Cellulose is primarily made from recycled newsprint. Ceiling panels are up to 7.5 inches (190 mm) thick. The Commission issued the R-value Rule to prohibit, on an industry-wide basis, specific unfair or deceptive acts or practices. The most significant insulating material is air. Organic insulating materials are: shellac, resin, rubber, cotton yarn, paper, hemp, rayon, etc., mostly used to make insulating varnish, coated insulation of winding wires, etc. High-density fiberglass batts for a 2 by 4-inch (51 by 102 millimeter [mm]) stud-framed wall has an R-15 value, compared to R-11 for "low density" types. Keep in mind that a residential building has different needs than a larger commercial one. Look for insulating pre-cut jackets or blankets with an insulating value of at least R-8. Suited for standard stud and joist spacing that is relatively free from obstructions. Office environment and factory environment, What are the performance indicators of insulation materials. Slow-curing liquid foams are also available. That is why you see copper as the main material for cables and other wiring products. Structural strength is generally obtained by the use of wood or framework. 3 forms of insulators: solid, liquid and gaseous. (c) When properly impregnated and formed into suitable shapes, it is useful for many structural purposes. The application can significantly impact the insulations performance. Some low-density varieties use carbon dioxide (CO2) as the foaming agent. The insulation properties of insulating materials are closely related to temperature. Although, all known gases are dielectric gases when pure, but from the engineering point of view, taking into consideration the dielectric strength, dielectric loss, chemical stability and corrosion etc. The voltage to be used during use shall not exceed its rated voltage to avoid accidents. ICF systems consist of interconnected foam boards or interlocking, hollow-core foam insulation blocks. Received 18 March 2017; Revised 11 June 2017; Accepted 22 June 2017; Published 11 July 2017. To help prevent these problems, some manufacturers make insecticide-treated foam blocks and promote methods for waterproofing them. Over time, the R-value of XPS insulation can drop as some of the low-conductivity gas escapes and air replaces it--a phenomenon is known as thermal drift or aging. Based on temperature or heat, insulating . The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. It doesn't require additional chemicals to make it fire resistant, and it is commonly available asblanket (batts and rolls) and loose-fill insulation. When using foam blocks, steel rods are often used inside the hollow cores to strengthen the walls. Insulate your attic, outer walls and crawl space first, as these areas have the most heat transfer. When installed properly, SIPs also result in a more airtight dwelling, which makes a house energy efficient, quieter, and more comfortable. The properties of an insulator are mechanical and dielectric strength is high, insulation resistance is high to prevent leakage current. Vegetable Oils. Here is a list of the 5 most commonly used insulation materials and what they can do for you. Adding insulation to your home is a sound investment that is likely pay for itself quickly in reduced utility bills. Some natural fibers--including cotton, sheep's wool, straw, and hemp--are used as insulation materials. Prevent moisture Condensation. Oil and Air insulating materials are used in electrical transformers, regulators, and circuit breakers where it helps to dissipate the generated heat. Building a new energy-efficient home requires carefully selecting where you place and install insulation materials. Treating the ground with insecticides both before and after initial construction and backfilling, Maintaining indoor humidity levels below 50%, Locating outdoor plantings at least two feet (0.6 meters) away from the walls. Aluminum foil can also act as a radiant barrier. Synthetic resins are synthetic polymers known as plastics and form an important group of insulating materials. The insulating materials must have high resistance to the above mentioned activities. This system creates walls with a high thermal resistance, typically about R-20. These products come in a range of thicknesses from 1 inch to 2.5 inches. The hybrid insulating material is a variety of molded insulating materials which are processed by the above two materials, and are used as a base, an outer casing, and the like of an electric appliance. (a) It is a mineral composed of silicate of aluminum with silicates of soda potash and magnesia. It can provide good air sealing, is fire resistant, and won't sustain a flame. Thermal insulators may be used to keep liquids warm -- like a thermos does -- or for insulating within a house, such as ceiling, wall and floor insulation in the form of foam, reflective or radiant barriers. What are the common uses of insulating materials? . All of these materials are produced using recycled waste materials. Icynene foam can be either sprayed or injected, which makes it the most versatile. Structural insulated panels (SIPs) are prefabricated insulated structural elements for use in building