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44-588: Robert Voigt (19 May 1913 – 25 November 1988) was a Danish wrestler . He competed in the men's Greco-Roman bantamweight at the 1936 Summer Olympics . He was eliminated after the fourth of six rounds. This biographical article relating to a Danish sport wrestler or wrestling coach is a stub . You can help Misplaced Pages by expanding it . Amateur wrestling At the middle school and high school levels, wrestlers compete in scholastic wrestling . In collegiate wrestling , there are minor differences in some scholastic wrestling rules. The rapid rise in

88-614: A boiler or heater to places in the house needing heat, such as baseboard heaters or radiators. PEX is suitable for recirculating hot water. Gradually, PEX became more accepted for more indoor plumbing uses, such as carrying pressurized water to fixtures throughout the house. Increasingly, since the 2000s, copper pipes as well as plastic PVC pipes are being replaced with PEX. PEX can be used for underground purposes, although one report suggested that appropriate "sleeves" be used for such applications. Benefits of using PEX in plumbing include: PEX has been approved for use in all fifty states of

132-445: A large impact on the resulting mechanical properties of PEX. One study looked at the effect of crosslinking low-density polyethylene (LDPE) with different amounts of dicumyl peroxide (DCP). It was found that increasing the weight percent of the peroxide crosslinker resulted in a lower degree of crystallinity , as observed via differential scanning calorimetry (DSC) . The degree to which a polymer crystallizes and crosslinks can have

176-409: 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. Upon further crosslinking (crosslinking degree about 80%), the individual macromolecules are eventually connected to

220-451: 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. 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: All PEX pipe

264-449: A significant impact on its properties, and it was indeed found that the increase in crosslinking degree and corresponding decrease in crystallinity correlated to a lower elongation at break . It was suggested that this was due to the higher presence of chemical crosslinks (the peroxides) compared to the physical crosslinks (formed by the crystallites), as chemical crosslinks tend to inhibit the elongation behavior of polymers. Additionally, it

308-830: 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

352-494: Is also mimicked by the thermoplastic ultra-high molecular weight polyethylene (UHMWPE) . However, PEX displays a stronger temperature and strain-rate dependence than UHMWPE. Additionally, PEX is notable for its high thermal stability. It displays improved creep behavior (i.e. resists creep deformation) and maintains high strength and hardness at very high temperatures compared to thermoplastic polyethylene. The type of initial polymer structure and amount of crosslinking can have

396-650: Is due to the introduction of crosslinks in the system, which can significantly improve the chemical, thermal, and mechanical properties of the polymer. While HDPE and PEX both display increases in the initial tangent modulus and yield stress under temperature or strain-rate increases when undergoing compression , HDPE tends to exhibit flow behavior after reaching a higher yield stress and PEX tends to exhibit strain-hardening after reaching its slightly lower yield stress. The latter exhibits some flow behavior but only after reaching higher true strains . The behavior observed in PEX

440-569: Is made between peroxide crosslinking (PE-Xa), silane crosslinking (PE-Xb), electron beam crosslinking (PE-Xc) and azo crosslinking (PE-Xd). [REDACTED] 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

484-629: Is mandatory to protect the ears from cauliflower ear and other injuries. Headgear is made from molded plastic polymer or vinyl coated energy absorbing foam over a rigid hard liner and strapped to the head tightly. In the international styles headgear is optional. Wrestling is conducted on a padded mat that must have excellent shock absorption, tear resistance, and compression qualities. Most mats are made of PVC rubber nitrile foam. Recent advances in technology have brought about new mats made using closed cell, cross-linked polyethylene foam covered in vinyl backed with non-woven polyester. The countries with

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528-406: 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

572-436: 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

616-508: 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

660-447: 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). PEX has significantly enhanced properties compared with ordinary PE. Almost all PEX used for pipe and tubing is made from high-density polyethylene (HDPE). PEX contains cross-linked bonds in

704-649: 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. This product in Canada has been discontinued due to water infiltrating between

748-671: Is up to all the standards listed. 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

792-415: Is very similar on the high school level. Amateur wrestling is a positionally-based form of grappling , and thus generally prohibits the following: While there is not much equipment that a wrestler wears, it is still highly specialized. A wrestling singlet is a one-piece, tight-fitting, colored, lycra uniform. The uniform is tight-fitting so as not to get grasped accidentally by the opponent and allows

836-605: The International Olympic Committee announced that women's freestyle wrestling would be added to the Olympic games in the 2004 Summer Olympic Games in Athens, Greece with a total of four different weight classes. Until the early 1990s, the majority of women who participated in the sport had no other choice but to join the available men's teams. At the high school level, this may still be required in some areas depending on

880-624: The National Wrestling Coaches Association for the past 6 years; the world's top 16 teams compete in this event. In 2004, Missouri Valley College held the first Women's National Wrestling Championships which honored four individual champions. Later, the event would be hosted by the University of the Cumberlands in 2006. Cross-linked polyethylene Cross-linked polyethylene , commonly abbreviated PEX , XPE or XLPE ,

924-470: The United States as well as Canada , including the state of California , which approved its use in 2009. California allowed the use of PEX for domestic water systems on a case-by-case basis only in 2007. This was due mostly to concerns about corrosion of the manifolds (rather than the tubing itself) and California allowed PEX to be used for hydronic radiant heating systems but not potable water. In 2009,

