Basic Analysis of Pultrusion Process

 

1. Pultrusion

Pultrusion is a continuous process for making scraps with a constant cross-section. Combining the words “pulling” and “squeezing”, pultrusion stretches the material as opposed to extrusion, which pushes the material.

 

2. Pultrusion Processing

In the standard pultrusion process, reinforcement materials (such as fibers or woven or braided strands) are impregnated with resin, then coupled with a separate preform system, and then pulled through a heated fixed die to polymerize the resin.

 

Impregnation can be accomplished by pulling the reinforcement through a bath or by injecting the resin into an injection cavity that is usually connected to the die. A variety of resin types can be used for pultrusion, including polyester, polyurethane, vinyl ester, and epoxy resins.

 

The resin provides resistance to the environment (i.e., corrosion resistance, UV resistance, impact resistance, etc.), while the glass provides strength in addition to fire safety.

 

 

Veils can also be added to prevent erosion or “fiber blooming” and provide corrosion and UV resistance.

 

The technology is not limited to thermosetting polymers. Recently, pultrusion has been successfully used with thermoplastic matrices such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET) by impregnating the glass fibers with a powder or wrapping them in a sheet of the thermoplastic matrix, which is then heated.

 

The ecological cleanliness of the finished products compared to composites based on thermosetting resins and the almost unlimited recycling (processing) possibilities after resource exhaustion seem to be compelling arguments in favor of reinforced thermoplastics.

 

For these reasons, industrial production and the use of a given material in highly industrialized countries have been growing by 8-10% per year in recent decades. New developments have given a practical boost to the manufacture of not only straight but also curved profiles, especially in the automotive sector, where the demand for this technology is growing.

 

The pultrusion technology for the manufacture of fiber composites with a polymer matrix appears to be energy-efficient and resource-saving.

 

Both economic and environmental factors favor the use of thermoplastic matrices, but due to the high viscosity of the melt, it is difficult to achieve high productivity and high-quality fiber filler impregnation with this type of matrix.

 

III. Application Areas

 

The products manufactured using this technology are widely used in the following industries:

In the agricultural and chemical industries, for the manufacture of resistant, corrosion-resistant slatted floors with enhanced strength characteristics for the construction of livestock facilities, chemical plants, etc.;

 

In the construction industry, for the production of glass fiber reinforcements, profiles, carcasses, reinforcements for PVC windows, etc.;

 

In the aerospace industry, for the manufacture of structural components for aircraft;

 

In sports and tourism, for the manufacture of equipment with enhanced strength characteristics: skis, ski poles, golf course flagpoles, tent and shed structures, etc.;

 

In the power industry In engineering, it is used to make dielectric structures, fiberglass rods for composite insulators, and support structures for signal block elements, as well as fiberglass profiles for transformers and electric motors;

 

In commercial production, long fiber molding material (LLM) pellets are used as raw materials to subsequently manufacture structures and products with enhanced strength and chemical properties;

 

In the automotive industry, it is used to produce vehicle structural parts and complex parts with enhanced stiffness, rigidity and lightness;

 

And boxers are used in many other industries and factories to meet high standards of chemical, dielectric and strength stability.

 

4. Pultrusion Equipment

 

Pultrusion machines are designed differently. Two types that are often used are reciprocating (hand-off) and continuous (cat track).

 

For the rounded corner pultrusion process, the layout of the machine has two moving stages, similar to the hand-pulled assembly of hand-off, but because the process is intermittent, only one puller and the die are mounted on the other puller.

 

Whether the platform moves linearly or circularly depends on the type of profile to be manufactured. The minimum radius of a linear machine with a rotating platform is about. 2 m For smaller radii, circular movement of the mold and gripper table is necessary.