Can Silicone Be Injection Molded?

When people think of injection molding, they often imagine rigid plastic parts rapidly formed under heat and pressure. But what about soft, flexible materials like silicone?

The answer is a resounding yes — silicone can be injection molded, and the process has become an essential part of modern manufacturing.

Through a technique known as Liquid Silicone Rubber (LSR) injection molding, manufacturers can produce durable, flexible, and high-precision parts used in everything from baby products and wearable devices to medical components and automotive seals.

What Is Liquid Silicone Rubber (LSR)?

Liquid Silicone Rubber (LSR) is a two-part thermosetting elastomer. Unlike thermoplastics, which can be melted and reshaped repeatedly, LSR undergoes an irreversible chemical reaction—called curing or vulcanization—when heated.

This process transforms the material from a low-viscosity liquid into a solid, permanently flexible, and stable component.

Because of these unique properties, LSR has become the preferred material for silicone injection molding, allowing for precise, automated, and efficient production of complex parts.

The Silicone Injection Molding Process Explained

The LSR injection molding process—also known as Liquid Injection Molding (LIM)—is highly automated and precise. It typically involves four main stages:

1. Material Preparation

Two liquid components (Part A and Part B) are stored in sealed drums. They are automatically metered and mixed in a 1:1 ratio, often with a platinum catalyst to start the curing reaction. At this stage, color pigments or additives can also be introduced to enhance performance or appearance.

2. Injection

The mixed silicone is injected under high pressure into a heated mold cavity. Because LSR has low viscosity, it can easily flow into intricate mold designs and reproduce fine details with high dimensional accuracy.

3. Curing

Inside the mold, heat (typically between 120°C and 200°C) triggers cross-linking, converting the liquid silicone into a solid, elastic component. This reaction is fast and controlled, resulting in short cycle times.

4. Ejection

Once cured, the part is automatically ejected from the mold, ready for use or secondary processing.

A key feature of this process is the cold runner system, which keeps the liquid silicone cool until it enters the heated mold. This prevents premature curing, reduces waste, and allows for continuous, high-volume production with minimal manual intervention.

Advantages of Silicone Injection Molding

Choosing silicone injection molding offers numerous benefits that combine material excellence with process efficiency:

1. Exceptional Precision for Complex Parts

LSR’s low viscosity and minimal shrinkage enable the creation of complex, detailed parts with tight tolerances, making it ideal for medical, automotive, and electronic components.

2. Superior Material Properties

Injection-molded silicone exhibits outstanding resistance to extreme temperatures, UV radiation, ozone, and chemicals. It also maintains elasticity and shape under prolonged compression, giving it excellent long-term durability.

3. High-Volume, Cost-Effective Manufacturing

The automated, repeatable nature of LSR injection molding ensures short cycle times and low labor costs, making it one of the most efficient methods for producing large quantities of silicone parts.

4. Biocompatibility and Safety

Medical- and food-grade silicones are non-toxic, hypoallergenic, and odorless. They meet biocompatibility standards, making them safe for products like baby bottle nipples, medical seals, and wearable devices.

5. Design Flexibility

LSR molding supports advanced techniques such as overmolding and insert molding, where silicone is molded directly over other materials like metal, glass, or plastic. This creates multi-material assemblies with superior sealing and ergonomic properties.

Common Applications of Silicone Injection Molding

Thanks to its versatility and reliability, injection molded silicone is used across a wide range of industries:

Industry	Typical Applications
Medical	Seals, gaskets, valves, catheters,   respiratory masks, surgical grips
Automotive	Gaskets, seals, wiring connectors, and   heat-resistant engine components
Electronics	Keypads, membranes, waterproof seals,   insulators, and flexible housings
Consumer Goods	Pacifiers, baby bottle nipples, kitchen   tools (spatulas, molds), wearable straps
Industrial	O-rings, diaphragms, dampers, and   high-performance seals for harsh environments

These applications showcase LSR’s combination of strength, flexibility, and chemical resistance, making it a preferred material for both consumer and industrial products.

Why Silicone Injection Molding Matters

The ability to injection mold silicone has opened up new possibilities for product design and performance. It allows manufacturers to achieve:

• Higher product consistency through automated precision

• Reduced waste due to the cold runner system

• Enhanced performance under extreme environmental conditions

• Scalable production for global demand

With these benefits, it’s easy to see why LSR injection molding continues to gain traction across industries seeking high-quality, flexible, and durable parts.

Conclusion

So, can silicone be injection molded? Absolutely.
Through the Liquid Silicone Rubber (LSR) injection molding process, manufacturers can create complex, high-performance silicone components that combine flexibility, strength, and precision.

Whether for medical devices, automotive parts, or consumer products, silicone injection molding delivers a powerful blend of efficiency, reliability, and versatility—making it one of the most important manufacturing technologies in use today.