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968-511: 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. PEX has significantly enhanced properties compared to ordinary PE. This

1012-428: The 2007 act. 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. The aluminium layer

1056-621: 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. Formal adoption of PEX into the CPC occurred on August 1, 2009, allowing local jurisdictions to approve its general use, although there were additional issues, and new approvals were issued in 2010 with revised wordings to

1100-522: The Cumberlands, Menlo College, Pacific University, and Neosho County CC. Cal-State Bakersfield are other schools that had a number of women competitors that only competed against each other or occasionally against Canadian college teams. As the sport continued to grow, coaches within women's wrestling formed the Women's Collegiate Wrestling Association (WCWA). This group created rules regarding eligibility, bylaws, and elected leaders for this association. Each year

1144-490: 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

1188-589: The MMT. 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

1232-560: 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

1276-666: 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. 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

1320-506: 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. In 2006, The Philadelphia Inquirer recommended that plumbing installers switch from copper pipes to PEX. In the early to mid 20th century, mass-produced plumbing pipes were made from galvanized steel. As users experienced problems with

1364-469: 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

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1408-409: The elongation at break decreased due to decreases in crystallinity. The presence of fillers can further strengthen PEX's mechanical properties. In the same study, the researchers looked at the effect of adding a filler known as montmorillonite (MMT) nanoclay and observed even higher Young's moduli and tensile strengths, indicating a strong interfacial interaction between the silane crosslinked LLDPE and

1452-473: The following ways: As in the international styles, collegiate wrestling awards points for takedowns and reversals. Penalty points are awarded in collegiate wrestling according to the current rules, which penalize moves that would impair the life or limb of the opponent. However, the manner how infractions are penalized and points awarded to the offended wrestler differ in some aspects from the international styles. Collegiate wrestling also awards points for: In

1496-402: The internal build-up of rust , which reduced water volume, these were replaced by copper pipes in the late 1960s. 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. Hydronic systems circulate water from

1540-457: The international styles, the format is now two three-minute periods. A wrestler wins the match when they were able to get more points than their opponent or 10 points lead in two rounds. For example, if one competitor gets a 10–0 lead in first the period, they will win by the superiority of points. Only a fall, injury default, or disqualification terminates the match; all other modes of victory result only in period termination. This format replaced

1584-535: The leading wrestlers in the Olympic Games and World Championships are Iran, the United States, Russia (and some of the former Soviet Union republics, especially Armenia, Georgia, Ukraine, Uzbekistan, Azerbaijan, and Kazakhstan), Bulgaria, Turkey, Hungary, Cuba, India, Canada, Japan, Pakistan, South and North Korea, Germany, and historically Sweden and Finland. Because of the successful growth in female participation,

1628-546: The number of intercollegiate programs continued to prosper with the WCWA now recognizing a total of 28 teams. Within these teams there are several who have National Collegiate Athletic Association (NCAA) affiliation and most of them are allowed to compete in the National Association of Intercollegiate Athletics (NAIA). There is also a national dual meet championship for women's intercollegiate teams that have been sponsored by

1672-578: The number of wrestlers. Brookline High School in Brookline, Massachusetts was the first public school in America to create a varsity girls wrestling team. Girls have at times still competed against boys. University of Minnesota-Morris was the first university to create a varsity women's wrestling team. UMM's head coach, Doug Reese, followed in the footsteps of other schools like Missouri Valley College that pioneered programs for female wrestlers. University of

1716-594: The old format of three two-minute periods played best two out of three. One side effect of the old format was that the losing wrestler could outscore the winner. For example, periods may be scored 3–2, 0–4, 1–0, leading to a total score of 4–6 but a win for the wrestler scoring fewer points. In collegiate wrestling, the period structure is different. A college match consists of one three-minute period, followed by two two-minute periods, with an overtime round if necessary. A high school match typically consists of three two-minute periods, with an overtime round if necessary. Under

1760-458: The popularity of the combat sport mixed martial arts (MMA) has increased interest in amateur wrestling due to its effectiveness within the sport and its consideration as a core discipline. Greco-Roman and freestyle differ in what holds are permitted; in Greco-Roman, the wrestlers are permitted to hold and attack only above the waist. In both Greco-Roman and freestyle, points can be scored in

1804-481: The referee to see each wrestler's body clearly when awarding points or a pin. Women wrestlers wear a higher cut singlet usually with a sports-bra underneath. Wrestling shoes are light, flexible, thin-soled, ankle-high sneakers that allow maximum speed and traction on the mat without giving up ankle support. The current rules call for laces (if any) to be covered so that they do not come untied during competition. In American high school and college wrestling headgear

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1848-425: The standard rules for collegiate wrestling, draws are not possible; this rule is sometimes modified for young wrestlers. A match can be won in the following ways: While having similar victory conditions with Greco-Roman and freestyle, such as wins by fall , decision , injury , and disqualification , victory conditions in collegiate wrestling differ on some points from the international styles: Dual meet scoring

1892-446: Was found that the maximum tensile strength tended to increase since the intermolecular forces between chains increases with additional crosslinks. Similar results have been found with the addition of silane crosslinkers. In another study, the amount of silane crosslinker added to linear low-density polyethylene (LLDPE) was varied. The resulting Young's modulus and maximum tensile strength increased with crosslinker concentration but

1936-605: 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. 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. A basic distinction

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