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PPR Pipes Increased Mechanical Strength To Improve Production

2018-11-15

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

Управляющие параметры процесса экструзии включают температуру формования, рабочее давление экструдера, скорость шнека, скорость экструзии и скорость тяги, скорость подачи, охлаждение и так далее.

1. Предварительная обработка сырья

Полиолефин является неабсорбирующим материалом, обычно с очень низким содержанием влаги, может удовлетворить потребности экструзии, но когда полиолефин содержит абсорбирующие пигменты, такие как технический углерод, чувствителен к влажности. Кроме того, при использовании материалов и наполнителей содержание воды будет увеличиваться. Влага не только приводит к тому, что внутренняя и внешняя части трубы становятся шероховатыми, но также может вызвать образование пузырьков в расплаве. Часто сырье следует предварительно обработать. Общее использование сушки, также может быть добавлено с соответствующей функцией осушения добавок. Такие как пеногасители. Температура сухого полиэтилена обычно составляет 60-90 градусов. При этой температуре PPR Pipes можно увеличить выход на 10-25%.

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.

Распределение температуры в цилиндре от зоны подачи к фильере может быть плоским, постепенным, уменьшающимся и смешанным В основном зависит от материальной точки и структуры экструдера.

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.

Температура набора матрицы, температура матрицы и формы сердечника влияют на качество поверхности трубы. В определенном диапазоне температура формы для литья под давлением и температура ядра для формы высоки, а чистота поверхности трубы высокая. Вообще говоря, в PPR Pipes температура выходного отверстия головки не должна превышать 220 градусов, температура расплава на входе головки составляет 200 градусов, а разница температур между входом и выходом головки машины не должна превышать 20 градусов. Потому что более высокая разница температур между расплавом и металлом вызовет явление кожи акулы. Чрезмерная температура расплава приводит к смерти. Но конкретное решение для реальной ситуации.

Температура расплава - это фактическая температура расплава, измеренная на конце шнека и, следовательно, зависимая переменная В основном зависит от скорости шнека и температуры установки ствола. Верхний предел температуры расплава экструдированной полиэтиленовой трубы обычно определяется как 230 градусов. Обычно лучше контролировать около 200 градусов. Ограничение температуры расплава полипропиленовой трубы обычно составляет 240 градусов. Температура расплава не должна быть слишком высокой. Как правило, учитывают ухудшение качества материалов, трубы PPR при слишком высокой температуре затруднят материал труб.

3. Контроль давления

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

Экструзионное формование полиэтиленовых труб в требованиях к температуре охлаждающей воды, как правило, низкое, обычно ниже 20 градусов, при производстве труб из PPR первый абзац температуры может быть несколько выше, последний - при более низком, что приводит к градиенту температуры. Также важно отрегулировать поток охлаждающей воды. Поток слишком велик, поверхность трубы неровная, что приводит к точечным ямам. Поток слишком мал, PPR Пропускает трубу по поверхности трубы для создания ярких пятен, которые легко отрывать, таких как неравномерное распределение, неравномерная толщина стенки трубы или овал.

6. Скорость шнека и экструзии

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. Traction speed

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. Он-лайн контроль качества и последующая обработка труб

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.