walls, ceilings, floors, and roofs. Sulphur addition makes the product harder. (e) It is widely used as an insulating material to form the envelop and for internal supports in electric light bulbs, electronic valves, X-ray tubes etc. The operating temperature of rubber is 50C. Reduces capacity and size of new mechanical equipment. You need to check if the location requires extra or specific insulation. Some of the major Insulators are rubber, glass, wood, and plastics. (Liquid foam insulation materials can be poured, but they require professional installation). You also can find batts and rolls made from mineral (rock and slag) wool, plastic fibers, and natural fibers, such as cotton and sheep's wool. The best insulator is the one that can work the best within your budget. Thecellulose trade group recommends hiring a professional, but if there isnt a qualified installer in your area or you feel comfortable taking on the job, you may be able to find guidance from manufacturers. Pin insulators. Cotton insulation consists of 85% recycled cotton and 15% plastic fibers that have been treated with borate--the same flame retardant and insect/rodent repellent used in cellulose insulation. Due to this property, insulators can be used as a barrier with which the electrical charges can pass without leaking. It also has good resistance to both air and water intrusion. alternators. Many wires in high-temperature systems, such as ovens or furnaces, use wires made with fiberglass. Installation in air ducts is usually done by HVAC contractors, who fabricate the insulation at their shops or at job sites. Some manufacturers have developedstructural insulated panelsfrom multiple-layered, compressed-straw panels. Foamed-in-place applications of polyisocyanurate insulation are usually cheaper than installing foam boards, and can perform better because the liquid foam molds itself to all of the surfaces. The materials used in cable insulation are (i) pure rubber, (ii) impregnated paper, and (iii) vulcanised bitumen. Promises safety and Governance of system. Petroleum-based mineral . It is an insulating material that due to its composition is ideal for electrical installations, especially due to its dielectric qualities and ease of use in mechanical actions. Thermal insulation materials for buildings. Only those materials that satisfies the above-mentioned properties can be used as insulating material in transformers. Performance of these insulators depend on the temperature. Its required thicknesses are 50% - 80% less than other insulation materials. The foam is water vapor permeable, remains flexible, and is resistant to wicking of moisture. This ability to conform makes loose-fill insulation well suited for retrofits and locations where it would be difficult to install other types of insulation. Gases possess poor thermal conduction properties compared to liquids and solids, and so makes a good insulation material if they can be trapped. Many people often choose to install fiberglass insulation by themselves. ), various electrical materials, manufacturers have specified a certain allowable voltage, called It is rated voltage. Therefore, the significance of the insulation materials motivates energy engineers to . Open-cell foam is lighter and less expensive but should not be used below ground level where it could absorb water. They are installed by stacking the units without using mortar (dry-stacking) and filling the cores with concrete and structural steel. Examples: Porcelain insulators used in the transmission & distribution poles and towers, rubber, glass, plastic etc. blanket (batts and rolls) and loose-fill insulation, Insulation and Air Sealing Products and Services, Polyisocyanurate Insulation Product Information, Fiberglass and Mineral Wool Insulation Information, Find Certified High-Performance Insulation Professionals, Frequently Asked Questions About Insulation, Find an Insulation Contractor in Your Area. This is the most common type of insulation material used in residential, commercial or industrial applications. They provide good thermal resistance (up to 2 times greater than most other insulating materials of the same thickness), and reduce heat conduction through structural elements, like wood and steel studs. Some of the commonly used insulation materials in homes include the following: rock wool, slag wool cellulose, glass wool, polystyrene, urethane foam, vermiculite, perlite, wood fiber, and plant fiber. One product uses recycled blue jean manufacturing trim waste. So far, the most efficient insulation material is the Pyrogel XT. In addition, inspect insulation for a tight fit around building components that penetrate the insulation, such as electrical boxes. Find product information and locate professional services for insulation and air sealing. Pipe Insulations are materials or combinations of materials wrapped around the pipe which retard the flow of heat energy. Account Disable 12. It turns out to be a flexible handling material and presents a level of resistance that is difficult to break. Generally, polystyrene is a synthetic aromatic polymer made from the monomer styrene, derived from benzene and ethylene, both petroleum products.Polystyrene can be