Silicone rubber is a high-performance elastomer that you can process as liquid variants. Like its solid and vulcanized counterparts, liquid silicone rubber has tons of applications. And these applications span various industries.
Wondering what precisely liquid silicone rubber is? Perhaps you want to know if this variant can suit your application well. In this article, we’ll go over everything you need to know about this silicone rubber type.
1. What is Liquid Silicone Rubber?
Liquid silicone rubber is a low viscosity polymer that you can injection mold into different shapes. Unlike solid variants, LSR has low molecular weight and shorter polymer chains. Still, LSR sees a lot of use in many industries, much like its solid counterpart.
Silicone rubber is a synthetic elastomer generally praised for its flexibility, durability, and non-toxicity. As you know, the alternative to silicone rubber is plastics.
You can also injection mold plastics into the shape you like. But they have naturally inferior qualities compared to silicone rubber.
Plastics are less durable and won’t withstand extreme temperatures. Moreover, plastic has high toxicity, so they’re not really considered eco-friendly.
2. The Chemical Composition of Silicone Rubber.
Silicone rubber, in general, has a siloxane bond (-Si-O-Si-) as its backbone.
From this backbone, manufacturers can add various organic chemicals to create different characteristics for the end silicone product. This siloxane bond is more robust than carbon (plastic’s backbone). And it’s responsible for silicone rubber’s sought-after qualities.
Siloxane bonds have a binding strength of 433kJ/mol, which is higher than carbon’s 355 kJ/mol. This higher bond strength gives silicone rubber superior temperature and chemical resistance. Silicone bonds also have low intermolecular reactions, giving LSRs high elasticity and flexibility.
3. The Mechanical Properties of Silicone Rubber
LSRs are viscous, meaning they have better flow properties than solid silicone rubber. You’ll notice that its physical appearance is similar to that of bubble gum or clay.
It also excels at certain mechanical properties compared to other variants. And it’s really why LSRs are the best choice for certain use cases.
All silicone rubber types have these desirable characteristics:
- High-temperature resistance (from -60°C to +250°C)
- Chemically stable
- Electrically resistant
- Environmentally friendly
The properties listed above are what attract most of LSR’s use-cases. But you’ll also find other properties where LSRs excel compared to different variants.
Here are the mechanical properties where LSRs shine the most.
- Odorless and tasteless
- Aging resistance
- Low compression set
4. Where Can You Use Liquid Silicone Rubber?
As you know, you can create numerous components out of liquid silicone rubber. No wonder you see it used in a wide range of applications. You’ll see LSRs applied to automotive, consumer products, and food processing, among many others.
Let’s look at some examples of industries that take advantage of LSRs.
LSRs are well-suited to the automotive industry because of their superior temperature resistance. Specific applications require performance under extreme temperatures. For instance, a component might be near an engine. Or, in some cases, it’s exposed to excessive friction.
Some examples of automotive products that you can manufacture out of LSR include:
- Wire harness seals and connectors
- Sealing covers
- Noise-dampening cushions
- Sensor seals
You can make countless unique consumer product components out of LSRs. And manufacturers are more than happy to take advantage of its many desirable characteristics. You may not know it, but chances are, many of the everyday stuff you use has liquid silicone rubber.
Here are some examples of LSR components used in typical consumer goods:
- Gasket, seals, and o-rings found in many appliances
- Keyboard buttons
- Cellphone casings
- Headphone surfaces
- Baby bottle tips and soothers
Did you know that certain silicone rubbers can pass FDA approval for use in food processing? Silicone rubber is widely considered safe for manufacturing and storing food products. And you can produce various food-grade materials out of liquid silicone rubber. Here are some of them:
- Kitchenware products (utensils, cookware, molds)
- Seals, gaskets, and o-rings for food manufacturing machinery
- Dairy tubings
- Food transfer packaging
- Brewery seals and tubings
We’ve really only touched the surface here. It’s not uncommon to see liquid silicone rubber in various industrial and manufacturing applications. Healthcare, cosmetics, and life sciences also use LSRs for many essential parts and materials.
5. Desirable Properties of Silicone Rubber Components.
Now that you know how different industries utilize LSRs, it’s time to look at the characteristics that make them so efficient. It really all comes down to silicone rubber’s many desirable properties over other elastomers. And that’s all thanks to its unique chemical structure and silicone backbone.
