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EXTRUSION DES THERMOPLASTIQUES
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EXTRUSION DES THERMOPLASTIQUES

Introduction to Plastic Extrusion

In this module, we will study the technique of plastic extrusion for thermoplastic materials. The main techniques include inflation extrusion and flat die extrusion. This branch of the plastics industry consists of 150 companies employing 7,000 people and processing 300,000 tons of material annually.

Types of Extrusion Techniques

  • Inflation extrusion
  • Flat die extrusion
  • Tube extrusion
  • Profile extrusion

Applications in Various Industries

  • Building sector: PVC pipes, flexible hoses, polyamide fittings
  • Automotive sector: flexible conduits for electrical wiring
  • Irrigation sector: polyethylene pipes for water supply
  • Construction sector: barriers, windows, wall coverings, roller shutters
  • Electrical sector: cable trays, plinths

Overview of Extrusion Process

Extrusion is a continuous process used to manufacture tubes and profiles with varying geometries and lengths. Objects can be classified as rods, tubes, single-wall profiles, or cellular profiles. They can be made from one or multiple thermoplastic materials.

Examples of Special Cases in Extrusion

  • Annular tubes
  • Pressure-resistant reinforced hoses
  • Multilayer fuel tubes composed of different materials
  • Coextruded profiles with different colors or hardness levels

Comparison with Other Transformation Processes

Extrusion is a continuous transformation process compared to other discontinuous processes like injection molding. To understand the concept better, examples are given using familiar objects such as toothpaste tubes and pastry bags.

Principle of Plastic Extrusion

Thermoplastic materials are typically in the form of pellets. When heated, they become malleable and can be extruded. The extrusion process involves feeding pellets into an extruder, melting them, and then shaping the material through a die.

General Process of Extrusion

The extrusion process consists of an extruder that melts the plastic pellets, a hot cylinder to soften the material, and an extrusion head that shapes the product.

  • Granules are fed into the extruder
  • The material is melted and compressed
  • It flows through the die to form the desired shape

Main Functions of the Installation

This section discusses the main functions of the installation, including plasticization, extrusion, shaping, cooling, drawing, and cutting.

Components of the Extrusion Line

  • The extrusion line consists of seven essential elements: extruder, extrusion head, shaper, cooling tank, air cooling tunnel, drawing device, and cutting device.

The Extruder

  • The extruder is a common element in all extrusion lines and performs two essential functions: plasticizing the polymer and feeding it to the extrusion head.
  • An example of an extruder is equipped with a 25mm diameter screw and includes a hopper, a cylinder maintained at temperature using heating collars and a fan.
  • It also has a three-zone screw design with a feeding chute and grids at the end. Different types of extruders are used in plastic workshops.

The Extrusion Head

  • The extrusion head shapes the polymer into a tube by using components such as punch holder, puncher, body, die holder ring, and heating collars.

Conformation Function

  • After shaping by the extrusion head, the malleable tube needs to be cooled to maintain its final shape. This is achieved through conformation function which includes vacuum tank and calibration ring.
  • Applying vacuum above water creates depression on the tube's periphery that presses it against the conformator's wall. Atmospheric pressure causes inflation and calibration according to desired dimensions. In some cases where materials tend to stick to conformator walls, water film is used for calibration instead.

Cooling Function

  • Tube cooling is accomplished by passing it through a cooling tank filled with cold water and an air-cooled tunnel.

Drawing and Cutting

  • The extrusion line includes a caterpillar drawing device that pulls the rigid tube at a constant linear speed through different stations. For flexible tubes, a belt drawing device is used to limit deformation.
  • At the end of the line, the rigid tube is cut to the desired length using a circular saw or can be wound into coils using a specific winding system.

Examples of Extrusion Lines

This section provides two examples of extrusion lines for different applications.

Example 1: PVC Sleeve Extrusion

  • A PVC sleeve with a diameter of 250mm is extruded at a linear speed of 1.6 meters per minute, with an extruder output of 400 kg per hour.

Example 2: Multilayer Coextrusion Line

  • A coextrusion line produces multilayer tubes with a length of 15 meters and an outer diameter of 8mm at a linear speed of 15 meters per minute. The extruder output for this line is 25 kg per hour.

Extrusion Lines for Profiles

This section introduces extrusion lines specifically designed for continuous production of profiles, including monolayer and cellular profiles.

Similarities to Tube Extrusion Lines

  • Extrusion lines for profiles share similarities with tube extrusion lines since tubes can be considered as special types of profiles.

Example: PVC Window Profile Extrusion Line

  • The head of the PVC window profile extrusion line consists of three vacuum conformators and a cooling tank where the profile is maintained in its final shape. A caterpillar drawing device is used to pull the profile along the line.

Demonstration of Profile Extrusion

  • The demonstration showcases a PVC profile extrusion head, including components such as body and feeding plate.

Conclusion

Extrusion lines are versatile systems used for various applications, including tube and profile production. These lines consist of several essential components that perform functions such as plasticization, shaping, cooling, drawing, and cutting. Examples of different extrusion lines were provided to illustrate their capabilities in producing various products.

