Foam plastic reaction injection molding process
DATE：2021/10/15 8:34:47 / READ： / SOURCE：This station
Foam plastic reaction injection molding process
Foam plastic reaction injection molding is actually a combination of chemical process and injection molding process. But compared with injection molding, there are two main differences. One is that the pressure of the reaction injection mold is very low, which makes the energy consumption and equipment cost of the reaction injection system lower than that of conventional injection molding. The other is that the raw materials for reaction injection are not formulated compounds, but chemical components, which form compounds after injection molding into parts. During the reaction injection process, each chemical component is fully catalyzed to initiate a very fast chemical reaction.
1. Raw materials
The raw materials and processing parameters for RM molding are shown in Table 9-3.
(1) Urethane (polyurethane after RIM molding) RIM molding is first applied to urethane, and many corresponding processing equipment are also designed for polyurethane RM molding. At present, the RM molding of polyurethane is still the most commercially valuable RM field, and in the ever-increasing competition, the RM technology of polyurethane is also constantly making new progress. The curing time of the parts is reduced from 60s to 30, and the dimensional stability of the flexible automobile instrument panel is improved by adding 10% to 15% of glass fiber. Now, polyurethane-based RM molded parts not only still dominate the automotive industry accessories field, but also have entered the markets of agricultural equipment, telephone communication equipment, household appliances and structural materials.
(2) Urea has not yet formed an RM molding system completely based on urea.
Because the reaction between isooxoester and amine is too fast. However, in most standard polyurethane formulations, a variety of important commercial formulations are used. This formulation uses polyols instead of ethanol as a supplement to inhibit the diamine chain. The viscosity of the diamine filling system increases rapidly after mixing, thereby reducing the degree of turbulence during mold filling and leading to faster and cleaner demolding. But even hindered diamines are still very fast (adiabatic gelation time is 2~3s), which is too fast for complex parts. Because the reaction speed is too fast, it is impossible to obtain high elastic modulus parts by increasing the ratio of diamine.
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