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Liquid Silicone Rubbers 

 

Silicone Products

What are liquid silicone rubbers(LSRs)?
Liquid silicone rubbers (LSRs ) are a two-component reactive formulation, which is cured at high temperatures after quantitative pumping and mixing by means of an injection molding system. The formulation means that each component contains a catalyst or cross-linking agent that reacts when the two fluids meet to provide predictable mechanical and chemical properties. They rely on fully automated processing and forming, which is the key to high-quality part output and sharply cost reduction achieved. Especially in the medical, automotive fine parts manufacturing is the primary choice.
Yongrui supplies multifunctional injection molding grade LSR, covering applications with harsh contact requirements, such as medical machinery, catering, water.
General purpose injection molding materials
  • Gas phase LSR
     
    It is a general-purpose two-component LSR. Suitable for the injection molding process, 20 hardness, has the same fluidity as water, and has a long pot life (3 days).
     
    It is a colorless and transparent two-component LSR with a hardness of 30 and a 1:1 ratio mixed in proportion. It has passed the US FDA 21 CFR 177.2600 and ROHS certification. Suitable for processing in injection molding systems.
    AB component, ratio 1:1, fast curing speed, transparent and high strength, in line with the requirements of the Food Sanitation Law, no burr, no runner molding.
     
    50 Shore A, two parts, food grade, injection grade LSR, mixing evenly according to 1:1, pot life is longer than 72 hours. High tear resistance, easy demoulding, and short molding time.
    Semi-permeable without impurities, 60 Shore A, two-component, 1:1 mixing, injection grade, the formula has passed FDA certification.
     
  • Precipitated LSR
     
    LSR72030AB 
    Part A/B, 1:1 pumping mixed, 30 Shore A, customizable coloring, super fast cure, no flash, no flow forming.
     
    2 components, materials are mixed according to a certain ratio (1:1), 40 Shore A hardness, a platinum catalyst, in line with the requirements for the production of food and sanitary utensils and other parts. The pot life after mixing is 3 days.
     
    LSR72050AB 
    Components A and B mixed and fed by 1:1, 50 Shore A hardness, platinum catalyzed. Unique rheology, the service life of about 72 hours.
     
     
    Translucent, 60 Shore A hardness, LSR injection molding, very short molding cycle, high-temperature curing, easy processing, meeting FDA standards. Flowable, good tear resistance.
  • High Transparent LSR

    LSR97015AB 
    Part A +/Part B, 15 Shore A hardness, injection molded, mixed in precise 1:1 ratio. High transparency, higher tear resistance, high biocompatibility, and long adaptation period (3-5 days) in a sealed state.
     
    20 Shore A hardness, two-component high transparency, fast curing grade, in line with injection molding process. Perfect biocompatibility, excellent tear resistance, and tensile strength.
    30 Shore A hardness, obtained FDA, BfR, A+B components, 1:1 mixing, especially suitable for liquid injection molding machines（LIMS）, fast curing, high purity and high transparency, stable mechanical properties.
    LSR97040AB 
    Two-component packaging, hardness: 40 Shore A, catalyst: platinum compound, short curing time. Unique tear resistance, and mobility.
     
    Packaging: component A + component B, 1:1 equal ratio mixing, hardness: 50 Shore A, processing equipment: injection machine. The service life is 3 days at room temperature 25C°.
     
    Hardness: 60 Shore A, grade: food, mixing ratio 1:1, curing process: LIM.
Special purpose injection molding material
LSR for bayby care products
LSR970XXAB series are high permeability silicone materials designed for mother and baby applications with high biocompatibility requirements.
Self-lubricating(Oil Bleeding) LSR
It has an ultra-low compression set, no secondary vulcanization, high tear strength, long-term controllable lubricity, and can meet the requirements of tear resistance, self-lubrication, and long life for installation and use.
Liquid Silicone Rubber for Electric Power
It is a LSR specially designed for power transmission and distribution applications such as high voltage cables.
Optically Clear Liquid Silicone Rubber
It has the advantages of long-lasting optical performance, high thermal stability, high definition, UV aging resistance, light transmittance above 94%, etc.
Medical Grade Liquid Silicone Rubber
Passed the biocompatibility test stipulated by regulations, anti-yellowing, resistant to repeated disinfection, high added value.
Self-adhesive
It is suitable for the combination of LSR and PC, PEBT, and polyester materials, and meets the design and processing requirements of complex structures between soft and hard materials.

 Chemical structure

The main agent of Liquid silicone rubbers (LSRs ) contain vinyl siloxane as the main polymer and platinum catalyst, and the secondary agent contains methyl hydrogen siloxane with a low degree of polymerization as the crosslinking agent and acetylenic alcohol retarder. The active polymer chains are reinforced by the addition of dehydroxylated silica fillers. In contrast to other elastomeric materials, this formulation uses a highly active platinum complex catalyst for crosslinking in a specific polyaddition system. LSRs are a thermosetting material with a certain viscosity and a consistency similar to paste, Unlike thermoplastic resins, it is limited to distributive mixing in a low-temperature sealing system before injection, and is simultaneously pressurized and fed into the heated mold cavity and vulcanized. It is different from solid silicone rubber (HTV)， this type of silicone compound has its own low viscosity characteristics that are too easily flowability, which is the key to adapting to special processing systems.

