What is the full form of xlpe?
Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, insulation for high tension (high voltage) electrical cables, and baby play mats. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.
Low-temperature impact strength, abrasion resistance and environmental stress cracking resistance can be increased significantly by crosslinking, whereas hardness and rigidity are somewhat reduced. Compared to thermoplastic polyethylene, PEX does not melt (analogous to elastomers) and is thermally resistant (over longer periods of up to 120 °C, for short periods without electrical or mechanical load up to 250 °C). With increasing crosslinking density also the maximum shear modulus increases (even at higher temperatures).[1][2] PEX has significantly enhanced properties compared with ordinary PE.[3]
Almost all PEX used for pipe and tubing is made from high-density polyethylene (HDPE). PEX contains cross-linked bonds in the polymer structure, changing the thermoplastic to a thermoset. Cross-linking is accomplished during or after the extrusion of the tubing. The required degree of cross-linking, according to ASTM Standard F876, is between 65% and 89%. A higher degree of cross-linking could result in brittleness and stress cracking of the material, while a lower degree of cross-linking could result in product with poorer physical properties.
A theoretically extreme degree of cross-linking is reached if only –CH2– bridges are placed between cross-linkings that are also –CH2– bridges and if the polymer structure's sum formula is (C3H4)n, then the structure is that of a diamond with all bonds replaced by –CH2– bridges. If 4 vertices of a cube c are placed where C-atoms of the diamond base are so that only one further diamond base atom lies inside c then 4 diamond base bonds lie in c and—because the bond angles are forced towards such maximal values that also here a diamond cubic crystal structure is already approached—it is expected that the C-atoms of these –CH2– bridges are posed on lines that are both orthogonal to diamond base bonds and parallel to faces of c.
Almost all cross-linkable polyethylene compounds (XLPE) for wire and cable applications are based on LDPE. XLPE-insulated cables have a rated maximum conductor temperature of 90 °C and an emergency rating up to 140 °C, depending on the standard used. They have a conductor short-circuit rating of 250 °C. XLPE has excellent dielectric properties, making it useful for medium voltage—1 to 69 kV AC, and high-voltage cables—up to 380 kV AC-voltage, and several hundred kV DC.
Numerous modifications in the basic polymer structure can be made to maximize productivity during the manufacturing process. For medium voltage applications, reactivity can be boosted significantly. This results in higher line speeds in cases where limitations in either the curing or cooling processes within the continuous vulcanization (CV) tubes used to cross-link the insulation.[citation needed] This is particularly useful for high-voltage cable and extra-high voltage cable applications, where degassing requirements can significantly lengthen cable manufacturing time.
Various methods can be used to prepare PEX from thermoplastic polyethylene (PE-LD, PE-LLD or PE-HD). The first PEX material was prepared in the 1930s, by irradiating the extruded tube with an electron beam. The electron beam processing method was made feasible in the 1970s, but was still expensive. In the 1960s, Engel cross-linking was developed. In this method, a peroxide is mixed with the HDPE before extruding.[4] In 1968, the Sioplas process using silicon hydride (silane) was patented, followed by another silane-based process, Monosil, in 1974. A process using vinylsilane followed in 1986.[citation needed]
A basic distinction is made between peroxide crosslinking (PE-Xa), silane crosslinking (PE-Xb), electron beam crosslinking (PE-Xc) and azo crosslinking (PE-Xd).[2]
Shown are the peroxide, the silane and irradiation crosslinking. In each method, a hydrogen atom is removed from the polyethylene chain (top center), either by radiation (hν) or by peroxides (R-O-O-R), forming a radical. Then, two radical chains can crosslink, either directly (bottom left) or indirectly via silane compounds (bottom right).
