When comparing PVC, UPVC, CPVC, PP, PE, PB, and PVDF
plastic pipes, it's essential to consider their individual properties and distinctions. Each type of
plastic pipe offers unique characteristics that cater to specific applications and operational requirements. PVC, UPVC, CPVC, PP, PE, PB, and PVDF pipes differ in terms of their temperature resistance, corrosion resistance, flexibility, pressure resistance, hygiene, flow capacity, and pipeline safety.
PVC
PVC (PolyVinylChloride), classified into seven grades (SG1-SG7) based on material hardness and performance, has a density of approximately 1.4 g/cm³. Products below SG4 are generally soft and require a large amount of plasticizer during molding. They are mainly used in the production of artificial leather, wire and cable insulation layers, seals, etc.
Products above SG5 are rigid and mainly used to make various pipes, such as drainage, electrical, postal, and fittings, as well as various boards, sheets, profiles, etc.
PVC has a molding shrinkage rate of 0.6-1.5% and exhibits good mechanical properties. It has excellent electrical properties, self-extinguishing characteristics, strong acid and alkali resistance, good chemical stability, and low cost, making it a widely used general-purpose plastic. However, its development is hindered by its low maximum operating temperature, which is around 80°C.
CPVC (Chlorinated PolyVinylChloride) resin is derived from the chlorination modification of polyvinyl chloride (PVC) resin, making it a new type of engineering plastic.
This product is white or light yellow in color, with odorless, tasteless, and non-toxic loose granules or powder.
After chlorination, the irregularity of molecular bonds in PVC resin increases, along with polarity, leading to greater solubility and chemical stability of the resin. This enhances its heat resistance, resistance to acids, alkalis, salts, oxidants, and other corrosive agents. The mechanical properties and heat deformation temperature are also improved. The chlorine content increases from 56.7% to 63-69%, while the Vicat softening temperature increases from 72-82°C to 90-125°C. The maximum operating temperature can reach 110°C, with a long-term operating temperature of 95°C. Among them, CORZAN CPVC exhibits superior performance indicators. Therefore, CPVC is a new type of engineering plastic with broad application prospects.
UPVC
UPVC pipes, with polyvinyl chloride (PVC) resin as the carrier, possess excellent properties such as accurate temperature sensitivity, timed melting, and rapid absorption of effective additives, which weaken the intermolecular forces of the resin chains. Additionally, they use world-renowned calcium-zinc composite heat stabilizers, which capture, inhibit, absorb, and neutralize the release of hydrogen chloride during the resin's exposure to high temperatures and melting. This process involves a double bond addition reaction with the polyolefin structure, replacing the active and unstable chlorine atoms in the molecule. This effectively and scientifically controls the catalytic degradation and oxidative decomposition of the resin in its molten state.
PP
PP pipes are a type of semi-crystalline material. They are harder and have a higher melting point compared to PE.
Homopolymer PP becomes very brittle above 0°C, so many commercial PP materials contain 1-4% ethylene as an irregular copolymer or a higher ratio of ethylene content as a block copolymer.
Copolymer PP materials have lower heat distortion temperatures (100°C), low transparency, low glossiness, and low rigidity but stronger impact resistance. The strength of PP increases with an increase in ethylene content.
The Vicat softening temperature of PP is 150°C.
Due to its high crystallinity, PP has good surface stiffness and scratch resistance. PP does not suffer from environmental stress cracking. Typically, PP is modified by adding glass fibers, metal additives, or thermoplastic elastomers.
The melt flow rate (MFR) of PP ranges from 1 to 40. PP materials with low MFR have better impact resistance but lower tensile strength. For materials with the same MFR, copolymer PP has higher strength than homopolymer PP. Due to crystallization, PP has a relatively high shrinkage rate, typically ranging from 1.8% to 2.5%. The uniformity of shrinkage is much better than materials like PE-HD. Adding 30% glass additives can reduce the shrinkage rate to 0.7%. Both homopolymer and copolymer PP materials have excellent moisture resistance, acid-base corrosion resistance, and solvent resistance. However, they are not resistant to aromatic hydrocarbons (such as benzene) and chlorinated hydrocarbons (carbon tetrachloride). PP also lacks antioxidant properties at high temperatures.
