What are the differences in applications between polypropylene and polyethylene products?

The person upstairs explained it in great detail! ! !

Polyethylene PE: It is milky white and translucent when uncolored, with a waxy texture； The product feels smooth to the touch, soft and flexible ； It can stretch a little. Generally, low-density polyethylene is softer and has better transparency ； High-density polyethylene is harder. 　　Common products: handbags, water pipes, oil drums, beverage bottles (milk bottles), daily necessities, etc. Polypropylene PP: It is white and translucent when uncolored, with a waxy texture ； It is lighter than polyethylene. It also has better transparency than polyethylene and is stiffer than polyethylene. 　　Common products: basins, barrels, furniture, films, woven bags, bottle caps, car bumpers, etc.

The article is reprinted from http://www.sdshuntong.net/industry/79.html. For more details, please click on the product introduction. Polyethylene pipes are regarded as the next generation of green piping materials due to their excellent hygiene properties as well as comprehensive mechanical and physical characteristics. The main raw material for producing cross-linked polyethylene pipes (PEX) is HDPE, along with additives such as initiators, cross-linking agents, and catalysts. It is manufactured using the advanced one-step (MONSOIL method) technology; ordinary polyethylene raw materials are combined with silane grafting agents to form chemical covalent bonds between the polymer chains, thereby replacing the original van der Waals forces and creating a three-dimensional network structure in the cross-linked polyethylene. The degree of cross-linking can reach 60%–89%, which confers excellent physical and chemical properties to this material. 　　7.1 Main characteristics of cross-linked polyethylene pipes: 7.1.1 Wide operating temperature range, allowing for long-term use at temperatures between -70°C and 95°C ； 　　7.1.2 It has a solid texture and high resistance to internal pressures; its burst pressure is greater than 5 Mpa at 20°C, greater than 2 Mpa at 95°C, and it can maintain its performance for up to 50 years at 95°C ； 　　7.1.3 It does not rust, has excellent resistance to chemical corrosion, and is highly resistant to environmental stress cracking; it can be used for transporting various chemicals and fluids that accelerate stress cracking in pipes, even at high temperatures ； 　　7.1.4 The low tension on the inner wall of the pipe makes it difficult for water with high surface tension to penetrate the inner wall, thereby effectively preventing the formation of scale. 　　7.1.6 Non-toxic, does not mildew, does not support bacterial growth; its hygiene meets the requirements specified in standard GB7219‑1998 \"Safety Evaluation Standards for Water Distribution Equipment and Protective Materials Used in Drinking Water Supply\" ； 　　7.1.6 The inner wall of the pipe is smooth, resulting in low fluid flow resistance and excellent hydraulic properties; at the same diameter, it can transport more fluid than metal pipes, and it also generates less noise ； 　　7.1.7 The thermal conductivity of plastic pipes is much lower than that of metal pipes; therefore, they have excellent insulation properties. When used in heating systems, no additional insulation is required, and heat loss is minimal ； 　　7.1.8 Good memory performance: When PEX pipes are heated to an appropriate temperature (below 180°C), they become transparent; upon cooling, they return to their original shape. Thus, any incorrect bends that may occur during use can be corrected using a heat gun, allowing for more convenient use ； 　　7.1.9 Light in weight, easy to transport, and simple to install; even non-professionals can carry out the installation smoothly, with the installation effort being less than half that required for metal pipes ； 　　7.1.10 The linear expansion coefficient of cross-linked polyethylene pipes is much higher than that of metal pipes; therefore, space for expansion and contraction must be provided during installation. 　　7.2 Main application areas of cross-linked polyethylene pipes: 7.2.1 Building cold and hot water as well as drinking water piping systems ； 　　7.2.2 Liquid food delivery pipelines in the food industry ； 　　7.2.3 Plumbing heating systems, central air conditioning piping systems, floor radiant heating ； Heating systems, solar water heater systems, etc ； 　　7.2.4 Piping for telecommunications and electricity ； 　　7.2.5 Industrial pipeline systems for electroplating, petrochemicals, etc.

I’m here to learn *; it looks really good

Polyethylene itself is divided into high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and metallocene polyethylene. In terms of processability, low-density polyethylene is easier to process, but due to its lower strength, it is sometimes used together with other types of polyethylene. In applications, different grades of polyethylene also vary; ordinary PE is used for films, pipes, and containers. High-density polyethylene can be used to produce gas transmission pipes. Metallocene PE has high strength and is often used in combination with conventional PE; however, it has poor processability, and the addition of appropriate processing aids is needed to prevent melt fracture. PE itself also has poor transparency, making it unsuitable for high-transparency products. PP has high strength but poor toughness; in technical terms, it has weak impact resistance. Therefore, it is generally used to make films, although the application areas of these films differ from those of PE films, with surface packaging and printing being the main uses. The transparency is very good. Regarding piping materials, simple PP is rarely used; cross-linked polypropylene, namely the common PPR pipes, is required. Due to its poor impact resistance, ordinary PP is prone to breaking; therefore, impact modifiers must be added in practical applications. In the case of bumpers, POE from Dow Chemical in the United States is used as a modifier to improve impact resistance. In my opinion, the above are practical work experiences, which are better than general theoretical explanations. Quite practical.

I bow down from upstairs – it’s so talented!