What are the properties and applications of liquid silicone rubber?

There is a wide range of silicone products in daily life, but why are liquid silicone rubbers so widely welcomed by everyone? In the following.

Liquid silicone rubber (LSR material) has excellent transparency, tear strength, resilience, yellowing resistance, thermal stability, water resistance, softness, air permeability, heat aging resistance, and weather resistance, while moderate viscosity, chemical resistance, good fluidity, easy operation, and high transparency of products, and has very good electrical properties, and it is a versatile material.

I will introduce the characteristics and uses of liquid silicone one by one

The latest application development of liquid silicone rubber

In recent years, the liquid rubber injection molding method (LIMS), that is, injection molding of liquid silicone rubber, has been widely popularized and promoted by the medical industry and other many industries. Recently, this method has become a molding method that has been widely concerned by industry insiders because it has the advantages of short-term automatic molding and composite molding plastics. Thermoplastic injection molding The following is an introduction to the latest trends in liquid silicone rubber injection molding and the materials suitable for this molding method

1. Liquid injection molding process of silicone rubber

The liquid silicone rubber lsr injection molding method, which began in the 1970s, is gradually gaining popularity, and the method of liquid silicone rubber molding has been recognized, starting with the introduction of the commonly used LIMS method.

If we explain LIMS (Liquid Silicone Rubber Injection Molding) in one sentence, it is a method in which an addition-cured liquid silicone rubber is delivered in an injection molding machine container by a pump and cured in the model and precise control of shot size From the process flow of these two methods and the difference in curing reactions.

The advantages of LIMS are several:

(1) Labor-saving

The processes of material conveying, measuring, mixing, and injection are continuously automated, reducing power consumption.

(2) Increased productivity

Seek to shorten the molding cycle by rapid curing.

(3) Improve the product quality

No reaction by-products are generated and no impurities are mixed in, demanding applications, and tight tolerances.

(4) Suitable for composite molding

Due to the good flowability of the material, low molding pressure, resistance, and a broad range of curing temperatures, it is a highly concentrated rubber. It is possible to perform composite molding in addition to embedded molded parts.

2. Latest technology development of LIMS

Not only is there a transition from a pure blending type with the above-mentioned advantages of the LIMS method, but recently there is an active development in the following two directions.

(1) Fully automatic forming: no flying edge, no runner, automatic molding

Due to liquid silicone rubber properties and chemical structure, the fully automated molding process has been studied from various aspects such as injection machines, molds, tooling, and materials. This method is of great interest not only in terms of labor-saving in process operation, but also in terms of reducing material cost because it does not produce useless cured materials, and from the perspective of environmental protection. The molding cycle (from injection to the next injection) is within 10s for micro products such as automotive skeleton oil seals, which can be done in a very short time, And cost-effectively. The lsr molding process allows complex part geometry and exact dimensions.

(2) Compound molding: Clamp insert molding, binary molding

Since the cross-linking reaction is in the form of addition curing, it can be molded to withstand extreme temperatures. Since no by-products such as peroxide decomposition residue are generated in the cross-linking reaction, The curing process does not require secondary vulcanization. Therefore, it is possible to perform integral molding resin, and binary molding, in which the seal part and the skeleton part become one unit by applying primer material, which has also become popular.

(3) Technology Applications

Silicone rubber has excellent properties (plug resistance, weather resistance, electrical insulation, flame resistance, etc.). High-consistency rubber (HCR) has a higher viscosity and is better suited to high-strength molding and extrusion processes. Due to these liquid silicone rubber performance characteristics, it is possible to make environmentally friendly molding based on fully automated molding, and integral molding with metals and organic resins. In addition, the material itself is transparent with colorability, so its applications cover many fields, such as (medical devices, computers, cell phones, etc.) buttons, nipples for milk bottles, (copiers, mold design, surgical tools, printers, etc.) rubber rollers, drug delivery devices, various automobile parts such as pipe joint seals and oil seals(automotive industry), anode cap for television picture tubes, diving supplies, etc. If you use LSR materials, you can also make any kind of three-dimensional shape that cannot be done on a flat surface.    (Candy mold mini cake decoration polymer clay craft resin, epoxy resin jewelry making) Custom liquid silicone gaskets and a variety of custom components.

3.No glue edge/no runner material for automatic molding

In recent years, a method known as rimless and runner molding has become popular in the injection molding of liquid silicone rubber. This is a molding method that does not produce useless curing materials and does not require secondary processing, i.e., a molding method that does not have injection ports or runners (even if there are, curing does not occur) and does not produce waste glue edges. Cost-effective.

In order to implement this molding method, the structure of the model and the finish of the parting surface, etc., the metering and discharge accuracy of the injection machine must meet the requirements, and even in terms of material, it must be a material that is difficult to generate waste glue edges. After the cavity is filled with rubber, the rubber flows into the parting surface due to excessive rubber or thermal expansion of silicone rubber and then becomes waste after curing. If the parting surface is designed to be narrower, it is difficult to generate the waste rubber edge, but at the same time, the air is not easy to drain away, so it becomes the reason for the air bubbles in the finished product.

Compared to previously used materials, the curing curve of this material is in a sharp turnaround (short time from the start of curing to the end of curing) Unlike many liquid silicones that have complicated mix ratios and very thick consistencies. By selecting the proper injection conditions for this type of material, i.e., before the material fills the cavity and curing has not yet begun, the material flows well, and when the material fills the cavity, curing ends immediately and the material does not flow onto the parting surface even though there is still residual pressure, preventing the formation of waste glue edges.

XJY Silicones - First choice VMQ silicone supplier of LSR

XJY Silicones, one of China's leading VMQ silicone resin/ VMQ silicone solution manufacturers, has 30+ years of R&D and manufacturing experience and 15+ related patents and technical assistance in the silicone industry, also can customize the silicone products according to the requirements of your LSR material.


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