Resin-based composite molding processes described (1): molding process-Iota

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News > Dynamic industry > Resin-based composite molding processes described (1): molding process

Resin-based composite molding processes described (1): molding process

Molding process is the production of composite materials in the most ancient and full of boundless energy a molding method. It is the amount of premix added to the metal or prepreg to the inner mold, heated, pressurized curing molding method.
The main advantage of molding process:
① high efficiency, easy to implement specialized and automated production;
② product high dimensional accuracy, good repeatability;
③ smooth surface, without the second modification;
④ forming a structure capable of complex products;
⑤ because of mass production, the price is relatively cheap.

Inadequacy of molding that mold manufacturing complex, large investment, plus compression machine limitations, the most suitable for mass production of small and medium sized composite products. With the continuous improvement and development of metal processing technology, press manufacturing level and synthetic resin process performance, press tonnage and increasing table size, compression molding material is relatively lower temperature and pressure, making the size of the molded product gradually to large-scale development, has been able to produce large automotive parts, bathtub, toilet overall components.
Molding process by reinforcing material variety of state and molding materials can be divided into the following categories:
① fiber material molding method
Is premixed or pre-impregnated fibrous molding material, into a mold, a method in a composite article at a certain temperature and pressure forming. The method is simple, and versatile. Depending on the specific operation, there premix molding and prepreg molding method.

② broken cloth molding method
The resin-impregnated glass fiber fabric glue or other fabrics, such as linen, organic fiber cloth, asbestos cloth or cotton and other bits and pieces, cut into pieces, and then heated compression molding composite products in a metal mold.

③ fabric molding method
Previously woven into a two-dimensional or three-dimensional fabric of the desired shape impregnating resin glue, and then placed in a metal mold for heat pressing the composite article.

④ laminated molding method
A laminated resin glue over glass fiber cloth or other fabric, cut into a desired shape, and then by heating in a metal mold or compression molding a composite article.

⑤ winding molding method
The continuous fiber prepreg resin over glue or fabric (belt), through a dedicated winding machine to provide certain tension and temperature, wrapped around the mandrel, and then placed in a mold for heating compression molding composite products.

⑥ plastic sheet (SMC) molding method
The SMC sheet according to product size, shape, thickness and other requirements of the crop cutting, the multilayer sheet is then laminated into the mold after the molded article is heated and pressurized.

⑦ preform molding method blanks
First chopped fiber manufactures similar shape and size of preform blanks, put in a metal mold, and then injecting the prepared binder (resin mixture) into the mold, at a certain temperature and pressure forming.
There are many varieties of molding material that can be pre-preg materials, premixed materials may also be blank. Molded feed varieties currently used are: prepreg tape, fiber premix, BMC, DMC, HMC, SMC, XMC, TMC and ZMC other varieties.

1, raw materials
(1) Synthesis of Resin
Composite molded articles used in molding a synthetic resin material having requirements: ① on the reinforcing material has good wetting properties, so as to form a good bond at the interface of synthetic resin and reinforcing material; ② appropriate viscosity and good flowability, in under the pressing conditions can be filled with a reinforcing material and uniformly throughout the die cavity; ③ having suitable curing speed under pressing conditions, and the curing process does not produce by-products or by-products and small in volume shrinkage; ④ molded article to meet specific performance requirements. Selection according to the above requirements, commonly used synthetic resins are: unsaturated polyester resins, epoxy resins, phenolic resins, vinyl resins, furan resins, silicone resins, polybutadiene resins, allyl ester, melamine resin, polyimide resin and the like. To make molded products meet specific performance indicators, after selecting the resin varieties and grades, but also select the appropriate auxiliary materials, fillers and pigments.
(2) reinforcing material
Molding compound commonly used in glass fiber reinforced materials mainly surgery silk, roving, there is twist roving, continuous glass fibers, glass fiber cloth, glass fiber mat, etc., also have a small selection of specialty products, asbestos felt, asbestos fabric (cloth) and asbestos paper and high-silica fibers, carbon fibers, organic fibers (such as aramid fibers, nylon fibers, etc.) and natural fibers (such as linen, cotton, scouring cloth, not scouring cloth, etc.) and other varieties. Sometimes with two or more fiber hybrid material for reinforcement.

(3) supporting material
Typically include a curing agent (initiator), accelerators, diluents, surface treatment agents, low profile additives, mold release agents, colorants (pigments) and other auxiliary materials and fillers.
2, preparation of the molding material
Glass fibers (or glass cloth) impregnated resin molding material, for example, the production process can be divided into two premixed law and prepreg method.

(1) premixed Act
First cut into 30 ~ 50mm glass fiber chopped fibers, fluffy kneader and after sufficiently kneading the resin glue to completely wet the resin glass fiber, and then by drying (drying) to an appropriate viscosity can be. Its characteristics are no loose fiber orientation, production capacity, this method of production of molded material hematocrit big, good liquidity, but during the preparation of fiber strength losses.

(2) prepreg method
Fiber prepreg method is the whole bundle of continuous glass fiber (or cloth) after dipping, drying, chopped together. Its characteristics are fiber bunches, more closely, the smaller the preparation of molding material in fiber strength loss, but slightly inferior compatibility and flowability of molding material between the feed beam.

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