What Is Pom Extrusion Pelletizing Line

A Polyoxymethylene (POM) extrusion pelletizing line is designed for the production of POM plastic pellets. These pellets are used in various applications due to POM’s excellent mechanical properties, chemical resistance, and dimensional stability. The process involves melting the raw POM resin, extruding it through a die, and then cutting the extrudate into pellets.

In this guide, GRANUWEL EXTRUSION will provide you with a comprehensive understanding of POM and the role of the POM extrusion pelletizing line in pom pelletizing process.

What is POM Matertial?

POM Material, also known as Polyoxymethylene, is a highly crystalline thermoplastic polymer commonly referred to as acetal, polyacetal, or polyformaldehyde.

Hermann Staudinger discovered Polyoxymethylene (POM) in the 1920s during his research on macromolecules. In 1952, DuPont successfully synthesized the material, and a patent for it was filed four years later.

POM is known for its high mechanical strength, rigidity and hardness, and excellent wear resistance over a wide range of temperatures.

POM is widely used in precision parts requiring high stiffness, low friction, and excellent dimensional stability.

Besides, POM hardly absorbs water, which makes it an ideal material to be used in contact with foods. Many types also conform to German Federal Institute for Risk Assessment (BfR) standards and FDA standards.

At room temperature, POM exhibits a distinct elastic limit with an elongation of 8%.

Below this elastic limit, POM demonstrates excellent resilience even under repeated stress, making it particularly suitable for spring elements. Its high stress rupture strength and low tendency to creep add to its advantages.

Under −50 °C to 120 °C, POM has higher rigidity and hardness than other thermoplastics thanks to its high crystallinity.

The mechanical properties of POM, combined with its good frictional and wear behavior, make it ideal for a wide range of technical applications in the processing industry.

What is POM Pellet? How POM Pellets are Made?

POM pellets are small, granulated forms of polyoxymethylene (POM) plastic, also known as acetal. These pellets are the raw material used in various manufacturing processes to produce plastic parts and products. 

POM Physical Modified Granulation

What is the difference between Pelletizing and Granulation?

Pelletizing refers to the choice of cutting method in a twin-screw equipment. POM (Polyoxymethylene) is a highly crystalline engineering plastic with a high viscosity that does not easily absorb moisture. It usually adopts a water-cooled strand pelletizing method. Granulation refers to the process of creating granules. POM is blended with other materials to compensate for its deficiencies in certain properties.

a. Toughening Modification

The primary method for toughening modification is blending. There are generally two approaches: one involves adding elastomers, such as BR, SBR, TPUR (thermoplastic polyurethane rubber), or acrylate elastomers, to enhance the toughness and impact strength of POM. The other approach uses non-elastic materials, mixing POM with substances like nylon or copolyamide, which have excellent comprehensive properties, or with rigid materials.

b. Enhanced Filling Modification

To achieve cost-effectiveness and noticeable performance improvements in plastic products, enhanced filling modification is employed. This typically involves adding inorganic materials, such as glass beads, talcum powder, mica, calcium carbonate, glass fiber, potassium titanate, and carbon fiber, to the resin. These additives improve the polymer’s strength, rigidity, and thermal deformation temperature while reducing costs.

c. Conductive Modification

Adding conductive carbon black is a common method for making conductive POM (Polyoxymethylene):

The addition of conductive carbon black generally ranges from 0.5% to 20%. However, using only carbon black can lead to a decrease in the thermal stability of POM. To reduce the amount of carbon black used, a method combining conductive carbon black with hydrophilic polymer compounds (such as PEG) is adopted, or a method involving the addition of thermal stabilizers primarily composed of formaldehyde scavengers is used to improve the thermal stability of the system.

In comparison, the use of carbon fibers not only significantly enhances various properties of POM, including self-lubrication, but also achieves good antistatic properties. For example, when 20% of carbon fibers with good conductivity are added, both the surface resistivity and volume resistivity of POM can reach the order of 1×10^2.

d. Other Modifications

Other modifications focus on enhancing the wear resistance, flame retardancy, and weather resistance of POM.

For example, flame-retardant POM masterbatch can be prepared by incorporating flame retardants like melamine, ammonium polyphosphate, and pentaerythritol diphosphate. Additionally, POM’s friction coefficient can be modified in various ways to develop self-lubricating composites.

POM Pellets Production Process

The process of pelletizing POM (Polyoxymethylene) involves several critical steps, each designed to transform raw materials into high-quality pellets. Here’s a detailed look at how a POM pelletizing line works:

1. Raw Material Preparation

The process begins with the preparation of raw materials. The primary raw material is formaldehyde or trioxane, which are carefully measured and mixed with any required additives such as stabilizers, lubricants, and colorants.

2. Polymerization

In this step, formaldehyde or trioxane undergoes polymerization. This chemical reaction is typically catalyzed by an acid to form long chains of POM. The polymerization reactor is the primary piece of equipment here, ensuring the correct chemical transformation.

3. Stabilization

Once the polymer chains are formed, they need to be stabilized to prevent degradation during processing and in end-use applications. Antioxidants and other stabilizers are mixed into the polymer melt to achieve this.

