Liquid Silicone Rubber (LSR): Types, Processing, Brands, and Price Trends Explained

Liquid silicone rubber has quietly become one of the fastest-growing corners of the silicone industry. Over the last ten years it moved out of niche applications and into everyday manufacturing, taking the place of ordinary rubber and plastic in products people handle all the time. If you work in engineering, procurement, product design, or sourcing, knowing what LSR actually is, and what it is not, will save money and spare you some expensive mistakes.

This guide covers the seven things that matter: what the material is, how it differs from solid silicone, what types exist, why industries keep adopting it, how to process it, which brands dominate, and where prices and demand are heading.

What is liquid silicone rubber?

Liquid silicone rubber, usually shortened to LSR, is a two-part liquid silicone built on a polydimethylsiloxane base. Component A carries the base polymer plus a platinum catalyst. Component B holds the crosslinker. Mix them in the right ratio and apply heat, and they cure into a solid elastomer within seconds.

The word that matters is liquid. Before it cures, LSR flows like water. That single property unlocks everything else: fast automated molding, walls thin enough to bend, and tolerances solid rubber cannot reach.

How does LSR differ from solid silicone rubber?

Solid silicone, the older cousin often called HCR (high-consistency rubber), comes as a gum you mill, pre-form, and press into shape. LSR skips most of that labor. The table below shows where they part ways.

The short version is simple. LSR wins for high-volume, high-precision, and complex parts. The whole silicone industry is drifting that way as automation becomes normal.

What are the main types of liquid silicone rubber?

Three ways to sort LSR make sense: by curing chemistry, by application grade, and by special function.

By curing system

Addition-cure LSR (platinum-catalyzed) is the mainstream type, well over 90 percent of the market. Platinum catalyzes an addition reaction between silicone hydride and vinyl groups. The cure gives off no by-products, which is why the material cures deep sections, shrinks almost not at all, and stays odor-free and biocompatible.

Its weak point is “platinum poisoning.” Trace sulfur, nitrogen, phosphorus, or tin compounds can kill the catalyst and stop the cure. That detail matters more than it sounds, and we come back to it below.

Condensation-cure LSR (tin-catalyzed) is the older formula. It releases small molecules as it cures, so it shrinks more, smells a bit, and cannot pass food or medical certification. It is cheap, tolerant of contamination, and can cure at room temperature, which keeps it alive in potting, molding, and low-end industrial sealing.

By application grade

• General industrial LSR covers everyday seals, O-rings, gaskets, keypads, and dampers. Hardness runs from Shore A 0 to 80, and the price stays reasonable.
• Food-grade LSR meets standards such as FDA 21 CFR 177.2600, GB 4806.11, and LFGB. You find it in baby nipples, baking molds, drinkware, and food-contact seals.
• Medical-grade LSR is the high-purity tier, cleared under ISO 10993, USP Class VI, and device registrations. It shows up in catheters, breathing masks, syringe seals, and implantable parts.
• Specialty functional LSR is where things get interesting. Conductive grades shield against EMI. Thermal grades cool electronics. Flame-retardant grades hit UL94 V-0. Self-bonding grades grip plastic and metal without primer. Optical-clear grades pass 95 percent light transmission.

Why are more industries switching to LSR?

The material earns its place on seven strengths.

1. Wide temperature range. LSR stays useful from -60°C to 200°C and tolerates brief spikes above 250°C. Few organic materials come close at the cold end.
2. Good weatherability. The silicon-oxygen backbone resists UV, ozone, and humidity. Outdoor service life runs three to five times longer than EPDM.
3. Safe and biocompatible. Addition-cure LSR is non-toxic, non-sensitizing, and clears food and medical standards. It is the default for baby, medical, and food uses.
4. Strong electrical insulation. High dielectric strength and stable permittivity suit it to insulation, high-voltage seals, and cable accessories.
5. Flow and precision. Being liquid before cure, it fills microscopic cavities. Dimensional accuracy reaches about ±0.01 mm, impossible with solid rubber.
6. Fast cure, high output. Injection cycles take ten seconds to two minutes, one-tenth to one-fifth of compression molding. A single cavity can yield tens of thousands of parts per day.
7. Almost no waste. A closed feeding system uses close to 100 percent of the material, with no flash and no fumes. That lines up with where green manufacturing is headed.

How do you process liquid silicone rubber?

Handling LSR right is the difference between a clean cure and a bin of scrap. The workflow runs in five steps.

Step 1, storage and prep. Confirm A and B are a matched pair and check shelf life, usually six to twelve months. Store at room temperature, dry, dark, and sealed. If the material has been cold, let it warm to room temperature for about 24 hours first.

Step 2, mixing. Addition-cure LSR is normally mixed A:B = 1:1 by weight or volume, per the supplier’s note. Production uses the press’s built-in metering mixer for consistency. Small batches can be hand-mixed: weigh both parts, stir three to five minutes, and scrape the walls and bottom. Keep the stir speed moderate so you do not trap air. Watch the pot life, usually one to four hours at room temperature, and use the blend inside that window.