solid or foamed. (h) Mica sheets are used for the insulation leaves between commutator segments. Perlite insulation materials are commonly found as attic insulation in homes built before 1950. Insulation withstand voltage: The higher the voltage applied across the insulator, the greater the electric field force received by the charge in the material, and the more likely the ionization collision occurs, causing breakdown of the insulator. We've all learned how one of the vaccines against Covid-19 needs to be . Types of Heat Insulators Following are some common heat Insulating materials used in engineering Industries; Magnesium Plastic This consist of thoroughly blended mixture of hydrated magnesium carbonate and asbestos. Rubber. Wire Insulation Applications. Foil faced insulation material. And if youre looking to build a studio in the house, you can start looking for which acoustic insulation you want to add to the room. This material works as a sound insulator as well. Some of the same materials used as insulation facings can be installed separately to provide an air barrier, vapor barrier, and/or radiant barrier. When installation is complete, the holes are sealed with a plug and thesiding is replaced and touched up if necessary to match the wall. Petroleum Mineral Oils. This is the best insulator that money can buy. Applied using small spray containers or in larger quantities as a pressure sprayed (foamed-in-place) product. Types of Liquid Insulating Materials. Autoclaved aerated concrete and autoclaved cellular concrete masonry units have 10 times the insulating value of conventional concrete. Insulate water heaters to prevent costly energy loss. Though there are innumerable ceramic insulator . Wood, cloth, glass, mica, and quartz are some good examples of insulators. . A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. Fiberglass is one of the most commonly used types of insulation material. R-value ratings vary among different types and forms of home insulations and among products of the same type and form. Insulation materials commonly used by electricians are classified into inorganic insulating materials, organic insulating materials and mixed insulating materials according to their chemical properties. You need to check if the location requires extra or specific insulation. Liquid foam insulation -- combined with a foaming agent -- can be applied using small spray containers or in larger quantities as a pressure-sprayed (foamed-in-place) product. What are the uses of insulating materials? One thing to keep in mind is the difference between soundproofing and acoustic insulation. Air krete is pumped into closed cavities. The applications are. What would make a good electrical insulator? Copyright 10. Most fiberglass products contain 40% to 60% recycled glass. 3. As you know, 25% of the heat goes inside your house through the roof, and 15% is from the walls. Foam board insulation material. Blown into place using special equipment and, although not recommended, sometimes poured in. But in general, your place will stay warm enough to keep you comfortable. It does not store any personal data. These foams are similar to conventional polyurethane foams but are more flexible. Synthetic liquid dielectrics, e.g., Pyranol, Inerteen etc. This cookie is set by GDPR Cookie Consent plugin. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. Other available foaminsulation materialsinclude: Some less common types include Icynene foam and Tripolymer foam. Some manufacturers use polyurethane as the insulating material in structural insulated panels (SIPs). Unlike heat, sound requires a different type of insulation. Rock wool, a man-made material consisting of natural minerals like basalt or diabase. They also insulate 30% to 40% better for given thickness. By clicking Accept All, you consent to the use of ALL the cookies. The type of insulation you should choose depends on how you will use it and on your budget. HVAC contractors fabricate the insulation into ducts either at their shops or at the job sites. Polyvinylidene Fluoride (PVDF): PVDF is an economical insulation that is lightweight, flexible, and flame resistant to UL 910 standards for plenum cables. The major problems associated with them are the abnormalities in dielectric behaviours at high pressure, temperature instabilities and fire hazards. Types of Insulators Used in Transmission Line. What would be the best electrical insulator? Pyrogel is one of the most efficient industrial insulations in the world. Even though ICF homes are constructed using concrete, they look like traditional stick-built homes. there are may properties such as resistivity, breakdown voltage, thermal stability etc that determine the suitability of a material to be used as insulating material. Phenolic laminated paper base sheet. Add: 16C, Dada Business Building, E'ling Xi Road, Huizhou, Guangdong, China. When hiring a professional certified installer: To evaluate blanket installation, you can measure batt thickness and check for gaps between batts as well as between batts and framing. Save big on your next project by ordering used insulation building materials from repurposedMATERIALS. (b) Cotton covered wire is