PVC single wall corrugated pipe historyPVC single wall corrugated pipe history
PVC single-wall corrugated pipe is made of PVC as the main raw material by extrusion blow molding. It is a new product developed in the 1970s abroad. PVC single-wall corrugated pipe utilizes the structure of its annular groove, which can combine the rigidity of rigid PVC pipe and the flexibility of the hose, so that the pipe has the characteristics of rigidity and softness. It can be used to transport certain liquids and gases and as a buried wire. casing.
Chinese name PVC single-wall corrugated pipe main raw material PVC production method extrusion blow molding was developed in the 1970s
table of Contents
2 Production process
3 Production equipment and characteristics
The inner and outer surfaces of the single-wall corrugated pipe are both corrugated. Although their flexibility and flexibility are excellent, their fluid resistance is large, and it is easy to cause the deposition of suspended matter at the groove of the inner surface. Therefore, PVC single-wall corrugated pipes are mostly small-diameter pipes with thin walls and low strength requirements that need to be bent freely, such as threading pipes, drain pipes, and exhaust pipes.
The single-wall corrugated pipe takes the inner diameter or outer diameter as the basic structural parameters. Others such as wall thickness, wave distance, wave thickness, etc. are determined based on the inner diameter or outer diameter. The height of the corrugation can be expressed by the wave depth coefficient K, which is the ratio of the outer diameter to the inner diameter of the bellows. The larger the value, the higher the height of the corrugation. The corrugated tube's waveform can be divided into spiral, U-shaped, C-shaped, S-shaped, V-shaped and Ω-shaped according to the geometric shape cut along the axial direction. The waveform has certain influence on the rigidity and strength of the tube.
The main difference between the production technology of PVC single-wall corrugated pipe and PVC ordinary pipe is that after extruding the tube blank with a circular cross-section, it is formed into a corrugated pipe in a corrugated blow molding mold while it is hot. For details, see the process flow and production described later Process and forming principles.
The PVC is mixed with appropriate additives in a certain proportion. Generally, a "Z" type kneader or a high-speed kneader is used to make the mixture uniform, granulated by an extruder or formed by twin-screw powder at one time. The rotation speed of the single screw extruder is generally 30 ~ 60r / min, and the head pressure is controlled to about 36 ~ 54MPa. The material should be fully plasticized, and compressed air can be used to freely expand into bubbles. After the extrusion is stable, insert the corrugated molding device and the extrusion die into the center. The center line of the two should be aligned. The extrusion die should be inserted into the molding die to be more than the distance of a pair of molding modules to ensure that the upper and lower modules are fully closed before molding product. The ring sequence grooves of the upper and lower forming dies must be aligned and should not be misaligned. The traction speed is generally controlled at about 6 ~ 10m / min. The inflation pressure is based on the principle that the annular groove of the product is blown completely, generally 0.15MPa. The temperature of the mold is controlled at about 45 ~ 60 ℃ to facilitate the basic shaping of the product before the mold is opened, and to avoid the extension of the corrugation pitch during winding.
Extrusion temperature control The feeding section is 145 ~ 160 ℃, the compression section is 165 ~ 175 ℃, the measuring section is 175 ~ 185 ℃, the head is 175 ℃ ~ 180 ℃, and the die is 170 ~ 180 ℃.
Production equipment and features
Extruders are generally equidistant and unequal depth, gradual screw (see extruder for soft poly grabbing vinyl pipe).
The corrugated forming device is mainly composed of forming mold, transmission system and control system. Among them, the forming mold is composed of dozens of pairs of continuous blow molding halves that are divided up and down, and the upper and lower dies are fixed on the two transmission belts by the crawler type. When the transmission system drives the mold to rotate, the upper and lower molds repeat the closing-opening action. The mold is closed to form the forming cavity of the round tube. After the bellows are blown to form the mold, the mold is opened to demold the product. The corrugated forming device simultaneously plays the role of product forming and traction.
PVC plastic corrugated wire and tube adopts ZBG 33008-89 standard.