Polypropylene (PP) is one of the lighter common plastics, with excellent electrical properties, making it suitable for use as a moisture-resistant and heat-resistant high-frequency insulation material. PP is a crystalline polymer, and its large volume change and high molecular orientation during melt solidification result in significant shrinkage (1.0%-1.5%). The effect of increasing temperature to reduce viscosity is not significant when PP is in a molten state. Therefore, in the molding process, the main focus should be on increasing injection pressure and shear rate to improve the molding quality of products.
PE
Polyethylene, abbreviated as PE, is the simplest polymer organic compound widely used in the world today. It is polymerized from ethylene and classified into high-density polyethylene (HDPE), medium-density polyethylene (MDPE), and low-density polyethylene (LDPE) based on density.
LDPE is relatively soft and is mainly produced by high-pressure polymerization. HDPE, on the other hand, has characteristics of rigidity, hardness, and high mechanical strength, and is mainly produced by low-pressure polymerization.
HDPE can be used to make containers, pipes, and high-frequency electrical insulation materials for radar and television. LDPE, produced in large quantities, is commonly used.
Polyethylene has a waxy texture with a smooth feel similar to wax. When not dyed, LDPE is transparent, while HDPE is opaque. Polyethylene is formed by the addition and polymerization reactions of ethylene (CH2=CH2), forming polymer chains with repeating –CH2– units. The properties of polyethylene depend on its polymerization method. HDPE, produced via Ziegler-Natta polymerization under moderate pressure (15-30 atm) and with organic compound catalysts, results in linear molecules with long chains and molecular weights reaching several hundred thousand. LDPE, produced under high pressure (100-300 MPa) and high temperature (190–210°C) with peroxide catalysts, forms branched structures.
Polyethylene is insoluble in water and has low water absorption. It only slightly dissolves in some chemical solvents like toluene and acetic acid, and even then, only at temperatures above 70°C. However, polyethylene particles can melt or solidify with temperature changes between 15°C and 40°C. When the temperature rises, it melts and absorbs heat, and when the temperature drops, it solidifies and releases heat. Due to its low water absorption and excellent insulation properties, it is widely used as a building material.
Applications of PP-R Cold and Hot Water Pipes
PP-R pipes are used in various applications including:
Cold and hot water systems within buildings, including centralized heating systems.
Heating systems within buildings, including floor and wall heating, as well as radiant heating systems.
Potable water supply systems for direct consumption.
Central (centralized) air conditioning systems.
Agricultural and garden irrigation systems.
Rainwater pipe networks.
Swimming pool pipe networks.
Solar energy facility pipe networks.
PP-R pipes are generally used for small-diameter pipes and can be installed visibly or concealed.
PB pipes, made of polybutene polymer materials, are widely used in developed countries such as Europe and America. PB pipes have replaced copper pipes as the preferred material for hot water supply pipelines.
PE Pipe
Temperature Resistance: PE water pipes have a low temperature embrittlement temperature and can be used in the range of -40°C to 60°C. There is no risk of pipe cracking during winter installation and construction.
Corrosion Resistance: Polyethylene is an inert material and can withstand various chemical media erosion without the need for corrosion protection. Chemical substances in the soil do not degrade the pipeline, and there is no occurrence of rot, rust, or corrosion.
Flexibility: The elongation at break of PE water pipes exceeds 800%, and local vibrations do not cause all pipes to vibrate, resulting in strong earthquake resistance. The flexibility of polyethylene allows PE water pipes to be coiled, reducing the need for a large number of connection fittings. They can bypass obstacles during construction, reducing construction difficulty.
Pressure Resistance: Due to the high crystallinity of HDPE, its strength and hardness increase accordingly. The tight fusion joints can withstand internal pressure, making it widely used in water supply and pressure pipeline systems.
Hygiene: PE water pipes are hygienic and non-toxic, preventing the growth of bacteria inside the pipe and avoiding secondary water pollution, thus effectively addressing the defect of pipeline contamination of water sources.
Flow Capacity: The smooth inner wall of PE water pipes reduces friction coefficient, fluid resistance, and head loss, preventing scaling and reducing pressure loss and energy consumption in pipeline transportation, leading to significant economic advantages.
Pipeline Safety: PE water pipes use heat fusion and electrofusion connections, with joint strength higher than that of the pipe itself. They can effectively resist circumferential and axial forces generated by internal pressure. With excellent sealing performance, there is no need to worry about interface distortion causing pipeline leakage.
