How to Use Polyvinyl Chloride and Chlorinated Polyvinyl Chloride Materials
When it comes to cooling tower materials, the configuration, material density, material thickness, material mechanical properties, support spans, and overall design application of materials should always be considered. The materials evaluated in this CTI standard are:
Hereafter called PVC
Chlorinated Polyvinyl Chloride
Hereafter called CPVC
Heat Elevated PVC
Hereafter called HPVC
Hereafter called PP
Fire Retardant Polypropylene
Hereafter called FR-PP
Hereafter called HDPE
Fire Retardant High-Density Polyethylene
Hereafter called FR-HDPE
PVC, or polyvinyl chloride, is a synthetic polymer. PVC, by nature, has a lower flammability risk, is easily thermoformed and extruded into complex shapes, and is rigid with minimal creep characteristics. For this reason, it is the third most manufactured synthetic plastic polymer. It is used in various industries, such as construction, clothing, and electronics. However, PVC is not easily used for injection molded products.
CPVC, or chlorinated polyvinyl chloride, is used in the manufacture of film fill and drift eliminators. Its manufacturing process further chlorinates traditional PVC and changes its composition, making it significantly more flexible than standard PVC.
CPVC has a heat deflection temperature of about 30°F (16.67°C) greater than PVC, making it a great material for high temperature applications. Blends of CPVC and PVC with intermediate heat resistance may also be available.
Both CPVC and blends of CPVC and PVC are more susceptible to ultraviolet degradation, and will lose impact resistance when exposed to UV. CPVC should only be used when the lower impact resistance and shorter useful life are considered.
HPVC, or heat elevated PVC, is used in the manufacture of film fills and drift eliminators. HPVC has a higher heat deflection temperature than PVC, but lower than CPVC. HPVC does not have the embrittlement problems of CPVC, and will add about 15oF (8.33°C) to the heat deflection temperature of PVC.
FR-PP, or fire retardant polypropylene, is commonly used in the manufacture of injection-molded products such as:
Thermoformed film fills
FR-PP can not be solvent or adhesively bonded, so for products requiring assembly, the design must include an alternate means to assemble.
High density polyethylene, or HDPE, is available in both sheet and rod form, for projects that require a higher level of strength and stiffness. HDPE will generally melt and drip in a fire, and is more flammable than PVC. It cannot easily be solvent or adhesively bonded, so for products requiring assembly, the design will most likely include an alternate means to assemble.
Copolymers may impart better impact resistance to the part. PE has a material density approximately 35% less than PVC and for the same design configuration should be supplied in an increased thickness to compare to PVC.
Plastic film thickness is intrinsic to the weatherability and durability of the finished product, but not the only indicator of the suitability of the product. Material formulation, product configuration geometry and other properties all have an engineering value in determining the strength of the product.
High density polyethylene with the addition of adequate fire retardant additives, of FR-HDPE, is used in the manufacturing of injection-molded products and extruded splash fill products. FR-HDPE will generally melt and drip in a fire, and is more flammable than PVC. FR-HDPE cannot easily be solvent or adhesively bonded, so for products requiring assembly, the design will most likely include an alternate means to assemble.
FR-PE inherently is softer and more susceptible to creep factors when loaded. Copolymers may impart better impact resistance to the part. FR- PE has a material density approximately 35% less than PVC and for the same design configuration should be supplied in an increased thickness to compare to PVC.
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