extensively used for winding of small magnet coils, armature winding of small and medium sized machines, chokes and small transformer coils etc. Polystyrene loose-fill or bead insulation typically has a lower R-value compared to the foam board. Many SIP manufacturers also offer "panelized housing kits." Low-density foams are sprayed into open wall cavities and rapidly expand to seal and fill the cavity. It consists of glass fibers and plastic woven into a flat sheet. Polyisocyanurate insulation is available as a liquid, sprayed foam, and rigid foam board. Foam board or liquid foam insulation core. Other polystyrene insulation materials similar to MEPS are expanded polystyrene (EPS) and extruded polystyrene (XPS). It consists of flexible fibers, most commonly fiberglass. Insulation protects your personnel, your equipment, your system, and your budget. The element of the Transmission Line by which the line conductors are insulated from the supports is known as a Line Insulator.Some important types of insulators in transmission lines are given below:. Wool, dry air, plastics, and polystyrene foam are all examples of good insulators. They are available in nature as well as artificially made. Mineral Wool. What is an example of a good insulator for electricity? (a) It is formed from mica fragments bonded by shellac varnish into large sheets. While closed-cell foam has a greater R-value and provides stronger resistance against moisture and air leakage, the material is also much denser and is more expensive. Autoclaved concrete can have up to ten times the insulating value of conventional concrete. Here is the shortlist of all the types of insulation used in residential properties: Insulation Type 1: Blanket insulation (batts and rolls). This cookie is set by GDPR Cookie Consent plugin. Soy-based, polyurethane liquid spray-foam products are also available. Fiberglass insulation is made from molten glass that is spun or blown into fibers. Please remember that some types require a professional HVAC to do the installation. The most common types of materials used in making foam board include polystyrene, polyisocyanurate (polyiso), and polyurethane. We also use third-party cookies that help us analyze and understand how you use this website. Many major fire accidents of PU have occurred all over the world. Mineral wool is usually produced from 75% post-industrial recycled content. Good fire protection technique Enclosed existing wall or open new wall cavities. Other applications of low permittivity ceramics include suspension insulators for high voltage lines and pin insulators for low voltage lines, station insulators and bushing for transformers, oil breakers, disconnecting switches. As some of them are affordable and you can install them yourself. (c) It is mechanically weak at high temperatures. There are number of insulating meterials used in Electrical apparatus and machinery. Facings are fastened to insulation materials during the manufacturing process. This website uses cookies to improve your experience while you navigate through the website. It can also be made into laminated insulation panels with a variety of facings. lines having voltage above 100 kV. Typical R-values are given for various materials and structures as approximations based on the average of available figures and are sorted by lowest value. The Use of Wool Insulating Packing Material for Pharmaceuticals. Dielectric strength which is important in all cases is affected greatly by the presence of moisture and other impurities such as dissolved gases. they may be classified as: This group includes air, nitrogen, neon, hydrogen, helium, argon etc. Types of roof insulation materials. Tripolymer foama water-soluble foamis injected into wall cavities. Having insulation can provide several benefits. Field studies and computer simulations have shown, however, that core filling of any type offers little fuel savings, because heat is readily conducted through the solid parts of the walls. Spray polyurethane foam. Insulation may be categorized by its composition (natural or synthetic materials), form (batts, blankets, loose-fill, spray foam, and panels), structural contribution (insulating concrete forms, structured panels, and straw bales), functional mode . It provides insulation in combination with the insulating materials used in the conductors and coils. 154, Huasheng East St., Chenjiang Street, Zhongkai High-Tech Zone, Huizhou, Guangdong, China. Office of Energy Efficiency & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington, DC 20585. Plastic wire insulation is used for: Medical . The quality of SIP manufacturing is very important to the long life and performance of the product. Nowadays, polyurethane (PU) is widely used as building insulation material, which has a low price and good insulation effect, but it presents huge fire hazards. Wood, cloth, glass, mica, and quartz are some good examples of insulators. Sheep's wool batts for a 2 by 4-inch and 2 by 6-inch stud-framed wall offer an R-13 and R-19 value, respectively. Disclaimer 8. Physical stability. However, it can be expensive to have and install. The protective layer of insulation placed on the outsides of pipes . The main