Extrusion Process

This section explains the extrusion process and the use of a vacuum to shape and cool the profiles.

Vacuum Shaping and Cooling

  • The extruded profile is shaped and cooled using a vacuum in a dry shaping machine.
  • The profile is brought into its final form while being cooled by cold water.
  • Different examples of extrusion heads are shown, including ones for complex cellular shapes and single-wall profiles.
  • Suction grooves inside the shaping machine apply pressure to shape the profile.
  • In rigid profiles, the upper pads of the caterpillar are adapted to match the product's geometry.

Automated Operations in Extrusion

This section discusses automated operations in extrusion lines, such as dimensional control and loop regulation.

Automated Operations

  • Apart from automated feeding, there are devices that ensure dimensional control and closed-loop regulation of the production line.
  • Ultrasonic or laser-based devices measure thickness or diameter of tubes for quality control.
  • Hot air torches can be used to achieve linearity in coextruded profiles like pool cover profiles.
  • Inkjet marking is used on extrusion lines, with some inks visible only under ultraviolet light.
  • Hot stamping is another automated decoration operation for certain profiles.
  • Plastic film can be used for protection, known as "plaque sage" when applied to extruded profiles.
  • Automatic assembly of seals, punching of roller shutter blades, and length measurement with a saw are other automated operations.

Assembly Processes

This section focuses on assembly processes involving tubes and profiles for various finished products.

Examples of Assembly Processes

  • A chemical industry pipeline is made from an extruded tube reinforced with fiberglass and polyester resin.
  • Medical equipment is assembled using extruded tubes and injected and blown parts in a cleanroom environment.
  • A PVC gate is made from rigid profiles, and roller shutter blades are automatically assembled.
  • Quality, partnership, rigor, adherence to customer specifications, and meeting deadlines are fundamental values in the plastics industry.

Quality Control

This section highlights the importance of quality control throughout the entire product lifecycle.

Importance of Quality Control

  • Total quality management is essential from product design to delivery and customer use.
  • Plastics manufacturers have established industrial organizations based on these values.
  • Quality control laboratories ensure material reception, dimensional control of semi-finished products, and approval of finished products made from assembled profiles.

Roles in Extrusion Process

This section describes the roles of different professionals involved in the extrusion process.

Roles in Extrusion Process

  • Engineers and technicians in design offices develop extruded profiles based on customer specifications.
  • Filieres design and manufacture extrusion heads and shaping machines.
  • Regulators start up and adjust the production line, while operators operate the line, perform self-inspections, assemble products, and package them.

Preparation of PVC Compounds

This section explains the preparation methods for PVC compounds used in extrusion.

Preparation Methods for PVC Compounds

  • Composters specialize in preparing powder or granules by mixing various components.
  • Two examples of PVC compounds are discussed - rigid PVC and flexible PVC - along with their composition involving additives like colorants and stabilizers.

New Section

This section provides an overview of a 25-meter high mixing tower used for the preparation of rigid and flexible PVC compounds.

Synoptic Analysis of the Mixing Tower (0:30:13 - 0:30:38)

  • The first phase of the process involves loading and weighing different components.
  • The second phase includes mixing the components in a rapid mixer, followed by cooling to form a powdery mixture called "prémics."

Components on the Second Floor (0:30:55 - 0:31:06)

  • On the second floor of the installation, there is an internal mixer and a cooler.

Final Phase of the Process (0:31:06 - 0:31:19)

  • In the final phase, there are two cases:
  • Case 1 involves packaging prémics as sifted powder in specific containers.
  • Case 2 involves extruding prémics into granules using a specialized extruder with a granulation head.

Packaging Powdered PVC (0:31:19 - 0:31:31)

  • The powdered PVC is packaged in specific containers.

Extrusion of Prémics into Granules (0:31:31 - 0:31.54)

  • Prémics is extruded into granules using a specific extruder equipped with a granulation head.

New Section

This section discusses how formulators collaborate closely with clients to adapt compound compositions according to product specifications for extruded products.

Collaboration with Clients (0.31.54 - 0.32.09)

  • Formulators work closely with clients to meet a wide range of product and market requirements while ensuring quality objectives.
  • Internal quality control laboratories are established to qualify and approve products through physical, thermal, and mechanical tests.

Evaluation in Quality Control Laboratories (0:32:09 - 0:32:49)

  • Quality control laboratories evaluate various aspects, including:
  • Rheological behavior of mixtures.
  • Colorability and color consistency.
  • Transformation of plasticized PVC on laboratory extruders to detect the presence of gel.

New Section

This section highlights the importance of evaluating the rheological behavior, colorability, and presence of gel in PVC compounds.

Rheological Behavior and Color Consistency (0:32:49 - 0:32:59)

  • The rheological behavior and color consistency of mixtures are evaluated in quality control laboratories.

Presence of Gel in PVC Compounds (0:32.59 - end)

  • Laboratory extruders are used to identify the presence of gel in plasticized PVC mixtures.

The transcript provided does not include a clear conclusion or additional sections.