Silicone rubber lasts roughly four times longer than rubber. It’s durable, versatile, and has tons of practical applications. No wonder it’s widely used in a wide array of industries. All silicone rubber share common properties. Still, not every silicone rubber is the same.
Silicone rubber can come in two main variants: solid and liquid. You can also classify silicone in the way it’s manufactured. One such method is via High-Temperature Vulcanizing which is what we usually call Solid Rubber.
HTV (high-temperature vulcanized) silicone rubber is one of the most widely used types of silicone out there. And you’ll know why in this article.
1. What is HTV Silicone?
HTV Silicone — High Temperature Vulcanized Silicone rubber, or HCR Silicone, also known as Heat-cured silicone rubber, high consistency rubber, is a high-quality variation of your typical elastomer. Like all silicone rubber types, it has exceptional strength and temperature resistance. It also has superior chemical inertness and aging resistance compared to rubber.
You can mold these materials into various shapes and products like you would with plastic. But unlike plastic, silicone rubber is biocompatible. It has almost zero detrimental effects on the environment. Silicone rubber is even considered safe for medical and food applications.
All silicone rubbers have a siloxane bond as their backbone. And it’s the reason why silicone rubber gets many of its desirable properties.
The siloxane backbone is superior to plastic’s carbon-based backbone. It boasts a binding strength of 433kJ/mol, higher than carbon’s 355 kJ/mol.
The HTV variant comes from reactive silicone gums. It maintains high molecular weight and a straight-chain arrangement of atoms.
You can enhance its properties via cross-linking to other materials. A good example would be using platinum catalysts through polyaddition systems.
HTV Silicone rubber comes from material in the methyl or vinyl group. This material is called polyorganosiloxane, a polymer made of silicone. Of course, you can just simply call it “raw rubber.”
The raw rubber (polyorganosiloxane) is then reinforced and incremented with fillers. This gives the end products their desired characteristics while increasing their performance.
The end product is a high viscosity solid rubber that’s partially vulcanized. It undergoes either compression molding, transfer molding, or rubber tubing extrusion. Manufacturers typically produce them in large batches.
HTV silicone rubber has two main characteristics that attract multi-industry use. It’s incredibly durable and chemically inert.
Many applications require materials that can withstand considerable stress, tension, and extreme temperatures. When it comes to these applications, very few can match HTV silicone rubber’s performance.
It can maintain its original shape and composition, even when constantly exposed to extremely high and low temperatures. It can withstand exposure to UV rays, ozone, or other environmental factors that can damage lesser polymers.
HTVs also possess exceptional aging resistance. These polymers can age without so much of a chemical reaction taking place.
All silicone rubbers have high chemical resistance, which means most chemicals can’t alter their properties.
HTVs are also hypoallergenic, so expect no bacteria growth and mold formation.
These qualities are what make silicone rubber pass food-grade and medical-grade standards. You’ll see silicone rubbers used in various medical and food processing applications, including products for infant care.
HTV is a variant of solid silicone rubber. And like liquid silicone, it has various applications. You’ll find that both solid and liquid silicone rubber almost provides the same advantages. But the main differing factors are viscosity and manufacturing processes.
If applications are related to everyday use, like consumer products, solid silicone is the typical go-to. This silicone class uses the cheaper compression molding manufacturing process. And this process fits perfectly for producing small batches.
Silicone typically costs twice as much as rubber but lasts four times longer. This makes silicone a more cost-effective solution. You’ll see HTV silicone rubber in the automotive, aerospace, electronics, construction, and chemical industries. And that’s just to name a few.
If you’re choosing a suitable material for a particular application, consider if it has the right mechanical properties. High-temperature vulcanized silicones have many mechanical properties that make them a cut above other polymers.
HTV silicone polymers have:
- Extreme temperature resistance (from -90 ℃ to even + 350 ℃.)
- High-tensile strength
- High tear strength
- Flame retardancy
- Thermal conductivity
- Excellent insulation
- Dielectric strength at high voltage
At the same time, HTV silicone rubber can meet almost all the environmental requirements, and it is a very green and practical raw material.
2. What is the Difference Between HTV Silicone and LSR?
Remember that silicone rubbers aren’t all the same. Besides HTV silicone, another widely used variant is liquid silicone rubber (LSR). Now, both of these silicone types rest on the same siloxane backbone. And they virtually have the same chemical composition.
So how exactly do these differ from each other? Let’s find out.
