LSR Select: Customizable Cure Speed, Temperature, and Durometer for Modern Molders

After five years of research and development, LSR Select has entered the commercial market, offering molders unprecedented flexibility in adjusting cure time, temperature, and durometer of liquid silicone rubber (LSR). This breakthrough moves beyond the constraints of traditional two‑part systems, enabling faster cures, lower processing temperatures, and finely tuned hardness values.

Novel One‑Part LSR System

Unlike conventional two‑pot LSRs, which blend a catalyst‑loaded resin with an inhibitor‑laden resin at a fixed 1:1 ratio, LSR Select is formulated from a single base resin plus two additive masterbatches: a platinum catalyst (typically 1% by weight) and a cure‑control agent (0–6% by weight). Adjusting the amount of the control agent delays or accelerates the gel and cure, giving molders direct control over cycle time and part quality.

Chris York, President of Elkem Silicones Americas, explains that this modular approach “free‑s the chemistry to do what it’s been capable of for years.” In practice, a lower control‑agent level can speed the cure of small parts, while a higher level can ensure complete fill of larger parts without premature gelation, yet still deliver a rapid overall cure.

Elkem reports productivity gains of 20–60% on conservative estimates, with some trials demonstrating improvements of up to 125% when using LSR Select’s adjustable cure profile.

Additional advantages include:

• Lower processing temperatures: LSR Select can be molded at 75–80 °C—or even below—without sacrificing cure speed. For instance, a 50‑second cure at 165–170 °C can now be achieved in 50 seconds at 100 °C.
• Tailored durometer: Mixing two base resins within the same two‑pot system allows production of intermediate Shore A hardness values. Elkem’s current catalog offers base resins in 20, 30, 40, 50, 60, and 70 Shore A, with medical‑grade variants available across the same range.
• Enhanced consistency: Batch variability has been reduced from ±3–5 to ±1–2 Shore A units, thanks to precise metering and the stable chemistry of LSR Select.
• Future‑ready additives: Elkem plans specialty additives—antimicrobial, self‑bleeding, self‑bonding, etc.—that will be compatible with standard base resins, eliminating the need for custom A‑B formulations.

Special Equipment Needed

The adoption of LSR Select hinged on advances in metering technology. Early prototypes were developed in partnership with Graco, but widespread deployment became feasible only after the introduction of the Elmet TOP 5000 P precision metering system in 2016. This unit offers ±0.1% accuracy in additive dosing, stable base resin pumping, and software that supports variable A‑B ratios for durometer blending.

Elkem is collaborating with other equipment manufacturers to broaden accessibility, and a growing number of customers in healthcare and industrial sectors have already adopted LSR Select in production.