Differences between liquid silica gel and solid silica gel

Posted on : Jan 14 , 2023 ， By  GREFEE

 Liquid silica gel

Compared with solid high-temperature vulcanized silicone rubber, the liquid silicone rubber is liquid rubber due to its good fluidity, fast vulcanization. Also,  it is more environmentally friendly, and can fully meet the food level requirements.

Solid silica gel

The solid silica gel is a kind of saturated polymer elastic materials having multiple advantages, like high temperature resistance, cold resistance, solvent resistance, creep resistance, adhesion resistance, electrical insulation, chemical resistance, and are widely used.

Comparison between liquid silica gel and solid silica gel

 1.External feature  

(1). Literately, the liquid silica gel is liquid state with flowability.

(2). The solid silica gel is solid state without flowability.

2.Safety

(1).The liquid silica gel is the transparent and safe food grade material without any vulcanizing agent and other auxiliary materials, sealed feeding molding.

(2).The solid silica gel is the clear and environmentally friendly material that requires vulcanizing agent during the forming process, and the open mold should be fed for molding.

3. Forming method

(1).The liquid silica gel is the injection molding liquid silicone rubber (LSR) and the curing equipment is injection molding machine.

The advantages of the injection molding machines include: simple operating process (no need for manual processes such as batching, rubber mixing, cutting and placing in the high-temperature rubber process, only one staff to take out the products), high products accuracy (the manual processes will be replaced by the  machine before forming), high yield (A/B rubber mixing and being formed within a few seconds under a certain temperature), staff number saving, electricity saving, material saving, etc. It can produce any products made of high temperature rubber.

(2).The raw material of the solid silica gel formation is solid. After mixing in the mixer, the cutting machine will cut the product and mold into appropriate sizes and thicknesses, and then put them into the mold, which will be molded at a certain temperature under the pressure molding machine. De-moulding is similar to plastic products, and the mold needs to be cleaned.

Six molding methods of silicone products

1. Molding is the most common method, which is mainly rely on mold matching. Compared to other methods, this is relatively simple and applicable to all silica gel products.The shape of the mold determines the shape of the silicone product. The molded silica gel products are usually formed by putting solid silica gel raw materials with vulcanizing agent into the high-temperature mold, and then applying pressure through the vulcanizing machine. The high-temperature sulfur is solidified. The hardness of molded silica gel is usually 30 ° – 80 °.

2. Ejection (injection)

This process requires high quality and is a combination of liquid silica gel and plastic.

The products presents good thermal stability, cold resistance, good electricity insulation, and no toxic substances produced when burning.

Thus, it is the irreplaceable material in the production and designing of health supplies, automotive, baby supplies, medical supplies, diving supplies, kitchen appliances, seals, etc.

3. Solid state injection

During the processing of the solid silica gel products, its conversion process is quite similar to that of liquid, but the production method is the same as that of solid, adopting the same machine and material. However, similar to the liquid silica gel, the mold is likely to be squeezed into the bottom of products. This method adopt the same level of hardness as that of solid silica gel, so the flowability is limited.

This processing method can avoid different appearance defects and the parting line is well controlled, mainly for avoiding some problems of appearance, beautiful parting and product quality. In the meantime, it has some drawbacks, like large using amount of glue, high cost, and complex processing. The middle plate of the mold must be added and the mold core needs to be lifted manually. The manpower is large, and the processing efficiency of the product is low. Thus, this is one of the reasons why less and less manufactures adopt this processing way.

4. Extrusion

Extrusion molding. Extruded silica gel products are usually extruded by an extrusion machine. Generally, the extruded silica gel is in a long shape, and the tubular silica gel can be cut at will. The shapes of products produced by the extrusion process are single, mostly is strip. Silicone tube is widely used in medical and mechanical equipment fields. It can also be used for caching in packaging materials.

5. Rolling

Silicone rubber is kneaded and mixed with white carbon black, silicone oil and other materials to make rubber mixture, and then rolled out of sheets.

There are obvious differences in physical and mechanical properties between longitudinal and transverse directions in films produced by calendering, which is called calendering effect. Specifically, the longitudinal tensile strength of the film is higher than the transverse tensile strength, the transverse tensile elongation of the film is higher than the longitudinal tensile strength, and the longitudinal shrinkage of the film is higher than the transverse tensile strength.

The calendering effect is the orientation result of macromolecules and needle like and sheet like compounds in the rubber compound along the rolling direction during the rolling process. The size of calendering effect is associated with the compound, caldering temperature, speed, and speed rates, which is suitable for large products, like silica film, and silicone plate, etc.

6. Pouring

Operation method of pouring or pouring injection: Pouring mold is used for relatively smooth or simple products. There is no mold line, it saves labor and time. It is to enclose the product or model you want to copy with plastic plate or glass plate, then pour the vacuum silica gel onto the product. Removing the product when the silica gel is dried and shape, and a mold is formed (the injection mold is generally made of silica gel with soft hardness, which is easy to de-mould and will not damage the products in the silica gel mold). It is the combination of solid and liquid, applications, such as mobile phone cases, sex toys, etc.

7. Coating

Rapid vulcanization; excellent adhesion, good fluidity, easy to de bubble. Catalyzed by platinum complex, non-toxic and odor free; Excellent thermal stability and cold resistance (use temperature: – 60 ℃~200 ℃). After molding, it obtains good air permeability, heat resistance and certain tensile strength.

Good slipper resistance: no pollution, low hardness, glue planting should  be firmly bonded. high tear strength, high transparency, good tensile properties. wear resistance, washing resistance, high temperature resistance, high three-dimensional level, the fabric is smooth, soft, flexible and has excellent texture and elasticity. It is resistant to water and dry cleaning.

Applicable to the cloth with anti-aging effect, like silicone gloves, rain shoes, etc.

How to distinguish the liquid silica gel and solid silica gel

Liquid silica gel products: high transparency, no smell, products have injection port.

Solid silica gel products: low transparency, there is a smell of vulcanizing agent or other covering vulcanizing agent, and the product has no rubber injection port.

Application field of liquid silica gel

Generally used into infant supplies, kitchen supplies and medical supplies can directly contact with food and human body.

Solid silica gel: widely used into daily necessities, industrial sundries and auto parts.

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