A low degree of crosslinking leads initially only to a multiplication of the molecular weight. The individual macromolecules are not linked and no covalent network is formed yet. Polyethylene that consists of those large molecules behaves similar to polyethylene of ultra high molecular weight (PE-UHMW), i.e. like a thermoplastic elastomer.[6]
Upon further crosslinking (crosslinking degree about 80%),[7] the individual macromolecules are eventually connected to a network. This crosslinked polyethylene (PE-X) is chemically seen a thermoset, it shows above the melting point rubber-elastic behavior and cannot be processed in the melt anymore.[6]
The degree of crosslinking (and hence the extent of the change) is different in intensity depending on the process. According to DIN 16892 (a quality requirement for pipes made of PE-X) at least the following degree of crosslinking must be achieved:[7]
All PEX pipe is manufactured with its design specifications listed directly on the pipe. These specifications are listed to explain the pipe's many standards as well as giving specific detailing about the manufacturer. The reason that all these specifications are given, are so that the installer is aware if the product is meeting standards for the necessary local codes. The labeling ensures the user that the tubing is up to all the standards listed.[8]
Materials used in PEX pipes in North America are defined by cell classifications that are described in ASTM standards, the most common being ASTM F876. Cell classifications for PEX include 0006, 0008, 1006, 1008, 3006, 3008, 5006 and 5008, the most common being 5006. Classifications 0306, 3306, 5206 and 5306 are also common, these materials containing ultraviolet blockers and/or inhibitors for limited UV resistance. In North America all PEX tubing products are manufactured to ASTM, NSF and CSA product standards, among them the aforementioned ASTM standard F876 as well as F877, NSF International standards NSF 14 and NSF 61 ("NSF-pw"), and Canadian Standards Association standard B137.5, to which the pipes are tested, certified and listed. The listings and certifications met by each product appear on the printline of the pipe or tubing to ensure the product is used in the proper applications for which it was designed.
In European standards. there are three classifications referred to as PEX-A, -B, and -C. The classes are not related to any type of rating system.
PEX-A is produced by the peroxide (Engel) method. This method performs "hot" cross-linking, above the crystal melting point. However, the process takes slightly longer than the other two methods as the polymer has to be kept at high temperature and pressure for long periods during the extrusion process. The cross-linked bonds are between carbon atoms.
The silane method, also called the "moisture cure" method, results in PEX-B. In this method, cross-linking is performed in a secondary post-extrusion process, producing cross-links between a cross-linking agent. The process is accelerated with heat and moisture. The cross-linked bonds are formed through silanol condensation between two grafted vinyltrimethoxysilane (VTMS) units, connecting the polyethylene chains with C-C-Si-O-Si-C-C bridges.
PEX-C is produced through electron beam processing, in a "cold" cross-linking process (below the crystal melting point). It provides less uniform, lower-degree cross-linking than the Engel method, especially at tube diameters over one inch (2.5 cm). When the process is not controlled properly, the outer layer of the tube may become brittle. However, it is the cleanest, most environmentally friendly method of the three, since it does not involve other chemicals and uses only high-energy electrons to split the carbon-hydrogen bonds and facilitate cross-linking.
PEX tubing is widely used to replace copper in plumbing applications. One estimate from 2006 was that residential use of PEX for delivering drinking water to home faucets was increasing by 40% annually.[9] In 2006, The Philadelphia Inquirer recommended that plumbing installers switch from copper pipes to PEX.[10]
In the early to mid 20th century, mass-produced plumbing pipes were made from galvanized steel. As users experienced problems with the internal build-up of rust, which reduced water volume, these were replaced by copper tubing in the late 1960s.[11] Plastic pipes with fittings using glue were used as well in later decades. Initially PEX tubing was the most popular way to transport water in hydronic radiant heating systems, and it was used first in hydronic systems from the 1960s onwards.[9] Hydronic systems circulate water from a boiler or heater to places in the house needing heat, such as baseboard heaters or radiators.[12] PEX is suitable for recirculating hot water.[13]
Gradually, PEX became more accepted for more indoor plumbing uses, such as carrying pressurized water to fixtures throughout the house. Increasingly, in the 2000s, copper pipes as well as plastic PVC pipes are being replaced with PEX.[11] PEX can be used for underground purposes, although one report suggested that appropriate "sleeves" be used for such applications.[13]
Benefits of using PEX in plumbing include:
PEX has been approved for use in all fifty states of the United States as well as Canada,[8] including the state of California, which approved its use in 2009.[13] California allowed the use of PEX for domestic water systems on a case-by-case basis only in 2007.[32] This was mostly due to concerns about corrosion of the manifolds (rather than the tubing itself) and was allowed to be used in California for hydronic radiant heating systems but not potable water. In 2009, the Building Standards Commission approved PEX plastic pipe and tubing to the California Plumbing Code (CPC), allowing its use in hospitals, clinics, residences, and commercial construction throughout the state.[13] Formal adoption of PEX into the CPC occurred on August 1, 2009, allowing local jurisdictions to approve its general use,[33] although there were additional issues, and new approvals were issued in 2010 with revised wordings to the 2007 act.[34]
Alternative plumbing choices include:
PEX-AL-PEX pipes, or AluPEX, or PEX/Aluminum/PEX, or Multilayer pipes are made of a layer of aluminum sandwiched between two layers of PEX. The metal layer serves as an oxygen barrier, stopping the oxygen diffusion through the polymer matrix, so it cannot dissolve into the water in the tube and corrode the metal components of the system.[35] The aluminium layer is thin, typically 1 or 2 mm, and provides some rigidity to the tube such that when bent it retains the shape formed (normal PEX tube will spring back to straight). The aluminium layer also provides additional structural rigidity such that the tube will be suitable for higher safe operating temperatures and pressures.
