Vacuum infusion: a description of the method, technology, installation and equipment

Composite materials are not the first year used in various spheres of industry and construction. Products of this kind significantly increase the characteristics of the element base in engineering, electronic devices and building materials. In this case, the composites differ in their performance properties, as determined by the manufacturing technology. The introduction into the production process of the vacuum technique of fabricating the material, for example, makes it possible to produce high-quality carbon. However, until recently, there was a problem of excluding excess resin, the presence of which caused the fragility of the product. To maximize the physical properties of the material through the elimination of resins, a vacuum infusion is used, which, although it does not guarantee the complete elimination of negative technological factors, but allows to endow the final product with low technical costs with low costs.

General information about the method

The essence of the method is to create a vacuum inside the working cavity, due to which impregnation of the reinforcing material and retraction of the resins occurs. As with other modern methods of producing composites, vacuum is used as the molding cavity - as a rule, a special film-bag is used to organize the process. Unlike the widespread method of contact forming, the installation of vacuum infusion, including a special matrix with a dry filler, allows the production of fiberglass with a minimum content of porous inclusions and a higher degree of reinforcement. For some consumers, another difference of this technique is important. It assumes a significant reduction in emissions of harmful substances. In particular, the amount of styrene is reduced, the presence of which often becomes an obstacle when using products in the construction of residential buildings.

Technology execution

First of all, a filler is placed on the prepared equipment with vacuum, which can be represented both by special substances and combined canvases. Then the technological layers are laid, thanks to which in the future the uniform distribution of the binder component must be ensured. Then the discharge is directed to the technological package, the channel of binder admission is opened, under the influence of the already active vacuum, there is a simultaneous filling of voids and impregnation with the filler. The percentage of porosity depends on the ambient temperature at which the vacuum infusion is performed. Technology implementation of the method in industrial conditions provides an average of 1-0.5% of the pores relative to the total weight of the composite product.

Equipment for the installation of vacuum infusion

The basis for the installation of infusion is the matrix mentioned above. This is in some ways a platform, the average size of which can match both the conventional laminate panel of a square shape, and the area of the production hall. From the point of view of the quality of the resulting composite, it is more important to wrap the matrix, on which the quality of the binder feed and the function of the vacuum depends. For the formation of vacuum in the system is responsible for a vacuum pump for infusion, with which it is ensured uniform pressure of consumables in the matrix platform. In other words, it creates the effect of suction of binding components.

To capture the resin is also used a special trap, which is a sealed container. This processing element collects excess resin formed during the impregnation of the reinforcing material. The trap also protects the pump from penetrating into it the same pitches. The work of infusion is impossible without qualitative reinforcement. The infrastructure of this part is represented by fittings and tubes that organize the work of channels for feeding binder material.

Fillers for matrix

The materials used for placement in the basic equipment are related to the reinforcement means. Actually, they form the basis of the future product and determine its operational properties to the greatest extent. Depending on the direction of production, these can be coal-filled fillers, basalt fabrics for insulation materials, Kevlar aramids, etc. A separate group presents materials for vacuum infusion, from which further fiberglass is obtained. It includes traditional fiberglass fabrics, glass woolen cloths, glass wool and glass mats. Combined tissues are also becoming more common. In particular, thanks to a combination of different technical and physical properties, aramid-carbon and aramid-basalt fillers are popular.

Auxiliary materials

This group of materials is used only for the organization of the infusion process itself and is not part of the final product. As the operation is completed, such substances are removed. The main component of this type is sacrificial tissue, which is designed to form an even internal cavity of the preform, which forms a vacuum infusion. Equipment is also protected by this fabric from displaced resins. The protective function of the sacrificial material is determined by the resistance of its structure to external influences and minimal adhesion. In addition, the list of compulsory auxiliary materials includes a conductive mesh designed to remove air and feed the resin to the reinforcing base. A vacuum film is also used in preparing the matrix. It is distinguished by an increased tensile modulus of about 400% and the ability to withstand temperatures above 100 ° C.

Binder component

On the binder is a great responsibility, so it has high demands. It should be a material with a low degree of viscosity and an exothermic peak, and at the same time high viability. Corresponding to these parameters, the substance will ensure a rapid absorption of the reinforcing material and preserve the optimal working structure. For this purpose, special resins are used, due to which a vacuum infusion can provide impregnation of substrates up to 10 mm thick. High viability is of particular importance in working with large products - this quality helps to complete the process before gelatinization occurs.

Organization of binder feeding

Practice is the organization of the infusion process in two schemes: circular and parallel. In the first case, the channel is placed along the perimeter of the matrix, and the places of supply of the binder are located in the niche of the vacuum ring. As a result, the resin movement is organized in the direction from the central point to the perimeter. This avoids the leakage of air currents, since the vacuum infusion will close the channel into the ring.

The organization of the parallel distribution of the binder involves the opposite placement of the vacuum channel and the point of supply of the resin. In this case, the resin moves from one side to the other. The disadvantages of this scheme are just the inflow of air around the perimeter of the rigging, which is excluded when annular pitch is applied.

Determinants of product quality

Minimizing the risk of obtaining a final product of unsatisfactory quality will allow monitoring of several parameters of the organization of the production process. First of all, they include the tightness of the vacuum - the shell material should not have holes or places of loose fitting to the filler. Further, the viscosity index of the resin is taken into account, which should not be higher than 600 mPa * s, otherwise the process will be slow and more likely to form voids. Much depends on the quality of the laying of tissue layers. The factory method of vacuum infusion is particularly demanding for the distribution of layers of carbon material. A correct calculation without uneven patches will increase the chances of obtaining a composite that is balanced in its internal structure.

Conclusion

Artificial materials are actively replacing traditional raw materials on the market. This process covers a wide range of areas. The distribution of synthetic plastics is explained by advantageous operating properties, which are endowed with the same carbon or fiberglass. In this context, vacuum infusion is only one of the technological means to ensure high technical and physical qualities of the resulting material. Initially, technologists developed this method as a tool for getting rid of the negative aspects of production. In particular, the infusion reduced the presence of voids in the structure of the material. In the future, the method demonstrated other positive qualities, which were expressed in increasing environmental purity, and in reducing the financial costs of production.