What is the difference between PVC and PP water pipes?

Raw Material Composition and Production Process

PVC Water Pipes

Raw Material Composition

PVC (polyvinyl chloride) resin is its primary component. To improve PVC's performance, various additives are added. For example, plasticizers increase the pipe's flexibility and plasticity, making it easier to shape during processing; stabilizers improve the pipe's heat and weather resistance, preventing degradation caused by heat, light, and other factors during use; and lubricants help reduce friction between the material and equipment during processing, improving production efficiency and the surface quality of the pipe.

Production Process

First, PVC resin and various additives are mixed in a specific proportion to form a mixture. This mixture is then fed into an extruder, where it undergoes heating and pressurization to melt the material and be extruded into a tube. The extruded pipe passes through a cooling and shaping device, where it is rapidly cooled and solidified by water or air cooling, forming a pipe of a specific size and shape. Finally, the pipe undergoes subsequent processing, such as cutting and flaring, as needed, to produce the finished PVC water pipe.

PP Water Pipe

Raw Material Composition

The main raw material is PP (polypropylene) resin. Depending on the specific application requirements, additives such as antioxidants and UV absorbers may be added. Antioxidants prevent oxidation during processing and use, extending the service life of the pipe. UV absorbers effectively absorb ultraviolet rays, improving the pipe's UV resistance and preventing degradation during outdoor use.

Production Process

The production process for PP water pipe is similar to that for PVC water pipe. The raw materials are first mixed thoroughly, and then the molten material is extruded into a pipe through an extruder. However, due to the different melting characteristics of PP resin and PVC, different process parameters such as temperature and pressure must be controlled during the extrusion process. After extrusion, PP pipes also undergo cooling, shaping, and cutting processes. Some PP pipes also undergo surface treatment to improve their appearance and scratch resistance.

Performance Comparison

Physical Properties

1. Hardness

PVC pipes have a relatively high hardness, which allows them to maintain good shape stability during installation and use, making them less susceptible to deformation. For example, when buried underground, they can withstand a certain amount of soil pressure without collapsing. PP pipes, on the other hand, have a relatively low hardness, but are more flexible and can bend to a certain extent without breaking, making them suitable for installation requiring curved pipes, such as around obstacles or in curved piping systems.

2. Density

PVC has a relatively high density, typically between 1.35 and 1.45 g/cm³. This makes PVC pipes relatively heavy, requiring more manpower to transport and install. PP pipes, on the other hand, have a lower density, typically between 0.9 and 0.91 g/cm³, making them lighter, easier to transport and install, and reducing construction costs and labor intensity. 3. Transparency

PVC water pipes are typically opaque or translucent, due to their raw materials and production process. PP water pipes, on the other hand, are generally translucent to opaque, with a relatively higher transparency than PVC. In some applications where the flow of media within the pipe needs to be observed, the translucency of PP water pipes may be advantageous.

Chemical Properties

1. Corrosion Resistance

Both types have excellent corrosion resistance. PVC water pipes are resistant to most chemicals, such as acids, alkalis, and salts, and can be used to transport various corrosive industrial wastewater and chemical liquids. PP water pipes also offer excellent corrosion resistance, especially against some organic solvents and chemicals, making them widely used in piping systems in the chemical and pharmaceutical industries.

2. Aging Resistance

PVC water pipes are susceptible to aging over time due to factors such as ultraviolet light, heat, and oxygen, resulting in surface discoloration and embrittlement. Therefore, when used outdoors, protective measures such as applying a sunscreen coating or underground installation are necessary.

PP water pipes have excellent aging resistance. Adding additives such as UV absorbers allows them to withstand long-term outdoor use without aging. However, PP water pipes can age faster in extreme environments such as high temperature and high humidity, so their selection and use should be tailored to the specific situation.

3. Hygienic Performance

PVC water pipes may contain toxic substances such as plasticizers during the production process. These substances can migrate into water under certain conditions, polluting the water quality. Therefore, PVC water pipes are generally not recommended for drinking water distribution systems.

PP water pipes, on the other hand, are non-toxic and odorless, meeting national drinking water hygiene standards and can be safely used in drinking water supply systems such as homes, schools, and hospitals, where high water quality requirements are required.

Mechanical Properties

1. Compressive Strength

PVC water pipes have high compressive strength and can withstand certain pressures without breaking. In building water supply and drainage systems, standard PVC water pipes can meet normal water pressure requirements. PP water pipes have relatively low compressive strength, but with the continuous advancement of material technology, some high-strength PP water pipes are now available that can withstand higher pressures. For example, in the hot water supply systems of some high-rise buildings, PP pipes with thickened walls or reinforced materials can ensure safe operation under long-term high pressure.

2. Impact Resistance

PVC pipes have relatively poor impact resistance and tend to become brittle in low temperatures, easily breaking when subjected to external impact. Therefore, when using PVC pipes in cold regions, insulation measures or cold-resistant PVC pipes are necessary. PP pipes have excellent impact resistance and maintain good toughness even in low temperatures, making them less susceptible to breaking. This has led to their widespread use in building water supply and drainage and outdoor plumbing projects in some cold regions.

3. Tensile Properties

PVC pipes have high tensile strength and can withstand certain tensile forces without breaking. When stretching or bending the pipe during installation is required, PVC pipes can meet these requirements to a certain extent. PP pipes also have good tensile properties and a certain degree of elasticity, allowing them to accommodate minor deformation and movement during operation.

