At the molecular level, LSR is based primarily on polysiloxane polymers, with silicon-oxygen (Si–O) backbones providing many of the material's characteristic properties.

The silicone polymer is reinforced with specially treated silica and combined with other formulation components to achieve the required hardness, strength, flow characteristics, curing behavior, color, and application performance.

A typical two-component LSR system works as follows:

Part A: Contains the silicone base and platinum catalyst.

Part B: Contains the silicone base and crosslinking components, typically including organohydrogenpolysiloxane.

Addition curing: When Parts A and B are mixed, the platinum-catalyzed reaction creates crosslinks within the silicone polymer network.

Curing: The mixed material is injected into a heated mold, where it rapidly cures into an elastic solid.

The exact formulation varies according to the manufacturer's technology and the intended application.

One of the most important differences between LSR and HCR is their physical form and processing method.

The choice between LSR and HCR depends on the part design, production volume, required tolerances, curing technology, material hardness, processing equipment, and cost targets.

For high-volume production of small, complex silicone components, LSR injection molding can provide significant advantages because material metering, mixing, injection, and molding can be highly automated.

LSR is selected for many demanding applications because it combines several properties that are difficult to achieve with conventional organic elastomers.

Some LSR grades are specifically formulated and tested for medical or healthcare applications, but LSR should not automatically be described as biocompatible.

Biocompatibility depends on the complete material formulation, manufacturing process, cleanliness, sterilization method, intended use, contact type, and applicable regulatory requirements.

Medical-grade silicone may be used in products such as:

• Medical seals and gaskets
• Tubing and fluid-management components
• Valves and diaphragms
• Respiratory components
• Wearable medical components
• Drug-delivery components
• Selected implantable applications

For medical applications, material selection should be based on the relevant technical documentation, regulatory requirements, and test reports rather than on the generic term "LSR."

For example, depending on the market and application, manufacturers may need to consider requirements related to ISO 10993, USP Class VI, FDA requirements, or other applicable standards and regulations.

To demonstrate how LSR material properties translate into actual product development, the HL-9960-xx-YL series from Guangdong Hailan New Material Technology Co., Ltd. provides an example of a specialized two-component addition-curing LSR.

The HL-9960 series is designed for rapid high-temperature curing and liquid injection molding and is intended for applications requiring a combination of:

• High transparency
• High mechanical strength
• Yellowing resistance
• Biocompatibility-related performance
• Precision molding capability

The product series includes:

• HL-9960-40-YL
• HL-9960-50-YL
• HL-9960-60-YL

Typical applications include laryngeal masks and negative-pressure bulbs.

According to the supplied product technical documentation, the series is documented for ISO 10993 biocompatibility requirements and has supporting compliance/certification documentation associated with FDA, LFGB, RoHS, and REACH.

Important: Certification and compliance should always be verified against the specific grade, current certificate or test report, intended application, and target market. Compliance of a raw silicone material does not automatically mean that the finished medical device is compliant.

The following values are representative technical data from the supplied HL-9960 series documentation.

Typical molding condition: 130°C / 5 minutes

These figures demonstrate the balance of hardness, strength, elasticity, tear resistance, and transparency that can be achieved with a specialized LSR formulation.

For example, HL-9960-40-YL provides a lower hardness of Shore A 40, while HL-9960-50-YL and HL-9960-60-YL provide progressively higher hardness.

The reported light transmittance is approximately 91%, demonstrating the high transparency of this product family.

These values should be treated as typical technical data, not universal guaranteed specifications for every production batch. Final material selection should always refer to the current TDS and applicable product specifications.

Request an HL-9960 Series

Different silicone products require different combinations of flexibility, stiffness, sealing performance, tensile strength, and tear resistance.

For this reason, LSR manufacturers often provide several hardness grades within one product series.

The most common processing method for LSR is Liquid Injection Molding (LIM).

Unlike solid HCR, LSR is delivered as a two-component liquid system that must be accurately metered and mixed before injection.

One of the important technical considerations when processing platinum-catalyzed LSR is cure inhibition.

Certain substances can interfere with the platinum-catalyzed curing reaction and result in incomplete or delayed curing.

Potential sources of inhibition include:

• Amines
• Sulfur-containing compounds
• Phosphorus-containing compounds
• Certain metal salts
• Some condensation-cure silicone systems
• Contaminated equipment or tooling

This issue becomes particularly important when a manufacturer changes silicone suppliers.

Residual material from a previous silicone formulation may remain in:

• Pumps
• Mixing systems
• Hoses
• Feed lines
• Tooling
• Storage systems

These residues may interfere with the curing behavior of the new LSR.

LSR injection molding offers several advantages for high-volume precision manufacturing.

LSR is used across a wide range of industries.