Manufacturing processes of materials
fiberglass
(pultrusion and manual molding).
Introduction
Development is a cyclical process in which problems and needs are solved, with these solutions come new problems and needs to solve. The development of materials is no exception.
However, the development of fiberglass reinforced plastics FRP (for its acronym in English) brought with it the opportunity to take advantage of this technology in new fields of industry. With this in mind, new production processes for FRP parts were created.
Initially, the development of reinforced plastics was only manual molding, however the processes have been improving and little by little this material has become a highly demanded material.
Each method has its advantages and disadvantages, so it is very important to know how it is done and what advantage is obtained from each one in order to choose the method that meets your needs.
pultrusion
There is a wide variety of manufacturing processes, in general, it consists of placing the reinforcement impregnated with a thermosetting resin in the shape and direction required to achieve certain characteristics. Always, the final compound will have superior properties to the separate components.
Pultrusion is a continuous, automatic and closed mold process, specially designed for high production volumes, in which case it is economically very profitable. It basically consists of pulling the resin-impregnated reinforcements and the corresponding catalytic system, through a high-temperature mold, in such a way that the curing of the resin inside occurs and profiles of constant section are obtained with the geometry of the mold. The reinforcements are impregnated with the resin by means of a resin bath located at the entrance of the mold or by injection of the latter inside the mold.
Among the methods developed are:
- Manual molding
- RTM (Resin Transfer Molding)
- HP-RTM (High Pressure Resin Transfer Model).
- HP-CRTM (High Pressure Compression RTM)
- RTM-Light
- INFUSION
- FILAMENTARY WINDING
- PULTRUSION
Manual molding
Manual molding is the oldest of the processes and they all come from it. Due to its versatility and practicality, it is the best known method.
This is an open mold process and consists of the orderly placement of layers of resin and reinforcement layers that are interspersed with each other and that, upon completion of the part's drying process, gives rise to an integral FRP part.
All these processes have in common the need for a mold, however, it is the way of placing resin and fiber that makes them special.
In manual molding, the resin and fiber are placed by hand with simple instruments such as rollers, brushes and spatulas.
- The mold is made by hand from wood or some other material, the idea is to obtain a cheap mold, a release agent is placed on the mold with the option of leaving the mold finish or placing a first layer for a smooth finish without mold imperfections .
- A generous layer of resin is placed, trying to spread it evenly so that it has the same thickness and there are no parts without resin on the mold.
- On top of the resin layer, the fiberglass reinforcement layer is placed in one of its presentations. These can be mat, which are a series of discontinuous, unoriented short fibers. Or in petatillo, which is a woven piece of long and oriented fibers, mostly perpendicular to each other. They can be oriented in the direction with greater requests according to the requirements of the project.
- On top of this, one more layer of resin is placed, completely wetting the reinforcement and preparing the surface for the next layer. It is very important to be careful when placing the resin and to place enough over the entire area of the mold. In this way, a piece without deficiencies due to delamination is obtained.
- The process is repeated until the project thickness is obtained. The last layer of reinforcement must be covered with resin to give it all the weather resistance that fiberglass offers. And in this way cure the piece completely.
- Now the piece must be allowed to carry out the curing process to be able to remove it from the mold and that it does not present deformations.
- The last part of the process is removing the excess and curing those final mods.
The most common use is in car repair to restore their surfaces. However, it is widely used to obtain parts that will not be subject to great demands, such as manhole covers, guards, sheets, gutters and grilles. In this process the percentage of reinforcement is 30-40%
Advantages:
It is very easy to run
Does not require special machinery or equipment
It is cheap
Does not require minimum parts
Disadvantages:
The end result depends on the skill of the workforce.
The arrangement of the fibers is not perfect and is limited.
Greater thicknesses are required due to the low percentage of reinforcement.