橡楚编辑部 6/23/2026 43 min read
LSR (Liquid Silicone Rubber) is a high-performance silicone material with excellent biocompatibility, temperature resistance, aging resistance and electrical insulation properties, which is widely used in medical, automotive, electronics, maternal and infant and other fields. This article systematically sorts out the core characteristics, common application scenarios, molding process points and material selection precautions of LSR liquid silicone rubber, helping practitioners quickly master the core application logic of this material and solve common problems in actual production.
LSR (Liquid Silicone Rubber) is a two-part, high-purity thermoset elastomer composed of linear polydimethylsiloxane (PDMS) polymers, reinforcing fillers, crosslinking agents, catalysts, and functional additives. Unlike room-temperature vulcanizing (RTV) silicones or high-consistency rubber (HCR), LSR features a low initial viscosity (1,000–1,000,000 cP at 25°C) that enables precision injection molding, while its crosslinked structure delivers unique performance unmatched by organic rubber alternatives.
Global demand for LSR reached 780,000 metric tons in 2023, driven by growth in medical devices, automotive electrification, and consumer wearables, with a projected CAGR of 6.8% through 2030. This guide breaks down LSR’s material properties, manufacturing processes, application-specific performance requirements, and quality control standards to support engineers and product designers in leveraging LSR for high-performance use cases.
LSR’s distinctive performance stems from its inorganic Si-O backbone (bond energy 452 kJ/mol, compared to 346 kJ/mol for C-C bonds in organic rubbers) and organic methyl side groups. This chemical structure delivers a unique balance of mechanical, thermal, and chemical resistance properties that can be tuned for specific end-use requirements.
Unfilled LSR has a Shore hardness range of 00–10 to A 70, while filled grades with fumed silica or functional fillers can reach Shore D 60 for structural applications. Table 1 outlines standard performance metrics for general-purpose and specialty LSR grades:
LSR’s thermal stability is one of its most notable advantages: it retains >70% of its room-temperature tensile strength after 1,000 hours of aging at 200°C, compared to nitrile rubber (NBR) which loses 80% of its strength under the same conditions. At low temperatures, LSR remains flexible down to -60°C for standard grades, with specialty low-Tg formulations usable at -100°C for aerospace cryogenic applications.
LSR is inherently resistant to water, dilute acids and bases, alcohols, and polar solvents, but is susceptible to swelling in non-polar solvents such as mineral oil, gasoline, and aromatic hydrocarbons. Functional modifications can be applied to tailor chemical resistance for specific environments:
LSR is also inherently biocompatible: medical grades meet ISO 10993-5 (cytotoxicity), ISO 10993-10 (irritation and sensitization), and USP Class VI requirements, while food-contact grades comply with FDA 21 CFR 177.2600 and EU 1935/2004 regulations.
LSR is almost exclusively processed via injection molding due to its low initial viscosity and fast high-temperature curing kinetics, though specialized processes exist for low-volume or large-format parts. Proper processing is critical to avoid defects such as incomplete filling, air entrapment, and under-curing that can compromise part performance.
LSR injection molding uses a two-component delivery system that mixes Part A (containing platinum catalyst) and Part B (containing crosslinking agent and inhibitors) in a 1:1 or 10:1 ratio immediately before injection. The process workflow includes four core stages:
For high-volume production, LSR molding is often integrated with in-mold assembly (IMA) to overmold LSR directly onto thermoplastic substrates (polycarbonate, PEEK, nylon) or metal inserts, eliminating secondary bonding steps. Bond strength between LSR and compatible thermoplastics can exceed 3 MPa, meeting structural requirements for automotive and medical components.
For low-volume, custom, or large-format parts that are not feasible with standard injection molding, three alternative processing methods are widely used:
Compression molding is ideal for low-volume parts (10–10,000 units) with large cross-sections, such as industrial gaskets or solar panel seals. Pre-mixed LSR is placed into an open mold cavity, the mold is closed and heated to 160–190°C under 10–50 bar of pressure, and cured for 2–10 minutes. Tooling costs are 70–90% lower than injection molding, but cycle times are 10–20x longer, and dimensional tolerances are wider (±0.5% vs. ±0.1% for injection molding).
