{"id":9377,"date":"2019-04-25T09:00:43","date_gmt":"2019-04-25T15:00:43","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=9377"},"modified":"2022-07-15T08:50:47","modified_gmt":"2022-07-15T14:50:47","slug":"pc-discover-the-flexibility-of-caulks-and-sealants","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/9377\/pc-discover-the-flexibility-of-caulks-and-sealants\/","title":{"rendered":"Discover the flexibility of caulks and sealants"},"content":{"rendered":"

\"WomanBoth caulks and sealants are intended to fill gaps, but they perform differently. Learn about the differences between the two, and discover their individual properties, applications, and chemistries.<\/p>\n

Caulk is an old boat-building term; sealant originated in home building. Some manufacturers use caulk as an all-purpose term and sealant to describe their high-performance products. Most often, the terms are used interchangeably.<\/p>\n

Properties<\/h3>\n

The main difference between a caulk and a sealant is elasticity1<\/sup>. Sealants are made from flexible materials, making them ideal for areas prone to expansion and contraction1<\/sup>. They are also somewhat waterproof, while not all caulks are.\u00a0 Some industry experts do not differentiate between the two; but they do distinguish between adhesives and sealants.<\/p>\n

Caulks are fairly rigid when dry, and are intended for use in areas with minimal expansion and contraction1<\/sup>. As stated, they are not necessarily waterproof, so they are a better fit for use indoors.<\/p>\n

They are not intended for areas exposed to high moisture levels, such as around kitchen sinks and in bathrooms. In building construction, a material that has the adhesive and cohesive properties to form a seal (ASTM C 717-07a) is known as a sealant.<\/p>\n

One- and two-part systems<\/h3>\n

There are one-part and two-part systems. One part cures with the interaction of the environment (moisture) or liberation of a component. A two-part system involves \u00a0a physical mixing immediately before application and a chemical cure between the 2 constituents.<\/p>\n

Applications and chemistries<\/h3>\n

Water-based caulks are the easiest with which to work because they apply without difficulty, are paintable, have little odor and clean up with water. They effectively fill gaps in baseboard and trim, as well as interior window and door frames.<\/p>\n

Since they are water-based, their application is dependent upon the weather with respect to temperature for interior use. For latex caulks, the ideal curing conditions are above 40\u00b0 F (4\u00b0 C). For exterior use, surface temperature is critical at application and during the full cure cycle to ensure optimal performance.<\/p>\n

Vinyl latex caulks<\/h3>\n

Within this category, there are sub-types of caulks with specific characteristics. Vinyl latex caulk has a useful life of around five years and is most suitable for small cracks in baseboards and small gaps around windows. Vinyl latex is non-flammable and paintable but is not very flexible. It hardens over time due to its vinyl chemistry, which lightly cross-links. It can also yellow somewhat over time.<\/p>\n

Acrylic caulks<\/h3>\n

Acrylic caulks are paintable and can be cleaned with water. However, their limited elasticity makes them susceptible to cracking in areas that experience large temperature swings. They are more durable than vinyl acrylic caulks.<\/p>\n

Acrylic caulk adheres to most surfaces and is best used on wood and masonry. It can be painted shortly after application and is available in pigments as well, allowing it to match many surfaces. It remains effective for 10 to 15 years, however, it is not recommended for an area that is subject to excessive water collection such as tubs or sinks. Acrylic caulk is flexible and maintains that flexibility over time.<\/p>\n

Tub and tile caulk<\/h3>\n

Tub and tile caulk is a specialty performance caulk. It has an added mildewcide to protect against mildew growth in kitchens and bathrooms where moisture can be excessive. Many formulations are a combination of an adhesive and a sealant. Other products utilize Ag+1<\/sup> ions for their antimicrobial properties.<\/p>\n

Siliconized acrylic caulk<\/h3>\n

Siliconized acrylic caulk is a type of sealant that combines silicone with acrylic latex formulas for improved water resistance. This medium-performance, water-based caulk can withstand greater movement than acrylic latex. It can be used interiorly or exteriorly with good adhesion, even to glass and ceramic tile. This caulk also comes in a variety of colors as well as clear formulas.<\/p>\n