The use of AluPex tubing has grown greatly since 2010. It is easy to work and position. Curves may be easily formed by hand. Tube exists for use with both hot and cold water and also for gas.[citation needed]
This product in Canada has been discontinued due to water infiltrating between the Layers resulting in premature failures.
There are two types of fitting that may be used. Crimped or compressive. Crimped connectors are less expensive but require a specialised crimping tool. Compression fittings are tightened with normal spanners and are designed to allow sections of the system to be easily disassembled, they are also popular for small works, esp. DIY, avoiding the need for extra tools.
A PEX tool kit includes a number of basic tools required for making fittings and connections with PEX tubing. In most cases, such kits are either bought at a local hardware store, plumbing supply store or assembled by either a home owner or a contractor. PEX tools kits range from under $100 and can go up to $300+. A typical PEX tool kit includes crimp tools, an expander tool for joining, clamp tools, PEX cutters, rings, boards, and staplers.[further explanation needed]
XLPE cable (Cross-linked polyethylene) is a type of electrical cable commonly used for power transmission and distribution. XLPE cable is made of a thermoset material, which means it is highly resistant to heat, moisture, and chemicals. This makes it an ideal choice for applications where the cable will be exposed to harsh environmental conditions, such as underground or underwater installations.
The XLPE insulation material is produced by chemically cross-linking polyethylene molecules. This process enhances the material’s strength and stability, improving its ability to withstand high temperatures and electrical stresses. XLPE cable has a higher operating temperature compared to PVC (polyvinyl chloride) insulated cables.
XLPE insulation performs at both high and low temperatures. Due to its structure, XLPE is extremely resistant to abrasion and other wear and tear. It also boasts resistance to high-voltage electricity, chemicals, and other hazardous materials. Cross-linked polyethylene insulation is also a more affordable option.
XLPE cable is commonly used in a wide range of applications, including power distribution in buildings, industrial installations, and utility power grids. It is available in various sizes and configurations, including single-core, multi-core, and screened cables. It can also be used for low-voltage, medium-voltage, and high-voltage applications.
In short, XLPE cable should be used in industries that expose wire and cable to:
XLPE cable can be used for plumbing, mining, and various electrical applications. Cross-linked polyethylene cables can also be found across the chemical industry and within the commercial and residential heating industry. Don’t forget about dentists’ offices and other medical institutions, groundskeeping at stadiums and other venues, and much more.
XLPE, as explained above, is cross-linked polyethylene material. PVC stands for polyvinyl chloride insulation.
The main difference is that XLPE can be used for high and low-tension applications. Its structure provides great resistance to abrasion, stress, and other wear and tear. PVC insulation cannot withstand as much pressure, meaning it is only suitable for low-tension applications.
Other differences:
XLPE (Cross-Linked Polyethylene) insulated cables are widely used in power transmission and distribution systems due to their excellent electrical, thermal, and mechanical properties. Different types of XLPE insulated cables are based on their application, construction, and voltage rating. Here are some of the common types:
The appropriate type of XLPE insulated cable selection depends on the application and voltage requirements.
Performance Wire and Cable utilizes XLPE insulation on USE-2 wires, RHW-2 cable, and RHH cable.
Right here! Performance Wire and Cable offers various types of XLPE cable. Contact us today or give us a call. Our wire and cable experts will help you determine which cross-linked polyethylene cable is perfect for your next job.
XLPE is an acronym for cross linked polyethylene. XLPE is a thermosetting polymer meaning that the material (polyethylene (PE)) is cured under heat and in that process forms bonds in all directions forming a three dimensional matrix.