Differences in Application Scenarios

Building Water Supply and Drainage Systems

PVC Pipes

They are widely used in building drainage systems, such as bathroom and kitchen drainage pipes, and stormwater drainage pipes on building exterior walls. Their corrosion resistance and price advantage make them a preferred material for drainage pipes. PVC pipes can also be used in cold water supply systems in buildings with less stringent water quality requirements, but care should be taken to select products that meet relevant standards to ensure water quality.

PP Pipes

Mainly used in building hot water supply systems, they can withstand high water temperatures, are non-toxic and hygienic, and ensure high hot water quality. In some high-end residential buildings and buildings with strict water quality requirements, PP pipes are also widely used in drinking water supply systems, providing users with safe and healthy drinking water.

Municipal Engineering

PVC Pipes

Commonly used in urban drainage systems, including sewage and stormwater pipes. Their large diameter and excellent corrosion resistance make them suitable for urban drainage needs. PVC pipes are also widely used in landscaping irrigation systems in some cities, transporting water to various irrigation areas. PP water pipes

While their application in municipal engineering is relatively limited, they are gradually gaining adoption in urban water supply pipeline renovation projects with high water quality requirements. Their corrosion resistance and hygienic properties effectively ensure the quality of urban water supply, reducing pipe aging and water pollution.

Agricultural irrigation

PVC water pipes

A common pipe material used in agricultural irrigation, they can be used in both surface and underground irrigation systems. Their low price and ease of installation have led to their widespread use in rural areas. For example, in border and furrow irrigation systems, PVC pipes can transport water from the source to the fields, irrigating crops.

PP water pipes

While their application in agricultural irrigation is relatively limited, they do find some use in areas where high-quality water is required for cash crops, such as flower and vegetable cultivation. Their hygienic properties are low in the growth of bacteria and algae, preventing contamination of irrigation water and improving crop quality. Industrial Sector

PVC Water Pipes

In some industrial settings, such as the chemical, electroplating, and printing and dyeing industries, PVC pipes can be used to transport corrosive industrial wastewater and chemical liquids. Their excellent corrosion resistance ensures that the pipes will not corrode and damage over long periods of use, reducing maintenance costs.

PP Water Pipes

Widely used in the chemical, pharmaceutical, and food and beverage industries, they can be used to transport various chemical raw materials, pharmaceuticals, and food-grade liquids. Their hygienic properties and corrosion resistance enable them to meet the stringent pipe requirements of these industries, ensuring product quality and production safety.

Installation and Maintenance

Installation

PVC water pipes: There are various connection methods, with the most common ones being gluing, rubber ring connections, and flange connections. Gluing is suitable for small-diameter pipes. Clean the connecting surfaces of the pipe and fitting, apply glue evenly, and quickly connect. Wait for the glue to cure.

Rubber ring connections are suitable for larger-diameter pipes. Place the rubber ring over the end of the pipe, then insert the pipe into the fitting. The elasticity of the rubber ring creates a sealed connection. Flange connections are generally used in locations that require frequent disassembly or require high sealing requirements. Flanges are bolted together with a gasket in between.

PP water pipes: Hot-melt connections are primarily used. Using specialized hot-melt tools, the connecting parts of the pipe and fitting are heated until molten. Then, the two are quickly butted together and pressure is applied. After cooling, a secure connection is formed. Hot-melt connections offer advantages such as secure connections and excellent sealing, but they require high operator skill and strict adherence to operating procedures to ensure a high-quality connection.

Maintenance

PVC water pipes: During use, care must be taken to protect the pipes from external impact and compression to prevent cracking or deformation. For buried PVC water pipes, precautions must be taken to prevent damage from ground subsidence or other construction activities. Additionally, regularly inspect pipe connections and promptly repair or replace any leaks.

PP water pipes: While PP water pipes are highly resistant to corrosion and aging, care must be taken to protect them from sharp objects during long-term use to prevent scratches on the surface. For PP water pipes exposed outdoors, regularly check their sun protection, insulation, and other protective measures to ensure they are intact. Repair any damage promptly. When used in hot water systems, carefully control the water temperature to avoid damage to the pipes caused by excessively high temperatures.

Market Price and Cost-Effectiveness

Price

Generally speaking, PVC water pipes are relatively inexpensive, primarily due to their low raw material costs and relatively simple production process. Prices vary depending on the specifications and quality of PVC water pipes. Ordinary small-diameter PVC water supply pipes can cost from a few to over ten yuan per meter, while large-diameter PVC drainage pipes can cost from tens to over a hundred yuan per meter, depending on the diameter and wall thickness.

PP water pipes are relatively expensive due to their high raw material costs and the complex processes and equipment required during production. Ordinary PP-R water supply pipes, for small diameters, can cost from a dozen to several dozen yuan per meter, while large-diameter PP pipes are more expensive.

Cost-Effectiveness

PVC pipes offer a high cost-effectiveness in applications where water quality requirements are low and the operating environment is relatively simple. Their low price can meet basic needs, such as in building drainage and agricultural irrigation.

In applications where water quality requirements are high and the operating environment is more complex, such as drinking water supply and hot water systems, PP pipes, while more expensive, offer excellent hygienic properties, heat resistance, and corrosion resistance, ensuring the long-term stability of the piping system and offering a high cost-effectiveness in the long term.

PVC and PP pipes each have their own unique characteristics and advantages in different application scenarios. When choosing the most suitable pipe material, consider a comprehensive consideration of factors such as the specific project requirements, the operating environment, and the water quality requirements.