Degradable plastics refer to a class of plastics whose various properties can meet the requirements of use, remain unchanged during the shelf life, and can be degraded into environmentally harmless substances under natural environment conditions after use. Therefore, it is also called environmentally degradable plastic.
There are a variety of new plastics: photodegradable plastics, biodegradable plastics, light/oxidative/biodegradable plastics, carbon dioxide-based biodegradable plastics, thermoplastic starch resin degradable plastics.
There are two main areas for the use of degradable plastics: one is the area where ordinary plastics were originally used. In these areas, the difficulty of collecting used or post-consumer plastic products will cause harm to the environment, such as agricultural mulch and single-use plastic packaging, and the second is areas where plastics are used instead of other materials. The use of degradable plastics in these areas can bring convenience, such as ball tacks for golf courses, and seedling fixing materials for tropical rainforest afforestation.
Specific applications are:
1.Agriculture, forestry and fishery, plastic film, water-retaining materials, seedling pots, seedbeds, rope nets, slow-release materials for pesticides and agricultural fertilizers.
2.Packaging industry, shopping bags, garbage bags, compost bags, disposable lunch boxes, instant noodle bowls, buffer packaging materials.
3.Sporting goods, golf tacks and tees
4.Hygiene products, women's hygiene products, baby diapers, medical mattresses, disposable haircuts.
5.Medical materials, bandages, clips, small sticks for cotton swabs, gloves, drug release materials, and surgical sutures and fracture fixation materials.
Nanjing Jieya also manufactures twin screw compounding extruder for bio-degradable material. We warmly welcome your inquiry.
A plastic extruder performs all of the following processes through a barrel with a screw and auger channel. The plastic pellets enter the barrel through a hopper at one finish of the barrel and are then transferred through the screw to the opposite finish of the barrel. What are the working principle and molding principles of a plastic extruder? The following is a detailed description.
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Pressure and shearing, etc., convert the solid plastic into a uniform and consistent melt and send the melt to the next process. The production of the melt involves processes such as mixing additives such as masterbatches, blending resins, and re-crushing. The finished melt must be homogeneous in consistency and temperature. The pressurization must be high enough to extrude the viscous polymer.
To have sufficient pressure, the depth of the threads on the screw decreases as the distance to the hopper increases. The external heating and the internal heat generated in the plastic and the screw due to friction softens and melts the plastic. The design requirements for plastic extruders often vary from polymer to polymer and from application to application. Many options involve discharge ports, multiple loading ports, special mixing devices along the screw, cooling and heating of the melt with or without an external heat source (adiabatic plastic extruders), the relative size of the gap variation between the screw and the barrel, and the number of screws. For example, twin-screw plastic extruders allow for more thorough mixing of the melt than single-screw plastic extruders. Tandem extrusion uses the melt-extruded from the first plastic extruder as feedstock for the second plastic extruder, which is typically used to produce extruded polyethylene foam.
D L the characteristic dimensions of plastic extruders are the diameter of the screw (D) and the ratio of the length of the screw (L) to the diameter D L/D (D) (L/D. Plastic extruders usually consist of at least three segments. The first section, near the L/D) filling hopper, is the filling section. Its function is to allow the material to enter the plastic extruder at a relatively smooth rate. In general, this section will be kept at a relatively low temperature to avoid clogging the charging channels. The second section is the compression section, where the melt is formed and the pressure is increased. The transition from the charging section to the compression section can be abrupt or gradual (gentle). The last half, the metering section, is adjacent to the plastic extruder outlet and its main operate is that the uniformity of the fabric flowing out of the plastic extruder. In this section, the material should have sufficient residence time to ensure uniformity of composition and temperature.
At the end of the barrel, the plastic melt leaves the plastic extruder through a head that is designed in an ideal shape for the extruded melt stream to pass through.