HTVs are manufactured solid, so it has higher molecular weight and longer polymer chains. It also has no fluidity due to its solid composition. HTV products often have lower transparency than those made from liquid silicone.
In terms of processing, HTVs go through milling machines, then cut into the desired size and thickness. Once cut, it goes into molding, where a curing agent is added.
Liquid silicone rubber contains polymers of lower molecular weight and shorter chains. It also has low viscosity, so it can flow freely rather than stay in place. Manufacturers create liquid silicone as two-component systems.
Component A is the platinum catalyst cure, and component B has the crosslinker. LSRs are injection-molded, shaping the polymer into the desired form and function.
3. What are the Types of Solid Silicone?
Here at GX, we provide two of the most efficient type of solid silicone rubber. Clients can either get their solid silicone as precipitated silicone rubber and fumed silicone rubber.
Precipitated silicone comes as opaque or translucent. When the silica gel is elongated, the silica gel will be stiff and pale, but it can not be stretched very long. It has a tensile strength of 4 – 6.9 Mpa, and we can elongate it 150 – 300% of its original size.
The precipitation method is to precipitate the silicon oxide after adding sodium silicate with sulfuric acid. The fineness is only 300-400 mesh.
This silicone type is mainly used for industrial products and consumer gifts.
Fumed silicone possesses high transparency. It has superior tensile strength compared to precipitated silicone, coming in at 7.8 – 10.0 Mpa. It also has a higher tear strength of 29.4 – 49 KN/m. It can be elongated to 700% of its original size.
Production of fumed silicone involves burning silicon tetrachloride and oxygen to produce silicon dioxide. The fineness reaches up to 1,000 mesh.
Fumed silicone rubber is ideal for food and medical-grade applications. You can also use it for other silicone tubes with special requirements.
Comparatively, the tensile strength and elongation of the phase adhesive with the same hardness are better than the precipitated silicone rubber, and its environmental protection index is also better. However, the raw material of fumed silicone rubber is expensive, the production cost is high, and the price is much higher than that of precipitated silicone.
Stability, durability, high and low-temperature resistance and high performance-to-price ratio make precipitated silicone rubber products widely used in the market.
4. What are the Methods of Solid Silicone Processing?
Compression molding is perhaps the most widely used processing method for solid silicone rubber. In this technique, the silicone rubber squeezes between the die machine and the mold punch before being vulcanized at a high temperature.
Manufacturers use mold plates, cavities, and alignment bushings and pins to mold the silicone into the desired shape and form. The uncured rubber goes into the mold cavity, where it will heat and pressurize in order to cure.
is another technique used in solid silicone processing. This method involves heating but may or may not include the use of pressure. During extrusion, the raw materials go through an extruder, where they are heated and pressurized.
The extrusion procedure lasts only a couple of seconds. However, the raw material goes through extreme temperatures ranging from 200 to 500 °C
This action molds the raw materials into the desired form using a die machine. The material then cools down and forms the end solid silicone product.
5. What Causes the Quality Defects of HTV Silicone Rubber?
Not every manufactured silicone product comes in as perfect. There are rare cases when a non-intended quality defect occurs. Let’s look at some of the most prevalent causes of defective HTV products.
- The raw materials used might contain impurities.
- It could be due to the trifunctional chain links in the raw rubber.
- Trace level volatile impurities might be present in the polymer.
- It could be due to the polymer’s molar mass size and distribution.
- The polymer vinyl content is distributed to the vulcanized compound.
- Polymer hydroxyl groups might play a role.
At GX Silicone, we always strive to ensure quality defects are non-existent, or at least, bare minimum.
We use various well-thought-out measures to eliminate defects and other inconsistencies:
- Enhancing the purity of the raw materials used
- Using a full range of equipment for testing the silicone rubber compounds
- Conducting strict quality assurance
- Improving all aspects of the production process
- Improving manufacturing efficiency and eliminating errors
- Eliminating traces of polymer hydroxyl groups
- Carefully controlling volatile polymer impurities
The Best HTV Silicone Rubber factory in China.
You might consider a lot of factors when choosing the proper silicone manufacturer. Still, deciding factors come down to who can provide the highest quality solutions at the most affordable prices. Of course, fantastic customer service is also something to ponder.
At GX Silicone, we strive to provide the best quality silicone materials the market can offer. We’re laser-focused on innovation while cutting costs for our clients and offering them exceptional support.
Learn more about our services here. Or contact us directly.