PP pipe extrusion molding process characteristics
As a generation of plastic ducts, PP ducts have a relatively high market share in the early 21st century. However, with the innovation and development of technology, PP ducts have been gradually eliminated by the market. As a third-generation product, PPR ducts add about 5-10% of PE materials in the production process to increase the flexibility of the product. Currently, the product share in the market exceeds 90%. PP ducts are produced with polyethylene as the masterbatch and carbon black as the color material through melting, extrusion, molding and other technologies. The role of carbon black is to ensure the good weather resistance and long-term thermal stability of the duct.
PP plastic raw material, chemical name: polypropylene, advantages: low density, strength, stiffness, hardness and heat resistance are better than low-pressure polyethylene, and can be used at about 100 degrees. It has non-conductive properties and high-frequency insulation and is not affected by humidity, but it becomes brittle, non-wearable, and easy to age at low temperatures. It is suitable for making general mechanical parts, corrosion-resistant parts and insulating parts. PPR (polypropylene random), also known as random copolymerized polypropylene (PPR), has good toughness, high strength, simple processing performance, and strong creep resistance at higher temperatures. It can be widely used in ducts, sheets, daily necessities, Production of packaging materials, components for household appliances and various films.
The extrusion molding process of PP duct is as follows:
1. Selection of raw materials: The resin used for extruded polypropylene ducts has a melt flow rate in the range of 0.2 to 3g/10min. Generally, resins with a melt flow rate in the range of 0.2 to 0.4g/10min are widely used.
2. The production process sequence of polypropylene duct: the same as the production process sequence of general-purpose polyethylene duct, the process sequence is as follows. Raw material opening bag to check quality→extruder plasticizes and melts raw material→mold forming tube blank→vacuum sizing sleeve cooling and sizing→vacuum spray cooling→duct cooling and cooling→traction→coiling→quality inspection→weight inspection and storage
3. Selection of equipment: Polypropylene ducts are mostly produced by general-purpose single-screw extruders. The screw structure is a gradient type with equal pitch and different depth, the length-to-diameter ratio is (25-30):1, and the compression ratio is 2.5-4. The structure of the molding die is mostly straight-through type, and the length of the straight part of the mandrel is L=(2~5)D (D is the diameter of the duct, the larger value is taken when the diameter is small, and the smaller value is taken when the diameter of the duct is large). The inner diameter of the sizing sleeve d=D/(1-δ) (D is the diameter of the duct, and δ is the shrinkage rate of the duct, generally δ=2.7% to 4.7%).
4. duct extrusion molding process temperature: the feeding section of the barrel is 150-165°C, the plasticizing section is 170-180°C, and the homogenizing section is 190-220°C. The forming mold temperature is 190-220°C.
The difference between pp duct and ppr duct is that ppr duct is more able to withstand high temperature than pp duct and has better flexibility. This is the product of the modification process of pp duct. The raw material of pp duct is polypropylene, and the full name of ppr duct is It is called three-type random copolymer polypropylene, which is actually made of polypropylene. The pp duct itself has the characteristics of safety, non-toxicity, high temperature resistance, corrosion resistance, and a very long service life. It is a new type of environmental protection. building materials.
In order to make pp ducts more widely used, it is necessary to modify the raw materials at this time. Take the ppr duct as an example, it is mainly used for domestic water pipes, and the safe temperature of the pp duct is about 60 degrees of hot water, which must be used in the living hall. In order to meet the characteristics of high temperature resistance, in poly In the propylene raw material, a small amount of PE material is added to improve the high temperature resistance of the pp duct. Although it becomes more flexible and reduces the weakness of low temperature brittleness, the rigidity and strength of the ppr duct are lower than that of the pp duct. So what everyone needs to understand is that pp duct is a general term for many ducts based on polypropylene, which includes ppr duct, pph duct, ppb duct and so on.