Another important part is the drive mechanism of the plastic extruder. It controls the rotational speed of the screw, which determines the output of the plastic extruder. The power required is determined by the viscosity (flow resistance) of the polymer. The viscosity of the polymer depends on the temperature and flow rate and decreases with increasing temperature and shear. Plastic extruders are equipped with screens that keep impurities out of the screen. To avoid downtime, the screens should be able to be changed automatically. This is especially important when processing resin with impurities, such as recycled material. The extruder's screw is divided into feeding section, plasticizing, melting section, temperature according to the process parameters of the plastic particles, the model according to the diameter of the screw 20, 36, 52, 65, 75, 95, 120, 135. Plastic particles heated by the movement of the screw to change the original state, there are many types, depending on the specific application. The capacity of the frequency conversion is proportional to the diameter of the screw and then adjusted according to the different raw materials.
The extrusion method of plastic extruders generally refers to the melting of plastic at a high temperature of about 200°C. The melted plastic is then passed through a die to form the desired shape. Extrusion molding requires a deep understanding of the characteristics of plastics and extensive experience in mold design and is a technically demanding molding method.
Extrusion molding is a method of a continuous flow of material through a die by heating and pressurizing in an extruder, also known as "extrusion molding". Compared with other molding methods, it has the advantages of high efficiency and low unit cost.
Extrusion is mainly used for molding thermoplastics, but it can also be used for some thermosets. Extruded products are continuous profiles, such as tubes, rods, wires, sheets, films, wire, and cable cladding, etc. In addition, it can also be used for mixing, plasticizing and granulating, coloring, blending, etc. plastics.
The extruded products can be called "profiles", which are also called "profiles" because of their irregular cross-sectional shape.
The twin screw extruder has the basic principles of single-screw extruder: solid conveying, melt pressurization and pumping, mixing and stripping and evaporation, but it is not limited to this. The development of twin screw extrusion theory is relatively late, coupled with its wide variety, messy screw shape, and messy extrusion process, which brings many difficulties to the research. And the following words will give you a brief introduction about the information of the twin screw extruder.
What is the future research direction of twin screw extruder?
What is the basic principle of a twin screw extruder?
What is the difference between a twin screw extruder and a traditional extruder?
1. Established the physical model and mathematical model of the twin screw extruder to guide the design of the twin screw extruder and the optimization of the extrusion process.
2. It is necessary to understand the relationship between the true state change, the mixing form, the whole process of the structure change and the later mixing and characteristics of two or more polymers and materials during the entire extrusion process.
3. As a twin screw extruder, it establishes the internal connection between the entire reaction process, speed and characteristics of the extrusion reaction molding and the screw structure and operating conditions. It can be extruded through reaction molding.
The twin screw extruder has the basic principles of single-screw extruder: solid conveying, melt pressurization and pumping, mixing and stripping and evaporation, but it is not limited to this. The development of twin screw extrusion theory is relatively late, coupled with its wide variety, messy screw shape, and messy extrusion process, which brings many difficulties to the research.
Generally speaking, the research of twin-screw extrusion theory is still in the development link, which is called "technology more than science". From the perspective of the entire extrusion process of a twin screw extruder, there are about three parts: the polymer's physical state change rule during the extrusion process, the basic principle of conveying, the conveying of solid melt, the exhaust phase and the law, and the establishment of mathematics The physical model is used to guide the planning of the twin screw extruder and the optimization of the extrusion system process.
The traditional extrusion molding process requires rotating a giant screw in the barrel. When using twin screw extrusion, the two screws mesh with each other and rotate together during the extrusion operation. They are installed in the housing on the spline shaft of the barrel. The twin screw extruder can simultaneously ensure food molding, heating, cooling, compression, mixing, pumping and even transportation.
At present, twin screw extruder has become the most common extruder with the largest variety and specifications in the world. Nanjing JlEYA has committed to fulfilling all the requirements of twin screw extruders. And it welcomes global customers to purchase.
The high efficiency of the single-screw extruderis mainly reflected in high output, low energy consumption, and low manufacturing cost. In terms of function, the plastic extruder has been used not only for extrusion molding and mixing processing of polymer materials but its use has been broadened to food, feed, electrode, building materials, packaging, ceramics, and other fields. So how to operate the single screw extruder? The following is a detailed introduction.
