Barrier Screws
Barrier screws play an important role in blown film extrusion. These screws are specially designed for barrier film so that the polymer can be properly melted and mixed. Let’s break down their design, purpose, and how they improve efficiency and safety.
Design of Barrier Screws
The design of the barrier screw is quite different from a normal single-flight screw because it has an extra “barrier flight” that keeps the melted material and the unmelted material separate. This solves many problems in the film, such as the problem of gels and unmelted particles.
1. Main Flight and Barrier Flight:
- There are two flights in the barrier screw; one is called the main flight, and the other is called the barrier flight.
- Both flights have different functions. When solid material is filled in the feed zone, the main flight pushes the solid polymer forward.
- Along with this, there is a barrier flight that separates the melted (melted polymer) and unmelted (solid) material.
2. Melt Channel and Solid Channel:
There are two channels in the barrier screw:
a) Solid Channel: In this type of channel, solid polymers (plastic granules) move.
b) Melt Channel: In this type of channel, when the material is completely melted, the polymer flows.
The barrier flight keeps these two channels separate so that the solids and melts do not mix.
Purpose of barrier screw in blown film extrusion
The main purpose of the barrier screw is that the material melts completely inside the barrel so that there is no troubleshooting when the final product is obtained. Because uneven melting is a big issue in blown film extrusion, such as gel formation, thickness variations, and many other types of problems can be created.
Some useful points of Barrier screw
- Uniform Melting: It ensures that the polymer is not overheated or underheated, so that the strength and clarity of the film are better.
- Better Mixing: A homogeneous blend of material is formed, which reduces defects.
- Higher Output: Barrier screws can process more material, which increases the production speed.
- Energy Efficiency: It consumes less energy because the material is melted properly.
- Less wear & tear: They are more durable than traditional screws.
Grooved Barrel.
- The design of the barrel is very important in the blown film extrusion process because the polymer is melted here and pressure buildup and flow are controlled. A grooved barrel is a specialized barrel design that helps in improving the efficiency, throughput, and stability of the extrusion system.
- It is specially used for HDPE (High-Density Polyethylene) and high-viscosity polymers like nylon because material feeding is a bit difficult in these.
- Let’s know in detail about the design, purpose, and how it improves efficiency and safety of the grooved barrel.
Design Of Grooved Barrel
- Normal barrels have a smooth surface design, but in grooved barrels, grooves or rigid designs are made on the surface so that when the material is fed into the feed zone, friction is easily generated between the surface and the material.
- This is done because when any material is fed into the feed zone, it starts slipping, due to which the material is unable to move forward and keeps moving at the same place. Because of this, the feed rate or specific output of the machine increases or decreases, which may cause unwanted wastage or quality-related problems.
- These grooves can be in an axial or helical pattern.
Applications of Grooved Barrel
- Better Material Feeding: Normal barrels have a higher chance of polymer slipping, which can make feeding inefficient. But this problem can be solved with the help of grooved barrels.
- Higher Pressure Build-up: It helps in generating more pressure, which ensures better melting and mixing.
- Increased Throughput: 20–40% more material can be processed as compared to normal barrels. Because there is no problem of material slip in it.
- More Stability: Uniform pressure and better grip keep the extrusion process stable, which also affects the film quality.
Note:
- Do you want to read more about Extrusion Zone?
- Do you want to more about screw and barrel?
Conclusion
- In the blown film extrusion process, both barrier screws and grooved barrels are designed to improve efficiency, throughput, and film quality.
- These components optimize melting, mixing, and pressure control, which confirms the strength, transparency, and uniform thickness of the final film.
- If high-quality blown film production is required, then the combination of barrier screw and grooved barrel can be best. This can take production efficiency, film consistency, and extrusion process stability to the next level.
- The right screw & barrel selection can maximize the performance of the extrusion system.
But the choice is yours; you should work keeping your budget in mind.
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