Like the former water-based sealants, it applies easily (best applied in temperatures above 40\u00b0 F), is non-flammable, paintable, mildew-resistant and cleans with water. It can endure moderate temperature changes and has a total life expectancy of about 25-35 years.<\/p>\n

Silicone sealants<\/h3>\n

The flexibility of silicone sealants allows them to keep a watertight seal, even in areas subject to wide temperature swings. They are not paintable, and over-applications must be cleaned with a solvent or scraped off after setting. Strong fumes may result when silicone sealants are freshly applied because of the liberation of acetic acid (acetoxy) or amines (amine and aminoxy), depending on the chemistry.<\/p>\n

They are good for use around bathtubs and sinks because they are water resistant with excellent adhesion to smooth surfaces such as metal, glass and tile. They also resist mold and mildew \u00a0growth. Silicone sealants do not generally adhere to masonry and do not adhere well to wood. However, they remain flexible after curing and are not affected by UV sunlight.<\/p>\n

The following is a typical silicone sealant formulation, provided by Gelest2<\/sup>, based on many of their raw materials:<\/p>\n\n\n\n\n\n\n\n\n\n\n
<\/td>\n%<\/strong><\/td>\n<\/td>\n<\/tr>\n
Polydimethylsiloxane, OH terminated 50,000cps<\/td>\n65.9<\/td>\nPolymer<\/td>\n<\/tr>\n
Polydimethylsiloxane, trimethylterminated, 1000cps<\/td>\n20<\/td>\nPlasticizer<\/td>\n<\/tr>\n
Methyltrioximinosilane<\/td>\n5<\/td>\nCross linker<\/td>\n<\/tr>\n
Aminopropyltriethoxysilane<\/td>\n1<\/td>\nAdhesion promoter<\/td>\n<\/tr>\n
150 sq.mfg surface area fumed silica<\/td>\n8<\/td>\nFiller<\/td>\n<\/tr>\n
Dibutyltin dilaurate<\/td>\n0.1<\/td>\nCatalyst<\/td>\n<\/tr>\n
Total<\/strong><\/td>\n100<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/h3>\n

UV resistance<\/h3>\n

Contrary to some beliefs, most sealants have reasonably good resistance to UV sunlight in either clear or pigmented products. However, there can be a misconception that clear sealants resist UV poorly. In actuality, the UV radiation mostly passes through and degrades the interface of the sealant and substrate, which can result in sealant adhesion failure.<\/p>\n

Polyurethane foam<\/h3>\n

Polyurethane foam is a sealant used for a variety of jobs, most often around electrical outputs, pipe penetrations and in large voids or openings where the elements can breach a structure. It expands to fill gaps, holes and voids, and is good for insulation purposes.<\/p>\n

Polyurethane foam also comes in different expansion rate formulas. It is easy to apply, cures quickly, is paintable and offers good adhesion. It is not overly resistant to UV and should be protected by painting.<\/p>\n

Butyl rubber sealants<\/h3>\n

Butyl rubber sealants are solvent-based with a life expectancy of only two to ten years due to their inherent chemistry. However, they are a \u00a0good choice for sealing against water in lap joints, such as gutters and for metals and masonry, as well as outside for chimneys.<\/p>\n

They are the best waterproofing sealant for below-grade applications, such as foundations.<\/p>\n

Synthetic rubber<\/h3>\n

Synthetic rubber is a relatively new caulk category. It is perhaps the most flexible product on the market. Synthetic rubber cures clear and is ideal for exterior joints that typically expand and contract. It can be applied in adverse weather conditions (wet and cold) and stretches and recovers easily without breaking.<\/p>\n

It’s also great for use on roofs, wood siding and joints that frequently show movement.<\/p>\n

Modified silicone polymer sealants<\/h3>\n

Modified silicone polymer sealants deliver excellent performance on vinyl, fiber cement, aluminum and wood siding. They combine the best characteristics of polyurethane, silicone and water-based products, offering permanent flexibility.<\/p>\n

They also can be applied in wet weather, low temperature applications and around exterior windows, doors and vents. Modified silicone can be painted with latex paint. They are one of the more expensive choices of sealants.<\/p>\n

Some of the critical and required performance testing includes the following:<\/p>\n