What's the Difference Between HTV Silicone and LSR?

HTV Silicone (high temperature vulcanized silicone) is a long chain elastomer with vinyl groups, filled by fumed or precipitated silica and other additives to create special property, is a kind of silicone rubber that is suitable for compression molding, silicone rubber transfer molding and rubber injection molding.

HTV Silicone's types: The method of dividing HTV is generally according to the application and performance, such as general-purpose type, low-compression permanent deformation type, low-shrinkage type, flame-retardant type, solvent-resistant type, high-temperature type, etc., but as a raw rubber production system, generally name them according to it’s base ingredients.

HTV is generally a high-polymerization polysiloxane with a molecular weight of 400,000 to 800,000. It is added with a reinforcing agent and various additives for mixing. The additives include fillers, vulcanizing agents (generally raw rubber without peroxide), structure control agent and modifier, etc.,and then the rubber compound is vulcanized in a mold at a pressure of about 5 MPa, and vulcanized at a high temperature of 120 to 130 ° C about 10 to 30 minutes. And after demolding ,product need second vulcanization for 24 hours in an oven at 200 to 250 ° C. Therefore, this kind of raw rubber is called high temperature vulcanized silicone rubber.

The reinforcing agent of silicone rubber is white carbon black (SiO2), which is divided into three types according to the production method : gas phase white carbon black, precipitated white carbon black and other forms of white carbon black. Each type can be divided into several grade according to the average particle diameter. Raw Silicone rubber’s strength property is very poor. Adding an appropriate amount of silica to strengthen, the strength of silicone can improve by more than 10 times. By adding different type of  pendant groups, can make different unique property silicone rubbers .

HTV Silicone’s Application

HTV silicone has been widely used in aerospace, munitions industry, automobile, fine chemicals, construction, electric and electronics, food processing, mechanical engineering, medical and pharmaceutical, cosmetics, home appliances, paper film, solar batteries, and semi conductor. Recently, the scope of silicone application has been expanding at a greater speed.

Notes: According to different curing temperature, Silicone can be classified into HTV Silicone Rubber (High Temperature Vulcanization Silicone and RTV Silicone Rubber( Room Temperature Vulcanization Silicone). Also, HTV Silicone is divided into Millable Type Silicone Rubber and Liquid Silicone Rubber by its degree of polymerization.

What is Liquid Silicone Rubber & LSR?

Liquid Silicone Rubber is a two-part platinum-cured elastomer material which starts out as two separate liquid components which are then precisely mixed together ,and to  be injected into a mold cavity to manufacture a part.

Liquid silicone rubber is heat resistant at high temperatures, such as 200 ºC. In addition, the cure system includes being cured by platunum catalyst.

These properties make LSR applicable to medical devices, baby nipples, swimming bands, mouthpiece for health care, food contact products for home appliances, and parts for electronics devices.

There are many types of LSR materials:

· Medical grades: Medical grade liquid silicone rubber are typically broken down to restrictive and unrestricted  can achieve the level of biocompatibility testing. It can achieve FDA requirement and is a good choice for medical device.

Self-lubricating: Self lubricating LSR can be mixed into the components. Once the silicone cures, this material will bloom to the surface to create a slippery surface. Then, 1.5 to 3 percent of a phenyl fluid is added to the silicone depending on the rate of fluid the customer wants to bloom.

· Conductive: Conductive-grade LSR is made by adding carbon black into LSR components. Conductive-grade LSR has very good mechanical properties.

· Self-bonding: Self-bonding Liquid Silicone is made by adding adhesion promoters, which mainly used on glass filled nylons, stainless steel, aluminum and polysulfones.

· Radio Opaque: Adding Barium sulfate into LSR material makes Radio Opaque LSR be detected under X-Ray.  Radio Opaque LSR is excellent for medical applications such as wound drains and catheters.

What's the difference between HTV and LSR?

Comparision of LSR and HTV.pdf