The following production processes are realized through one production line

4. Extrusion

The stabilized polymer melt is then fed into an extruder. The extruder is a machine that heats the polymer to a precise temperature, allowing it to flow smoothly through the system. Inside the extruder, the polymer is pushed through a die, which shapes it into long, thin strands.

5. Cooling

After extrusion, the hot polymer strands need to be cooled down. They are typically passed through a water bath or air cooling system, which solidifies the strands while maintaining their shape.

6. Pelletizing

The cooled strands are then fed into a pelletizer. This machine cuts the strands into uniform pellets, usually a few millimeters in length. The cutting mechanism can be either a rotating knife or a fixed blade system.

7. Drying

To remove any residual moisture from the pellets, they are passed through a drying system. This step ensures that the pellets are completely dry, which is essential for their performance in further processing and applications.

8. Screening and Quality Control

The dried pellets are then screened to remove any oversized or undersized pieces, ensuring uniformity. Quality control checks are performed to verify the chemical composition, physical properties, and appearance of the pellets.

Application Of POM pellets?

POM possesses metal-like hardness, strength, and stiffness, and maintains excellent self-lubrication, good fatigue resistance, and elasticity across a wide range of temperatures and humidity levels. Additionally, it exhibits strong chemical resistance. POM is replacing metals in many traditional markets, such as zinc, brass, aluminum, and steel, at a lower cost than many other engineering plastics. Since its introduction, POM has been widely used in electronics and electrical appliances, machinery, instrumentation, daily light industry, automotive, construction materials, agriculture, and other fields. It also shows promising growth in many new applications, such as medical technology and sports equipment.

1. Automotive Industry

Gears and Bearings: POM is used to manufacture gears, bearings, and bushings due to its durability and low friction.

Fuel System Components: It is used in fuel pump components and valve housings because of its resistance to fuels and chemicals.

Interior and Exterior Trim: POM is employed in clips, fasteners, and other small parts due to its strength and ease of molding.

2. Consumer Goods

Household Appliances: POM is used in components of kitchen appliances, such as coffee machines and washing machines, because of its resistance to wear and chemicals.

Zippers and Fasteners: Its low friction and high strength make it ideal for zippers, buttons, and fasteners.

Toys: POM is used in durable and low-wear toy components.

3. Industrial Applications

Conveyor Belts: POM is used in conveyor belt components due to its low friction and wear resistance.

Machine Parts: It is used in manufacturing precision parts for machines and equipment.

Electrical and Electronics: POM is used in insulators, connectors, and switches due to its excellent electrical insulating properties.

4. Medical Devices

Surgical Instruments: POM’s strength and biocompatibility make it suitable for surgical instruments and diagnostic devices.

Dental Tools: It is used in dental tools and orthodontic components.

5. Textile Industry

Textile Machinery: POM is used in parts of textile machinery, such as rollers and gears, due to its high wear resistance and low friction.

6. Construction

Window and Door Components: POM is used in window and door hardware for its durability and ease of machining.

Plumbing Fittings: Its chemical resistance makes it suitable for various plumbing applications.

7. Sporting Goods

Sports Equipment: POM is used in components of sports equipment, such as skateboards, inline skates, and bicycles, due to its strength and low friction.

POM pellets are versatile and are utilized across a wide range of industries due to their excellent mechanical properties, chemical resistance, and ease of processing. They are particularly valuable in applications requiring precision, durability, and low friction.

Is POM plastic safe?

Polyoxymethylene (POM) plastic is generally considered safe for a variety of applications, but its safety depends on the specific use and context. Here are some key points regarding the safety of POM plastic:

1. Chemical Safety

Resistance to Chemicals: POM is resistant to many chemicals, solvents, and fuels, which helps it maintain its integrity in various environments.

Non-Toxic: In its solid form, POM is non-toxic and is often used in applications that require contact with food and water.

2. Food Safety

Food-Grade Approval: POM can be formulated to meet FDA standards for food contact materials, making it safe for use in food processing equipment, kitchen utensils, and packaging.

3. Thermal Stability

Heat Resistance: POM has good thermal stability at moderate temperatures, which helps prevent degradation and the release of harmful substances under normal usage conditions.

4. Mechanical Safety

Durability and Strength: Its high mechanical strength and durability make it a reliable choice for precision parts, reducing the risk of breakage and associated hazards.

5. Potential Risks

Decomposition: At high temperatures, POM can decompose and release formaldehyde gas, which is toxic. Proper processing and handling are essential to minimize this risk.

Flammability: POM is flammable, so it should be used with caution in environments where it might be exposed to high heat or open flames.

6. Environmental and Health Considerations

Biodegradability: POM is not biodegradable, so proper disposal and recycling are important to minimize environmental impact.

Manufacturing Safety: During manufacturing, adequate ventilation and safety measures should be in place to handle any potential emissions.

POM plastic is safe for many applications, especially when used as intended and within recommended temperature ranges. It is widely used in automotive, consumer goods, medical devices, and food industry applications. However, handling and processing should be done carefully to avoid the risks associated with high-temperature decomposition and flammability.