Prepreg is a combination of resin matrix and reinforcing body made of continuous fiber or fabric impregnated with resin substrate under strictly controlled conditions, and is the intermediate material for the fabrication of composites, which can be used directly to manufacture various composite materials.
A． Quality Requirements for prepreg materials
Prepreg is the basis of composite properties, its quality is directly related to the quality of composite materials, composite molding process performance and mechanical properties depends on the performance of Prepreg. Therefore, Prepreg is important for the application and development of composites. The basic requirements for prepreg are generally as follows:
1. Resin matrix and reinforcement to match: reinforcement surface treatment and resin to be basically compatible, such composites may have excellent interlayer strength.
2. With proper viscosity and paving: viscosity should not be too large, so that the laying of the wrong, can be separately re-paving, and non-destructive pre-leaching material. On the other hand, viscosity can not be too small, if the viscosity is too small, at the working temperature, two prepreg can not be pasted together, so can not be futie paste on the mold, remove the external force will bounce back, from the mold.
3. The resin content deviation should be as low as possible: at least in ± 3%% to ensure that the composite fiber volume and mechanical properties of stability. In particular, non-absorbent prepreg, resin content deviation is best controlled in ± 1%%.
4. Volatile content as small as possible: general control within 2%, to reduce the pore content in composites to improve the mechanical properties of composites. The volatile content of the main bearing component Prepreg is controlled by 0.8%%.
5. Long storage life: usually requires a viscous storage period at room temperature greater than 1 months,-18 degrees Celsius greater than 6 months, aiming to meet the composite paving technology and mechanical performance requirements.
6. Curing molding has a wider pressurized belt: that is, in a wider temperature range of pressure, can obtain the desired composite materials, but performance has no significant impact.
7. Suitable mobility: The resin flow of the prepreg with the prepreg can be suitably larger, so that the resin is evenly distributed and saturated with reinforcing material; the resin flow of prepreg in the sandwich structure panel should be smaller, so that the panels and the core material can be firmly combined.
Two． The use characteristics of prepreg
1. Can control the content and arrangement of enhanced body;
2. Easy to pave;
3. Prepreg completely, no bubble, can produce high-quality surface products;
4. More secure during production;
5. Manufacturing processes are more costly.
Three． Production Technology of Prepreg
The production of prepreg is the process of resin impregnated fibers (or fabrics), the use of the production process of broken resin substrate different types.
The pretreatment method of thermosetting resin substrate is a mature process. The prepreg of thermosetting resins is mainly divided into two processes: solution Impregnation method and Hot melt method. The two processes have advantages and disadvantages and complement each other. It is estimated that the two kinds of production processes will be present at the same time to meet the different needs, but the hot melt method is becoming more and more popular. In foreign countries, the production of Hot melt is realized by automatic monitoring of process, using computer to control the thickness of plastic film in the mould stage, thus ensuring uniformity of resin content.