5.1 Temperature Resistance
Silicone rubber can withstand an extremely high temperature range. It won’t melt at temperatures as high as 220 – 300 °C. On the flip side, it can also withstand cold temperatures as low as – 50 °C.
This exceptional resistance makes LSRs suitable for long-term use and heavy-duty applications.
5.2 Electrical Resistance
Silicone rubber parts have a high resistance to electricity. This makes them perfect insulators for various functions. On its own, it can resist corona discharge while complementing the conductivity of its end product.
Because of this characteristic, LSRs can mold into various pieces of electrical components.
5.3 Chemical Resistance
One of the properties that make silicone rubber long-lasting is its ability to resist external substances. This elastomer shows high resistance to various chemicals, oxygen, ozone, and UV rays, even at extreme temperatures.
Perhaps one of the most desirable characteristics of silicone rubbers is their versatility. Regardless of type, whether solid or liquid, you can cast silicone rubber into any shape or form to satisfy any specifications.
You can even modify its formulation to maximize or downplay a certain property. Say that you want your end product to be more electrically conductive. To make this so, you just add additional chemicals into the formula.
6. Why Choose Liquid Silicone Rubber Instead of Solid Silicone?
The properties mentioned above are standard for all silicone rubber end products. Whether solid, liquid, or HTV, the base elastomer will possess all of these natural qualities. But what exactly makes liquid silicone different? Why choose liquid silicone over solid?
Let’s look at some properties where LSR excels more than other silicone rubber types.
Liquid silicone rubber is formulated to be safer than solid silicone rubber and HTV. And they typically see a lot of use for food-grade and medical-grade applications.
That’s hardly surprising since liquid silicone has hypoallergenic properties. It can resist mold and bacteria growth, perfect for products that come into contact with food and human skin. It’s also non-corrosive and the most non-toxic of all silicone rubber variants.
Because of these qualities, LSRs can easily meet FDA, UPS, ISO, and CFR standards.
LSRs are injection-molded to shape the polymer into the desired form and function. For this process, manufacturers use a needle valve to control the material injected into the mold. You can adjust this valve to get the desired speed and pressure.
Because of this versatility, you can achieve a design that’s stable and accurate. LSRs are also denser than solid silicone rubber, so they can flow much better in tiny mold spaces, producing more precise shapes.
Liquid silicone rubber has more remarkable properties compared to solid silicone and HTV. End products can resist a broader range of operating temperatures. This temperature ranges from -50 °C to 300 °C.
LSRs also have a broader range of hardness that comes in at 10 to 80 using a Shore A durometer. And they also typically have better electrical insulation and environmental resistance.
LSR production is much quicker compared to solid silicone. And it also provides more in terms of production output.
Solid silicone is compression molded. And once milled, you’ll need to trim it down to get the right size and thickness for molding. Long story short, the process will take longer, along with the curing time.
On the other hand, liquid silicone has a shorter curing time and a faster overall production process. The molding starts when the injection machine extracts the A and B groups from its barrel at a 1:1 ratio.
The extracts are then thoroughly mixed and injected into the mold cavities under the desired speed and pressure. Because of the shorter cure time, the LSR goes out into the mold with little to no rubber flashings.
Due to their faster production time, LSRs are the ideal choice if you need products in big batches and high volumes.
7. Choose the Right LSR Manufacturer
Ready to take advantage of liquid silicone rubber for your application? You’d want to ensure you’re working with the right LSR silicone rubber manufacturer—one who can precisely provide what you need.
At GX silicone, we’re laser-focused on delivering exceptional silicone rubber materials for a broad range of applications. Take a look at our wide range of silicone manufacturer services. Whatever your application may be, expect to get your end products at the exact specifications.
About GX Silicone
Shenzhen GX Silicone Co. Ltd is a premier manufacturer and supplier of LSR (liquid silicone rubber) and HTV (High-Temperature Vulcanizing) solid silicone rubber in China. Our high-quality silicone products are used in diverse fields and industries, with satisfied clients the world over.
We value innovation and give a lot of attention to perfecting our products through effective R&D and state-of-the-art test centers.
Our more than eighty available silicone rubber compounds provide unparalleled quality. And we’re fully equipped to offer custom silicone rubber with properties based on specifications.