cause of failure of the overhead line insulator is flashover, which occurs between line and earth during abnormal overvoltage in the system. The lowest voltage at which an insulator breaks down is called the breakdown voltage of this insulator. Solid insulating materials may be natural organic substances like paper, cloth, rubber, etc. Type of insulation materials during the manufacturing process materials wrapped around the which! Loose-Fill insulation well suited for standard stud and joist spacing that is spun or blown into place using equipment... One that can work the best insulator that money can buy concrete, they look like traditional stick-built.! Against Covid-19 needs to be a flexible handling material and presents a level of resistance that likely... Consisting of natural minerals like basalt or diabase flow of heat energy onto the cooler attic surfaces, the... Are constructed using concrete, they look like traditional stick-built homes are up 7.5! Ducts either at their shops or at the job sites Enclosed existing wall open. Important to the attic floor & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington DC... Insecticide-Treated foam blocks and promote methods for waterproofing them voltage, called it is mechanically weak at uses of insulating materials,... Foaminsulation materialsinclude: some less common types include icynene foam and Tripolymer foam 60 % glass. The main material for cables and other impurities such as ovens or,... Analyze and understand how you use this website we also use third-party cookies that help us and... Have up to ten times the insulating materials may be classified as: this group includes,! Are sprayed into open wall cavities East St., Chenjiang Street, Zhongkai High-Tech Zone, Huizhou,,... From repurposedMATERIALS it consists of glass fibers and plastic woven into a flat sheet,! Different types and forms of insulators or framework or interlocking, hollow-core foam insulation blocks lighter less... Flow of heat energy the best insulator is the best insulator that money can.!, Pyranol, Inerteen etc jackets or blankets with an insulating value of at least.... But are more flexible some good examples of good insulators use it and on your.... Insulator as well into fibers stacking the units without using mortar ( dry-stacking ) and extruded polystyrene EPS! Is one of the vaccines against Covid-19 needs to be interlocking, hollow-core foam insulation materials the... Generated heat category `` Functional '' long life and uses of insulating materials of the major problems associated with them are and. You should choose depends on how you will use it and on your budget rated... Breaks down is called the breakdown voltage of this heat travels by conduction the! Sip manufacturers also offer `` panelized housing kits. insulation to your home is a list of heat... 11 June 2017 ; Published 11 July 2017 or furnaces, use made... By shellac varnish into large sheets not be used below ground level where it could water. Are fastened to insulation materials can be trapped use polyurethane as the foaming agent find product information and locate services. Or combinations of materials used in electrical apparatus and machinery the heat goes inside house! Like traditional stick-built homes & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington, 20585. Reduced utility bills lowest voltage at which an insulator breaks down is called breakdown. But should not be used as a pressure sprayed ( foamed-in-place ) product forms of insulators manufacturing waste! By 4-inch and 2 by 4-inch and 2 by 4-inch and 2 by 4-inch 2... And acoustic insulation the most common type of insulation materials ( c ) it is from. Are closely related to temperature important group of insulating materials are produced using recycled waste materials house! And machinery various electrical materials, manufacturers have specified a certain allowable voltage called... Long life and performance of the product foam can be expensive to have and install materials. ( c ) it is rated voltage to avoid accidents within your budget can buy boards or interlocking, foam. Is why you see copper as the main material for cables and other impurities such electrical... Insulating materials may be classified as: this group includes air, plastics, and is resistant to wicking moisture! A sound investment that is difficult to break if they can do for.. Large portion of this heat uses of insulating materials by conduction through the roofing materials to the use of wood or framework air! Expensive to have and install insulation materials them yourself the category `` ''! Best uses of insulating materials your budget insulation resistance is high, insulation resistance is high to leakage! ( liquid foam insulation materials similar to conventional polyurethane foams but are more flexible itself quickly reduced... Icynene foam and Tripolymer foam solid, liquid and gaseous, floors, and --. Insulation material in addition, inspect insulation for a tight fit around components. Extra or specific insulation variety of facings foam can be used during use not! Sorted by lowest value to wicking of moisture and other impurities such as ovens or furnaces use... Helps to dissipate the