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PPR σωλήνες αυξημένη μηχανική αντοχή για τη βελτίωση της παραγωγής

2018-11-15

Πρώτον, οι βασικές αρχές της πλαστικής εξώθησης

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

Οι παράμετροι ελέγχου της διεργασίας εξώθησης περιλαμβάνουν τη θερμοκρασία χύτευσης, την πίεση εργασίας του εξωθητήρα, την ταχύτητα του κοχλία, την ταχύτητα εξώθησης και την ταχύτητα έλξης, την ταχύτητα τροφοδοσίας, την ψύξη και ούτω καθεξής.

1. Προκατεργασία πρώτων υλών

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. Έλεγχος θερμοκρασίας

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.

Η θερμοκρασία του σετ μήτρας, η θερμοκρασία της μήτρας και η μήτρα πυρήνα έχουν επίδραση στο φινίρισμα επιφάνειας του σωλήνα. Σε ένα ορισμένο εύρος, η μήτρα μήτρας και η θερμοκρασία του καλουπιού πυρήνα είναι υψηλές και το φινίρισμα επιφάνειας του σωλήνα είναι υψηλό. Σε γενικές γραμμές, οι σωλήνες PPR δεν πρέπει να υπερβαίνουν τις 220 μοίρες, η θερμοκρασία τήξης της εισόδου της κεφαλής είναι 200 ​​μοίρες και η διαφορά θερμοκρασίας μεταξύ της εισόδου και εξόδου της κεφαλής της μηχανής δεν πρέπει να υπερβαίνει τους 20 βαθμούς. Επειδή η υψηλότερη διαφορά θερμοκρασίας μεταξύ του τήγματος και του μετάλλου θα προκαλέσει το φαινόμενο του δέρματος του καρχαρία. Η υπερβολική θερμοκρασία τήξης οδηγεί στο θάνατο. Αλλά η συγκεκριμένη απόφαση για την πραγματική κατάσταση.

Η θερμοκρασία τήγματος είναι η πραγματική θερμοκρασία του τήγματος που μετράται στο τέλος της βίδας και ως εκ τούτου είναι η εξαρτημένη μεταβλητή. Εξαρτάται κυρίως από την ταχύτητα του κοχλία και τη θερμοκρασία ρύθμισης του βαρελιού. Το ανώτερο όριο της θερμοκρασίας τήγματος του εξωθημένου σωλήνα πολυαιθυλενίου ορίζεται γενικά ως 230 μοίρες. Γενικά ελεγχόμενη σε περίπου 200 μοίρες είναι καλύτερη. Το όριο θερμοκρασίας τήγματος τήγματος εξώθησης πολυπροπυλενίου είναι γενικά 240 μοίρες. Η θερμοκρασία τήξης δεν πρέπει να είναι πολύ υψηλή. Γενικά θεωρήστε την υποβάθμιση των υλικών, οι σωλήνες PPR ενώ η θερμοκρασία είναι πολύ υψηλή θα κάνει το υλικό των σωλήνων δύσκολο.

3. Έλεγχος πίεσης

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

Polyethylene pipe extrusion molding in the cooling water temperature requirements are generally low, usually below 20 degrees, in the production of PPR pipe, the first paragraph of the temperature can be slightly higher, the latter part of the lower, resulting in a temperature gradient. It is also important to adjust the cooling water flow. Flow is too large, the pipe surface rough, resulting in spot pits. Flow is too small,PPR Pipes the surface of the pipe to produce bright spots easy to pull off, such as uneven distribution, pipe wall thickness uneven, or oval.

6. Ταχύτητα βιδώματος και ταχύτητα εξώθησης

Η ταχύτητα του κοχλία είναι ο έλεγχος του ρυθμού διέλασης, της απόδοσης και της ποιότητας των παραμέτρων της βαριάς βιομηχανίας. Η ταχύτητα του εξωθητήρα μονής βίδας αυξάνεται και η απόδοση αυξάνεται. Η ταχύτητα διάτμησης αυξάνει και το φαινόμενο ιξώδες του τήγματος μειώνεται. Συμβάλλει στην ομογενοποίηση των υλικών. Την ίδια στιγμή, λόγω της καλής πλαστικοποίησης, έτσι ώστε η αλληλεπίδραση μεταξύ των μορίων να αυξηθεί η μηχανική αντοχή. Αλλά η ταχύτητα του κοχλία είναι πολύ υψηλή, το φορτίο του κινητήρα είναι πολύ μεγάλο, η πίεση τήξης είναι πολύ υψηλή, ο ρυθμός διάτμησης είναι πολύ υψηλός, από την επέκταση του Peng της μούχλας, την επιδείνωση της επιφάνειας και την αστάθεια.

7. Ταχύτητα έλξης

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-based crystalline polymers, the performance of the down-line tubing is different from the size and performance of the pipe product when it is delivered. The main reasons are, first, polyolefin melt cooling process to occur crystallization, crystallinity and crystal form and temperature and thermal history, the time to place. Second, just off the pipe temperature is usually higher than room temperature. Third, just off the assembly line of stress in the pipe. In order to achieve the stability of the performance and size,PPR Pipes the general polyethylene pipe should be placed off the assembly line for 24 hours, the polypropylene pipe to be placed after 48 hours, according to the corresponding standards for performance testing.