Continuous extrusion is used to produce long, uniform LSR profiles such as tubing, sealing strips, and wire insulation. Mixed LSR is forced through a custom die at 5–20 bar, then cured in a heated hot air oven (200–250°C) or via UV irradiation for thin-walled profiles. Extruded LSR tubing can achieve wall thicknesses as low as 0.1 mm and inner diameter tolerances of ±0.02 mm for medical catheter applications.
Additive manufacturing for LSR has advanced significantly since 2020, with two commercialized technologies:
3D printed LSR has 80–90% of the mechanical strength of molded LSR, making it suitable for prototyping and low-volume custom parts, though high material costs and slow print speeds limit widespread high-volume adoption.
LSR’s versatility makes it suitable for a wide range of industries, but material selection and design must account for unique end-use requirements to ensure long-term performance and regulatory compliance.
LSR is the material of choice for 60% of implantable and disposable medical components manufactured today, due to its biocompatibility, sterilization resistance, and soft, skin-friendly feel. Common use cases include:
Key design considerations for medical LSR parts include avoiding sharp corners that can trap bacteria, specifying post-curing to reduce extractables to <0.1% of total part weight, and selecting grades with clear traceability from raw material batch to finished part for regulatory audits.
The global shift to electric vehicles (EVs) has driven a 12% annual growth in LSR demand for automotive applications, as LSR outperforms organic rubbers in high-temperature, high-voltage EV environments. Core use cases include:
For automotive applications, LSR grades must meet ISO 16750 road vehicle environmental standards, including resistance to road salts, brake fluid, and engine oils, and have a service life rating of ≥15 years or 250,000 km.
LSR is widely used in consumer wearables and electronics due to its soft tactile feel, UV resistance, and water-proofing capabilities. Common applications include:
Design considerations for consumer electronics LSR parts include selecting UV-stabilized grades that have <3 ΔE color change after 1,000 hours of sun exposure, and adding surface coatings such as plasma treatment or Parylene to reduce fingerprint accumulation and improve scratch resistance.
Consistent LSR part performance requires rigorous quality control across the entire supply chain, from raw material incoming inspection to finished part validation. Adherence to standardized testing methods ensures that parts meet specified performance requirements for their intended use case.
Raw LSR material is tested upon receipt to verify consistency between batches, with standard tests including:
In-process testing during manufacturing includes:
Finished LSR parts undergo a series of performance tests tailored to their end-use application, with standard test methods outlined in Table 2:
For critical applications such as medical implants or automotive battery seals, accelerated life testing is also conducted, including 1,000+ thermal cycles between minimum and maximum service temperatures, and 10,000+ cycle durability testing for dynamic sealing components. Non-destructive testing methods such as optical inspection, X-ray scanning, and helium leak testing are used to detect micro-cracks, voids, and sealing defects in finished parts without damaging them.
LSR Liquid Silicone Rubber is a uniquely versatile high-performance elastomer that bridges the gap between soft, flexible materials and durable, temperature-resistant engineering polymers. Its combination of thermal stability, biocompatibility, low-temperature flexibility, and precision processability makes it the material of choice for a growing range of medical, automotive, consumer electronics, and industrial applications where organic rubbers cannot meet performance requirements.
As material science advances, next-generation LSR formulations including self-healing grades, recyclable thermoset LSR, and high-strength nanocomposite grades are expected to expand its use case further, particularly in sustainable manufacturing and high-stress structural applications. For product designers and engineers, success with LSR depends on aligning material selection, processing method, and design choices with end-use performance and regulatory requirements, leveraging the material’s unique properties to create parts that deliver longer service life, higher reliability, and lower total cost of ownership than alternative materials.