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PPR Pipes Increased Mechanical Strength To Improve Production


First, the basic principles of plastic extrusion

Plastic processing industry is a highly integrated technology industry. It involves the polymer chemistry, polymer physics, interface theory, plastic machinery, plastic processing mold, formula design principles and process control and so on. The theory of extrusion mainly studies the movement and change of plastic in the extruder. The relationship between the three physical states of the polymer,PPR Pipes the relationship between the screw structure, the plastic properties and the processing conditions of the polymer in the different temperature range under the action of a certain external force in the extruder. So as to carry out reasonable process control. In order to achieve the purpose of improving the production and quality of plastic products. Plastic polymer materials, heated at constant pressure, in different temperature range, there are glass, high elasticity, viscous flow of three physical state. General plastic molding temperature above the viscous temperature.

Second, polyolefin pipe extrusion molding process control

The control parameters of the extrusion process include molding temperature, extruder working pressure, screw speed, extrusion speed and traction speed, feeding speed, cooling and so on.

1. Pretreatment of raw materials

Polyolefin is a non-absorbent material, usually very low moisture content, can meet the needs of extrusion, but when the polyolefin containing absorbent pigments, such as carbon black, the humidity sensitive. In addition, when the use of materials and fillers, the water content will increase. Moisture not only causes the inside and outside of the pipe to be rough, but also may cause bubbles in the melt. Often the raw materials should be pretreated. General use of drying, can also be added with a corresponding dehumidification function of the additives. Such as defoamers. PE dry temperature is generally 60-90 degrees. At this temperature,PPR Pipes the yield can be increased by 10% to 25%.

2. temperature control

Extrusion molding temperature is necessary to promote the plasticization of molding materials and plastic melt flow. The material of the plastic and the quality and yield of products has a very important impact. Plastic Extrusion The theoretical temperature window is between the viscosity flow temperature and the degradation temperature. The temperature range is wide for polyolefins. Usually above the melting point, 280 degrees or less can be processed. To correctly control the extrusion molding temperature, we must first understand the temperature limit of the material being processed and its physical properties of the relationship. To find out its characteristics and laws in order to choose a better temperature range for extrusion molding. Therefore, the temperature setting should take into account the following aspects: First, the polymer itself, such as melting point,PPR Pipes molecular weight size and distribution, melt index and so on. Followed by the performance of the equipment. Some equipment, the feed section of the temperature on the host of a great impact on the current. Again, by observing the tube die extrusion tube surface is smooth. Whether the bubble and other phenomena to judge.

The extrusion temperature includes the set temperature of the heater and the melt temperature. The heating temperature is the temperature provided by the external heater. The melt temperature refers to the temperature of the material between the front of the screw and the head.

The barrel temperature distribution, from the feed zone to the die, may be flat, incremental, decreasing and mixed. Mainly depends on the material point and the structure of the extruder.

Head set the temperature, in order to obtain better appearance and mechanical properties, and reduce the melt outlet expansion, the general control of the body temperature is lower, the machine head temperature is higher. The machine head temperature is high, can make the material smoothly into the mold, but the shape of the extruded material is poor, the shrinkage increases. Head temperature is low, the material plastic bad, melt viscosity, nose pressure rise. Although this will make the product too dense, after the shrinkage rate is small,PPR Pipes the product shape stability is good, but the processing is more difficult, from the mold expansion larger, the product surface rough. But also lead to increased backpressure extruder, equipment load, power consumption also increases.

The temperature of the die set, the temperature of the die and the core mold have an effect on the surface finish of the pipe. In a certain range, the die mold and the core mold temperature are high and the surface finish of the pipe is high. Generally speaking,PPR Pipes the temperature of the die outlet should not exceed 220 degrees, the melt temperature of the inlet of the head is 200 degrees, and the temperature difference between the inlet and outlet of the machine head should not exceed 20 degrees. Because the higher temperature difference between the melt and the metal will cause the shark skin phenomenon. Excessive melt temperature leads to die. But the specific decision to the actual situation.

