Differences between PE pipes and PVC pipes

This post was last edited by zxx0877 on 2011-6-17 at 11:23. Comparison of the characteristics and main uses of various plastic pipes: PVC pipes have good tensile and compressive strength, but their flexibility is lower than that of other plastic pipes. They offer excellent corrosion resistance, and their price is the lowest among all types of plastic pipes; however, they become brittle at low temperatures. Connection methods include bonding, socket gasket connection, and flange threading. They are used for water supply and drainage, irrigation, gas supply and exhaust in residential areas, as well as in industries and agriculture, and also for electrical conduit, rainwater pipes, and industrial corrosion-resistant pipes. CPVC pipes boast outstanding heat resistance, with a heat deformation temperature of 100°C, and they also have good chemical resistance. Connection methods include bonding and flange threading. Used for hot water pipes. PE pipes are lightweight, flexible, have good low-temperature resistance, are non-toxic, and are relatively inexpensive. They have high impact resistance, but lower compressive and tensile strength. Connection methods include heat welding and flange threading. Used for drinking water pipes, rainwater pipes, gas pipelines, and industrial corrosion-resistant pipes. PP pipes have good corrosion resistance, along with good strength, high surface hardness, and smooth surfaces. They also possess some heat resistance. Connection methods include heat welding and flange threading. Used for pipes carrying chemical wastewater, seawater, oil, and for irrigation purposes, as well as as heating pipes in indoor concrete floors. ABS pipes have excellent corrosion resistance, are lightweight, and have higher heat resistance than PE and PVC, but they are more expensive. Adhesive bonding, flange threading – used for drain pipes, conveyance pipes, sewage pipes, underground cable conduits, and highly corrosion-resistant industrial pipes. PB pipes have a strength level between PE and PP, and flexibility between LDPE and HDPE; their key advantages include creep resistance (resistance to cold deformation), the ability to remain intact after repeated bending, temperature resistance, and good chemical resistance. Hot melt welding, flange threading – used for water supply pipes, hot and cold water pipes, gas pipes, and pipes buried underground. GRP pipes offer excellent corrosion resistance, are lightweight, have high strength, and allow for good design flexibility. Socket gasket connection, flange connection – widely used in petrochemical pipelines and large-diameter water supply and drainage pipes. For PE and PP-R pipes, hot melt or electrofusion welding is employed; however, these methods are complex and can lead to defects such as material accumulation, resulting in stress concentration and affecting the long-term performance of the pipes. From the perspective of long-term hygiene, the aluminum layer in aluminum-plastic pipes prevents oxygen from penetrating, which reduces the risk of microbial and algal growth. Generally, antioxidants can be added to the outer PE layer without causing contamination of the water inside the pipe. In contrast, PE pipes and PP-R pipes cannot prevent oxygen from entering, allowing microorganisms and algae to thrive and thus affecting the hygiene of drinking water ； It also contains large amounts of antioxidants, which can easily cause water pollution. In terms of high-temperature resistance, the national standards for aluminum-plastic pipes specify a long-term operating temperature of 95°C and a maximum operating temperature of 110°C, which is more than sufficient to meet the needs of household water use ； The performance of PE pipes declines rapidly as the temperature rises, and they are only suitable for transporting cold water ； According to the national standards for PP-R, the long-term operating temperature is 70°C, with a maximum operating temperature of 95°C; this imposes certain limitations on its use in hot water pipes. In terms of aging resistance, aluminum-plastic pipes have a stable molecular structure; the inner and outer PE layers are separated from each other, allowing sufficient amounts of light-resistant and antioxidant stabilizers to be added to the outer layer without affecting the hygiene of the inner layer that comes into contact with water ； PE pipes have a stable molecular structure, but their single-layer structure makes it difficult to add stabilizers, which can lead to secondary contamination of the water inside the pipes ； PP-R pipes contain a large number of unstable tertiary carbon atoms, and are prone to aging due to exposure to light, oxygen, and impurities. Comparison of the properties of PE pipes and PVC pipes: I. Property comparison – Items: PE solid-wall pipes, PVC-U pipes. Pressure resistance: At the current level of technology and according to **standards, PE pipes with a standard size ratio of SDR 11 can achieve a maximum nominal pressure of 16 kg/cm2. According to international standards, for PVC-U pipes with a nominal outer diameter greater than 90 mm, when the standard size ratio is 11, the maximum nominal pressure is 25 kg/cm2. Raw material composition and product appearance: PE pipes are manufactured through extrusion using 100% pure raw material pellets (which are polymerized from these raw materials, even when carbon black and antioxidants are added). No fillers or plasticizers are used; the surface of the pipe is smooth and clean, with neat and uniform cuts, and it remains crack-free over the long term. PVC-U pipes are manufactured through extrusion by mixing PVC powder with fillers such as stone dust, stabilizers, and other materials. The plasticity of the stone powder and the amount of stabilizer added affect the properties of the pipes. The density of PE pipes is 0.92–0.96 g/cm2, which is relatively low; it is only 3/4 of the weight of PVC. PVC-U pipes have a density of 1.4 g/cm2, which is relatively high. The impact resistance of PE pipes is exceptionally high; it is 6 times that of PVC pipes. Even when heavy objects are placed directly on the pipe, it does not break. PVC-U pipes have poor impact resistance; they will crack if subjected to direct impact from heavy objects. The typical temperature limits for PE pipes are a softening point of 121°C and a embrittlement point of -80°C; their usable temperature range is between -40°C and 100°C. Thanks to their excellent resistance to low-temperature brittleness, they are particularly suitable for use in colder regions. The Vicat softening point of PVC-U pipes is 80°C, and their embrittlement point is -18°C. The recommended operating temperature range is from -5°C to 60°C; when the temperature drops below 5°C in winter, there is a risk of cracking. Flame-retardant PE pipes are materials with slow combustion properties; however, they do not catch fire in low-oxygen conditions. Therefore, pipelines buried underground, whether used for transporting gas or water or as cable sleeves, can be used safely. PVC pipes are self-extinguishing materials; they will extinguish on their own after being ignited for a while, and therefore can be used as water supply and drainage pipes indoors and outdoors. In terms of hygiene, PE plastic is an inert, non-polar material; no lead-containing heavy metal salts are added as stabilizers during its processing, so it is free from any toxicity. It also does not react with ordinary acids or bases, making it the ideal material for transporting drinking water. During the processing of PVC-U pipes, necessary additives such as stabilizers, fillers, lubricants, and colorants must be added; compounds containing lead, arsenic, cadmium, and tin can be harmful to health if accumulated over time. PVC materials contain chlorine, and they produce the carcinogenic substance dioxins during combustion, which can have adverse effects on human health and the environment. Connection performance: PE pipes are usually connected using heat fusion or electro-heat fusion; these welding methods are safe and reliable, with a welding strength of up to 100%. Among them, the electrothermal fusion welding method is the fastest and safest option; it is not affected by human factors, which is why no other connection methods can replace it in gas pipelines. PVC pipes are commonly connected using adhesives, gaskets, or flanges, and all of these connection methods are affected to some extent by human factors. Weather-resistant PE pipes are made from pure raw materials, and carbon black that can filter out sunlight ultraviolet rays is added to them, giving them excellent weather resistance. PVC pipes contain stone dust and volatile plasticizers, and exposure to sunlight for extended periods can cause them to crack, become brittle, and age.