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Preparation work before starting the machine
1. For single-screw extruder extrusion production of materials, should meet the required drying requirements, if necessary, further drying.
2. According to the variety of products, size, select the head specifications, the machine will be installed in the order of the column, installed head flange, die body, mouth die, porous plate, and filter network.
3. Connect the compressed air pipe, install the core mold electric heating rod head heating ring, check the water system.
4. Adjust the gap evenly in all parts of the mouth die and check whether the centerline of the main machine and the auxiliary machine are aligned.
5. Start the single-screw extruder of each running equipment, check whether the operation is normal, and find faults in time to eliminate.
6. Turn on the electric heater, the head, body, and auxiliary machine evenly heated up, to be the temperature of each part than the normal production temperature of about 10 degrees, constant temperature of 30 ~ 60 minutes so that the machine temperature inside and outside the same.
Start-up is an important part of the production, poor control will damage the screw and head, the temperature is too high will cause plastic decomposition, the temperature is too low will damage the screw, barrel, and head. The start-up steps are as follows.
1. Start the machine at low speed, idle, check the screw for any abnormalities and motor, amperage meter current no overload phenomenon, the pressure gauge is normal. Machine idling should not be too long to prevent the screw and barrel-scraping grinding.
2. Gradually add a small amount of material, wait for the material extrusion out of the die, before the normal addition of material. Before the plastic is extruded, no one should be in front of the mouth die to prevent casualties.
3. After the plastic is extruded, it is necessary to lead the extruded material slowly on the cooling and shaping, traction equipment, and start this equipment beforehand. Then, according to the control instrument indication value and the requirements of the extruded products, each link will be properly adjusted until the extrusion operation reaches the normal state.
4. Cutting and sampling, checking whether the appearance meets the requirements, whether the size meets the standard, quickly testing the performance, and then adjusting the extrusion process according to the requirements of quality, so that the products meet the standard requirements.
1. Stop feeding, extrude the plastic in the single screw extruder and turn off the power of the barrel and head for the next operation.
2. Shut off the power of the main machine and the auxiliary machines at the same time.
3. Open the head connection flange, clean the porous plate and various parts of the head, when cleaning, should use copper rods, copper pieces, after cleaning, apply a little oil. Screw, barrel clean up, if necessary, the screw from the end of the machine out of the top, clean up after recovery, in general, available for the transition of material cleanup.
4. Extrusion of polyolefin plastics, usually in the extruder full load shutdown (with material shutdown), when the air should be prevented from entering the barrel, so as not to oxidize the material and affect the quality of the product when continuing production. For polyvinyl chloride plastics, can also stop with material, then close the material door, reduce the temperature at the head connection body (flange) 10 ~ 20 degrees, to stop the machine after the material squeeze net.
5. Close the total power and cooling water main valve.
If you still have questions, you can consult our company. Our company's website is https://www.njjyextrusion.com/
Material delivery method
In a single-screw extruder, there is friction drag in the solids conveying section and viscous drag in the melt conveying section. The friction properties of the solid material and the viscosity of the molten material determine the conveying behavior. If some materials have poor friction properties, if the feeding problem is not solved, it will be difficult to feed the materials into the single-screw extruder. In twin-screw extruders, especially intermeshing twin-screw extruders, the conveying of materials is to some extent forward displacement transmission, and the degree of forward displacement depends on the relationship between the flight of one screw and that of the other screw. the proximity of the relative screw grooves. The screw geometry of the closely intermeshing counter-rotating extruder results in a high degree of positive displacement delivery characteristics.
Material flow velocity field
At present, the flow velocity distribution of the material in the single-screw extruder has been described quite clearly, while the flow velocity distribution of the material in the twin-screw extruder is quite complicated and difficult to describe. Many researchers just do not consider the material flow in the meshing area to analyze the flow velocity field of the material, but these analysis results are very different from the actual situation. Because the mixing characteristics and overall behavior of a twin-screw extruder are primarily determined by the leakage flow that occurs in the intermeshing zone, the flow situation in the intermeshing zone is quite complex. The complex flow spectrum of the material in the twin-screw extruder shows macroscopic advantages that the single-screw extruder cannot match, such as sufficient mixing, good heat transfer, large melting capacity, strong exhaust capacity and good temperature control of the material, etc.
