RTV stands for room temperature vulcanizing, a type of silicone rubber that cures into a flexible, durable seal without needing heat. It’s the silicone you’ll find in caulk tubes at hardware stores, gasket makers for engines, and even medical devices. The term “vulcanizing” refers to the chemical process that transforms the silicone from a paste into a solid rubber, and the key distinction of RTV is that this happens at ordinary room temperature rather than in an oven or mold press.
RTV can also refer to ritonavir, an antiviral medication used in HIV treatment and as a key component of Paxlovid for COVID-19. Both meanings are covered below.
How RTV Silicone Cures
When you squeeze RTV silicone out of a tube or cartridge, moisture in the air kicks off the curing process. Water molecules react with special groups on the ends of the silicone polymer chains, creating new bonding sites. Those sites then link neighboring chains together through strong silicon-oxygen-silicon bonds, building a cross-linked network that gives the cured material its rubbery strength and flexibility. This reaction starts at the exposed surface and works inward, which means thicker applications take longer to cure all the way through.
A typical one-part RTV silicone becomes tack-free in roughly 15 to 20 minutes, with a full cure taking about 24 hours for standard bead thickness. Humidity, temperature, and how thick you’ve applied it all affect that timeline. In very dry conditions, curing slows noticeably because there’s less atmospheric moisture to drive the reaction.
One-Part vs. Two-Part RTV
One-part RTV silicone is the type most people encounter. It comes ready to use straight from the tube, and atmospheric moisture is the only trigger it needs. Inside the sealed package, a water-scavenging ingredient keeps everything stable on the shelf. Once you open it, the air does the rest.
Two-part RTV systems work differently. You mix a base with a separate curing agent, and the chemical reaction between them drives the cure, no moisture required. This is a significant advantage for thick castings, molds, or encapsulations where moisture from the air can’t easily penetrate deep into the material. Two-part systems cure evenly throughout, regardless of thickness, making them the standard choice for industrial molding, prototype casting, and electronics potting.
Acetoxy vs. Neutral Cure
One-part RTV silicones split into two main families based on what they release as they cure. Acetoxy silicones give off acetic acid during curing, which produces a strong vinegar smell you’ll recognize from basic bathroom caulk. They cure faster, but that acidity can corrode sensitive materials like copper, marble, concrete, and some metals.
Neutral cure silicones (sometimes called alkoxy or oxime cure) produce far milder byproducts and little to no odor. They’re the better choice for electronics, mirrors with silver backing, natural stone, and any substrate that might react badly to acid. The tradeoff is a slightly slower cure time.
Common Uses for RTV Silicone
- Automotive gaskets: RTV silicone replaces or supplements traditional gaskets on oil pans, valve covers, and water pumps, holding up well against engine heat and vibration.
- Construction sealants: Window frames, bathroom fixtures, and exterior joints rely on RTV for waterproof, flexible seals that move with thermal expansion.
- Electronics: Neutral cure RTV protects circuit boards and connectors from moisture and dust without corroding components.
- Mold making: Two-part RTV is widely used to create flexible molds for casting resin, wax, plaster, and concrete.
- Medical devices: Certain medical-grade RTV silicones meet biocompatibility standards set by ISO 10993 and USP testing, making them suitable for devices that contact skin or tissue.
Temperature and Durability
Cured RTV silicone handles a wide temperature range, generally performing well from around -60°C to 200°C (-76°F to 392°F), with some specialty formulations rated even higher. This thermal stability is one of the reasons it’s preferred for automotive and aerospace applications where organic rubber seals would degrade. RTV also resists UV light, ozone, and most chemicals, so outdoor joints and seals hold up for years without cracking or shrinking.
RTV as a Drug Abbreviation: Ritonavir
In medicine, RTV is shorthand for ritonavir, an antiviral drug originally developed to fight HIV. Ritonavir blocks a viral enzyme that HIV needs to assemble new infectious copies of itself. Without that enzyme functioning, the virus produces only defective, non-infectious particles.
Ritonavir’s most important role today, though, is as a “booster” for other medications. It powerfully blocks a liver enzyme responsible for breaking down roughly 60% of all available drugs. When taken alongside another antiviral, ritonavir slows the breakdown of that partner drug, keeping its blood levels high enough to be effective. This boosting trick is used in several HIV treatment combinations and became widely known through Paxlovid, the COVID-19 antiviral. Each dose of Paxlovid pairs 300 mg of the active antiviral with 100 mg of ritonavir, taken twice daily for five days. Without the ritonavir component, the active drug would be cleared from the body too quickly to work.
Because ritonavir so effectively blocks that liver enzyme, it interacts with a long list of other medications. Certain heart rhythm drugs, blood thinners, cholesterol-lowering statins, sedatives, and ergot-based migraine treatments cannot be taken at the same time. Anyone prescribed ritonavir or Paxlovid needs a careful review of all their current medications to avoid dangerous interactions where other drugs build up to toxic levels in the bloodstream.