the utilization of the internal surface of the catalyst, and the product molecules generated at the depth of the pores will not easily escape from the pores, and it is easy to cause deep side reactions.

The pore structure of silica gel is related to the manufacturing method and conditions, such as gelation, aging, pH, temperature, time during washing, etc. The commercially available silicone can be reamed by a reaming process.

The common method is to place it in an autoclave and add water or a salt-containing aqueous solution (such as sodium carbonate, or sodium acetate) for hot pressing. For example, hot pressing at 320 ° C and 10 MPa can make the specific surface area and average pore diameter respectively The 135 m2 / g and 123 silica gels became 26.9 m2 / g and 508.

Conclusion:

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