The development and application of twin screw extruders are increasingly eye-catching. Many aspects of the performance of single and twin screw extruders that dominate the extrusion industry can no longer meet the requirements of blending, filling, reinforcement, toughening and other modifications.
What is the structure of the twin screw extruder?
How does the twin screw extruder prevent material degradation?
What are the structural characteristics of the twin screw extruder?
The twin screw extruder, a unique modular screw block is designed on the screw shaft, which is broken three times within a pitch, called a mixing screw block. Corresponding to these gaps, there are three rows of mixing blocks arranged on the inner sleeve of the barrel. The pin and the screw reciprocate in the axial direction at the same time in the process of radial rotation. The twin screw extruder moves in the axial direction once every time it rotates. Due to this special movement mode and the effect of mixing and sorting screws and pins, the material is not only sheared between the mixing pins and the irregular trapezoidal mixing blocks. And it is transported back and forth. The countercurrent movement of the material adds a very useful axial mixing movement to the radial mixing. The melt is continuously cut, turned, kneaded and stretched, and the twin screw extruder regularly interrupts the simple Layered shear mixing.
Due to the simultaneous mixing in the radial and axial directions of the twin screw extruder, the mixing effect is enhanced and the best dispersion mixing and distributed mixing are ensured, so the homogenization time is short. In addition, the mutual engagement of the mixing pin and the screw block also improves the self-cleaning ability of the barrel. The twin screw extruder can ensure stable working pressure through proper screw block combination, without uncontrollable pressure and temperature fluctuations, and prevent material degradation in the barrel.
1. The main machine barrel and screw are assembled by building blocks
The barrel of the twin screw extruder is composed of multiple sets of open and closed barrels. The split barrel can be opened quickly and conveniently for easy cleaning and maintenance; the screw is composed of various mixing sleeves on the mandrel Composed of screw block and conveying screw block. The barrel and screw can be flexibly formed into an ideal form according to different types of materials and different technological requirements.
2. Unique design of gear box and swing box
The twin screw extruder realizes the axial reciprocating movement of the screw while rotating. Every time the screw rotates, it reciprocates once, and the thread is interrupted three times, thus producing a strong mixing effect. The mixing effect is in the axial direction rather than the radial direction, and occurs between the thread and the pin. All materials in the screw channel are subjected to uniform shear stress, instead of a thin layer of material being sheared.
Great products begin with the best engineering staff, and Nanjing JlEYA is ready to assist you with your technical requirements for twin screw extruder.
The single-screw extruder has a simple design and a low price, so it is widespread and demand on the market was high.
What are the application areas and benefits of single-screw extruders?
What is the development history of the single-screw extruder?
What are the main technical parameters of the single-screw extruder?
The single-screw extruder is mainly used for extruding soft and hard polyvinyl chloride, polyethylene, and other thermoplastic. It can process a variety of plastic products such as films, tubes, plates, tapes, etc., can also be used for granulation.
The single-screw extruder is characterized by advanced design, high quality, good plasticization, and low energy consumption. It uses an evolutionary drive that is characterized by low noise development, stable operation, high load capacity, and long service life.
The single-screw extruder is one of the most important devices for the processing of plastic molding parts. It uses external energy transfer and heat transfer of external heating elements to carry out the transport of plastics solids, compaction, melting, shielding, and extrusion forms.
Since the birth of the snail extruder, it has evolved from an ordinary snail extruder to a new type of snail extruder after almost a hundred years of development. Although there are many types of new single-screw extruders, the extrusion machine is the same.
The extrusion process of the traditional snail extruder is realized by heating outside the cylinder, solid and cylinder, snail friction, and melting shear force.