पिघला हुआ तापमान पेंच के अंत में मापा गया पिघल का वास्तविक तापमान होता है और इसलिए यह आश्रित चर होता है। मुख्य रूप से पेंच गति और बैरल सेटिंग तापमान पर निर्भर करता है। एक्सट्रूडेड पॉलीथीन पाइप के पिघले हुए तापमान की ऊपरी सीमा को आमतौर पर 230 डिग्री के रूप में परिभाषित किया जाता है। आमतौर पर लगभग 200 डिग्री पर नियंत्रित करना बेहतर होता है। पॉलीप्रोपाइलीन पाइप बाहर निकालना पिघल तापमान की सीमा आम तौर पर 240 डिग्री है। पिघला हुआ तापमान बहुत अधिक नहीं होना चाहिए। आम तौर पर सामग्री के पतन पर विचार करें, पीपीआर पाइप जबकि तापमान बहुत अधिक है, पाइप सामग्री को कठिन बना देगा।

3. Pressure control

The most important pressure parameter in the extrusion process is the melt pressure, that is, the head pressure, in general, increase the melt pressure, will reduce the output of the extruder, leaving the product density increased, is conducive to improving product quality. But the pressure is too large,PPR Pipes will bring security problems. Melt pressure and the size of raw materials, screw structure, screw speed, process temperature, the mesh mesh number, porous plate and other factors. The melt pressure is usually controlled between 10 and 30 MPa.

4. Vacuum setting

Vacuum stereotypes mainly control the vacuum and cooling speed of the two parameters. Usually in the appearance of the quality of the pipe to meet the premise, the vacuum should be as low as possible, so that the pipe stress is small, the product in the storage process deformation small.

5. cool down

ठंडा पानी के तापमान की आवश्यकताओं में पॉलीथीन पाइप बाहर निकालना मोल्डिंग आमतौर पर कम होता है, आमतौर पर 20 डिग्री से नीचे, पीपीआर पाइप के उत्पादन में, तापमान का पहला पैराग्राफ थोड़ा अधिक हो सकता है, निचले हिस्से का उत्तरार्द्ध, जिसके परिणामस्वरूप तापमान ढाल होता है। शीतलन जल प्रवाह को समायोजित करना भी महत्वपूर्ण है। प्रवाह बहुत बड़ा है, पाइप की सतह खुरदरी, जिसके परिणामस्वरूप स्पॉट गड्ढे हैं। प्रवाह बहुत छोटा है, पीपीआर पाइप की सतह को खींचना आसान बनाने के लिए उज्ज्वल धब्बे पैदा करता है, जैसे असमान वितरण, पाइप की दीवार की मोटाई असमान, या अंडाकार।

6. Screw speed and extrusion speed

Screw speed is to control the extrusion rate, yield and product quality of heavy industry parameters. The speed of the single screw extruder increases and the yield increases. The shear rate increases and the apparent viscosity of the melt decreases. Is conducive to the homogenization of materials. At the same time due to good plasticization, so that the interaction between the molecules increased mechanical strength. But the screw speed is too high, the motor load is too large, the melt pressure is too high, the shear rate is too high, from the mold Peng expansion, the surface deterioration, and the amount of instability.

7. कर्षण गति

Traction speed directly affects the product wall thickness, dimensional tolerance, performance and appearance, traction speed ratio to be stable, and the traction speed and pipe extrusion speed match. The ratio of the traction speed to the extrusion line velocity reflects the degree of orientation that the product may occur, which is called the draw ratio and must be equal to or greater than 1. The traction speed increases and the temperature of the cooling stereotypes is constant , Then the product in the sizing sleeve, cooling the water tank to stay in the time is relatively short, after the cooling of the finished product will also be more inside the residual heat, the heat will make the product in the process of pulling the orientation of the orientation structure has occurred ,PPR Pipes Resulting in a reduction in the degree of orientation of the article. The faster the traction speed, the thinner the wall thickness of the pipe, the greater the shrinkage of the finished product after cooling. The slower the traction speed, the thicker the pipe wall thickness, the more likely to lead to stowage between the die and the sizing sleeve. Destruction of normal extrusion production. Therefore, the extrusion process in the extrusion speed and traction speed must be well controlled.

8. On - line quality control and post - processing of pipe

Polyolefin- आधारित क्रिस्टलीय पॉलिमर, डाउन-लाइन टयूबिंग का प्रदर्शन वितरित होने पर पाइप उत्पाद के आकार और प्रदर्शन से अलग होता है। मुख्य कारण हैं, सबसे पहले, क्रिस्टलीकरण, क्रिस्टलीयता और क्रिस्टल के रूप और तापमान और थर्मल इतिहास, जगह के समय होने के लिए पॉलीओलफिन पिघलने की प्रक्रिया। दूसरा, बस पाइप का तापमान आमतौर पर कमरे के तापमान से अधिक होता है। तीसरा, पाइप में तनाव की विधानसभा रेखा से दूर। प्रदर्शन और आकार की स्थिरता को प्राप्त करने के लिए, पीपीआर पाइप्स को सामान्य पॉलीथीन पाइप को 24 घंटे के लिए विधानसभा लाइन से दूर रखा जाना चाहिए, पॉलीप्रोपाइलीन पाइप को प्रदर्शन परीक्षण के लिए संबंधित मानकों के अनुसार, 48 घंटे के बाद रखा जाना चाहिए।