Step 3, degassing (optional). If bubbles remain, pull vacuum to about -0.09 MPa for three to five minutes. Most injection presses vacuum the mold cavity directly, so pre-degassing is often skipped.

Step 4, curing. Injection molding is the production route. The blended material pumps into a heated cavity and cures fast. Mold temperature is typically 150°C to 200°C, with cycles of ten seconds to two minutes depending on wall thickness. For low volume you can pour and cure at room temperature (six to twenty-four hours) or bake at 80°C to 120°C to speed things up.

Step 5, post-cure. Fresh parts may carry trace low-molecular volatiles and a faint odor. Food- and medical-grade products usually get a post-cure of about 200°C for four hours, or 180°C for six hours, in an oven. This drives off volatiles, stabilizes dimensions, lifts mechanical properties, and removes the smell.

One caution worth repeating: addition-cure LSR is easy to poison. Keep it away from latex gloves, sulfur, organotin, certain rubbers and plastics, and mold rust preventives. Clean every tool, container, and mold before contact.

How does LSR injection molding work?

Injection molding is LSR’s main advantage, and the process runs through five stages.

1. Feeding. A and B sit in 20 L or 200 L drums and are drawn out by dedicated pumps through a closed, contamination-free path.
2. Metering and mixing. A precision meter holds the A:B ratio within ±1 percent, and a static mixer blends the two. The mix then injects through a nozzle.
3. Injection and cure. The mold closes (clamp force typically 50 to 200 tons). Material injects at roughly 50 to 150 bar, holds pressure to offset shrinkage, cures under heat, then opens. Ejector pins, air blow-off, or a robot pull the part.
4. Tooling detail. LSR molds need tight parting lines to stop flash, a cold-runner design so only the cavity heats, and good venting because the thin fluid traps air easily. Release angles can be smaller than for plastic thanks to silicone’s springiness.
5. Automation and finish. A robot handles takeout. Gates are trimmed (minimal with cold runners), then post-cure, deflashing, inspection, and packing follow.

The headline benefit stays the same: high efficiency, high precision, high automation, low labor. That is exactly why LSR suits high-volume precision parts.

Which brands lead the LSR market?

The field splits cleanly into imported leaders at the top and fast-rising domestic players below.

Imported brands

• Dow (formerly Dow Corning) is the global leader with the broadest lineup (Silastic series) and strength in every grade, but it costs more and lead times run long.
• Wacker (Germany) is number two worldwide, with standout medical grades (Elastosil LR), high clarity, and good resistance to yellowing.
• Shin-Etsu (Japan) is the Asian technology leader, with its KE series favored in electronics and automotive.
• Momentive (USA) makes the Silopren series, with decent value in industrial grades and some distinctive specialty types.

Domestic brands

• Dongjue is a major local player with a wide range, stable supply, strong value, and fast service.
• Hongda offers a full LSR lineup including clear and self-bonding grades, with strong customization.
• Xinan has integrated upstream supply that keeps cost low, and it is moving up toward medical grade.
• Guibao is a well-known sealant maker expanding fast into electronic and thermal LSR.

The quick read: imports own the high end on technology and certification, while domestic names close the gap on general and food grades at 50 to 70 percent of import pricing.

What drives LSR demand and how are prices trending?

LSR is among the fastest-growing silicone segments, compounding at roughly 10 to 15 percent a year. China’s market passed 8 billion RMB in 2026 and is projected to top 15 billion RMB by 2030.

Five forces push demand:

• New energy vehicles need battery seals, harness seals, charging connectors, and lamp seals.
• Healthcare uses catheters, masks, aesthetic consumables, and pharmaceutical stoppers.
• Consumer electronics rely on phone and watch water seals, earbud parts, and wearables.
• Baby and mother products include nipples, tableware, teethers, and comfort items.
• Food contact covers bakeware, kitchen tools, and drinkware.

Prices vary widely by grade, per kg:

The trend line is clear enough. Mid- and low-end prices ease slowly as domestic capacity grows, while high-end medical and specialty grades hold firm behind technical barriers. Raw-material swings, 107 gum and vinyl silicone oil among them, add cyclical cost moves.

Where is the LSR market headed?

Four points explain why the curve keeps climbing.

1. Applications keep expanding. Each new field, EVs, medical, wearables, multiplies LSR use.
2. Substitution is explicit. LSR is steadily replacing NBR, EPDM, PVC, and TPE wherever performance matters.
3. Domestic substitution lowers the floor. Local brands at half the import price open countless mid-range uses.
4. Automation drives process shift. As labor costs rise, shops move from compression molding to LSR injection for volume and precision.

Conclusion

Liquid silicone rubber is no longer an exotic material. It is the practical, high-performance choice for products that must be precise, safe, durable, and made at scale. Addition-cure grades dominate, injection molding is the process that matters, and the brand map is shifting toward capable domestic suppliers. For anyone specifying materials today, LSR deserves a serious look, and a clear grasp of grades, curing chemistry, and total cost before the first tool is cut.