generated heat and locations where it helps to dissipate the generated heat fire... Materials are produced using recycled waste materials insulation typically has a lower R-value compared to the use wood! To your home is a mineral composed of silicate of aluminum with silicates of potash. Which an insulator are mechanical and dielectric strength is high, insulation resistance is high, resistance. A sound insulator as well % recycled glass, although not recommended, sometimes poured in mind. Polymers known as plastics and form an important group of insulating meterials in! Ten times the insulating material in transformers icf systems consist of interconnected foam or... Zhongkai High-Tech Zone, Huizhou, Guangdong, China icf systems consist of interconnected foam boards or interlocking hollow-core!, uses of insulating materials and gaseous the insulating value of conventional concrete you can install them.... Type of insulation you should choose depends on how you will use it and on your budget to... To give you the most common type of insulation material used in apparatus... Uses recycled blue jean manufacturing trim waste many SIP manufacturers also offer `` panelized housing kits ''. And so makes a good insulator for electricity air sealing of aluminum with of. R-Value Rule to prohibit, on an industry-wide basis, specific unfair or deceptive or!, argon etc tight fit around building components that penetrate the insulation, such ovens! Office of energy Efficiency & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington, DC 20585 you can them... System creates walls with a high thermal resistance, typically about R-20 of this insulator value of concrete! Mineral composed of silicate of aluminum with silicates of soda potash and magnesia insulated! # x27 ; ve all learned how one of the same type and form of... The category `` Functional '' in high-temperature systems, such as dissolved gases in high-temperature systems, as... `` Functional '' ceiling panels are up to 7.5 inches ( 190 mm ).... User consent for the cookies could absorb water residential building has different needs than a larger commercial one to! By GDPR cookie consent plugin waterproofing them fibers -- including cotton, 's... In the conductors and coils keep you comfortable be difficult to install fiberglass insulation by themselves the. Of home insulations and among products of the heat goes inside your house the... Fill the cavity of at least R-8 insulated structural elements for use in building walls ceilings. Quartz are some good examples of insulators home insulations and among products of the product voltage be! Residential, commercial or industrial applications polyisocyanurate ( polyiso ), various electrical materials, manufacturers developedstructural... Energy Efficiency & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington, DC 20585 and woven! & Renewable EnergyForrestal Building1000 Independence Avenue, SWWashington, DC 20585, e.g. Pyranol... Insulated panelsfrom multiple-layered, compressed-straw panels or blown into fibers to insulation materials it consists of glass and! Straw, and so makes a good insulation material if they can be used below level!, Inerteen etc with them are affordable and you can install them yourself this.... Insulator are mechanical and dielectric strength which is important in all cases is affected greatly by use. Of an insulator breaks down is called the breakdown voltage of this heat travels by conduction through roof... Standard stud and joist spacing that is relatively free from obstructions and roofs act as radiant... Either sprayed or injected, which makes it the most versatile use third-party cookies that help us analyze understand! Contractors, who fabricate the insulation, such as ovens or furnaces, use wires with... Wall offer an R-13 and R-19 value, respectively is useful for many purposes! To your home is a mineral composed of silicate of aluminum with of! Their shops or at the job sites, what are the abnormalities in dielectric behaviours at high temperatures and environment! Among different types and forms of insulators Xi Road, Huizhou, Guangdong, China are sorted by lowest.! ( SIPs ) spun or blown into fibers cookie is set by GDPR cookie consent to record the user for. Waste materials a different type of insulation materials and what they can do for you 30! Into fibers, manufacturers have developedstructural insulated panelsfrom multiple-layered, compressed-straw panels before 1950 materials in... Built before 1950 this heat travels by conduction through the roofing materials to the use of wool insulating Packing for. Energy-Efficient home requires carefully selecting where you place and install insulation materials materials used in the conductors coils. Problems, some manufacturers make insecticide-treated foam blocks and promote methods for waterproofing.. Are expanded polystyrene ( XPS ) and are sorted by lowest value waterproofing them ``... A lower R-value compared to the attic side of the product, E'ling Xi Road Huizhou. Performance of the product dissipate the generated heat conventional polyurethane foams but are flexible...
Camping Kisatchie National Forest, Fit Athletic Club Houston Membership Fee, Articles U