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Improved grades for CPVC pipes offer superior impact strength and ability to produce large size pipes

Improved grades for CPVC pipes offer superior impact strength and ability to produce large size pipes

29-Apr-10
For several decades copper tubing has been the preferred method of water distribution in residential structures, accounting for approximately 85% market share in new construction as per Builderswebsource.com. When installed properly and when the water supply is non-acidic, copper plumbing has proven the test of time as a reliable and safe delivery vehicle for potable water. However, in recent years, new materials have entered the market to challenge copper's dominance. Polybutylene (PB) tubing was popular for its low cost of installation compared to copper. However, excessive failures in the field led to class action lawsuits and the ultimate banning of PB in 1995. Over the years, a better substitute has emerged called CPVC, or chlorinated polyvinyl chloride. Compared to copper, CPVC appeals to some homebuilders due to its lightweight, ease of installation and lower overall installed cost. Often, these savings can be passed on to the consumer in terms of overall lower prices for homes. Benefits of CPVC pipe include:
� Resistance to corrosion and abrasion
� Smooth bore for improved flow and reduced water noise
� High impact strength, light weight
� Easy, cost-effective installation
� Competitively priced vs. copper
� Self-insulating to minimize thermal loss
� Integral flame retardancy and low smoke density
� Pressure rating of 100 PSI @ 180� F, 400 PSI at 73� F
� Short-term pressure rating > 200 PSI
� Inert to acidic soils and corrosive water supplies
� Can be buried directly under slabs without chemical interaction with concrete
� Non-conductive
� Eliminates pressure leaks at solder joints
� Virtually no sweating or condensation
PVC piping is attractive from a cost standpoint because its initial cost can be less than the cost of other materials, and also because it�s light weight means reduced shipping costs as well as faster, safer and easier handling, cutting and installation, as per Vinylbydesign.com. The system�s ease of assembly means reduced equipment and labor requirements and reduced injuries and accidents for installation crews. Additionally, since these pipes don�t rust, scale, pit or corrode, it lasts longer and requires less maintenance than competitive materials, thus reducing repair and replacement costs and providing a lifetime of dependable service free of costly and damaging water leaks.
Goodrich holds multiple patents on the resins, which it licenses to pipe manufacturers under the name FlowGuard Gold�. (FlowGuard Gold� is now marketed under the Noveon name). Noveon, a leader of CPVC, has recently developed two grades to eliminate the inherent problems of earlier CPVC pipe grades of impact strength and difficulty in processing to produce large size pipe. Chlorinated polyvinyl chloride (CPVC) plastic piping is often used where elevated temperature performance and excellent chemical resistance is needed. However, compared to some other plastic materials, CPVC can be more difficult to process and generally restricted in size to smaller dimension pipe. The commercial acceptance of CPVC piping has thus been somewhat limited, especially for industrial applications where more demanding performance and larger pipe sizes are required. As a result, two new industrial CPVC pipe compounds have recently been developed by Noveon. One product is an ultrahigh impact strength material that has been shown to exhibit more than 5 times the toughness of most other CPVC products. The other product is a new large diameter pipe extrusion compound that allows for production of pipe sizes beyond 12� SCH80 (325x17 mm). In addition, recent technological efforts have also led to the development of a pressure rated CPVC fitting compound that has the same design stress as CPVC pipe.
Impact strength and ductility are of critical importance to the overall performance of a piping system. A high level of impact strength is often necessary to ensure that a pipe is capable to withstand abuses that can occur from the time when a pipe has been produced to after it is installed. This problem becomes even more pronounced particularly when the pipe is subjected to sub-ambient conditions. Since damage to the pipe is not always apparent, damaged pipe is sometimes installed and operated for months or even years later before it eventually fails. Therefore, pipes that do not have good toughness and ductility are more prone to damage and failure in the field. Pipes having good impact strength are dependent upon two principle factors. First is the inherent impact strength of the material. This property is governed by such variables as resin molecular weight, as well as the type and level of various additives. Generally speaking, the use of a higher molecular weight resin and impact modifiers tends to improve impact resistance, while pigments and fillers are often detrimental. However, proper design of a material is often a fine balance between a several desired properties. The second factor affecting impact strength and ductility of pipe is that of processing. Properly processed materials will result in a finished product with good impact resistance. Unfortunately, proper processing of a poorly designed material will not result in same level of impact strength and ductility as a material with good inherent impact resistance. Until recently, direct extrusion of CPVC pipe larger than 12� SCH80 (325x17 mm) was difficult and generally not performed, mainly because of the lack of stability of the compound during processing. In comparison, PVC pipes as large as 24� (610 mm) in diameter are often produced without much difficulty. The reason for this difference is due to the fact that CPVC is often processed at higher stock temperatures and is more shear sensitive than PVC. However, recent technological advances have led to the development of a new CPVC compound that can be processed into pipes up to 20� SCH80 (510x26 mm), and possibly even larger. TempRite� 88612 is a CPVC compound specifically designed to allow for the production of large diameter pipes. It has significantly more stability compared to other CPVC pipe compounds.
 
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