Pipes/piping crosslinked polyethylene

For example, Tables 4 and 5 give the values of two basic properties for two types of polyolefin pipes crosslinked polyethylene XPE SDR 9 (degree of cross-linking, 64- 89%) and polybutylene PB 21-SDR 11. 

Heat-shrink crosslinked polyethylene DIN 30672 Flame or heat gun in fieid 1-25-2-25 Utiiised for coating of field weld joints and repairs on extruded polyethylene coated pipes. Careful application required to achieve consistent bond. 

ISO 10146 1997 Crosslinked polyethylene (PE-X) pipes - Effect of time and temperature on the expected strength... 

ISO 15875-1 2003 Plastics piping systems for hot and cold water installations - Crosslinked polyethylene (PE-X) - Part 1 General... 

ISO 15875-5 2003 Plastics piping systems for hot and cold water installations - Crosslinked polyethylene (PE-X) - Part 5 Fitness for purpose of the system ISO/TS 15875-7 2003 Plastics piping systems for hot and cold water installations - Crosslinked polyethylene (PE-X) - Part 7 Guidance for the assessment of conformity... 

FT-IR spectroscopy has been used in the investigation of welding crosslinked polyethylene pipes [23]. Three types of crosslinking systems were used namely, peroxide (PEXa), silane (PEXb) and electron beam (PEXc). Scholten and co-workers [23] observed that only PEXa pipes have a satisfactory electrofusion quality. The strength of electrofusion welds of PEXb and PEXc pipes is not acceptable. The most likely explanation for the differences in weld quality is related to the adhesion theory and more specifically to differences in composition. Figure 5.6 shows the infrared spectra of medium density polyethylene (MDPE), PEXa, PEXb and PEXc. 

Peroxide crosslinked ionomer mixtures made from the abovementioned raw materials may be used in contact with fatty foods under certain limited conditions, according to their raw materials and additives. Vinyl chloride and vinylidene chloride should not be used in materials having either ionic (ionomer) or physical (e.g. through electron beam irradiation) crosslinks. Crosslinked polyethylene can be used for the manufacture of food contact materials, e.g. for drinking water pipes and fittings. The cross-linking can be done using either peroxide or electron beam irradiation. 

Unidelta S.p.A. Crosslinked polyethylene pipes. In Technical Handbook T4001, 2000. 

Vinyl functional silanes have been used for over 35 years to crosslink polyethylene. The most common commercial products using this crosslinking technology are crosslinked PE insulations for the global wire and cable market [11] and crosslinked HDPE pipes for potable water and natural gas. Some work recently has been done to combine this crosslinking technology with wood-filled polyethylene. 

Polyolefin floor coverings (PP and PE), power cables with PE coverings and HDPE pipes and wall covering materials, halogen free linear low-density PE and thermoset crosslinked polyethylene are all suggested as alternatives to PVC by Greenpeace. 

Sodium nonoxynol-6 phosphate floor heating piping, domestic Polyethylene, crosslinked floor insulation Perlite... 

Piping in transfer lines should be free of loops and pockets. Unloading connections may be flexible hose (typically 50-mm) lined with acid-resistant rubber, crosslinked polyethylene, or a fluorocarbon polymer. These hoses should not have quick disconnects. They should be inspected after every use. A sight glass on the transfer line will let the operator know when transfer is complete. 

ISO 10147 1994 Pipes and fittings made of crosslinked polyethylene (PE-X) - Estimation of the degree of crosslinking by determination of the gel content. 

Crosslinked polyethylene Piping Heat shrinkable tubing Rotational moulded tanks... 

For hot water systems, (i.e., in underfloor heating systems and for hot water distribution), pipes are mainly polybutylene (PB), which can be used in systems with a continuous operating temperature of 82 °C and can survive short peak temperatures of up to about 110 °C, as well as crosslinked polyethylene (XLPE) with improved creep resistances, that can withstand operating temperatures for the same range as PB. The heat dispersion is optimised by these plastic piping systems by using the heat storing capacity of the floor. 

Borealis is a major supplier of polyethylene resins for crosslinking polyethylene pipe applications under the tradename BorPEX, offering resins with a HLMI (MI ) between about 3-10 over densities of 0.944-0.955... 

Crosslinked polyethylene pipe with higher gel content (81%), Figure 5.295 right, tested with water as the exterior and interior medium exhibits brittle failure only... 

By replacing water as the exterior medium with air, embrittlement occurs after just 20,000 h. Fracture is initiated at degraded, oxidized areas in the pipe wall. These oxidized areas (that occur only in polyolefin pipe) are discolored and covered by cracks, illustrating the degree of embrittlement. The brittle failure mode of crosslinked polyethylene pipe with less than 68% gel content is Stage 2 failure. 

Brittle failure mode of crosslinked polyethylene pipe with higher gel contents qualifies as Stage 3 failure [191]. 

There are many applications for polyolefin compounds in the processing of pipes, tubings, and fittings from polyethylene (PE), crosslinked polyethylene (XPE), biaxially oriented polyethylene (PEO), polypropylene, and polybutylene. 

TABLE 4 Mechanical properties for crosslinked polyethylene (XPE-SDR 9) and polybutylene (PB21-SDR 9) pipes... 

The same reference lines are recommended for PB pipes by ISO 12230 and, for crosslinked polyethylene PE-X pipes, by ISO 10146. 

Case Study 2 Crosslinked Polyethylene (PEX) Pipe and Tubing... 

An example system is PVC and polyethylene wire and cabling irradiated to improve stresscracking resistance, abrasion resistance, high-temperature properties and flame retardance, via controlled electron-beam crosslinking (Loan, 1977). Additionally electron-beam crosslinking is utilized to impart memory into a polymer system, such as crosslinked PE materials for heat-shrinkable films and pipe applications (Baird, 1977). The control of electron-beam processing has advanced the quality of cell size and shape of PE foams via control of crosslink distribution (Paterson, 1984). 

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