"friction coefficient" and "friction force", "viscosity" and "shear tension" are the main factors influencing the performance of conventional screw extruders. The extrusion process from the machine is unstable and difficult to control, especially for some heat-sensitive plastics with poor thermal stability and high viscosity.
1. Screw diameter: refers to the diameter of the outer circle of the screw, marked with D, and the unit is millimeter (mm).
2. Proportion of screw length to diameter: refers to the ratio of the length L of the working part of the screw (the length of the threaded part, i.e. the length from the center line of the feed opening to the end of the screw) and the screw diameter D, expressed by L/D.
3. Snail speed range: refers to the highest speed of the snail up to the lowest speed of the snail; n is used to represent the speed of the snail, and the unit is revolutions per minute (U/min).
4. The power of the main screw drive engine: expressed by P, the unit is kilowatt (kW).
5. Heating performance of the extruder cylinder: expressed by E is the unit kilowatt (kV).
6. The output capacity of the extruder: expressed by Q, the unit is kilogram per hour (kg/h).
7. The height of the extruder rim: refers to the distance from the center line of the screw to the ground, expressed by H, and the unit is millimeters (mm).
8. Extruder outer dimensions: refers to total length (x) total width (x) total height expressed by L x B x H, and the unit is millimeters or meters (m m or m)
9. Extruder quality: expressed in W, the unit is kilogram or tonne (kg or t).
We can see the huge role that single-screw extruders play in the production industry, and they have become indispensable components. And Nanjing JlEYA a Chinese pioneer in single-screw extruder production,has committed to providing the most suitable single-screw extruder at a reasonable price, and whatever it takes to satisfy the customer’s needs.
Each type of product in the plastic extruder line has its operating characteristics, and a detailed understanding of its operating characteristics is necessary to give full play to the effectiveness of the machine. The following is a detailed description of the operating procedures and maintenance methods for plastic extruders.
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The plastic extruder is one of the machine types, master the extruder operation points, the correct and reasonable use of a plastic extruder. The use of plastic screw extruder includes a series of links such as installation, adjustment, commissioning, operation, maintenance, and repair of the machine, and its use has the commonality of general machines, mainly in the drive motor and reduction and speed change device. However, the working system of the plastic screw extruder, the extrusion system, is unique, and special attention should be paid to its characteristics when using the plastic screw extruder. Extruder manuals generally have clear provisions for the installation, adjustment, and commissioning of the machine, here the main points of the operation, maintenance, and repair of the plastic screw extruder are briefly described as follows: in particular, to correctly grasp the structural characteristics of the screw, heating and cooling management instrumentation characteristics and assembly, the correct extrusion process conditions, the correct operation of the machine.
1.Pastic extruder equipment should be placed in a ventilated position to ensure that the heat of the motor work prolongs its life; the machine should be kept well grounded.
⒉Regularly check the tool screws, the plastic extruder after 1 hour of use, with tools to tighten the moving knife, fixed knife screws, to strengthen the fixed between the blade and the knife frame; should be regularly filled with lubricating oil to ensure the lubrication between the bearings; to ensure the sharpness of the cutting edge of the tool, should always check the tool to ensure its sharpness, to reduce unnecessary damage to other parts caused by the blunt lack of the blade; regularly check whether the belt is loose, and timely tightening.
3. Restart - Before starting the plastic extruder for the second time, the remaining debris in the machine chamber should be cleared to reduce the starting resistance. Periodically open the inertia cover and pulley cover to clear the ash outlet under the flange, which can cause the powder to enter the shaft bearing.
4. Replacement parts - When replacing knives, the clearance between the moving and fixed knives should be 0.8 MM for crushers over 20 HP and 0.5 MM for crushers under 20 HP. The thinner the recycled material is, the gap can be adjusted appropriately larger.
If you need to know more, you can consult our company. The company focused on co-rotating twin-screw compounding extruders with the core of the various R&D and manufacturing, such as a twin-screw extruder, mini twin screw extruder, plastic extruder, parallel twin-screw extruder, and so on, the application covers compounding mixing modified granulation, polymerization, devolatilization, step molding, renewable recycling, and other fields.