Properties

Since liquid silicone rubbers (LSRs ) are silicone materials, so they have many inherent properties. One of its most prominent features is biocompatibility, which means that they can be directly in contact with human tissue and blood, and can be used as a tissue or organ substitute for short-term or long-term implantation in the human body without qualitative changes. Compared with other organic elastomers and thermoplastic materials, they have high fatigue resistance, can withstand extensive operating temperatures from -60 °C to +250 °C, and maintains consistent mechanical properties after experiencing various harsh environments. LSRs have an excellent processing economy and is suitable for short-cycle continuous automated molding production. They also have a wide range of adaptability including clear or other colors to meet application needs. Compared with glass, it has higher safety performance and energy efficiency, and the entire crosslinking process does not generate waste, thereby effectively reducing waste generation and energy required for processing. LSRs not only have the same properties as ordinary silicone rubber (heat resistance, radiation resistance, oil resistance) but also can be customized according to the final purpose of use, such as adding chemical additives to enhance electrical properties, making them become the optimal choice for high voltage insulation, protection of thermal conductivity and electrical.

Why use Liquid silicone rubbers(LSRs )?

Liquid silicone rubbers are suitable for applications in many fields by virtue of their special processing advantages. In the application of new energy vehicles, they provide a perfect combination of unique rheology properties, low compression set with a liquid injection molding process, which can meet the design requirements of automotive high-pressure elastic parts for rapid thermal cycling, complex, dimensional high accuracy and light weight. LSRs have flammability, wear resistance, and high flexibility, which makes up for the lack of ordinary insulating thermoplastic materials, and also has the characteristics of light weight, which can reduce the weight of automobiles and carbon dioxide emissions, and that lets it become the preferred material for electrical protection and thermal protection of automobile wires and cables.
 
Compared with polyvinyl chloride, LSRs are chemically inert and has almost no reaction with direct contact with human skin or blood, which can bring comfort and safety to long-term skin contact and can be reused after disinfection. It is the best choice for rubber parts suppliers. In baby care applications, post-vulcanization-free custom LSRs have high tear resistance, making it resistant to high mechanical stress, such as the stress that may occur when babies use pacifiers and feeding bottles.
Catalytic System - Platinum
The mechanical properties (tensile, tear strength) of LSR materials need to be cured to meet the requirements of use. The cured (crosslinking) process of LSR is usually related to metal platinum, and the chemical reaction (addition reaction) between the Si-V bond and the Si-H bond is rapidly completed under the action of a platinum catalyst. The LSR series produced by Yongrui are all designated to configure platinum compounds with higher active components in a certain proportion.

Compared with traditional organotin compounds, the advantages of using platinum complexes are as follows:
❐ Platinum cured means safe, clean, and resistant to yellowing or blackening.
❐ Free of secondary curing treatment, delete non-automatic process.
❐ Meet higher hygienic requirements and pass the medical certification, such as FDA, LFGB, and USP Class VI.
❐ Usually, platinum-based catalysts are inert at low temperatures, and catalysis is triggered only at temperatures above 120°C. They are more adaptable to high temperatures, and LSR can be used in more application scenarios, such as the combination of 2-shot injection molding and thermoplastic elastomers.
❐ Tin cured is usually limited to architecture and electronics, while LSR is usually used in medical-grade industries, such as medical machinery, mother, and baby.
Molding process and its benefits
Liquid silicone rubber processing is equipped with an injection molding machine, which makes it possible to shorten the cycle processing time and produce high-quality products from mixing to fully automated molding. The raw material is directly injected into the mold from the raw material barrel without contact with the environment, thereby reducing the pollution in the production process of the product and eliminating impurities. Compared with solid silicone rubber molding, it avoids the problem of uneven force. The injection molding process has the characteristics of high precision and high product shape, especially suitable for small to medium parts so that the product size can achieve high precision (+/0.01mm), more stable, effectively avoiding burrs and burrs caused by overflowing glue, and a more beautiful appearance. In addition, injection molding can also realize the benefits of ultra-thin wall and long shape of the product. Fully automated processing and molding is not only beneficial to reduce labor costs, but also effectively improves and guarantees production capacity to meet the needs of mass production. 
 
In order to combine multiple materials into a single component, the LSR over-molding process (secondary injection molding) can also be used. This process enhances the friction of the parts, reduces or eliminates the composition process, and ensures that it is not easy to fall off during the assembly process and has high reliability and cost controllability.
LSRs questions answering
Ex-factory packaging
There are various packaging methods for shipments in the market, and most manufacturers carry out personalized packaging according to the different components of A and B or the different ways of use. We will fully consider the usage habits of global users in the selection of packaging, and use "straight barrels" with convenience as the primary criterion, that is, packaging barrels with the same diameter at the top and bottom. There will be a liner bag in the barrel to ensure that the product is clean when delivered to the customer. 
 
Straight barrels are mainly in the following two specifications: one is a 20L plastic barrel, the other is a 200L iron barrel, and the barrels are generally blue, white, and yellow in three colors. Customers can use color to distinguish A and B components. Due to its particularity, the packaging barrels of LSR are forbidden to be stacked.
General terms and conditions
Sample fee or freight, 100% TT before shipment.
 
For general orders, a 50% prepayment is charged before delivery and the balance needs to be paid by the customer before shipment.
Free samples and lead time
For regular stock samples, we can apply to the company for free 500g samples for new customers. If the customer has a forwarder agent(Air, Land, sea) in China, the forwarder agent can be directly sampled at the door. If our forwarder agent is required to carry out the transportation, it shall be charged according to the actual freight. The general sample time is 2-5 days.

For samples customized according to customer performance or usage, the lead time is generally 5-7 days. 
 
After the customer confirms the samples, the lead time for bulk goods is generally 7-10 days. The actual situation of the factory shall prevail, please contact us for more details.

Our advantages

  • Technical support
    Proven and proven technology

  • Sample

    Free LSR sample​​​​​​​

  •  Quality

    Stable and high-quality production process

  • R&D

    Adhere to follow-up research and development
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