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The thickening effect of magnesium oxide in BMC materials

Hebei Messi Biology Co., Ltd. stated that BMC material is the abbreviation of Bulk Molding Compounds, which is bulk molding compound. It is often called unsaturated polyester bulk molding compound in China. Its main raw materials are GF (chopped glass fiber), UP (unsaturated resin), MD (filler) and various additives that are fully mixed into a dough-shaped prepreg. BMC requires that the thickening speed of the resin paste should be fast, and the thickening stability of each batch of BMC materials should be good. However, when the commonly used magnesium oxide powder thickener is added to the resin paste, the viscosity rises sometimes fast and sometimes slowly. The reason is that the magnesium oxide powder is added under high-speed stirring, and the light magnesium oxide powder can easily cause the powder to fly, causing the amount of thickener in each batch of resin paste to be high and low. Therefore, the present invention uses inactive resin to disperse magnesium oxide powder in advance and prepare magnesium oxide paste thickener to solve the problem of unstable thickening.

During the preparation process of BMC resin paste, magnesium oxide is added using a dry powder addition method, so unless extremely high stirring speed is used, the powdery thickener cannot be properly dispersed evenly. If an extremely high stirring speed is used, the magnesium oxide powder will fly, making it difficult to control the added amount stably. At the same time, the temperature of the resin paste during thickening is as high as 40-50°C. Affected by this high temperature, the resin paste will thicken very quickly, which is contrary to the ideal thickening effect. This will cause the final viscosity of different batches of BMC resin paste to be unstable.

High reactive magnesium oxide

The present invention uses inactive polyester resin as a dispersant to pre-disperse magnesium oxide powder, then grinds and thickens the paste, and adds it in liquid form to improve the dispersion unevenness, so as to improve the viscosity stability between each tank of resin paste, thereby improving Product quality problems and reduce defective rates.

The preparation method of magnesium oxide paste thickened BMC material includes the following steps:

(1) Mix magnesium oxide and inactive resin and pre-disperse it in a disperser at 1000 rpm for 10 minutes. Grind it evenly with a grinder to obtain a magnesium oxide paste thickener for later use;

(2) Stir the matrix resin in the disperser at 1200 rpm for 2 minutes, add the curing agent, stir at 1200 rpm for 8 minutes, then add the magnesium oxide paste thickener and stir at 1200 rpm for 1 minute to obtain Resin paste is reserved;

(3) Knead the inorganic mineral filler and release agent in a kneader for 5 minutes, add the resin paste obtained in step (2), knead for 6 minutes, add reinforcing fibers, and continue kneading for 9 minutes to obtain.

Hebei Messi Biology Co., Ltd. stated that magnesium oxide paste uses inactive polyester resin as a dispersant to pre-disperse magnesium oxide powder, and then grinds it and adds it to the BMC material in liquid form. Compared with the existing technology, the method solves the problem of adding magnesium oxide powder thickener in the existing technology, and has lower production cost and simple process. At the same time, the viscosity and mechanical properties of the prepared BMC material are more stable.

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